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Personnel

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  1. Introduction to Robotics (ES159)Advanced Introduction to Robotics (ES259)Spring 2010Ahmed Fathi ES159/ES259

  2. Personnel • Instructor: • Me • TFs: ES159/ES259

  3. Primary: M. Spong, S. Hutchinson, and M. Vidyasagar, “Robot Modeling and Control”, Wiley Texts Secondary: Li, Murray, Sastry, “A Mathematical Introduction to Robotic Manipulation”, CRC Press ES159/ES259

  4. Course outline • First 2/3: traditional analysis of robotic manipulators • Homogeneous transforms • Forward/inverse kinematics • Velocity kinematics, dynamics • Motion planning • Control • Final 1/3: introduction to special topics • Sensors and actuators • Mobile agents, SLAM • Computer vision • MEMS, microrobotics • Surgical robotics, teleoperation • Biomimetic systems ES159/ES259

  5. Introduction • Historical perspective • The acclaimed Czech playwright Karel Capek (1890-1938) made the first use of the word ‘robot’, from the Czech word for forced labor or serf. • The use of the word Robot was introduced into his play R.U.R. (Rossum's Universal Robots) which opened in Prague in January 1921. In R.U.R., Capek poses a paradise, where the machines initially bring so many benefits but in the end bring an equal amount of blight in the form of unemployment and social unrest. • Science fiction • Asimov, among others glorified the term ‘robotics’, particularly in I, Robot, and early films such as Metropolis (1927) paired robots with a dystopic society • Formal definition (Robot Institute of America): • "A reprogrammable, multifunctional manipulator designed to move material, parts, tools, or specialized devices through various programmed motions for the performance of a variety of tasks". ES159/ES259

  6. Common applications • Industrial • Robotic assembly • Commercial • Household chores • Military • Medical • Robot-assisted surgery ES159/ES259

  7. Common applications • Planetary Exploration • Fast, Cheap, and Out of Control • Mars rover • Undersea exploration ES159/ES259

  8. 01_01 Industrial robots • High precision and repetitive tasks • Pick and place, painting, etc • Hazardous environments ES159/ES259

  9. 01_03 Representations • For the majority of this class, we will consider robotic manipulators as open or closed chains of links and joints • Two types of joints: revolute (q) and prismatic (d) ES159/ES259

  10. Definitions • End-effector/Tool • Device that is in direct contact with the environment. Usually very task-specific • Configuration • Complete specification of every point on a manipulator • set of all possible configurations is the configuration space • For rigid links, it is sufficient to specify the configuration space by the joint angles • State space • Current configuration (joint positions θ) and velocities • Work space • The reachable space the tool can achieve • Reachable workspace • Dextrous workspace ES159/ES259

  11. 01_06 Common configurations: wrists • Many manipulators will be a sequential chain of links and joints forming the ‘arm’ with multiple DOFs concentrated at the ‘wrist’ ES159/ES259

  12. 01_10 Workspace: elbow manipulator ES159/ES259

  13. 01_12 Common configurations: Stanford arm (RRP) • Spherical manipulator (workspace forms a set of concentric spheres) ES159/ES259

  14. 01_14 Common configurations: SCARA (RRP) ES159/ES259

  15. 01_15 Common configurations: cylindrical robot (RPP) • workspace forms a cylinder ES159/ES259

  16. 01_16 Common configurations: Cartesian robot (PPP) • Increased structural rigidity, higher precision • Pick and place operations ES159/ES259

  17. 01_17 Workspace comparison (a) spherical (b) SCARA (c) cylindrical (d) Cartesian ES159/ES259

  18. 6DOF Stewart platform 01_18 Parallel manipulators • some of the links will form a closed chain with ground • Advantages: • Motors can be proximal: less powerful, higher bandwidth, easier to control • Disadvantages: • Generally less motion, kinematics can be challenging ES159/ES259

  19. Simple example: control of a 2DOF planar manipulator 01_19 • Move from ‘home’ position and follow the path AB with a constant contact force F all using visual feedback ES159/ES259

  20. 0 1 2 0 1 2 01_20 Coordinate frames & forward kinematics • Three coordinate frames: • Positions: • Orientation of the tool frame: ES159/ES259

  21. 01_21 Inverse kinematics • Find the joint angles for a desired tool position • Two solutions!: elbow up and elbow down ES159/ES259

  22. State space includes velocity Inverse of Jacobian gives the joint velocities: This inverse does not exist when q2 = 0 or p, called singular configuration or singularity 01_23 Velocity kinematics: the Jacobian ES159/ES259

  23. 01_24 Path planning • In general, move tool from position A to position B while avoiding singularities and collisions • This generates a path in the work space which can be used to solve for joint angles as a function of time (usually polynomials) • Many methods: e.g. potential fields • Can apply to mobile agents or a manipulator configuration ES159/ES259

  24. desired trajectory controller error system dynamics measured trajectory (w/ sensor noise) actual trajectory 01_24 Joint control • Once a path is generated, we can create a desired tool path/velocity • Use inverse kinematics and Jacobian to create desired joint trajectories ES159/ES259

  25. General multivariable control overview joint controllers motor dynamics manipulator dynamics desired joint torques state estimation sensors estimated configuration inverse kinematics, Jacobian desired trajectory ES159/ES259

  26. Sensors and actuators • sensors • Motor encoders (internal) • Inertial Measurement Units • Vision (external) • Contact and force sensors • motors/actuators • Electromagnetic • Pneumatic/hydraulic • electroactive • Electrostatic • Piezoelectric • Basic quantities for both: • Bandwidth • Dynamic range • sensitivity ES159/ES259

  27. Next class… • Homogeneous transforms as the basis for forward and inverse kinematics • Come talk to me if you have questions or concerns! ES159/ES259