The natural frequency-based power assist control for lower body with HAL-3

It is thought that the dynamic motions with lower limbs such as walking can be made more effectively by moving each joint along to its natural frequency. If the natural frequency were able to be modified purposefully, the effective motion could be performed at any angular frequency around joint. We realized that with the exoskeleton-type powered suit, HAL (Hybrid Assistive Leg)-3 we developed for walking aid. In this research, we considered the operator´s leg as pendulum model, identified the physical parameters around human´s knee joints, tried to adjust the impedance, and applied that to pendular movement of leg. The effectiveness of adjusting the natural frequency in power assist control can be confirmed through the experiments evaluated with myoelectricity.