Robustness issues in robot control

A scheme is presented for the accurate trajectory control of robot manipulators in the presence of model uncertainty and disturbances. Based on the suction control methodology (an extension of sliding mode control), the scheme addresses the following problem: given the extent of parametric uncertainty (such as imprecisions or inertias, geometry, loads) and the frequency range of unmodeled dynamics (such as unmodeled structural modes, neglected time-delays), design a nonlinear feedback controller to achieve optimal tracking performance (in a suitable sense). The methodology is compared with algorithms such as the computed torque method, and is shown to combine in practice improved performance with simpler and more tractable controller designs. Extensions to compliant motion control are also discussed.