| Truly accurate positioning of the end effector of robotic manipulators is made possible through the use of direct measurements of that position. However, the flexibility of the robot structure between the actuator and the measurement at the end effector, in conjunction with nonlinear friction at the actuators, makes control of such manipulators to high levels of precision difficult. Pulse modulation control has been used successfully in the past for precise positioning of mechanical systems under the influence of nonlinear friction. This work analyses the use of pulse modulation control for a mechanical system with both nonlinear friction and structure flexibility. Conditions for the closed loop stability of the discrete, nonlinear system are derived. Conditions on the plant for when the flexibility can be ignored are shown. A pulse modulation controller for a flexible manipulator is presented. Adaptive forms of the controller are given. |
