Acceleration Based Force-Impedance Control of a 6-dof Parallel Robotic Manipulator

An acceleration based force-impedance controller is presented in this paper. The proposed control strategy is applied to a six-dof parallel robotic mini-manipulator: the robotic controlled impedance device (RCID). The control strategy involves three cascade controllers: an inner acceleration controller, built as a set of six single-input- single-output (SISO) acceleration controllers (one per manipulator axis), an impedance task-space controller, and an outer force controller. The proposed control strategy enables two kinds of manipulator behaviour: force limited impedance control and position limited force control. The type of behaviour only depends on the chosen manipulator trajectories. The RCID may be used as a force-impedance controlled auxiliary device, coupled in series with a position controlled industrial robot, or as a stand-alone force feedback display, that may be used as a master manipulator in master-slave telemanipulated systems or as a haptic device interacting with virtual environments. Experimental results of the RCID used as an auxiliary device working coupled to an industrial manipulator are presented.