Nabila Shawki, Georgios Lazarou, and Douglas R. Isenberg
Computed-torque control, Lyapunov stability, performance analysis, nonlinear control
This paper presents an investigation into the stability of a computed-torque controlled robot that is handling a payload without the aid of an adaptive control technique. The research considers a two-link planar manipulator moving a point mass as a payload. Initially, the stability of the desired setpoint for the system of the robot with a payload is analysed using Lyapunov’s first method. It is found that the stability of the setpoint becomes inconclusive as the mass of the payload increases. An estimate of the radius of the region of attraction around the setpoint is formulated using Lyapunov’s second method as the mass increases. To assist in this analysis, a bound on the nonlinear perturbation caused by the payload has been determined. Numerical simulations of the robot manipulating variously sized payloads are presented for validating the analysis. Finally, a performance analysis is presented by varying the damping ratio and the mass of the payload.
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