A globally stable output feedback PD-INP-D regulator for robot manipulators

This paper deals with the position control problem of designing asymptotically stable proportional plus integral regulators with only position feedback for robot manipulators with uncertain and varying-time payload. Proposed is a simple class of robot regulators consisting of a linear PD plus an integral action driven by NP-D controller, where the velocity feedback is replaced by a filtered position feedback. By using Lyapunov´s direct method and LaSalle´s invariance principle, the simple explicit conditions on the regulator gains to ensure global asymptotic stability are provided. The theoretical analysis and simulation results show that the output feedback PD-I^NP-D control laws can be tuned to recover the performance of a state feedback PD-I^NP-D control laws, that is, the output feedback PD-INP-D control law has the same fast convergence, good flexibility and strong robustness as the state feedback one and the same optimum response can be achieved by a set of control parameters in the whole control domain, even under the case that the payload is changed abruptly.