QuickSilver Controls develops servo control technology for microstep motors. Their system uses a standard 2-phase stepper motor but controls the current in the motor windings using a closed-loop servo controller with position feedback from an encoder. This allows the motor to be driven like a servo motor, with variable speed and torque control for applications requiring precision, speed, and efficiency compared to traditional stepper systems. The document provides background on stepper motors and servo motors, and explains how QuickSilver's technology combines aspects of both to achieve servo performance from lower-cost stepper motors.
1) A servo is a feedback control system that controls the position or motion of a mechanical system. It receives an input signal and uses feedback to control velocity and position.
2) An electrical servo system relies on electrical energy and feedback to provide fast, accurate, and remote control. It has an error detector, amplifier, and error corrector to match the controlled variable to a reference signal.
3) A DC servo motor uses separate power sources for the field and armature windings. It can be field controlled, where the field is controlled by feedback, or armature controlled, where the armature is controlled by feedback. Field control provides slower response while armature control provides faster response.
Written-pole electric motors utilize concepts from induction, hysteresis, and permanent magnet motors. They allow speed and frequency to be independent by enabling a controlled variable number of poles through a "writing" coil. This overcomes limitations of conventional motors having a fixed number of poles. A written-pole motor consists of a rotor layer and excitation winding to magnetize portions of the rotor. It operates in start, transition, and run modes. Compared to conventional motors, written-pole motors have lower starting current, higher efficiency, unity power factor, and can ride through power disturbances. Their main applications are for irrigation pumps and systems where three-phase power is unavailable.
ommon motion systems use three types of control methods. They are position control, velocity control and torque control.
The majority of Newport’s motion systems use position control. This type of control moves the load from one known fixed position to another known fixed position. Feedback, or closed-loop positioning, is important for precise positioning.
Velocity control moves the load continuously for a certain time interval or moves the load from one place to another at a prescribed velocity. Newport’s systems use both encoder and tachometer feedback to regulate velocity.
Torque control measures the current applied to a motor with a known torque coefficient in order to develop a known constant torque. Newport’s motion systems do not employ this method of control.
This document provides information on ABB's BSM N-series AC servo motors, including:
- The BSM N-series provides low inertia and high torque for excellent dynamic performance and high machine throughput.
- Motors are available in sizes from 50mm to 100mm frame sizes with continuous torques ranging from 3.9 lb-in to 354 lb-in.
- Performance curves and specifications are provided for various motor models.
The document discusses AC servo motors. It covers the principle, characteristics, types, applications and sizing of AC servo motors. Some key points include:
- AC servo motors use permanent magnets and feedback from encoders to provide high torque and precision control.
- Characteristics like speed, torque, frame size, and encoder options can be selected for the application.
- Standard and special motors are used in applications like machine tools, semiconductor equipment, medical devices and more.
- Success stories demonstrate how AC servo motors replaced hydraulic systems and improved textile machines, simulators and other special purpose machines.
- Motor sizing software is available to help customers select the optimized motor for their application.
1) A servo motor is a motor that is part of a servomechanism and is typically paired with an encoder to provide position and speed feedback. It requires a controller to compare the feedback to a reference signal and correct any errors.
2) There are two main types of servo motors - AC and DC. DC servo motors are preferred for high power applications due to their higher efficiency. DC servo motors have field and armature windings that can be controlled separately to provide precise torque control.
3) A DC servo motor works by using an amplified error signal from a position sensor to control either the field or armature winding, depending on the application. This allows the motor's torque to be controlled to minimize
A servo motor works by using feedback to precisely control the position of its output shaft. It contains a small DC motor, gears that reduce speed while increasing torque, and a feedback sensor to monitor position. An electronic circuit compares the actual position to the desired position from an input signal and powers the motor in the direction needed to minimize any error. This allows servo motors to automatically rotate and hold their shaft at specific angular positions commanded by pulse signals, making them well-suited for robotic applications requiring precise motion control.
This document provides an overview of different types of motors including stepper motors, servo motors, DC motors, and AC motors. It discusses the basic components and operating principles of stepper motors and servo motors. Some key points covered include:
- Stepper motors can be precisely controlled by computer and are well-suited for applications requiring precise positioning or speed control.
- Servo motors produce high torque at all speeds including zero speed and can hold a static position precisely.
- The document compares characteristics of DC servo motors and hybrid stepper motors such as cost, reliability, setup complexity, efficiency, and vibration.
- Finally, examples of applications for stepper motors and servo motors in industrial machinery, computer peripherals
1) A servo is a feedback control system that controls the position or motion of a mechanical system. It receives an input signal and uses feedback to control velocity and position.
2) An electrical servo system relies on electrical energy and feedback to provide fast, accurate, and remote control. It has an error detector, amplifier, and error corrector to match the controlled variable to a reference signal.
3) A DC servo motor uses separate power sources for the field and armature windings. It can be field controlled, where the field is controlled by feedback, or armature controlled, where the armature is controlled by feedback. Field control provides slower response while armature control provides faster response.
Written-pole electric motors utilize concepts from induction, hysteresis, and permanent magnet motors. They allow speed and frequency to be independent by enabling a controlled variable number of poles through a "writing" coil. This overcomes limitations of conventional motors having a fixed number of poles. A written-pole motor consists of a rotor layer and excitation winding to magnetize portions of the rotor. It operates in start, transition, and run modes. Compared to conventional motors, written-pole motors have lower starting current, higher efficiency, unity power factor, and can ride through power disturbances. Their main applications are for irrigation pumps and systems where three-phase power is unavailable.
ommon motion systems use three types of control methods. They are position control, velocity control and torque control.
The majority of Newport’s motion systems use position control. This type of control moves the load from one known fixed position to another known fixed position. Feedback, or closed-loop positioning, is important for precise positioning.
Velocity control moves the load continuously for a certain time interval or moves the load from one place to another at a prescribed velocity. Newport’s systems use both encoder and tachometer feedback to regulate velocity.
Torque control measures the current applied to a motor with a known torque coefficient in order to develop a known constant torque. Newport’s motion systems do not employ this method of control.
This document provides information on ABB's BSM N-series AC servo motors, including:
- The BSM N-series provides low inertia and high torque for excellent dynamic performance and high machine throughput.
- Motors are available in sizes from 50mm to 100mm frame sizes with continuous torques ranging from 3.9 lb-in to 354 lb-in.
- Performance curves and specifications are provided for various motor models.
The document discusses AC servo motors. It covers the principle, characteristics, types, applications and sizing of AC servo motors. Some key points include:
- AC servo motors use permanent magnets and feedback from encoders to provide high torque and precision control.
- Characteristics like speed, torque, frame size, and encoder options can be selected for the application.
- Standard and special motors are used in applications like machine tools, semiconductor equipment, medical devices and more.
- Success stories demonstrate how AC servo motors replaced hydraulic systems and improved textile machines, simulators and other special purpose machines.
- Motor sizing software is available to help customers select the optimized motor for their application.
1) A servo motor is a motor that is part of a servomechanism and is typically paired with an encoder to provide position and speed feedback. It requires a controller to compare the feedback to a reference signal and correct any errors.
2) There are two main types of servo motors - AC and DC. DC servo motors are preferred for high power applications due to their higher efficiency. DC servo motors have field and armature windings that can be controlled separately to provide precise torque control.
3) A DC servo motor works by using an amplified error signal from a position sensor to control either the field or armature winding, depending on the application. This allows the motor's torque to be controlled to minimize
A servo motor works by using feedback to precisely control the position of its output shaft. It contains a small DC motor, gears that reduce speed while increasing torque, and a feedback sensor to monitor position. An electronic circuit compares the actual position to the desired position from an input signal and powers the motor in the direction needed to minimize any error. This allows servo motors to automatically rotate and hold their shaft at specific angular positions commanded by pulse signals, making them well-suited for robotic applications requiring precise motion control.
