Robust control of robot manipulators by MIMO disturbance observer

A robot manipulator control method using disturbance observer in task space and a simple coordinate transformation by the transposed Jacobian matrix has been proposed. The control method can realize a simple control algorithm with less computation power for large degree-of-freedom robot manipulators. However, the inertia variation depending on manipulator configuration is large due to the simplification of the control algorithm. Therefore, the decoupled error of the system, i.e. nondiagonal elements of the input matrix in the state space, caused by compensation error of the disturbance observer influences accuracy of the control system. In this paper, the authors introduce a new MIMO (multi-input-multi-output) disturbance observer, which can regard the nondiagonal elements of the inertia matrix as a control parameter. Moreover, a simple design method for disturbance observer system considering quadratic stability is introduced. The accuracy of the robot manipulator control is improved as compared to that of the conventional disturbance observer system by these strategies.