A robot suit with hardware-based safety devices: Transient response analysis of a velocity-based safety device

We have developed a rehabilitation robot suit with two hardware-based safety devices - the "velocity-based safety device" and the "torque-based safety device". The robot suit assists a patient´s knee joint. The torque-based safety device stops the robot suit if it detects an unexpected high joint torque. Similarly, the velocity-based safety device stops the robot suit if it detects an unexpected high joint angular velocity. The safety devices work even when the computer breaks down, because they consist of only passive mechanical components without actuators, controllers, or batteries. However, we have never analyzed the transient response of the velocity-based safety device. In order to design the velocity-based safety device efficiently, we need to analyze the transient response. In this paper, we firstly review the robot suit equipped with the safety devices. Secondly, we analyze the transient response of the velocity-based safety device. Thirdly, we simulate the transient response of a new velocity-based safety device in order to demonstrate the usefulness of the transient response analysis. Finally, we present experimental results to verify the effectiveness of the transient response analysis.