This document provides an overview of different types of motors including stepper motors, servo motors, DC motors, and AC motors. It discusses the basic components and operating principles of stepper motors and servo motors. Some key points covered include:
- Stepper motors can be precisely controlled by computer and are well-suited for applications requiring precise positioning or speed control.
- Servo motors produce high torque at all speeds including zero speed and can hold a static position precisely.
- The document compares characteristics of DC servo motors and hybrid stepper motors such as cost, reliability, setup complexity, efficiency, and vibration.
- Finally, examples of applications for stepper motors and servo motors in industrial machinery, computer peripherals
Stepper Motor Types, Advantages And Applicationselprocus
A stepper motor is an electromechanical device which converts electrical pulses into discrete mechanical movements. The shaft or spindle of a stepper motor rotates in discrete step increments when electrical command pulses are
applied to it in the proper sequence. The motors rotation has several direct relationships to these applied input pulses. The sequence of the applied pulses is directly related to the direction of motor shafts rotation. The speed of the
motor shafts rotation is directly related to the frequency of the input pulses and the length of rotation is directly related to the number of input pulses applied.
This document provides an overview of stepper motors, including:
- Their working principle is that they rotate through discrete angular steps in response to input current pulses. They come in different types like permanent magnet, variable reluctance, and hybrid.
- Applications include computer peripherals, textile machines, robotics, printers, drives, machine tools, and process controls where incremental motion is required.
- Advantages are low cost, high reliability, and high torque at low speeds. Disadvantages include resonance effects at low speeds and decreasing torque with increasing speed.
- Stepper motors are brushless DC motors that rotate in discrete steps in response to control signals. They are excellent for positioning applications as their rotation can be accurately controlled.
- There are three main types of stepper motors: permanent magnet, variable reluctance, and hybrid. Permanent magnet motors are the most common.
- Key components include the rotor, stator, and windings. Pulses sent to the windings energize the stator poles and rotate the motor.
- Stepper motors have advantages like low cost control, simplicity, and ability to operate without feedback but disadvantages like higher current draw and need for a driver circuit.
- Common applications include printers, CNC machines, robotics, and
The document discusses stepper motors. It begins with an introduction that defines a stepper motor as a device that converts electrical pulses into discrete mechanical movements, with the shaft rotating in steps proportional to the input pulses. It then covers stepper motor operation, types including variable reluctance, permanent magnet and hybrid, advantages, applications in devices like printers and CD drives, and stepping modes like full step and microstepping.
A stepper motor is an electric motor that rotates in discrete steps. It uses electromagnetic coils to move a rotor in synchronized steps. There are three main types of stepper motors: variable reluctance, permanent magnet, and hybrid synchronous. Stepper motors are commonly used in industrial applications like printers, robotics, and CNC machines due to their precise positioning ability without the need for feedback sensors.
The document discusses stepper motors. It begins by introducing the three members of the presentation group and listing the contents to be covered, which include the introduction, working principle, speed control methodology, applications, advantages, and limitations of stepper motors. It then defines a stepper motor as a brushless DC electric motor that divides a full rotation into a number of equal steps. The document goes on to describe the three main types of stepper motors and explain their working principles. It also discusses the various ways to control the speed of stepper motors, including using series resistance, gearboxes, and voltage regulation. Finally, the common applications, advantages, and limitations of stepper motors are summarized.
The document discusses different types of stepper motors, including their construction, operation, advantages, disadvantages and applications. It describes permanent magnet stepper motors, variable reluctance stepper motors, and hybrid stepper motors. Key points covered include how stepper motors convert electrical pulses into precise rotational movements without feedback, and their use in computer-controlled systems like CNC machines, printers, and robotics.
This document discusses factors to consider when selecting a servo motor and drive for an application. It outlines key sizing factors like inertia ratio, speed, maximum torque at speed, and RMS torque at speed. An inertia ratio between 2:1 and 5:1 is typical, with higher ratios requiring a motor with more inertia or changes to reduce load inertia. It also provides information on synchronous vs induction servo motors and their relative advantages. In general, a modest motor oversizing of up to 20% is acceptable.
The document discusses servos, including where they are used, their advantages, and disadvantages. Servos are commonly used in remote-controlled toys, industrial applications, robotics, and food services. They have advantages like high output power, closed feedback loops, efficiency, and torque. However, they require tuning, have limited peak torque, and can be damaged by overloads. They also have a bewildering variety of components and usually cost more than stepper motors.
The document discusses AC servomotors. It defines a servomotor as a rotary actuator that allows precise control of position, velocity, and acceleration using a motor, position sensor, and controller. Servomotors are used in closed-loop control systems. The document describes the key components of a typical servo system and explains how the motor works with a controller and amplifier to receive position commands from a PLC. It provides details on the construction and speed-torque characteristics of AC servomotors that make them suitable for servo applications.
A stepper motor works by having its rotor move in discrete steps in response to electrical pulses received by its stator windings. There are three main types - variable-reluctance motors which have a rotor that changes the magnetic circuit as it rotates; permanent magnet motors which have a permanent magnet rotor driven by stator windings; and hybrid motors which combine aspects of the first two. Stepper motors have advantages like excellent response to starting and stopping commands and ability to achieve low synchronous speeds, but disadvantages like potential resonances if not controlled properly and difficulty operating at extremely high speeds.
Servo motors have an output shaft that can be positioned to specific angular positions by sending a coded signal. They are constructed from basic DC motors with added gear reduction, a position sensor, and control circuitry. There are two main types - DC servo motors which are controlled by DC command signals applied directly to coils, and AC servo motors which are controlled by AC command signals. Servo motors offer advantages for sewing machines by allowing precise control of speed and silent operation when not engaged.
A servo motor is a motor that uses feedback to control its motion and position. It consists of a motor, control board, and potentiometer connected to the output shaft. The potentiometer allows the control circuitry to monitor the shaft position and provide feedback to move the shaft to the desired angle between 0 and 180 degrees. Servo motors are used in applications like robotics and CNC machinery where precise control of motion and position is required. They are controlled through pulse width modulation signals that determine the shaft position based on pulse duration. Common types are rotary and linear servo motors that can have encoders or resolvers for position feedback.
The document discusses different types of stepper motors: permanent magnet stepper motors, variable reluctance stepper motors, and hybrid stepper motors. It notes that hybrid stepper motors combine features of permanent magnet and variable reluctance stepper motors. It also lists several advantages of stepper motors, including precise positioning, full torque at standstill, reliability, and proportional speed control through pulse input frequency.
This document provides an introduction to DC motors and stepper motors. It discusses the basic components and workings of brushed DC motors, which were one of the earliest electric motor designs due to their simple and easy to control nature. It then describes stepper motors, which differ from DC motors in that their commutation is controlled externally rather than with a commutator. Key aspects of stepper motors covered include their voltage rating, resistance-per-winding, degrees per step, and unipolar and bipolar configurations. The document concludes by discussing how to identify the wires of a stepper motor and provides a basic program for controlling a stepper motor by firing the signal wires in sequence.
this presentation gives a clear idea of how the servo motor and servo drive working explained in detail and attached video have a clear idea of how servo motor works......enjoy, i hope you will like this.... :)
Stepper motors are capable of precise motion in increments and convert electronic pulses into proportional mechanical movement. They have a rotor inside a stator with electromagnets that pull the rotor teeth into alignment as different coils are energized, resulting in rotation. There are several types including permanent magnet, variable reluctance, and hybrid. Stepper motors can operate in full or half step modes, rotating the shaft by 90 or 45 degrees respectively with each pulse. They are used in applications like printers, CNC machines, and disk drives where precise positioning is needed.
