Robotics: Lecture 2 Robotic System- General concepts
- 1. ROBOTICS الرحيم الرحمن اهلل بسم Lecture 2 Robotic System
- 2. 09/19/24 LECTURE TOPICS Definitions and general concepts. Symbolic Representation of Robots. Robotic Systems. Classification of Robotic Manipulators.
- 3. 09/19/24 ROBOT The term robot was first introduced into our vocabulary by the Czech playwright Karel Capek in 1920. The word robota being the Czech word for work.
- 4. 09/19/24 ROBOTICS Robotics is a relatively young field of modern technology that crosses traditional engineering boundaries. Understanding the complexity of robots and their applications requires knowledge of electrical engineering, mechanical engineering, systems and industrial engineering, computer science, economics, and mathematics. New disciplines of engineering, such as manufacturing engineering, applications engineering, and knowledge engineering have emerged to deal with the complexity of the field of robotics and factory automation.
- 6. 09/19/24 ROBOT DEFINITION An official definition of a robot comes from the Robot Institute of America (RIA): “ A robot is a reprogrammable multifunctional manipulator designed to move material, parts, tools, or specialized devices through variable programmed motions for the performance of a variety of tasks” .
- 7. 09/19/24 7 ROBOT APPLICATIONS Robots are used when the task is difficult manually, or dangerous, such as: welding, painting industries. electronics assembly. underwater and space exploration. hazardous applications in government labs, nuclear facilities, and medical labs.
- 8. 09/19/24 SYMBOLIC REPRESENTATION OF ROBOTS Robot Manipulators are composed of links connected by joints to form a kinematic chain. Joints are typically rotary (revolute) or linear (prismatic). A revolute joint is like a hinge and allows relative rotation between two links. A prismatic joint allows a linear relative motion between two links. We denote revolute joints by R and prismatic joints by P.
- 10. 09/19/24 If we have a three-link arm with three revolute joints is an RRR arm. Each joint represents the interconnection between two links.
- 11. 12 Definitions
- 12. 09/19/24 THE ROBOT ARM FREE BODY DIAGRAM (FBD) 13
- 13. 09/19/24 DEGREES OF FREEDOM (DOF) The degrees of freedom, or DOF, is a very important term to understand. Each degree of freedom is a joint on the arm, a place where it can bend or rotate or translate. 14
- 14. 09/19/24 DEGREES-OF-FREEDOM An object is said to have n degrees-of-freedom (DOF) if its configuration can be minimally specified by n parameters. Thus, the number of DOF is equal to the dimension of the configuration space. For a robot manipulator, the number of joints determines the number DOF.
- 15. 09/19/24 16 You can typically identify the number of degrees of freedom by the number of actuators on the robot arm. (thus joints) when building a robot arm you want as enough degrees of freedom allowed for your application.
- 16. 17 4 DOF Robot Arm
- 17. 18 5 DOF Robot Arm
- 18. 09/19/24 a manipulator should typically possess at least six independent DOF. With fewer than six DOF the arm cannot reach every point in its work environment with arbitrary orientation. Certain applications such as reaching around or behind obstacles may require more than six DOF. A manipulator having more than six links is referred to as a kinematically redundant manipulator. The difficulty of controlling a manipulator increases rapidly with the number of links.
- 19. 09/19/24 WRISTS AND END-EFFECTORS The joints in the kinematic chain between the arm and end-effector are referred to as the wrist.
- 20. 09/19/24 THE WORKSPACE The workspace of a manipulator is the total volume swept out by the end-effector as the manipulator executes all possible motions. The workspace is constrained by the geometry of the manipulator as well as mechanical constraints on the joints.
- 21. 09/19/24 ACCURACY AND REPEATABILITY The accuracy of a manipulator is a measure of how close the manipulator can come to a given point within its workspace. Repeatability is a measure of how close a manipulator can return to a previously taught point.
- 23. 09/19/24 CLASSIFICATION OF ROBOTIC MANIPULATORS Robot manipulators can be classified by several criteria: Power source. Application area. Method of control. Geometry.
- 24. 09/19/24 1-POWER SOURCE Typically, robots are either electrically, hydraulically, or pneumatically powered. Hydraulic actuators are unrivaled in their speed of response and torque producing capability. Therefore hydraulic robots are used primarily for lifting heavy loads. The drawbacks of hydraulic robots are that they tend to leak hydraulic fluid, require much more peripheral equipment (such as pumps, which require more maintenance), and they are noisy.
- 25. 09/19/24 1-POWER SOURCE Electrical robots driven by DC- or AC-servo motors are increasingly popular since they are cheaper, cleaner and quieter. Pneumatic robots are inexpensive and simple but cannot be controlled precisely. As a result, pneumatic robots are limited in their range of applications and popularity.
- 26. 09/19/24 2-APPLICATION AREA Robots are often classified by application into assembly and non-assembly robots. Assembly robots tend to be small, electrically driven and either revolute or SCARA in design. The main non-assembly application areas to date have been in welding, spray painting, material handling, and machine loading and unloading.
- 27. 09/19/24 3-METHOD OF CONTROL Robots are classified by control method into: Servo robots Non-servo robots. The earliest robots were non-servo robots. These robots are essentially open-loop devices. Servo robots use closed-loop computer control to determine their motion.
- 28. 09/19/24 GEOMETRY Most industrial manipulators at the present time have six or fewer degrees-of-freedom. These manipulators are usually classified kinematically on the basis of the first three joints of the arm to: Articulated (RRR) Spherical (RRP) SCARA (RRP) Cylindrical (RPP) Cartesian (PPP).
- 29. 09/19/24
- 30. 09/19/24 FURTHER READING “Robot Modeling and Control “ , By: Mark W. Spong, Chapter 1.
Editor's Notes
- #27: Selective Compliant Articulated Robot for Assembly