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UNIT VI Robot Technology

UNIT VI Robot Technology. History of Robot 1922 Czech author Karel Capek wrote a story called Rossum’s Universal Robots and introduced the word “ Rabota ”(meaning worker or slave labour or forced labour ) 1954 George Devol developed the first programmable Robot.

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UNIT VI Robot Technology

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  1. UNIT VI Robot Technology

  2. History of Robot • 1922 Czech author Karel Capek wrote a story called Rossum’s Universal Robots and introduced the word “Rabota”(meaning worker or slave labour or forced labour) • 1954 George Devol developed the first programmable Robot. • 1955 Denavit and Hartenberg developed the homogenous transformation matrices • 1962 Unimation was formed, first industrial Robots appeared. • 1973 Cincinnati Milacron introduced the T3 model robot, which became very popular in industry.

  3. Laws of Robotics • On the contrary, to avoid dangers of mechanization, a science writer “Isaac Asimov” in 1942 gave Three laws of robotics. • 1. A robot may not harm a human being, or, through inaction, allow a human being to come to harm. • 2. A robot must obey the orders given to it by human beings except where such orders would conflict with the First Law. • 3. A robot must protect its own existence, as long as such • protection does not conflict with the First or Second Law

  4. AUTOMATION and ROBOTICS • Automation • The technology that is concerned with the use of mechanical, electrical and Computer-based systems to control production processes. • E.g. transfer lines, mechanized assembly machines, feedback control systems, numerically controlled machines tools. • Robotics • Robots are mechanical devices which assist industrial automation.

  5. Types of Automation 1. Fixed Automation – used when volume of Production is very high and variety is low. 2. Programmable Automation – volume of production is relatively low and their is variety of Products to be made high. 3. Flexible Automation - lies in between fixed and programmable automation.

  6. Where Robotics Fit It coincide most closely with Programmable automation.

  7. Definition OF ROBOTICS • “Machine in the form of human” • “ Mechanism that can move automatically” • “A robot is re-programmable, multi-functional manipulator designed to move material, parts, tools, or specialized devices through variable programmed motions for the performance of a variety of tasks.” (Robotics Institute of America)

  8. Where Used and Applied • Welding • Painting • Surface finishing • Aerospace and automotive industries • Light assembly such as in the micro-electronics industries, or consumer products industries • Inspection of parts (e.g., CMM) • Underwater and space exploration • Hazardous waste remediation

  9. Basic Components of Robots • Manipulator : This is the main body of the Robot and consists of links, joints and structural elements of the Robot. • 2. End effectors : This is the part that generally handles objects, makes connection to other machines, or performs the required tasks. • 3. Actuators : Actuators are the muscles of the manipulators. Common types of actuators are servomotors, stepper motors, pneumatic cylinders etc.

  10. 4. Sensors : Sensors are used to collect information about the internal state of the robot or to communicate with the outside environment. Robots are often equipped with external sensory devices such as a vision system, touch and tactile sensors etc which help to communicate with the environment 5. Controller : The controller receives data from the computer, controls the motions of the actuator and coordinates these motions with the sensory feedback information.

  11. Types of Robot Joints 1. Rotary (Revolute) Joints: Rotary joints produces pure rotary motion. Most of the rotary joints are electrical driven, either by stepper motors or, more commonly by servomotors. 2. Linear (Prismatic) Joints : The linear joints produces pure linear or translatory motion. The linear joints are driven by hydraulic cylinders, pneumatic cylinder or linear electric actuators.

  12. Degree of Freedom • The number of independent movements that an object can perform in a 3D space is termed as the degrees of freedom – three position and three for orientation. • Six degree of freedom can be categorised into • 3 DoFs associated with arm and body of the robot. – Vertical, Radial, Rotational. • 3 DoFs associated with robot wrist – Wrist Pitch, Wrist Yaw, Wrist Roll

  13. Robot Configurations • 1. Cartesian/Rectangular Gantry(3P) • Provides 3 linear motion along 3 mutually perpendicular axis X, Y and Z. • No rotary motion • Work envelop is Rectangular • Used for assembly, palletizing and machine tool loading.