The document discusses different types of motors used in robotics including AC motors, DC motors, DC geared motors, stepper motors, and servo motors. It provides details on the functioning and applications of each motor type, with DC geared motors and servo motors being most commonly used in robotics due to their ability to provide considerable torque and change direction with the same power supply. Controller circuits like H-bridges are used to control the direction of DC motors.
This document describes the construction and working of a stepper motor. It discusses the three main types of stepper motors: variable reluctance, permanent magnet, and hybrid synchronous. It explains how each type works in one phase on, two phase on, half step, and microstepping modes. Applications mentioned include uses in industry like manufacturing equipment, as well as computer peripherals and business machines. Phase current waveforms are also covered for different stepping modes.
Actuators convert energy into mechanical motion or force. They play an important role in robotics and automation by allowing controllers to move robotic joints and limbs. The document discusses various types of actuators including electric actuators like servomotors, stepper motors, and DC motors as well as hydraulic and pneumatic actuators. It provides details on the characteristics, working principles, applications and advantages of common electric actuators like servomotors and stepper motors. Servo motors provide precise rotational or linear movement while stepper motors move in discrete steps making them well-suited for applications requiring positional accuracy.
A stepper motor converts electrical pulses into discrete mechanical movements of its shaft. The shaft rotates in discrete step increments that correspond directly to the sequence and frequency of input pulses. There are three main types of stepper motors: variable-reluctance, permanent magnet, and hybrid. Stepper motors provide controlled movement and are well-suited for applications that require control of rotation angle, speed, position, and synchronization. They have advantages like full torque at standstill and excellent response to starting, stopping, and reversing.
Stepper Motor Types, Advantages And Applicationselprocus
A stepper motor is an electromechanical device which converts electrical pulses into discrete mechanical movements. The shaft or spindle of a stepper motor rotates in discrete step increments when electrical command pulses are
applied to it in the proper sequence. The motors rotation has several direct relationships to these applied input pulses. The sequence of the applied pulses is directly related to the direction of motor shafts rotation. The speed of the
motor shafts rotation is directly related to the frequency of the input pulses and the length of rotation is directly related to the number of input pulses applied.
This document provides an overview of stepper motors, including:
- Their working principle is that they rotate through discrete angular steps in response to input current pulses. They come in different types like permanent magnet, variable reluctance, and hybrid.
- Applications include computer peripherals, textile machines, robotics, printers, drives, machine tools, and process controls where incremental motion is required.
- Advantages are low cost, high reliability, and high torque at low speeds. Disadvantages include resonance effects at low speeds and decreasing torque with increasing speed.
- Stepper motors are brushless DC motors that rotate in discrete steps in response to control signals. They are excellent for positioning applications as their rotation can be accurately controlled.
- There are three main types of stepper motors: permanent magnet, variable reluctance, and hybrid. Permanent magnet motors are the most common.
- Key components include the rotor, stator, and windings. Pulses sent to the windings energize the stator poles and rotate the motor.
- Stepper motors have advantages like low cost control, simplicity, and ability to operate without feedback but disadvantages like higher current draw and need for a driver circuit.
- Common applications include printers, CNC machines, robotics, and
The document discusses stepper motors. It begins with an introduction that defines a stepper motor as a device that converts electrical pulses into discrete mechanical movements, with the shaft rotating in steps proportional to the input pulses. It then covers stepper motor operation, types including variable reluctance, permanent magnet and hybrid, advantages, applications in devices like printers and CD drives, and stepping modes like full step and microstepping.
A stepper motor is an electric motor that rotates in discrete steps. It uses electromagnetic coils to move a rotor in synchronized steps. There are three main types of stepper motors: variable reluctance, permanent magnet, and hybrid synchronous. Stepper motors are commonly used in industrial applications like printers, robotics, and CNC machines due to their precise positioning ability without the need for feedback sensors.
The document discusses stepper motors. It begins by introducing the three members of the presentation group and listing the contents to be covered, which include the introduction, working principle, speed control methodology, applications, advantages, and limitations of stepper motors. It then defines a stepper motor as a brushless DC electric motor that divides a full rotation into a number of equal steps. The document goes on to describe the three main types of stepper motors and explain their working principles. It also discusses the various ways to control the speed of stepper motors, including using series resistance, gearboxes, and voltage regulation. Finally, the common applications, advantages, and limitations of stepper motors are summarized.
The document discusses different types of stepper motors, including their construction, operation, advantages, disadvantages and applications. It describes permanent magnet stepper motors, variable reluctance stepper motors, and hybrid stepper motors. Key points covered include how stepper motors convert electrical pulses into precise rotational movements without feedback, and their use in computer-controlled systems like CNC machines, printers, and robotics.
This document discusses factors to consider when selecting a servo motor and drive for an application. It outlines key sizing factors like inertia ratio, speed, maximum torque at speed, and RMS torque at speed. An inertia ratio between 2:1 and 5:1 is typical, with higher ratios requiring a motor with more inertia or changes to reduce load inertia. It also provides information on synchronous vs induction servo motors and their relative advantages. In general, a modest motor oversizing of up to 20% is acceptable.
The document discusses servos, including where they are used, their advantages, and disadvantages. Servos are commonly used in remote-controlled toys, industrial applications, robotics, and food services. They have advantages like high output power, closed feedback loops, efficiency, and torque. However, they require tuning, have limited peak torque, and can be damaged by overloads. They also have a bewildering variety of components and usually cost more than stepper motors.
The document discusses AC servomotors. It defines a servomotor as a rotary actuator that allows precise control of position, velocity, and acceleration using a motor, position sensor, and controller. Servomotors are used in closed-loop control systems. The document describes the key components of a typical servo system and explains how the motor works with a controller and amplifier to receive position commands from a PLC. It provides details on the construction and speed-torque characteristics of AC servomotors that make them suitable for servo applications.
A stepper motor works by having its rotor move in discrete steps in response to electrical pulses received by its stator windings. There are three main types - variable-reluctance motors which have a rotor that changes the magnetic circuit as it rotates; permanent magnet motors which have a permanent magnet rotor driven by stator windings; and hybrid motors which combine aspects of the first two. Stepper motors have advantages like excellent response to starting and stopping commands and ability to achieve low synchronous speeds, but disadvantages like potential resonances if not controlled properly and difficulty operating at extremely high speeds.
Servo motors have an output shaft that can be positioned to specific angular positions by sending a coded signal. They are constructed from basic DC motors with added gear reduction, a position sensor, and control circuitry. There are two main types - DC servo motors which are controlled by DC command signals applied directly to coils, and AC servo motors which are controlled by AC command signals. Servo motors offer advantages for sewing machines by allowing precise control of speed and silent operation when not engaged.
A servo motor is a motor that uses feedback to control its motion and position. It consists of a motor, control board, and potentiometer connected to the output shaft. The potentiometer allows the control circuitry to monitor the shaft position and provide feedback to move the shaft to the desired angle between 0 and 180 degrees. Servo motors are used in applications like robotics and CNC machinery where precise control of motion and position is required. They are controlled through pulse width modulation signals that determine the shaft position based on pulse duration. Common types are rotary and linear servo motors that can have encoders or resolvers for position feedback.
The document discusses different types of stepper motors: permanent magnet stepper motors, variable reluctance stepper motors, and hybrid stepper motors. It notes that hybrid stepper motors combine features of permanent magnet and variable reluctance stepper motors. It also lists several advantages of stepper motors, including precise positioning, full torque at standstill, reliability, and proportional speed control through pulse input frequency.
