Mechatronics, Actuators, Industrial robots fundamentals

1. Department of Mechanical Engineering
JSS Academy of Technical Education, Bangalore-560060
MECHATRONICS
(Course Code:17ME753)

2. MECHATRONICS
CHAPTER 6: Integration

3. • Introduction & background
• Advanced actuators
• Pneumatic actuators
• Industrial Robot
• Different parts of a Robot-Controller
• Drive, Arm, End Effectors & Sensor
• Functional requirements of robot.
Module 3

4. Introduction
• An actuator is a device that actuates or used to produce motion or action
• Device that coverts an input energy into motion or mechanical energy.
• Input (mainly electrical signal, air, fluids)
The input energy for the actuators can be;
1. Manual (e.g., levers and jacks)
2. Hydraulic or pneumatic (e.g., pistons and valves)
3. Thermal (e.g., bimetallic switches or levers)
4. Electric (e.g., motors and resonators)
Basic Concepts of Actuators

5. Introduction
In the transducers unit;
• A transducer is a device that converts one form of energy to another form.
Definition of an actuator: (Based on transducers)
• Actuator can be a specific type of a transducer.
E.g.; An electric motor is an actuator. (both actuator and a transducer)
(As it converts electrical energy to mechanical energy).
Basic Concepts of Actuators

6. Classification of Actuators
Actuators
Type of
Motion
Linear
Rotary
Type of
Medium
Hydraulic
Pneumatic
Electrical
Mechanical
• Linear actuator: Solenoid, Hydraulic / Pneumatic
• Rotary actuator: Motor, Hydraulic / Pneumatic

7. Introduction
In mechanical actuators, a rotary motion is converted into linear motion.
E.g.: Gears, Rails, Pulley, Chain, Springs etc.
Mechanical Actuators
• Hydraulics generates higher energy than any other system.
• All systems involving high loads are operated by hydraulic actuators in which oil
pressure is applied on mechanical actuator to give an output in terms of rotary or
linear motion.
E.g. Steering gear of ship: Hydraulic pressure is used to move the rudder actuator.
Hydraulic Actuators

8. Introduction
• Electrical energy is used to actuate a mechanical system using magnetic field i.e.
EMF.
E.g.: Electrical motor operated valve and magnetic valve actuator or solenoid valve.
In solenoid valve, the electrical signal will magnetize the upper portion of the valve,
which will attract the valve seat and open the system. When electrical supply is
removed, valve gets shut by spring action.
Electrical Actuators

9. Introduction
Hybrid Actuators
• Combination of the above systems which controls / actuates the mechanical
element of the system.
• E.g. Thermo hydraulic Electronic actuators
Used in operating valves in hot water system, wherein hot water is used along
with electronic system, acting as control for the valve.

10. Industrial Robot

11. Introduction
• An industrial robot is a general-purpose, programmable machine.
• It has human-like characteristics, also resembles as of humans in its physical
structure, respond to sensory signals, in a manner that is similar to humans.
• Mechanical arms are used for various industry tasks.
• Sensory perceptive devices such as sensors allow the robots to;
• Communicate and interact with other machines
• Take simple decisions.
Industrial Robot

12. Introduction
The general commercial and technological advantages of robots:
• Operates in hazardous or uncomfortable work environments.
• Performs its work cycle with a consistency and repeatability over a long period.
• Robots can be reprogrammed.
• Robots can be connected to the computer systems and other robotics systems.
• Can be controlled by wireless control technologies.
• Overall enhances the productivity and efficiency of automation industry.
Industrial Robot

13. • The manipulator of an industrial robot consists of a series of joints and links.
• Robot anatomy deals with study of different joints, links and physical construction.
• A robotic joint provides relative motion between two links.
• Each joint, or axis, provides a certain Degree-of-freedom (DOF) of motion.
• In most cases, only one degree-of-freedom is associated with each joint.
• The complexity of the robot is according to the total number of DOF they possess.
Industrial Robot
Different parts of a Robot Controller

14. • Robots are mounted upon a stationary base (e.g. Floor).
• From the base, a joint-link numbering scheme is
recognized as shown in Fig.
• The robotic base and its connection to the first joint are
termed as link-0.
• The first joint in the sequence is joint-1.
• Link-0 is the input link for joint-1, & the output link from
joint-1 is link-1, which leads to joint-2.
• Thus link 1 is the output link for joint-1 and input link for
joint-2.
• This joint-link-numbering scheme is followed for all joints
and links in the robotic systems.
Industrial Robot
Different parts of a Robot Controller

15. Manipulator of a robot

16. Industrial Robot
Different parts of a Robot Controller
• All industrial robots have mechanical joints, classified into following five types
as shown in fig.

