Development of a knee joint assist suit with hardware-based safety devices (Proposal and design of the assist suit)

Abstract

When developing rehabilitation assist suits, safety consideration for patients is crucial. Computer-aided control techniques can improve their safety. However, when the computer breaks down, the assist suit may be dangerous for the user because of its unintentional motion. Therefore, assist suits with hardware-based safety devices are desired to guarantee safety even when the computers do not operate properly. In this paper, we present a new rehabilitation assist suit equipped with a velocity-based safety device and a torque limiter. The assist suit assists a patient's knee joint. The velocity-based safety device switches off the assist suit's motor if it detects an unexpected high joint angular velocity. The torque limiter cuts off the torque transmission if it detects an unexpected high joint torque. These safety devices will work even when the computer breaks down, because they consist of only passive mechanical components without actuators, controllers, or batteries. Firstly, we describe the features of the assist suit with the safety devices. Secondly, we introduce the structure of the assist suit. Thirdly, we explain the structure and mechanism of the velocity-based safety device. Fourthly, we show the prototype assist suit that we have developed. Finally, we present experimental results to verify the effectiveness of the velocity-based safety device installed on the developed assist suit.

Keywords

• robot
• design
• mechanism
• rehabilitation assist suit
• mechanical safety device