Biomechanical Evaluation of Compliance Joint Knee Exoskeleton During Normal Gait

Musculoskeletal modeling is a cost-effective way to design and test wearable robots, ensuring maximum efficiency for individuals. This article explores the simulation of exoskeletons to support the lower limbs and reduce the metabolic cost of walking. The exoskeleton consists of a flexible joint as an actuator made up of four elastomers that store the negative power of the knee joint during the walking cycle as energy, and release it to assist the wearer in the next phase of walking. The Computed Muscle Control (CMC) algorithm in OpenSim is used to find joint torque, total metabolic savings, and the resulting changes in muscle activity. Subsequently, the behavior of implementing the passive exoskeleton is evaluated and the results are compared to a semi-active robot on lower body limbs. The study concluded that while the passive robot exerts extra force on the hamstring muscles in the first half of the swing phase and increases the torque applied to the knee joint. It decreases the activity of the quadriceps muscles in the second half. To compensate for this problem exoskeletons are commonly equipped with a motor. However, this article's findings suggest that utilizing the motorized robot, while decreasing the torque in the targeted joint, actually boosts the performance of surrounding muscles and consumes more metabolic energy than in a passive state.

Keywords:

Knee exoskeleton , Gait rehabilitation , Musculoskeletal modelling , Muscle activation force , Metabolic cost