High-Precision Impedance Control Method for Flexible Base Moving Manipulators

Abstract

Abstract The general problem of impedance control is addressed for a robotic manipulator with a moving flexible base. Impedance control imposes a relation between force and displacement at the contact point with the environment. The concept of impedance control of flexible base moving manipulators (FBMMs) is rather new and is being considered. The dynamic of the manipulator is decomposed into slow and fast dynamics using the singular perturbation method. A new sliding mode impedance control (SMIC) method using an element on the end-effector is proposed for high-precision impedance control of FBMMs. The SMIC method as a robust impedance control law is derived for the slow dynamics. The asymptotic stability of the overall system is guaranteed using a combined control law comprising the impedance control law for the slow dynamics and a feedback control law for the fast dynamics. Active control on the end-effector (ACEE) is able to eliminate the force chatter at the contact. This proposed sliding mode impedance controller with active end-effector control (SMIC/ACEE) was simulated for two models. The first model is a simple FBMM composed of a 2-d.o.f. planar manipulator and a 1-d.o.f. moving base with flexibility in between. The second model is an advanced 10-d.o.f. FBMM composed of a 4-d.o.f. manipulator and a 6-d.o.f. moving base with flexibility. This controller provides the desired position/force control accurately with satisfactory damped vibration at both soft and hard contact. ACEE as the control element on the end-effector was able to eliminate chattering of position and force about their desired values. Composite SMIC/ACEE represents a new framework for high-precision impedance control of moving and/or flexible base robotic manipulators. Keywords: SLIDING MODE IMPEDANCE CONTROLFLEXIBLE BASE MOBILE MANIPULATORSINGULAR PERTURBATIONEND-EFFECTOR