1. Mechatronics 1 Week 9 & 10

2. Learning Outcomes By the end of week 9-10 session, students will understand the control system of industrial robots.

3. Course Outline Overview. Gear Box. DC Motor. Closed loop model. Stability analysis on : damping ratio, moment inertia & controller gain. Robot control system as a multi input multi output system (brief introduction). Latest development of robot control system.

4. HOW DOES A ROBOT MOVE ? Controller Board dynamics i/p o/p Torque DC Motor Torque t o/p (movement)

5. Control System (1) Based on its dynamic behaviour, a control system can then be developed. Different dynamic behaviour requires different control system. Most industrial robots comes with conventional PID (Proportional, Derivative, Integral) control system. Source : World Robot Statistics, 2000, United Nations & IFR.

6. Control System (2) Computer DC MotorMechanical Links -- ++

7. Problems How to obtain a desired system by maintaining the characteristic equation. Maintaining characteristic equation means keeping the damping ratio larger than 1*). By observing the equations, one can adjust the robot parameters in such away so that the required damping ratio value can be obtained. *) For the sake of safety, in a robot control system, the value of damping ratio should be bigger than 1.

8. Robot System Robot Arm Operating System Teach Pendant (Teaching Box) Host Computer Control Unit (Controller)

9. Programming Mode Teach Pendant –On Line Host Computer –On Line –Off Line –Simulation

10. Programming Types Textual Programming –Sitting in front of a computer terminal (host computer). –Requires robot programming knowledge. Teaching by Showing –Physically moving the robot arm through a sequence of position. –Requires no robot programming knowledge.

11. Programming Types (2) Teaching by Showing (cont’d) : –Lead Through Programming (sometimes referred to Lead by Nose). The robot may be equipped with a special attachment. Ideally used for continuous path purposes, e.g. paint spraying. Difficulties arise in an area close to the work volume boundaries.

12. Programming Types (3) Teaching by Showing (cont’d) –Walk Through Programming. It requires a teach pendant (teaching box) to deliver commands to a robot. Once a correct position and orientation of end effector is attained, this posture is then stored in a control unit. The robot then accomplishes its job according to the stored information during a play back mode.

13. Robot Programming Language Special/ Dedicated Programming Language –Specifically developed for the purpose of robot specific area. –Poor structure. –Interpreter type. Robot Library Via Common/ Popular Computer Language. –Specific subroutine is developed for the purpose of manipulating object with robot arm. –Utilizing a good structure of common computer languages, e.g. Pascal.

14. Control Unit It provides capability to communicate with a robot via the aforementioned programming mode. It stores the required movement provided by the host computer, and hence once programmed, the robot can operate in the manufacturing floor without the use of host computer (just the robot alone with its control unit). It carries out the joint interpolation for intermediate path during a play back session. Main job is controlling the robot movement.

15. Control Unit Implementation Slow Movement Fast Movement Notice that basically velocity control can be carried out via position control.

16. Robot Programming Language Special/ Dedicated Programming Language –Specifically developed for the purpose of robot specific area. –Poor structure. –Interpreter type. Robot Library Via Common/ Popular Computer Language. –Specific subroutine is developed for the purpose of manipulating object with robot arm. –Utilizing a good structure of common computer languages, e.g. Pascal.