Introduction to Robotics Analysis, systems, Applications

1. Introduction to RoboticsAnalysis, systems, Applications

2. What is a robot? • Joseph Engelberger, a pioneer in industrial robotics: "I can't define a robot, but I know one when I see one."

3. Arkin (1998) “An intelligent robot is a machine able to extract information from its environment and use knowledge about its world to move safely in a meaningful and purposive manner”

4. What is Robotics? • Robotics is the art, knowledge base, and the know-how of designing, applying, and using robots in human endeavors. • Robotics is an interdisciplinary subject that benefits from mechanical engineering, electrical and electronic engineering, computer science, biology, and many other disciplines.

5. What is a Robot ? • Random House Dictionary A machine that resembles a human being and does mechanical routine tasks on command. • Robotics Association of America An industrial robot is a re-programmable, multifunctional manipulator designed to move materials, parts, tools, or specialized devices through variable programmed motions for the performance of a variety of tasks.

6. What is a Robot ? • A manipulator (or an industrial robot) is composed of a series of links connected to each other via joints. Each joint usually has an actuator (a motor for eg.) connected to it. • These actuators are used to cause relative motion between successive links. One end of the manipulator is usually connected to a stable base and the other end is used to deploy a tool.

7. Classification of Robots - JIRA (Japanese Industrial Robot Association) Class1: Manual-Handling Device Class2: Fixed Sequence Robot Class3: Variable Sequence Robot Class4: Playback Robot Class5: Numerical Control Robot Class6: Intelligent Robot

8. Classification of Robots - RIA (Robotics Institute of America) Variable Sequence Robot(Class3) Playback Robot(Class4) Numerical Control Robot(Class5) Intelligent Robot(Class6)

9. Classification of Robots AFR (Association FranÇaise de Robotique) Type A: Manual Handling Devices/ telerobotics Type B: Automatic Handling Devices/ predetermined cycles Type C: Programmable, Servo controlled robot, continuous point-to-point trajectories Type D: Same type with C, but it can acquire information.

10. What are the parts of a robot? • Manipulator • Pedestal • Controller • End Effectors • Power Source

11. Manipulator • Base • Appendages • Shoulder • Arm • Grippers

12. Robot Anatomy • Manipulator consists of joints and links • Joints provide relative motion • Links are rigid members between joints • Each joint provides a “degree-of-freedom” Link3 Joint3 End of Arm Link2 Link1 Joint2 Joint1 Link0 Base

13. Robot Anatomy • Robot manipulator consists of two sections: • Body-and-arm – for positioning of objects in the robot's work volume • Wrist assembly – for orientation of objects Link3 Joint3 End of Arm Link2 Link1 Joint2 Joint1 Link0 Base

14. Manipulator Joints • Translational motion • Linear joint (type L) • Orthogonal joint (type O) • Rotary motion • Rotational joint (type R) • Twisting joint (type T) • Revolving joint (type V)

15. Polar Coordinate Body-and-Arm Assembly • Notation TRL: • Consists of a sliding arm (L joint) actuated relative to the body, which can rotate about both a vertical axis (T joint) and horizontal axis (R joint)

16. Cylindrical Body-and-Arm Assembly • Notation TLO: • Consists of a vertical column, relative to which an arm assembly is moved up or down • The arm can be moved in or out relative to the column

17. Cartesian Coordinate Body-and-Arm Assembly • Notation LOO: • Consists of three sliding joints, two of which are orthogonal • Other names include rectilinear robot and x-y-z robot

18. Jointed-Arm Robot • Notation TRR:

19. SCARA Robot • Notation VRO • Similar to jointed-arm robot except that vertical axes are used for shoulder and elbow joints to be compliant in horizontal direction for vertical insertion tasks

20. Wrist Configurations • End effector is attached to wrist assembly • Function of wrist assembly is to orient end effector • Body-and-arm determines global position of end effector • Two or three degrees of freedom: • Roll • Pitch • Yaw • Notation :RRT

21. Example • Sketch following manipulator configurations • (a) TRT:R, (b) TVR:TR, (c) RR:T. Solution:

22. Robots degrees of freedom • Degrees of Freedom: Number of independent position variables which would has to be specified to locate all parts of a mechanism. • In most manipulators this is usually the number of joints.