This document provides an introduction to DC motors and stepper motors. It discusses the basic components and workings of brushed DC motors, which were one of the earliest electric motor designs due to their simple and easy to control nature. It then describes stepper motors, which differ from DC motors in that their commutation is controlled externally rather than with a commutator. Key aspects of stepper motors covered include their voltage rating, resistance-per-winding, degrees per step, and unipolar and bipolar configurations. The document concludes by discussing how to identify the wires of a stepper motor and provides a basic program for controlling a stepper motor by firing the signal wires in sequence.
this presentation gives a clear idea of how the servo motor and servo drive working explained in detail and attached video have a clear idea of how servo motor works......enjoy, i hope you will like this.... :)
Stepper motors are capable of precise motion in increments and convert electronic pulses into proportional mechanical movement. They have a rotor inside a stator with electromagnets that pull the rotor teeth into alignment as different coils are energized, resulting in rotation. There are several types including permanent magnet, variable reluctance, and hybrid. Stepper motors can operate in full or half step modes, rotating the shaft by 90 or 45 degrees respectively with each pulse. They are used in applications like printers, CNC machines, and disk drives where precise positioning is needed.
The document discusses different types of motors used in robotics including AC motors, DC motors, DC geared motors, stepper motors, and servo motors. It provides details on the functioning and applications of each motor type, with DC geared motors and servo motors being most commonly used in robotics due to their ability to provide considerable torque and change direction with the same power supply. Controller circuits like H-bridges are used to control the direction of DC motors.
This document describes the construction and working of a stepper motor. It discusses the three main types of stepper motors: variable reluctance, permanent magnet, and hybrid synchronous. It explains how each type works in one phase on, two phase on, half step, and microstepping modes. Applications mentioned include uses in industry like manufacturing equipment, as well as computer peripherals and business machines. Phase current waveforms are also covered for different stepping modes.
Actuators convert energy into mechanical motion or force. They play an important role in robotics and automation by allowing controllers to move robotic joints and limbs. The document discusses various types of actuators including electric actuators like servomotors, stepper motors, and DC motors as well as hydraulic and pneumatic actuators. It provides details on the characteristics, working principles, applications and advantages of common electric actuators like servomotors and stepper motors. Servo motors provide precise rotational or linear movement while stepper motors move in discrete steps making them well-suited for applications requiring positional accuracy.
A stepper motor converts electrical pulses into discrete mechanical movements of its shaft. The shaft rotates in discrete step increments that correspond directly to the sequence and frequency of input pulses. There are three main types of stepper motors: variable-reluctance, permanent magnet, and hybrid. Stepper motors provide controlled movement and are well-suited for applications that require control of rotation angle, speed, position, and synchronization. They have advantages like full torque at standstill and excellent response to starting, stopping, and reversing.
The document describes experiments using a stepper motor control trainer. Experiment 1 operates a stepper motor in unipolar mode in full step operation. Experiment 2 also operates in unipolar mode but in half step operation. Experiment 3 operates the motor in bipolar mode. Experiment 4 operates the motor in bipolar mode without current sense feedback. The experiments allow students to learn different stepper motor operating modes and configurations.
A stepper motor is a brushless DC motor that rotates in discrete step increments when electrical pulses are applied in a sequence. There are three main types - variable reluctance, permanent magnet, and hybrid. Stepper motors provide controlled movement and are well-suited for applications requiring rotation angle, speed, position, and synchronization control. They generate torque depending on factors like step rate and current. Stepper motors find applications in computer-controlled precision positioning equipment, industrial machines, and commercial devices like printers.
Here, I am uploading our b.tech final year project paper which is published in IRJET Journal.
We done a project on Vector speed control of induction motor.
This paper is completely written in simple words and this is the most easiest way of explaining.
And also ,here i am providing a youtube link how we done this project and its matlab simulation circuit and result analyzing...etc..,
Our teammates are :-1)Samala Ranjith
2)Sammoji Rajinikanth
3)Shyamala Karunakar Reddy
4) K V V P Chari (our guide)
This document provides an overview of different types of electric motors, including DC motors, stepper motors, and their operating principles. It discusses conventional brushed DC motors and how they work using commutator and brushes. Brushless DC motors are also covered, noting they use electronic commutation instead of mechanical brushes. Stepper motors are introduced as motors that rotate in discrete steps when electrical pulses are applied. Their operation and characteristics such as resolution are explained. Applications of different motor types are briefly mentioned.
This document discusses speed control methods for three-phase induction motors. It describes various speed control techniques including stator voltage control, stator frequency control, V/F control, and static rotor resistance control. It explains the advantages of speed control, such as energy savings and meeting different process requirements. Industrial applications of induction motor drives are also mentioned, such as in fans, compressors, pumps and machine tools.
This document provides an overview of different types of motors used in computer numerical control (CNC) machines. It describes the basic components and working principles of motors. It then compares alternating current (AC) and direct current (DC) motors, discussing stepper motors, servo mechanisms, and the motors typically used in CNC machines including spindle motors and linear motors. Key selection criteria for motors in CNC applications include revolutions per minute, torque, standards compliance, power requirements, and motor load.
A driver circuit is required to properly operate a DC motor or servomotor. DC motors can be controlled to operate in any of the four quadrants. Servomotors allow for precise control of position and velocity through feedback sensors and sophisticated controllers. Common types of motors discussed include DC motors, AC induction motors, stepper motors, and brushless DC motors. Brushless DC motors are increasingly used due to their higher efficiency, longer lifespan, lower noise, and ability to achieve precise motion control compared to brushed DC motors.
This document describes scalar (V/f) control of 3-phase induction motors using TMS320F2803x microcontrollers. Scalar control is a simpler form of motor control that can provide satisfactory steady-state response. It explores using the TMS320F2803x devices to implement scalar control through variable voltage and frequency control of an induction motor. The system is built incrementally, starting with basic voltage and frequency generation and expanding to include closed-loop speed control. Experimental results are presented at each build level.
Motors convert electrical energy to mechanical motion. There are several types of motors used in robotics, including AC motors, DC motors, DC servo motors, and stepper motors. Stepper motors are used in the CEENBot and offer advantages over DC motors like accurate wheel positioning, high holding torque, and open-loop speed control without position feedback. A stepper motor works by digitally switching electromagnets around a permanent magnet rotor to precisely rotate it through a sequence of steps.
Introduction to AC Motors with constructional details.pptdatamboli
This document provides an overview of different types of motors used in robotics, including their characteristics and principles of operation. It discusses AC motors, DC motors, DC servo motors, and stepper motors. It specifically describes how the CEENBot uses stepper motors that provide accurate wheel positioning and speed control without position feedback. The stepper motors have a 1.8 degree resolution and precisely control wheel rotation through electromagnetic phases controlled by a microprocessor.
Speed Control of BLDC Motor with Four Quadrant Operation Using dsPICijsrd.com
Brushless DC (BLDC) motor drives are becoming more popular in industrial and traction applications. Hence the control of BLDC motor in four quadrants is very vital. The flexibility of the drive system is increased using digital controller. In this paper the PWM signals for driving the power inverter bridge for BLDC motor have been successfully implemented using a dsPIC controller and the motor can be controlled in all the four quadrants without any loss of power .Energy is conserved during regenerative braking period. The digital controller dsPIC, is advantageous over other controller, as it combines the calculation capability of digital signal processor and controlling capability of PIC microcontroller to achieve a precise control. Simulation of the proposed model is done by using MATLAB/Simulink.
The document discusses various methods of speed control for induction motors, including rotor resistance control. Rotor resistance control involves connecting a variable external resistance to the rotor circuit of a wound rotor induction motor to control its speed. This is done by varying the effective rotor resistance using a chopper. The torque-speed characteristics show that increasing rotor resistance increases slip and reduces motor speed at constant torque. However, rotor resistance control is not suitable for squirrel cage motors and has low efficiency due to losses in the external resistance.
Automated screw thread quality checking using SMAC LAR55 actuator new produc...Electromate
The document discusses an automated screw thread quality checking solution using SMAC LAR55 actuators. It allows 100% inspection of screw threads to check for issues like oversizing, cross-threading, depth, and pitch. This can help automakers meet higher quality standards by eliminating defective parts and providing immediate feedback. The LAR55's precision Z-theta motion makes it suitable for automatically checking screw threads.
