Enhanced robust performance oriented integrated planning and control of a robotic manipulator with online instantaneous violent disturbances

Abstract

Robotic manipulators suffer from various modeling uncertainties, which generally deteriorate motion control performance. These uncertainties are commonly treated as a lumped disturbance which is then addressed by those disturbance estimation and attenuation control (DEAC) approaches. Although existing DEAC algorithms have shown their effectiveness of rejecting normal disturbances with moderate amplitudes and slow variations, they cannot work well in the presence of an instantaneous violent disturbance (IVD). An IVD is typically characterized by the short duration and large amplitude which exceeds the control input limit of a robotic joint. Consequently, the actual trajectory of a robotic manipulator will deviate from its desired trajectory significantly. Given this issue, an enhanced robust performance oriented two-loop framework which integrates minimum-time trajectory planning and nonlinear control is proposed in this paper. Specifically, a nonlinear adaptive robust controller is synthesized in the inner loop to handle both structured and unstructured uncertainties, while a synchronized trajectory planning algorithm is devised in the outer loop to force the deviated trajectory converging to the desired trajectory in minimum time. Comparative experiments on a robotic manipulator under IVDs show that the deviated trajectory is recovered fastest by the proposed approach.