Hydraulic Artificial Muscle-Powered Knee Support Wearable Device with Four-bar Linkage Mechanism

Hydraulic cylinders have been selected as actuator in earlier exoskeletons due to low weight and high force density. In this paper, we propose a knee exoskeleton using Hydraulic Artificial Muscle (HAM) and four-bar knee joint mechanism. The HAM has similar advantages to hydraulic cylinders, but lighter and compliance, making it suitable for wearable robot applications. To allow the device to better comform to human knee kinematics, a four-bar linkage mechanism was utilized. The human knee biomechanics is a combination of rolling and sliding on the condyle, which can be emulated using four-bar linkage. To adapt the HAM to the link mechanism, we proposed and Angled Bar as a modification to the existing mechanism. The Angled Bar adjusts the torque output and motion range of the proposed device.