Design and research of a multi-mode hip joint assistive mechanism based on a double cam

Abstract Lower limb-assisted exoskeletons can provide payloads and support, but the hip joints of current lower limb-assisted exoskeletons have problems such as single mechanisms, few degrees of freedom, and limitations in the types of gaits that can be acted upon. To address these problems, a novel double-cam hip joint assist mechanism is proposed for walking, running, and carrying gait situations. The double cam and two rectangular compression springs with different stiffness are used to satisfy the differences in exoskeleton assistance requirements in multiple gaits. First, biomechanical simulation of walking, running, and carrying movements is carried out with OpenSim to obtain the hip joint angle and torque data, and then the structural design of the assist mechanism is carried out. Hip joint angle planning and contour solving are carried out for the contour lines of the cams, so that the cam contour lines are assist according to different hip joint angles, and the stiffness of compression springs is determined by D’Alembert’s principle, and the assist torques are analyzed. Meanwhile, a human–machine coupling model was established for theoretical analysis. Finally, the muscle power change curves were exported using OpenSim, and the assistance was verified by comparison.