Movements of knee joints are relative motions between tibia and femur, which include rolling and sliding. Conventional wearable knee assistive device utilized a hinge joint and generates nonnegligible mismatched motions under deep flexions. To assist the knee motion including the deep flexion, we developed a polycentric assistive device for knee joints (PAD-KJ) by using two gears with the same module and different radii. These radii were designed so that the center of the smaller gear moves on the trajectory of the knee joint with small error. According to the results of parametric design, the minimum error was about 3 mm to the model trajectory of knee joint. We also proposed a torque generator for this joint. The combination of a lever arm and a linear spring with the pair of gears successfully generated the assistive torque for standing motions. According to an evaluation test, the maximum torque of the single unit was about 1.2 Nm and the assistive torque in real usage will be 4.8 Nm.

Ankle-foot orthoses (AFOs) are orthotic devices that support the movement of the ankles of disabled people, for example, those suffering from hemiplegia or peroneal nerve palsy. We have developed an intelligently controllable AFO (i-AFO) in which the ankle torque is controlled by a compact magnetorheological fluid brake. Gait-control tests with the i-AFO were performed for a patient with flaccid paralysis of the ankles, who has difficulty in voluntary movement of the peripheral part of the inferior limb, and physical limitations on his ankles. By using the i-AFO, his gait control was improved by prevention of drop foot in the swing phase and by forward promotion in the stance phase.

In this study, we propose a leg-robot with a Compact MR Fluid Clutch (CMRFC) to realize haptic control of abnormal spastic movements of brain-injured patients. This system can be used in the practical training for trainees of physical therapy. Additionally, we will study to figure out the physiological mechanism of spastic movements of human with the process to simulate patient-like spastic motion by this robot. In this paper, basic structure and mechanism of the leg-robot with CMRFC are explained. Finally, experimental results of some kinds of haptic control for spastic movements are described.

ER fluid has rheological characteristics which can be controlled by the electric field. Using particle-type ER fluid, we developed a brake device. In this study, this ER brake was used in an isokinetic exercise system for rehabilitation training under restriction of constant rotational speed of a joint during exercise. Such a passive system using a brake is basically safe for human use.