An overview of the various kinematic models in both parallel and serial robot...Electromate
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Discover top-tier mobile app development services, offering innovative solutions for iOS and Android. Enhance your business with custom, user-friendly mobile applications.
AppSec PNW: Android and iOS Application Security with MobSFAjin Abraham
Mobile Security Framework - MobSF is a free and open source automated mobile application security testing environment designed to help security engineers, researchers, developers, and penetration testers to identify security vulnerabilities, malicious behaviours and privacy concerns in mobile applications using static and dynamic analysis. It supports all the popular mobile application binaries and source code formats built for Android and iOS devices. In addition to automated security assessment, it also offers an interactive testing environment to build and execute scenario based test/fuzz cases against the application.
This talk covers:
Using MobSF for static analysis of mobile applications.
Interactive dynamic security assessment of Android and iOS applications.
Solving Mobile app CTF challenges.
Reverse engineering and runtime analysis of Mobile malware.
How to shift left and integrate MobSF/mobsfscan SAST and DAST in your build pipeline.
5th LF Energy Power Grid Model Meet-up SlidesDanBrown980551
5th Power Grid Model Meet-up
It is with great pleasure that we extend to you an invitation to the 5th Power Grid Model Meet-up, scheduled for 6th June 2024. This event will adopt a hybrid format, allowing participants to join us either through an online Mircosoft Teams session or in person at TU/e located at Den Dolech 2, Eindhoven, Netherlands. The meet-up will be hosted by Eindhoven University of Technology (TU/e), a research university specializing in engineering science & technology.
Power Grid Model
The global energy transition is placing new and unprecedented demands on Distribution System Operators (DSOs). Alongside upgrades to grid capacity, processes such as digitization, capacity optimization, and congestion management are becoming vital for delivering reliable services.
Power Grid Model is an open source project from Linux Foundation Energy and provides a calculation engine that is increasingly essential for DSOs. It offers a standards-based foundation enabling real-time power systems analysis, simulations of electrical power grids, and sophisticated what-if analysis. In addition, it enables in-depth studies and analysis of the electrical power grid’s behavior and performance. This comprehensive model incorporates essential factors such as power generation capacity, electrical losses, voltage levels, power flows, and system stability.
Power Grid Model is currently being applied in a wide variety of use cases, including grid planning, expansion, reliability, and congestion studies. It can also help in analyzing the impact of renewable energy integration, assessing the effects of disturbances or faults, and developing strategies for grid control and optimization.
What to expect
For the upcoming meetup we are organizing, we have an exciting lineup of activities planned:
-Insightful presentations covering two practical applications of the Power Grid Model.
-An update on the latest advancements in Power Grid -Model technology during the first and second quarters of 2024.
-An interactive brainstorming session to discuss and propose new feature requests.
-An opportunity to connect with fellow Power Grid Model enthusiasts and users.
For the full video of this presentation, please visit: https://www.edge-ai-vision.com/2024/06/how-axelera-ai-uses-digital-compute-in-memory-to-deliver-fast-and-energy-efficient-computer-vision-a-presentation-from-axelera-ai/
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As artificial intelligence inference transitions from cloud environments to edge locations, computer vision applications achieve heightened responsiveness, reliability and privacy. This migration, however, introduces the challenge of operating within the stringent confines of resource constraints typical at the edge, including small form factors, low energy budgets and diminished memory and computational capacities. Axelera AI addresses these challenges through an innovative approach of performing digital computations within memory itself. This technique facilitates the realization of high-performance, energy-efficient and cost-effective computer vision capabilities at the thin and thick edge, extending the frontier of what is achievable with current technologies.
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Conversational agents, or chatbots, are increasingly used to access all sorts of services using natural language. While open-domain chatbots - like ChatGPT - can converse on any topic, task-oriented chatbots - the focus of this paper - are designed for specific tasks, like booking a flight, obtaining customer support, or setting an appointment. Like any other software, task-oriented chatbots need to be properly tested, usually by defining and executing test scenarios (i.e., sequences of user-chatbot interactions). However, there is currently a lack of methods to quantify the completeness and strength of such test scenarios, which can lead to low-quality tests, and hence to buggy chatbots.
To fill this gap, we propose adapting mutation testing (MuT) for task-oriented chatbots. To this end, we introduce a set of mutation operators that emulate faults in chatbot designs, an architecture that enables MuT on chatbots built using heterogeneous technologies, and a practical realisation as an Eclipse plugin. Moreover, we evaluate the applicability, effectiveness and efficiency of our approach on open-source chatbots, with promising results.
Introduction of Cybersecurity with OSS at Code Europe 2024Hiroshi SHIBATA
I develop the Ruby programming language, RubyGems, and Bundler, which are package managers for Ruby. Today, I will introduce how to enhance the security of your application using open-source software (OSS) examples from Ruby and RubyGems.
The first topic is CVE (Common Vulnerabilities and Exposures). I have published CVEs many times. But what exactly is a CVE? I'll provide a basic understanding of CVEs and explain how to detect and handle vulnerabilities in OSS.
Next, let's discuss package managers. Package managers play a critical role in the OSS ecosystem. I'll explain how to manage library dependencies in your application.
I'll share insights into how the Ruby and RubyGems core team works to keep our ecosystem safe. By the end of this talk, you'll have a better understanding of how to safeguard your code.
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Skybuffer SAM4U tool for SAP license adoptionTatiana Kojar
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zkStudyClub - LatticeFold: A Lattice-based Folding Scheme and its Application...Alex Pruden
Folding is a recent technique for building efficient recursive SNARKs. Several elegant folding protocols have been proposed, such as Nova, Supernova, Hypernova, Protostar, and others. However, all of them rely on an additively homomorphic commitment scheme based on discrete log, and are therefore not post-quantum secure. In this work we present LatticeFold, the first lattice-based folding protocol based on the Module SIS problem. This folding protocol naturally leads to an efficient recursive lattice-based SNARK and an efficient PCD scheme. LatticeFold supports folding low-degree relations, such as R1CS, as well as high-degree relations, such as CCS. The key challenge is to construct a secure folding protocol that works with the Ajtai commitment scheme. The difficulty, is ensuring that extracted witnesses are low norm through many rounds of folding. We present a novel technique using the sumcheck protocol to ensure that extracted witnesses are always low norm no matter how many rounds of folding are used. Our evaluation of the final proof system suggests that it is as performant as Hypernova, while providing post-quantum security.
Paper Link: https://eprint.iacr.org/2024/257
Essentials of Automations: Exploring Attributes & Automation ParametersSafe Software
Building automations in FME Flow can save time, money, and help businesses scale by eliminating data silos and providing data to stakeholders in real-time. One essential component to orchestrating complex automations is the use of attributes & automation parameters (both formerly known as “keys”). In fact, it’s unlikely you’ll ever build an Automation without using these components, but what exactly are they?
Attributes & automation parameters enable the automation author to pass data values from one automation component to the next. During this webinar, our FME Flow Specialists will cover leveraging the three types of these output attributes & parameters in FME Flow: Event, Custom, and Automation. As a bonus, they’ll also be making use of the Split-Merge Block functionality.
You’ll leave this webinar with a better understanding of how to maximize the potential of automations by making use of attributes & automation parameters, with the ultimate goal of setting your enterprise integration workflows up on autopilot.
In the realm of cybersecurity, offensive security practices act as a critical shield. By simulating real-world attacks in a controlled environment, these techniques expose vulnerabilities before malicious actors can exploit them. This proactive approach allows manufacturers to identify and fix weaknesses, significantly enhancing system security.
This presentation delves into the development of a system designed to mimic Galileo's Open Service signal using software-defined radio (SDR) technology. We'll begin with a foundational overview of both Global Navigation Satellite Systems (GNSS) and the intricacies of digital signal processing.
