Improve the Performance of Active Knee Prosthesis During Stairs Ascent by Using the Leading Reference Control System

Strong coupling between the human and machine exists in many cyborg and bionic systems (CBS). Some input signals for control system barely change after the outputs work. In this situation, it is hard for the controller to calculate the required reference output of system. For example, in the stance phase of stairs ascent gait using an active knee prosthesis (AKP), most AKPs use the Inertial Measurement Unit (IMU) signal and the Ground Reaction Forces (GRF) signal to control the output of knee joint torque. However, these two signals hardly change unless the controlled object (joint torque) is already close to the actual requirement. Therefore, this study introduces a leading reference control system (LRCS) that uses an overshoot reference value to make the AKP more effective in providing positive energy in the abovementioned situation. In addition, the LRCS with different parameters was evaluated through the experiments of stairs ascent with AKP. Results show that LRCS with the suitable parameter can provide greater torque output when going upstairs, making the subject go upstairs easier.