A basic study on passive force display and rehabilitation system with redundant brakes

Several 2-DOF rehabilitation robots for upper limbs have been proposed so far, and clinical effectiveness was reported in several studies for the aged people or patients with stroke. We developed the quasi 3-DOF rehabilitation system ldquoHybrid PLEMOrdquo which has 2-DOF force-feedback function in working plane but its working plane can be adjusted the inclination. Hybrid-PLEMO is a compact, low-cost rehabilitation system for upper limbs with high safety by using ER fluid brakes or ER fluid actuators and it can be switched between active type and passive type. However, there are some directions and link positions for which it is difficult to display the force when Hybrid-PLEMO works at passive type. To solve this problem, a method for improvement of controllability using redundant brakes had been suggested. In our study, two novel methods are presented on the performance evaluation of passive-type force display system with redundant brakes. Using these methods, we evaluate the performances of 2-DOF passive-type force display system with and without redundant brakes. In this paper, the developed passive force display system are outlined. Besides, two novel performance evaluation methods of the passive-type force display system with redundant brakes are presented and basic experiment is also discussed.