| To design a controller, through, which the robot manipulator can perform fast and accurate motion or provide excellent dynamic response in joint torque, requires precise and high performance actuators that can provide high torque. Actuators that use harmonic drive system as speed reducer are very efficient for high torque transmission. However, the harmonic drive performances are limited by friction. The non-linear friction characteristics limit the actuator capacities and do not allow robot to accomplish complex tasks that require precise torque control.;With these in mind, several manipulator control methods have been developed. One solution is to ensure that the dynamics of robot actuator is similar to that of reference model. In this thesis, a disturbance estimator based on adjustment of a difference between the real and the reference dynamics of the joint is introduced. The joint reference model includes desired (ideal) joint dynamics and its formulation is described by simple dynamics equation. The proposed control law realises a nonlinear decoupling control, without calculation of the inverse dynamics, and is robust against the parameter variations and uncertainties of mass properties of the links. |