17. Controller, Drive, Arm, End Effectors & Sensor

18. Drive system
• The three types of drive systems are commonly used to actuate joints;
1. Electric drives: e.g. Electric motors, Servo-motors or Stepper motors
2. Hydraulic drives
3. Pneumatic drives
Drive System - Introduction
E.g.: Piston-cylinder systems or rotary vane actuators
• To power the joints of the Robot

19. Characteristics / Selection of Drive system
• Speed of operation
• Load Carrying capacity
• Power consumption
• Positional accuracy / Repeatability
• Dynamic performance / Stability
• Cost
Drive System - Introduction

20. Drive
• Pneumatic drives: Used for smaller, simpler robotic applications.
• Electric & Hydraulic drives: Sophisticated industrial robots.
• Commercial applications; prefers electric motor, as they are compatible with
computing systems.
• Hydraulic systems, although not as flexible as electrical drives, generally
used where larger speeds are required also, to carry out heavy duty
operations.
Drive - Introduction

21. Robot Control Systems
• To perform as per the program instructions, the joint movements of an
industrial robot must be accurately controlled.
• Microprocessor based controllers are used to control the robots.

22. 1. Limited Sequence Control
2. Play back with Point-to-Point Control
3. Play back with Continuous Path Control
4. Intelligent Control
Types of Robot Control Systems

23. Types of control
1. Limited Sequence Control
• Used for simple motion cycles, such as pick and place operations
• Controlled by setting limit switches and/or mechanical stops together with a sequencer to
coordinate and time the actuation of the joints.
• Feedback loops may be used to inform the controller that the action has been performed, so that
the program can move to the next step.
• Precision of such control system is less.
• It is generally used in pneumatically driven robots.

24. Types of control
2. Play back with Point-to-Point Control
• Playback control uses a controller with memory to record motion
sequences in a work cycle, as well as associated locations and other
parameters, and then plays back the work cycle during program
execution.
• Point-to-point control means individual robot positions are recorded in
the memory.
• These positions include both mechanical stops for each joint, and the
set of values that represent locations in the range of each joint.
• Feedback control is used to confirm that the individual joints achieve
the specified locations in the program

25. Types of control
2. Play back with Point-to-Point Control
• Application: Machine loading and unloading applications
• Complex applications: spot welding (resistance welding), assembly, grinding, inspection,
palletizing, and depalletizing.

26. Types of control
3. Play back with Continuous Path Control
• Continuous-path motion is an extension of the point-to-point method.
• The difference is that continuous path involves the utilization of more points and its path can be
an arc, a circle, or a straight line.
• Continuous-path program can have several thousand points.
• Continuous path control refers to a control system capable of continuous simultaneous control of
two or more axes.
• Programming of the path of motion is accomplished by an operator physically moving the end
effector of the robot through its path of motion. While the operator is moving the robot through its
motion, the positions of the various axes are recorded on some constant time frame.
• The robot remembers, the exact path through which the programmer moves the manipulator,
also the speed at which the programmer moves the manipulator.

27. Types of control
3. Play back with Continuous Path Control
• The major difference between the continuous path control and the standard point-to-point control
is the control’s ability to remember thousands of programmed points in the continuous path,
whereas the point-to-point control is limited to several hundred points of memory..

28. Types of control
4. Intelligent Control
• An intelligent robot exhibits behavior that makes it intelligent.
• E.g. It may have capacity to interact with its ambient surroundings; decision-making capability;
ability to communicate with humans; ability to carry out computational analysis during the work
cycle; and responsiveness to advanced sensor inputs.
• Also possess the playback facilities. However it requires a high level of computer control, and an
advanced programming language to input the decision-making logic and other ‘intelligence’ into
the memory.