The presentation culminates in a live demonstration. We'll showcase the manipulation of Galileo's Open Service pilot signal, simulating an attack on various software and hardware systems. This practical demonstration serves to highlight the potential consequences of unaddressed vulnerabilities, emphasizing the importance of offensive security practices in safeguarding critical infrastructure.
Main news related to the CCS TSI 2023 (2023/1695)Jakub Marek
An English 🇬🇧 translation of a presentation to the speech I gave about the main changes brought by CCS TSI 2023 at the biggest Czech conference on Communications and signalling systems on Railways, which was held in Clarion Hotel Olomouc from 7th to 9th November 2023 (konferenceszt.cz). Attended by around 500 participants and 200 on-line followers.
The original Czech 🇨🇿 version of the presentation can be found here: https://www.slideshare.net/slideshow/hlavni-novinky-souvisejici-s-ccs-tsi-2023-2023-1695/269688092 .
The videorecording (in Czech) from the presentation is available here: https://youtu.be/WzjJWm4IyPk?si=SImb06tuXGb30BEH .
1. White Paper:QCI-WP003 QuickSilver Controls, Inc.
Date: 14 March 2008 www.QuickSilverControls.com
Property of QuickSilver Controls, Inc. Page 1 of 10 This document is subject to change without notice.
QuickControl® and QCI® are Registered Trademarks of QuickSilver Controls, Inc.
SilverLode™, SilverNugget™, SilverDust™, PVIA™, QuickSilver Controls™, and AntiHunt™ are trademarks of
QuickSilver Controls, Inc..
Servo Control Of A Microstep Motor
This document describes how QuickSilver
provides servo control of a microstep
motor and the resulting advantages.
Simple Explanation
Stepper Drive and Motor
The common stepper motor is more
accurately a 100 pole, 2 phase, AC motor.
A stepper drive steps (or microsteps) the current in the two phases to move the motor to
discrete positions. A stepped sine wave is generated as the drive rotates the motor. The
frequency of the sine wave increases as the speed increases, but the amplitude remains
constant.
Servo Drive And Motor
A common servo motor is more accurately a 4 to
12 pole, 3 phase, AC brushless motor. When
compared to a stepper, the common servo motor
has fewer poles and 3 phases instead of 2. Like
a stepper drive, a servo drive sets the current in
the 3 phases to move the motor to a position.
Unlike a stepper drive, the servo drive generates a variable amplitude sine wave to change
both speed and torque. The servo drive uses feedback from the motor (typically an encoder)
to set the sine wave’s frequency and amplitude (speed and torque respectively). Note, the use
of feedback to continually adjust current is what allows the system to be called a “servo” not
the motor’s construction.
QuickSilver’s Servo
Drive and Motor
QuickSilver combines these
two technologies. QuickSilver
uses a 100 pole, 2 phase, AC
motor (typical stepper). It sets
the current in these 2 phases to
move the motor to a position.
The encoder is used to generate a smooth sine wave of varying frequency and amplitude to
adjust speed and torque respectively.
Note, this is not just adjusting the position (i.e. position maintenance), commonly done by stepper
drives. We have a full 4-quadrant, variable frequency, servo loop that adjusts the current every 120
microseconds. Our technology gives you all the performance of a traditional servo motor at the cost of
a traditional microstep motor. Our motors are physically the same as what the industry calls microstep
motors, but with our patented drive technology, we make servo motors out of them.
PHASE B
PHASE A
OPEN LOOP
STEPPER DRIVER
OPEN LOOP DRIVE
DIRECTION
STEP
STEPPER MOTOR
FIXED WAVEFORM
TORQUE SETTING DEPENDENT
CLOSED LOOP SERVO
STEP MOTOR
2 PHASE
=
PHASE A
PHASE B AC MOTOR
FEEDBACK DEPENDENT
VARIABLE WAVEFORM
PHASE B
PHASE A
PHASE C
3 PHASE AC
SERVO MOTOR
WITH ENCODER
CLOSE LOOP
SERVO DRIVER
CLOSED LOOP SERVO
2. White Paper:QCI-WP003 QuickSilver Controls, Inc.
QuickSilver Controls, Inc. Page 2 of 10
Detailed Explanation
Stepper Drive and Motor
PHASE B
PHASE A
OPEN LOOP
STEPPER DRIVER
OPEN LOOP DRIVE
DIRECTION
STEP
STEPPER MOTOR
FIXED WAVEFORM
TORQUE SETTING DEPENDENT
The common stepper motor is more accurately a 100 pole, 2 phase, AC motor. A stepper
drive steps (or microsteps) the current in the two phases to move the motor to discrete
positions. A rough sine wave is generated as the drive rotates the motor. The frequency of the
sine wave increases as the commanded speed increases, but the amplitude remains constant.
The permanent magnet in the rotor is attracted to the magnetic field generated by the
windings. To produce torque, the motor requires a following error, as no torque is produced
when the rotor magnet is fully aligned with the stator field. A variation in load torque
requirements causes a variation in the following angle, with braking causing an overshoot if the
motor must supply negative torque (braking). Exceeding the torque capabilities of the motor
may cause the motor to lose steps, change speed, or even change direction! The normal
prevention for these errors involves limiting the use of torque to approximately 1/3 to ½ of the
motor capability as well as careful tailoring of the motion profile. This may be especially difficult
in the presence of varying load and variable system backlash.
The torque produced by this system varies with the following angle between the stator field
and the rotor magnet. Each step change in position of the winding fields results in an impulse
in the driving torque. The amplitude of these impulses is by microstepping, but the impulse
nature remains, imparting acoustical noise to the system. The torque variation with position
error may be approximated a rotary spring; this spring interacts with the rotary inertia of the
system producing strong resonances which may produce ringing and long settling times as
well as frequencies of operation with little effective torque. See the FAQ.
3. White Paper:QCI-WP003 QuickSilver Controls, Inc.
QuickSilver Controls, Inc. Page 3 of 10
Servo Drive And Motor
PHASE B
PHASE A
PHASE C
AC MOTOR
3 PHASE
SERVOMOTOR
3-PHASE
3-PHASE CLOSED LOOP
A common servo motor is more accurately a 4 to 12 pole, 3 phase, AC or DC brushless motor.
When compared to a stepper, the common servo motor has fewer poles and 3 phases instead
of 2. Like a stepper drive, a servo drive sets the current in the 3 phases to move the motor to
a position. There are three types of drives in common use: AC brushless use sinusoidal
commutation while DC brushless commonly use either a 6 step or 12 step commutation. The
commutation circuits/subroutines of the drive vary the current to the windings as the rotor
moves, keeping the angle between the stator field and the rotor near the optimal point to
produce torque. In the case of the sinusoidal AC brushless controllers, this angle may be
closely regulated, minimizing the torque ripple in the system. The 6 step and 12 step DC
brushless designs, with their larger commutation steps, more closely approximate the discrete
steps in commutation of the DC brush motor with limited commutator segments. The larger
steps result in larger variation in the angle between the stator field and the rotor magnet,
resulting in greater torque ripple.
The most significant differences between the open loop stepper and the servo drive are how
the speed of the drive is determined and how the torque is regulated. The stepper drive varies
the position and speed of the stator field without regard for the rotor position, whereas the
servo motor varies position and speed of the stator field as a direct result of position in the
process of commutation. The torque of the stepper is passively modulated by the variation of
the following error between the stator magnetic field and the rotor, where as the servo requires
a feedback sensor to measure the error between commanded position and actual position,
with the control equation actively varying the strength of the stator field to vary the torque. In
the case of the servo, a sudden change in load requirements may introduce position error, but
not the loss of synchronism between drive and the motor as the drive is made aware of the
motor dynamics by the feedback sensor.
