Electric Drive Systems for Robotics

1. ELECTRIC DRIVE SYSTEMS

2. SERVO MOTOR

4. Principle
Servo motors are geared DC motors with the closed-loop circuitry
incorporated within them. The basic configuration of a servo motor
composed of a DC motor, gearbox, potentiometer and control circuit.
DC motor is used to move a gearbox with a large reduction ratio. The
final shaft imposes a force on the external load and simultaneously
acts on the axis of the feedback potentiometer. So, the potentiometer
senses the position of the axis and sends a corresponding voltage to
an operational amplifier. This voltage compared to the input voltage,
that determines the desired position of the shaft, producing a voltage
in the output of the comparator. This voltage powers the motor such
that the shaft moves in the necessary direction to align with the angle
that corresponds to the voltage applied to the input.

5. Specifications
1. Weight
2. Size
3. Speed
4. Torque
5. Voltage
6. Connector Type

6. Application
1. Robotics
2. Conveyor Belts.
3. Camera Auto focus
4. Robotic Vehicles
5. Tracking System
6. Metal Cutting & Metal Forming Machines
7. Antenna Positioning
8. Woodworking/CNC
9. Textiles
10. Printing Presses/Printers

7. Advantages
1. High output power relative to motor size and power
2. Encoder determines accuracy and resolution.
3. Resonance and vibration free operation
4. High efficiency
5. There is no out-of-step condition, as heavy load placed on the motor the driver
will increase the current to the motor
6. High speed operation is possible

8. Disadvantages
1. Require tuning to stabilize feedback loop
2. Complex, require encoder
3. Poor motor cooling
4. Motor can be damaged by sustained overload.

9. STEPPER MOTOR

11. Principle
• The stepper motor rotor is a permanent magnet, when the current
flows through the stator winding, the stator winding to produce a vector
magnetic field. The magnetic field drives the rotor to rotate by an angle
so that the pair of magnetic fields of the rotor and the magnetic field
direction of the stator are consistent. When the stator's vector magnetic
field is rotated by an angle, the rotor also rotates with the magnetic
field at an angle. Each time an electrical pulse is input, the motor
rotates one degree further. The angular displacement it outputs is
proportional to the number of pulses input and the speed is
proportional to the pulse frequency. Change the order of winding
power, the motor will reverse. Therefore, it can control the rotation of
the stepping motor by controlling the number of pulses, the frequency
and the electrical sequence of each phase winding of the motor.

12. Specifications
1. Step angle.
2. Phase Voltage
3. Current / Winding.
4. Resistance / winding
5. Inductance/ windingl
6. Rotor Inertia
7. Weight

13. Application
1. They are used in numeric control of machine tools.
2. Used in tape drives, floppy disc drives, printers and electric watches.
3. The stepper motor also use in X-Y plotter and robotics.
4. It has wide application in textile industries and integrated circuit
fabrications.
5. The other applications of the Stepper Motor are in spacecrafts launched
for scientific explorations of the planets etc.
6. These motors also find a variety of commercial, medical and military
applications and also used in the production of science fiction movies.
7. Stepper motors of microwatts are used in the wrist watches.
8. In the machine tool, the stepper motors with ratings of several tens of

14. Advantages
1. Low cost
2. High reliability
3. High torque at low speeds
4. Simple, rugged construction that operates in almost any
environment

15. Disadvantages
• Rsonance effect often exhibited at low Speed & Decreasing torque

17. BLDC MOTOR

19. Principle
• Stator windings of a BLDC motor are connected to a control
circuit (an integrated switching circuit). The control circuit
energizes proper winding at proper time, in a pattern which
rotates around the stator. The rotor magnet tries to align with
the energized electromagnet of the stator, and as soon as it
aligns, the next electromagnet is energized. Thus the rotor
keeps running

20. Application
1. Linear motors
2. Servomotors
3. Actuators for industrial robots
4. Extruder drive motors
5. Feed drives for CNC machine tools

21. Specifications
1. Rated Capacity
2. Input Voltage
3. Rated Current (Max.)
4. Starting current
5. Overcurrent Limit
6. Speed Range
7. Overvoltage Limit
8. Motor feedback
9. Commutation
10. Mode of operation
11. Features
12. Operating temp./Humidity
13. Vibration

22. Advantages
1. Higher torque to weight ratio
2. Increased torque per watt of power input (increased efficiency)
3. Increased reliability and lower maintenance requirements
4. Reduced operational and mechanical noise
5. Longer lifespan (no brush and commutator erosion)
6. Elimination of ionizing sparks from the commutator (ESD)
7. Near-elimination of electromagnetic interference (EMI)

23. Disadvantages
1. Expensive
2. Complex Wiring