29. Types of control
4. Intelligent Control
Significant developments:
• Performing tasks such as moving among a variety of machines and equipment
in the shop floor and avoiding collisions; recognizing, picking, and properly
gripping the correct raw material or workpiece; transporting a workpiece to a
machine for processing or inspection; and assembling the components into a
final product.

30. End Effectors
• An end effector is usually attached to the robot’s wrist, and it allows the robot to
accomplish a specific task / operation.
• End effectors are generally custom engineered and fabricated for each different
operation.
• There are two general categories of end effectors viz. grippers and tools.

31. End Effectors
• To grasp and hold the object.
• Machine loading and unloading.
• Pick parts from the conveyor.
• Arrange the parts on Pallet / Palletizing.
Grippers
The function / purpose of the grippers are;

32. End Effectors
• Single gripper: Only one grasping device, machine loading and unloading
• Double gripper: Two gripping device, simultaneously loading and unloading,
independent operations.
• Multiple gripper: Two or more grasping device, holding large flat object.
• Internal gripper: Grasp the internal surface of the object .
• External gripper: Grasp the external surface of the object .
Classification of Grippers

33. End Effectors
• Various end-effectors, grippers are summarized as follows;
Type of End effector Description
Mechanical gripper
Two or more fingers, actuated by robot controller to open and close on a
work part.
Vacuum gripper Suction cups are used to hold flat objects.
Magnetized Device For handle ferrous materials
Adhesive devices For holding flexible materials, like fabric / light weight materials
Simple mechanical
devices
Hooks and scoops.
Dual grippers
• Mechanical gripper with two gripping devices in one end-effecter.
• Used for machine loading and unloading.
• It reduces cycle time per part by gripping two work parts at the same time.

34. End Effectors
• Various end-effectors, grippers are summarized as follows;
Type of End effector Description
Interchangeable
fingers
Mechanical gripper with an arrangement to have modular fingers to
accommodate different sizes work part.
Sensory feedback
fingers
Mechanical gripper with sensory feedback capabilities in the
fingers to aid locating the work part; and to determine correct grip force to
apply (for fragile work parts).
Multiple fingered
grippers
Mechanical gripper as per the general anatomy of human hand
Standard grippers
commercially available grippers, reducing the need to custom-design a
gripper for separate robot applications.

35. Mechanical gripper Vacuum gripper Magnetic gripper Adhesive gripper
Multi-finger gripper

36. End Effectors
• Various end-effectors, grippers are summarized as follows;
• The robot end effecter may also use tools.
• Tools are used to perform processing operations on the work part.
E.g. Spot welding, Arc welding, and Spray painting.
• Tools also can be mounted at robotic manipulator spindle to carry out
machining work such as drilling, routing, grinding, etc.

37. Sensors in Robotics
• Generally two categories of sensors used in robotics.
1. Internal purposes
2. External purposes.
Internal sensors: To monitor and control the various joints of the robot.
They form a feedback control loop with the robot controller.
Examples of internal sensors: Potentiometers and optical encoders, while
tachometers of various types are deployed to control the speed of the robot arm.

38. Sensors in Robotics
External sensors: To control the operations of the robot.
They form a feedback control loop with the robot controller.
Examples of External sensors: Limit switches, that determine whether a part has
been positioned properly, or whether a part is ready to be picked up from an
unloading bay.

39. Various sensors used in robotics are outlined
Sensors Description
Tactile sensor
To determine whether contact is made between sensor and another object
• Touch sensors: indicates the contact
• Force sensors: indicates the magnitude of force with the object.
Proximity / Range
sensor
To determine how close an object is to the sensor.
Optical sensor
Photocells and other photometric devices are used to detect the presence or
absence of objects.
Machine vision Used in robotics for inspection, parts identification, guidance.
Others
Measurement of temperature, fluid pressure, fluid flow, electrical voltage,
current, and other physical properties.

40. Applications of robots in industry and manufacturing
Functional requirements of robot

41. Situations
Functional requirements of robot
• Hazardous / unsafe / unhealthy, uncomfortable, work environments for humans,
• Repetitive work cycle
• Difficulty in handling for humans
• Multi-shift operation
• Infrequent changeovers: Long production runs where changeovers are infrequent
• Material Handling Applications
• Processing Operations: Spot / Arc welding, spray painting / coating