Note: The use of feedback to actively adjust torque by adjusting the winding currents is what
allows the system to be called a “servo”. It is not the construction of the motor.
4. White Paper:QCI-WP003 QuickSilver Controls, Inc.
QuickSilver Controls, Inc. Page 4 of 10
Unlike a stepper drive, the servo drive generates variable amplitude drive waveform to change
both speed and torque.
QuickSilver’s Servo Drive and Motor
CLOSED LOOP SERVO
STEP MOTOR
2 PHASE
=
PHASE A
PHASE B AC MOTOR
FEEDBACK DEPENDENT
VARIABLE WAVEFORM
QuickSilver combines these two technologies. QuickSilver uses a 100 pole, 2 phase, AC
motor (typical stepper). When operating in closed loop mode, the currents to the two phases
are modulated in a sinusoidal manner with the phase and frequency controlled by the feedback
encoder, and the amplitude controlled by a control law based on the target and actual
trajectories. This mode of operation is in the same manner as was for the three phase AC
brushless servos, with full 4-quadrant (drive and regenerative breaking) capabilities. This is not
just the common “position maintenance” mode with an open loop stepper and an encoder to
adjusting the position of a stepper at the end of travel to after it has lost steps.
QuickSilver takes advantage of the high torque capability available with high pole count motors
designed for use as steppers as well as their low cost made available by the economies of
scale for this motor type. We also take advantage of the ability of these motors to passively
hold position when stopped by automatically switching between closed loop operation and a
monitored open loop operation when stationary. This Anti-Hunt™ capability prevents the
dithering or hunting commonly present in servo systems when stationary. If the error is caused
to exceed the set position error threshold, the system reverts to closed loop until it again
reduces the position error to below the configured limits.
5. White Paper:QCI-WP003 QuickSilver Controls, Inc.
QuickSilver Controls, Inc. Page 5 of 10
Advantages
Advantages over Servo:
• 2 to 4 Times the Holding Torque in the same size package.
• Superior Torque Up to 1000-2000 RPM.
• 100:1 Inertial Miss-match
o Eliminates Gearheads
• Cost
• Single Cable For Motor and Encoder
• Anti-Hunt™: No Servo Dither
Advantages over Stepper
• Higher Speed
• No low-speed and mid-speed Resonances (see FAQ below)
• 4 Times More Efficient (Typical)
o Less Heating
o Lower Energy Costs
o See FAQ Below
• More Usable Torque
Our motors yield 2 to 4 times the continuous torque of comparably sized traditional servo
motors due to their high pole count. This effect is termed “magnetic gearing” due to the torque
multiplication associated with increased pole counts. The high resulting torque often allows
these motors to directly drive a load without the need of an intervening gearbox leading to the
industry term “High-Torque Direct Drive” motors.
Quicksilver combines the high torque capabilities of the motor with patented motion control and
digital drive techniques, providing direct drive capability for high inertial loads.
These load inertias may be as large as 100 times the motor inertia (100:1 inertia mismatch)
while still providing smooth responsive positioning control. Traditional systems typically cannot
exceed a 10:1 inertial mismatch. This often eliminates gearheads for inertial mismatch
reduction.
QuickSilver’s Technology
Software within the DSP models the motor as well as the driver, eliminating costly offset-and-
noise-prone current sense circuitry. The model controls the on-chip PWM peripherals, directly
controlling the timing of the full bridge drivers to the motor windings. The result is a true all-
digital control system.
This drive technology incorporates a patented “gated anti-phase” methodology which provides
full 4 quadrant control of the motor windings with excellent linearity through zero. The use of
modeling allows predictive control of the motor drivers, minimizing the effects of time lag in the
control loop, allowing very low inductance motors to be used. The low time constant of the
resulting system produces highly dynamic results: 1.8 degree “step motors” operating to
approximately 4000 RPM.
6. White Paper:QCI-WP003 QuickSilver Controls, Inc.
QuickSilver Controls, Inc. Page 6 of 10
The motor – which most controllers employ as an open loop step motor – is operated as a high
pole-count PM synchronous AC motor. The phase current is sinusoidally commutated as the
motor rotates, with the control loop varying the magnitude of the current and thus the torque to
achieve the desired position. Closed loop control of the motor eliminates low speed
resonances by eliminating their source (see FAQ below), while simultaneously minimizing the
heat produced and maximizing the available torque to the application. The result is faster and
more precise motions for the end user, with enough energy cost savings to provide a rapid ROI
over the apparently less expensive open-loop stepper system.
Motor History
The early history of electric power generation split early into two camps, Alternating current
(AC) and Direct current (DC) by Westinghouse and Edison, respectively. The DC motors could
be operated easily at variable speeds, but required a brush commutator to keep the motor
spinning, while the AC motors (synchronous and induction) tended to operate over a much
narrower speed range, tied to the power line frequency, unless special techniques were used.
The commutator typically consisted of metal segments connected to (typically) the rotor
windings, with the DC power applied through sliding contacts made of carbon, metal, or a mix
of the two. These brushes generated electrical noise, dust, and they required regular
maintenance. These were improved upon by moving the coils to the stator, and providing
chopped waveforms to the coils by means of electronic switches.
A precision DC brush motor has many commutating segments, and thus is able to compensate
for the rotation of the rotor by adjusting the angle of the magnetic field of the rotor with respect
to the stator in many small steps. This helps keep the torque produced steady and reduces
cogging. Each segment produces a step in an approximately sinusoidal commutation
waveform (by changing the paths of the current through the windings in the rotor. Most
Brushless DC motors, on the other hand, use 3 hard switched phases controlled by position
sensors to produce this function. These motors often have specialized windings and magnetic
structures to produce “Trapezoidal” waveforms to minimize the toque ripple as these motors
rotate. Special care is needed to precisely locate the commutating point for these units as even
a small phase error may produce a significant pulsating torquei
. DC Brushless motors with
approximately sinusoidal Back EMF waveforms driven with trapezoidal waveforms also
produce significant toque ripple in their operation.
The variable speed control of the AC motors came from a different starting point. Commonly
three phase motors were used with variable speed drives which produced a variable speed
variable amplitude 3 phase sine waves to operate these motors at the desired speed. This
process has been applied to both synchronous and induction AC motors. These motors are
typically wound for sinusoidal back EMF.
The AC servo motor, also called a Brushless AC servo motor grows out of this second branch,
using sinusoidal drive signals with sinusoidal back EMF motors. The speed and amplitude of
the sine waves is based on the desired torque as well as the motor type. For AC synchronous
motors, the frequency and phase are locked to the speed and position of the rotor with respect
to the stator. The control of the AC induction motors also involves controlling the rate of slip
between the rotor and the stator to control the rotor currents and thus the torque produced by
the interaction of the rotor magnetic field with the stator field. The advantage of the AC servos
is that by making use of continuously varying sine waves rather than discontinuous trapezoidal
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waveforms, smoother operation may be obtained, even in the face of slight phasing errors. The
disadvantage is that the accurate generation of multiple sine waveforms is not a simple task.
Where as the DC brushless driver could use a relatively simple switched inverter with DC
current sensing in the ground leg to set the wanted average DC current through the motor, the
AC drive must generate a sine wave through each winding, requiring multiple control loops and
multiple current sensors (or estimators).
The bipolar stepper motor is a high pole count synchronous AC motor. The speed of a
synchronous motor is proportional to the line frequency and inversely proportional to the
number of poles. That is, a synchronous motor moves forward one pole pair for each 360
electrical degrees of the applied sine wave. A stepper motor, having commonly 100 poles (50
pairs), produces a reduced speed of operation. This effect is often referred to as magnetic
gearing. This high pole count has the same effect as physical gears in that the speed is
reduced and the torque is increased from the motor in proportion to the number of poles.