  14. 2. Cylindrical (R2P) • Cylindrical coordinate Robots have 2 linear (prismatic) joints and one rotary (revolute) joint. • Work envelop is Cylindrical. • Application- loading and unloading of machine tool.

  15. 3. Spherical joint (2RP) • They follow a spherical coordinate system, which has one linear (prismatic) joints and two revolute joint. • Work envelop spherical shell. • Application – used for spot welding and manipulation of heavy loads.

  16. 4. Articulated (Jointed – Arm ) configuration • An articulated robot’s joints are all revolute, similar to a human’s arm. • Types – 1. Revolute Robots 2. SCARA Robots • Revolute Robots – similar to human arms • Spherical Work Envelop • Application – spray painting, seam welding, spot welding, assembly, heavy material handling.

  17. 2. Selective Compliance Assembly Robot Arm (SCARA) (2R1P): • They have two revolute joints that are parallel and allow the Robot to move in a horizontal plane, plus an additional prismatic joint that moves vertically • Work envelop is cylindrical and much larger than all other configuration. • Applicaton – suitable for assembly operation where it is expected to perform the insertion tasks.

  18. End Effectors of Robot • End Effectors is a device that is attached to the wrist of the robot arm so as to enable the robot to perform a specific task. • Types- 1. Gripper 2. Tools • Grippers – • Grippers are the end effectors used for holding the parts or objects. • Tools – • In many applications, robot is required to operate tools rather than handling the parts. In such cases, tools are used as end effectors. • The examples – spot welding tool, arc welding torch, spray painting nozzle etc.

  19. Primary Vendors · Fanuc (Japan) · Kuka (Germany) · ABB (Sweden, US) · Adept (US) · Panasonic (Japan) · Seiko (Japan) · Sankyo (Japan) · Motoman (Japan) · Mitsubishi (Japan) Typical Costs: $20 K - $80 K

  20. Robot Repeatability & Accuracy • ISO 9283:1998 Norm for Industrial Robots: • Repeatability: positional deviation from the average of displacement. (max speed and max payload) • Accuracy: ability to position, at a desired target point within the work volume. (max speed and max payload) • Warm robot to steady state conditions • 2. Send identical commands to bring the robot to 3 different positions in sequence. • 3. Measure the reached position using 2 cameras and an optical target carried by the robot, or other instruments.

  21. Supporting Technologies · Vision systems · End-of-arm tooling· Compliance devices · Manipulation devices· Welding technologies · Lasers· Proximity sensors · Wrist sensor (forces/torques)· Control software/hardware · Part delivery systems· Application software · Interface software· Operating systems · Programming languages· Communication systems · I/O devices

  22. Advantages • Greater flexibility, re-programmability, kinematics dexterity • Greater response time to inputs than humans • Improved product quality • Maximize capital intensive equipment in multiple work shifts • Accident reduction • Reduction of hazardous exposure for human workers • Automation less susceptible to work stoppages

  23. Disadvantages • Replacement of human labor • Greater unemployment • Significant retraining costs for both unemployed and users of new technology • Advertised technology does not always disclose some of the hidden disadvantages • Hidden costs because of the associated technology that must be purchased and integrated into a functioning cell. Typically, a functioning cell will cost 3-10 times the cost of the robot.

  24. Limitations • Assembly dexterity does not match that of human beings, particularly where eye-hand coordination required. • Payload to robot weight ratio is poor, often less than 5%. • Robot structural configuration may limit joint movement. • Work volumes can be constrained by parts or tooling/sensors added to the robot. • Robot repeatability/accuracy can constrain the range of potential applications. • Closed architectures of modern robot control systems make it difficult to automate cells.

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