23. DOF of a Rigid Body In a plane In space

24. Degrees of Freedom As DOF 3 position 3D Space = 6 DOF 3 orientation In robotics: DOF = number of independently driven joints positioning accuracy computational complexity cost flexibility power transmission is more difficult

25. The Six Possible Lower Pair Joints

26. Degree of freedom - one joint one degree of freedom Simple robots - 3 degrees of freedom in X,Y,Z axis Modern robot arms have up to 7 degrees of freedom XYZ, Roll, Pitch and Yaw The human arm can be used to demonstrate the degrees of freedom. Crust Crawler- 5 degrees of freedom Degrees of Freedom

27. Applying adhesive to a pane of glass Transferring ICs from a pallet to a holding location Camera monitoring of products Transferring & Stacking Cartesian Robot Applications

28. The Humanoid Robot Previously developed for recreational and entertainment value. Research into use for household chores, aid for elderly aid

29. Robots degrees of freedom Consider what is the degree of Fig. 3 1 D.O.F. 2 D.O.F. 3 D.O.F. Fig. 1.3 A Fanuc P-15 robot. Reprinted with permission from Fanuc Robotics, North America, Inc.

30. Robot Joints Prismatic Joint: Linear, No rotation involved. (Hydraulic or pneumatic cylinder) Revolute Joint: Rotary, (electrically driven with stepper motor, servo motor)

31. Robot Coordinates Fig. 1.4  Cartesian/rectangular/gantry (3P) : 3 cylinders joint  Cylindrical (R2P) : 2 Prismatic joint and 1 revolute joint  Spherical (2RP) : 1 Prismatic joint and 2 revolute joint  Articulated/anthropomorphic (3R) : All revolute(Human arm)  Selective Compliance Assembly Robot Arm (SCARA): 2 paralleled revolute joint and 1 additional prismatic joint

32. Robot Reference Frames Fig. 1.6 A robot’s World, Joint, and Tool reference frames. Most robots may be programmed to move relative to either of these reference frames.

33. Robot Workspace Fig. 1.7 Typical workspaces for common robot configurations

34. Actuators Motors- control the movement of a robot. Identified as Actuators there are three common types DC Motor Stepper Motor Servo motor Stepper motor

35. Joint Drive Systems • Electric • Uses electric motors to actuate individual joints • Preferred drive system in today's robots • Hydraulic • Uses hydraulic pistons and rotary vane actuators • Pneumatic • Typically limited to smaller robots and simple material transfer applications

36. DC Motors Most common and cheapest Powered with two wires from source Draws large amounts of current Cannot be wired straight from a PIC Does not offer accuracy or speed control

37. Stepper Motors Stepper has many electromagnets Stepper controlled by sequential turning on and off of magnets Each pulse moves another step, providing a step angle Example shows a step angle of 90° Poor control with a large angle Better step angle achieved with the toothed disc

38. Stepper motor operation Step1

39. Stepper motor operation Step 2

40. Stepper motor operation Step 3

41. Stepper motor operation Step 4

42. Servo motors Servo offers smoothest control Rotate to a specific point Offer good torque and control Ideal for powering robot arms etc. However: Degree of revolution is limited Not suitable for applications which require continuous rotation

43. Servo motors Contain motor, gearbox, driver controller and potentiometer Three wires - 0v, 5v and PIC signal Potentiometer connected to gearbox - monitors movement Provides feedback If position is distorted - automatic correction + 5V

44. Servo motors Operation Pulse Width Modulation (0.75ms to 2.25ms) Pulse Width takes servo from 0° to 150° rotation Continuous stream every 20ms On programming block, pulse width and output pin must be set. Pulse width can also be expressed as a variable

45. Controller (The brain) • Issues instructions to the robot. • Controls peripheral devices. • Interfaces with robot. • Interfaces with humans.

46. Robot Control Systems • Limited sequence control – pick-and-place operations using mechanical stops to set positions • Playback with point-to-point control – records work cycle as a sequence of points, then plays back the sequence during program execution • Playback with continuous path control – greater memory capacity and/or interpolation capability to execute paths (in addition to points) • Intelligent control – exhibits behavior that makes it seem intelligent, e.g., responds to sensor inputs, makes decisions, communicates with humans

47. Robot Control System Cell Supervisor Level 2 Controller & Program Level 1 Joint 1 Joint 2 Joint 3 Joint 4 Joint 5 Joint 6 Sensors Level 0

48. End Effectors (The hand) • Spray paint attachments • Welding attachments • Vacuum heads • Hands • Grippers

49. End Effectors Tools: Tools are used where a specific operation needs to be carried out such as welding, painting drilling etc. - the tool is attached to the mounting plate. Grippers: mechanical, magnetic and pneumatic. Mechanical: Two fingered most common, also multi-fingered available Applies force that causes enough friction between object to allow for it to be lifted Not suitable for some objects which may be delicate / brittle

50. End Effectors Magnetic: Ferrous materials required Electro and permanent magnets used Pneumatic: Suction cups from plastic or rubber Smooth even surface required Weight & size of object determines size and number of cups