High pole count AC synchronous motors were first produced to run from line frequency to
provide a low speed/high torque motion without gears. Other engineers noticed that these
same motors could be operated at variable speeds down to zero by switching the current
through the phases, which was very useful for controlling machine tools. The stepper motor
was “born.”
These motors, due to their high pole count, have very high torque constants. Their use in open
loop positioning, however, also requires a steep torque vs. position characteristic so as to have
the motor come to rest over a narrow angle range even in the presence of friction and load.
The high pole count helps here as well. With their typical sinusoidal torque constant repeating
every two poles, the higher the pole count, the smaller the mechanical angle corresponding to
a full electrical cycle. Thus for a given motor size, not only does the torque scale up roughly
proportional to the pole count, but so does the number of electrical cycles. This means that
quadrupling the number of poles makes for some four time the torque with the electrical cycle
increment in one quarter of the mechanical angle. The maximum slope of such a sine wave
shaped torque curve is sixteen times as steep. In comparing a 6 pole motor to a 100 pole (1.8
degree) stepper, these combined effects results in a torque slope factor which is some 278
times as steep. This characteristic high stiffness has allowed the use of stepper motors in high
accuracy open loop operation.
Their extensive incorporation into open loop designs has led to their production in large
quantities leading to optimized tooling with the benefits of quantity of scale: High Quality and
Low Price. The desire to make these motors perform smoother motions has led to motors
optimized for “micro-stepping” - that is having a good sinusoidal torque constant and low
detent torque characteristics.
It is these same motor characteristics that improved the open loop “stepper-motor” operation,
namely high torque constant, high torque to inertia ratio, sinusoidal per-phase torque
constants, and low cogging torque, that are equally useful to closed loop servo control of these
high pole count, poly-phase AC synchronous motors.
The use of Permanent Magnet AC Servo Motors is increasing due to the higher efficiency
compared to induction motors with a more comparable price than past years due to the
increased cost of copper and the reduced cost of magnets.
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Frequently Asked Questions
What Makes It A “Servo”?
The Merriam-Webster Dictionaryii
defines a servomechanism as “an automatic device for
controlling large amounts of power by means of very small amounts of power and
automatically correcting the performance of a mechanism.”
One of the earlier known servoiii
(from Latin Servus slave) systems dates back to
approximately 270BC and was a regulator for the water level used by the water clocks of the
day to help them keep more accurate time by keeping the water level constant, and thereby
the water pressure exiting the tank constant. The water passed through a fixed size orifice and
filled a fixed volume before it dumped and refilled. Each dumping of the volume represented
one “tick” of the clock. The water level regulator worked similarly to the float mechanism used
in current day toilet tanks. In this case, the feedback is in the form of the level of the float, and
the difference in level from the desired level operates a valve so as to keep the water level
within the desired range.
Servo motion control systems use position and/or velocity sensors to measure the difference
between the desired and actual operation of the actuator. Amplifiers (electronic, mechanical,
hydraulic, magnetic, etc.) are used to increase the power of the error signal and to affect the
operation of the actuator so as to make the actuator perform the desired motion. The
SilverLode™ system uses optical incremental encoders to measure the motor rotary position,
digital signal processors to process it, and drive electronics to provide the power drive to the
motor to effect the motion.
But Do Not Stepper Motors Have Resonance Problems?
Stepper motor resonance arises in open loop operation due to the steep torque vs. position
error characteristics of an open loop stepper operating in the vicinity of the zero error angle.
When disturbed from this zero error angle (or that angle is suddenly changed, such as by
changing the currents through the windings as happens when the motor is “stepped”), the rotor
of the motor operates as a rotary pendulum, the resulting torque of the motor causing the rotor
to accelerate towards and then pass by the equilibrium point, only to then slow and reverse
again with a slightly lower amplitude due to losses, repeating until the rotor finally comes to
rest at the (new) equilibrium point. If the motor is pulsed near the resonance frequency, the
pendulum effect will cause the amplitude of this oscillation to continue to grow until the rotor is
more than 2 full steps away from the original equilibrium point. At this point the nearest new
equilibrium point is now 4 steps (one full electrical cycle) away from the old equilibrium point,
and the generated torque will cause the rotor to accelerate toward that point. The motor has
lost synchronization with the applied waveform and thus “lost” steps. According to the speed of
operation, the motor may stall, may operate erratically, or may even change speed and
direction!
What Causes The Low Speed Resonance In A Stepmotor?
The low speed resonance of the open loop step motor is a result of the motor operating as a
spring-mass system about its equilibrium point. The motor torque is approximately a sinusoidal
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function of its position error. This “spring” interacts with the rotary inertia of the motor to form,
in essence, a rotary pendulum. As the motor is stepped (or microstepped) the equilibrium point
is moved, causing the “pendulum” to seek the new equilibrium point. If the stepping rate
approaches the natural frequency of this “pendulum”, the amplitude of the swinging increases,
often causing the motor to lose synchronization with its drive signals.
When this same motor is operated as an AC servo motor, the commutation keeps the
magnetic field positioned so as to produce the maximum torque for the commanded current
magnitude. A perturbation of the rotor angle results in the magnetic field shifting rather than the
torque changing. Without the position dependent torque term, the spring effect is eliminated as
well as the associated low speed resonance problem.
But Don’t Stepper Motors Run Hot?
A side benefit of operating the motor at the optimal torque angle is that only the current needed
to produce the torque actually needed is applied to the motor. There is not a need to supply full
current unless the peak torque is being utilized. Given that the “rule of thumb” for operation of
a stepper motor is to only use approximately 30% to 50% of the available torque, that same
motor operated as a servo in the same application requires only 30% to 50% current. The main
heating in the windings is P=I2
R, thus at 50% current, the heating is only 25% as compared to
the open loop stepper, while at 30% utilization the heating is only 9%! The result is that the
same “stepper motor”, when used as a servo may be operated quieter, smoother, and cooler,
and with higher available torque while running over a wider range of speeds. And these
improvements are available while at the same time avoiding the low speed resonance effects
of the open loop stepper.
But How Can The Motor Draw 2 Amps When The 48v Power
Supply Is Only Supplying 160 Ma?
The driver and controller form what is effectively as step-down switching power supply. The
power into the Controller, minus the relatively low losses of the driver and the power to the
DSP and other electronics, produces the mechanical output power from the motor plus motor
heating. When the motor is stopped, there is no mechanical output power (P=speed * Torque),
and thus the power into the motor is all heating. In the case of a motor with a 1.2 ohm winding,
this is on the order 4.8W, and would account for approximately 100mA at 48v. Additional input
power is required for the electronics including the losses in the drivers; in the given example
this would account for the other 60mA of supply current. The low current usage only lasts while
the motor is not providing mechanical work. As the motor spins faster and/or the torque
increases, the mechanical output power increases. This additional power must be supplied
from the power supply, and the input current goes up.
What Is Anti-Hunt™?
Just because the motor can be operated as a high performance servo system does not mean
that it can not be switched back to its humble open loop beginning. When the motor is
sufficiently close to the desired position, the operating mode of the motor can be switched to
open loop operation at a user defined current level. With the servo loop turned off, the hunting
or dithering of the servo loop is eliminated. If the motor position is disturbed or another motion
is requested, the servo operation is then restored. This allows for rapid motions with quick
settling as afforded by the servo control while still retaining the ability to stop solidly without
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dithering. This eliminates acoustical noise and movement that would affect applications such
as imaging. The ability to eliminate dithering when stopped also reduces wear on any attached
lead screws or gears that the continual hunting of a servo may cause even when there is no
motion commanded, often extending the life of the attached mechanism.
i
http://www.ornl.gov/~webworks/cpr/pres/107923_.pdf
ii
www.merriam.com
iii
originally http://www.control-systems.net/recursos/articulos/002.htm, no longer posted, but may be available on
www.archive.org