Design and Validation of an Underactuated Modular Exoskeleton With Multijoint Coupling Assistance for Enhancing Human Locomotion With Reduced Hip Impact

Knee and ankle single-joint exoskeletons enhance human locomotion but can impact the hip joint. This article introduces a multijoint coupling assistance mechanism and a modular exoskeleton prototype that avoids negative effects on the hip joint. During the stance phase, it sequentially assists the knee and ankle with one quasi-direct drive motor without affecting other joints, and reduces hip joint load in the swing phase. A controller trained on inertial measurement unit data from both legs determines the gait phase and generates corresponding biological torque. Experiments showed a 9.08% decrease in peak fascia lata muscle activity and an 18.32% reduction in peak hip joint torque when using the exoskeleton. This study reports that reducing the impact on the hip joint when assisting a single joint such as the knee or ankle can enhance the overall assistance performance of the exoskeleton.