Modeling and control of a novel home-based cable-driven parallel platform robot: PACER

This paper focuses on various control strategies for a modular cable-articulated parallel robotic manipulator called PACER (Parallel Articulated-Cable Exercise Robot). The proposed robotic device is comprised of multiple cables and a single antagonistically actuated prismatic joint which connects a six degrees-of-freedom moving platform to a fixed base. This novel design provides an attractive architecture for implementation of a home-based rehabilitation device as an alternative to expensive serial robots. In this paper, after deriving the dynamic equations via Newton-Euler formulation, the development of different control strategies in the context of upper limb rehabilitation in three-dimensional space will be examined. The various control modes include: (i) passive mode through feedback linearization for recovering functionalities of the joints at the first step of post-stroke rehabilitation, (ii) active mode via admittance controller for assisting patient to do tasks better, and finally (iii) resistive mode via stiffness controller for increasing the muscle strength. This is now evaluated via a simulation case-study and development of a physical testbed is underway. Since the human arm consists of seven degrees-of-freedom, and daily activities of upper limbs are combination of motions of these simple joints, this proposed design with various control strategies has enormous potential for neurological remapping and brain plasticity in post-stroke patients with upper limb injuries.