Introduction to Robotics Analysis systems Applications What

Introduction to Robotics Analysis, systems, Applications

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

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” l

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

What is a Robot ? Random House Dictionary A machine that resembles a human being and does mechanical routine tasks on command. l 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. l

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. l 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. l

Classification of Robots - JIRA (Japanese Industrial Robot Association) Class 1: Class 2: Class 3: Class 4: Class 5: Class 6: Manual-Handling Device Fixed Sequence Robot Variable Sequence Robot Playback Robot Numerical Control Robot Intelligent Robot

Classification of Robots - RIA (Robotics Institute of America) Variable Sequence Robot(Class 3) Playback Robot(Class 4) Numerical Control Robot(Class 5) Intelligent Robot(Class 6)

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.

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

Manipulator • Base • Appendages -Shoulder -Arm -Grippers

Robot Anatomy l Manipulator consists of joints and links provide relative motion l Links are rigid members between joints l Each joint provides a “degree-of-freedom” Joint 3 Link 3 End of Arm l Joints Link 2 Link 1 Joint 2 Joint 1 Link 0 Base

Robot Anatomy l Robot manipulator consists of two sections: l Body-and-arm Joint 3 – for positioning of objects in the Link 1 robot's work volume l Wrist assembly – for Joint 1 orientation of objects Link 0 Link 3 End of Arm Link 2 Joint 2 Base

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

Polar Coordinate Body-and-Arm Assembly l Notation TRL: l 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)

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

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

Jointed-Arm Robot l Notation TRR:

SCARA Robot Notation VRO l 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 l

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

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

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. l In most manipulators this is usually the number of joints. l

DOF of a Rigid Body In a plane In space

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

The Six Possible Lower Pair Joints

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

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

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

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

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

Robot Coordinates Fig. 1. 4 Cartesian/rectangular/gantry (3 P) : 3 cylinders joint Cylindrical (R 2 P) : 2 Prismatic joint and 1 revolute joint Spherical (2 RP) : 1 Prismatic joint and 2 revolute joint Articulated/anthropomorphic (3 R) : All revolute(Human arm) Selective Compliance Assembly Robot Arm (SCARA): 2 paralleled revolute joint and 1 additional prismatic joint

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.

Robot Workspace Fig. 1. 7 Typical workspaces for common robot configurations

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

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

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

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

Stepper motor operation Step 1

Stepper motor operation Step 2

Stepper motor operation Step 3

Stepper motor operation Step 4

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

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

Servo motors Operation Pulse Width Modulation (0. 75 ms to 2. 25 ms) l Pulse Width takes servo from 0° to 150° rotation l Continuous stream every 20 ms l On programming block, pulse width and output pin must be set. l Pulse width can also be expressed as a variable l

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

Robot Control Systems l l 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

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

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

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: l Two fingered most common, also multi-fingered available l Applies force that causes enough friction between object to allow for it to be lifted l Not suitable for some objects which may be delicate / brittle

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

End Effectors The special tooling for a robot that enables it to perform a specific task l Two types: l l Grippers – to grasp and manipulate objects (e. g. , parts) during work cycle l Tools – to perform a process, e. g. , spot welding, spray painting

Grippers and Tools

Working Envelope

Power Source (The food) • Electric • Pneumatic • Hydraulic

Robot Languages Microcomputer Machine Language Level: the most basic and very efficient but difficult to understand to follow. Point-to-Point Level: Funky Cincinnati Milacron’s T 3 It lacks branching, sensory information. Primitive Motion Level: VAL by Unimation™ Interpreter based language. Structured Programming Level: Task-Oriented Level: This is a compiler based but more difficult to learn. Not exist yet and proposed IBM in the 1980 s.

Robot Programming l Leadthrough programming l Work cycle is taught to robot by moving the manipulator through the required motion cycle and simultaneously entering the program into controller memory for later playback l Robot programming languages l Textual programming language to enter commands into robot controller l Simulation and off-line programming

Robot Programming l l l Textural programming languages Enhanced sensor capabilities Improved output capabilities to control external equipment Program logic Computations and data processing Communications with supervisory computers

Leadthrough Programming 1. Powered leadthrough l l 2. Common for pointto-point robots Uses teach pendant Manual leadthrough l Convenient for continuous path control robots

Motion Commands MOVE P 1 HERE P 1 - used during lead through of manipulator MOVES P 1 DMOVE(4, 125) APPROACH P 1, 40 MM DEPART 40 MM DEFINE PATH 123 = PATH(P 1, P 2, P 3) MOVE PATH 123 SPEED 75

Interlock and Sensor Commands Interlock Commands WAIT 20, ON SIGNAL 10, 6. 0 REACT 25, SAFESTOP Gripper Commands OPEN CLOSE 25 MM

Simulation and Off-Line Programming

Example A robot performs a loading and unloading operation for a machine tool as follows: l l Robot pick up part from conveyor and loads into machine (Time=5. 5 sec) Machining cycle (automatic). (Time=33. 0 sec) Robot retrieves part from machine and deposits to outgoing conveyor. (Time=4. 8 sec) Robot moves back to pickup position. (Time=1. 7 sec) Every 30 work parts, the cutting tools in the machine are changed which takes 3. 0 minutes. The uptime efficiency of the robot is 97%; and the uptime efficiency of the

Solution Tc = 5. 5 + 33. 0 + 4. 8 + 1. 7 = 45 sec/cycle Tool change time Ttc = 180 sec/30 pc = 6 sec/pc Robot uptime ER = 0. 97, lost time = 0. 03. Machine tool uptime EM = 0. 98, lost time = 0. 02. Total time = Tc + Ttc/30 = 45 + 6 = 51 sec = 0. 85 min/pc Rc = 60/0. 85 = 70. 59 pc/hr