Application of optimal preview and adaptive controllers for robotics manipulator with control input constraints

In this paper an optimal preview controller and an adaptive controller are synthesized to control the motion of n-degrees of freedom direct drive robotics manipulator. The optimal preview controller is implemented offline and the optimal problem is solved at an arbitrary operating point of a prespecified optimal trajectory. Design of the proposed adaptive controller is based on minimum variance control with a model reference which depends on the nominal values of the position and angular velocity of the manipulator´s joints. The parameters of the adaptive controller are estimated online using the least squares algorithm. In the proposed two controllers, the end effector´s velocity of the manipulator is monitored in a servo loop, as well as the position and angular velocity of each joint of the manipulator are compelled to track their nominal values. These two controllers comprise n-input vector of the actuators torque, and 6-output vector of the linear and angular end effector´s velocities. The actuators of the direct drive manipulator are taken as permanent magnet motors. Their dynamics and constraints are considered in the proposed two controllers. Extensive digital computer simulations are made to demonstrate the tracking performance, robustness and applicability of the optimal preview and adaptive controllers. Comparison between their performance are also demonstrated