Control of robotic manipulators with input/output delays

Input/output delays in a control system can pose significant impediments to the stabilization problem. Recently, passivity based control has emerged as a promising approach to guarantee delay independent stability of passive systems with delays in the input-output channel. In this paper we study two problems in motion control of rigid robots with input/output delays. The first problem is the classical set-point control problem of rigid robots where we demonstrate that the use of the scattering variables can stabilize an otherwise unstable system for arbitrary constant time delays. The second problem we address is that of stabilizing a rigid robot with external stiffness and input/output delays using bounded output feedback. Employing the the scattering transformation, and by encoding the inputs and outputs in the scattering variables, we show that the mechanical system can be asymptotically stabilized independent of the input-output delays. The proposed algorithms are numerically verified on a two-degree-of-freedom manipulator.