Passive-type rehabilitation system for upper limbs which can display the exact resistance force in the orientation opposite to hand motion

Abstract

In these days, there are many patients with ataxia, which is paralysis caused by a brain stroke or asynergia. Early detection of functional deterioration and sufficient rehabilitative training are necessary for these patients. Rehabilitation support systems for upper limbs using force display devices are expected to quantify the effects of rehabilitative training and enhance the motivation of patients. The application of passive-type force display devices unactuated by motors is especially desirable for its high safety. There are, however, some orientations and positions for which it is difficult to display force in an unactuated force display systems using only passive elements. To solve this problem, a method for the improvement of controllability using larger number of brakes than the degree of freedom of system had been suggested. This method made it possible to display more various force power and orientations than could be done with previous systems. However, the system with the larger number of brakes often become huge system. In this study, we have developed a rehabilitation system for the upper limbs which use only the same number of brakes as the degree of freedom but can display the resistance force in the orientation opposite to operator's motion in any orientations and link posture: "Neo-PLEMO".

A Semi-passive Planar Manipulandum for Upper-Extremity Rehabilitation

“…With these brakes in the current prototype, it is possible to achieve pure resistive forces ( F̂ ) ranging up to 77N in any direction along the workspace. Many semi-passive devices have used custom electro/magnetorheological fluid brakes because they permit high torques, direct electronic control, fast actuation times, and smooth operation; 25,20,36 however cost is still prohibitive to these brakes that use ”smart fluids” for actuation, and few options are available commercially. Alternatively, friction brake pads are a low-cost option capable of producing extremely high torques, 40 but these brakes are not under direct electronic control and stiction in these systems tend to make the forces unpredictable.…”

“…Many of these devices are aimed to provide a 3-dimensional reaching workspace, but this requires them to have bulky systems to counterbalance the device weight. 40,10 Whereas others have a configuration that does not allow for extensive steering forces, 25,20 or are incapable of providing large resistances. 36 …”