Design and Adaptive Compliance Control of a Wearable Walk Assist Device

The ability to walk independently is a predominant feature that human beings are bestowed with by nature. People with moving disabilities face many challenges in day-to-day activities and they have to rely on others to perform their day-to-day activities. Robotic walk-assist technology has the ability to play an indispensable role in improving the mobility of people who are suffering from walking disabilities. However, there are several technical challenges, such as safe interaction of human and robotic walk-assist devices, and control of highly nonlinear dynamic systems. This paper proposes a preliminary design of an assistive device for elderly persons having poor mobility. An adaptive inertia-related controller is employed for the desired tracking control of hip and knee joints of the walk assist device. The mass estimation of both hip and knee links is estimated through the proposed adaptive controller, which plays an important role if people of different weights and sizes opt to use the same device. Moreover, the adaptive control scheme is coupled with a compliant spring-mass-damper reference model to realize a compliance control for the hip and knee joints of the exoskeleton wearable walk-assist robotic device. Simulation results validate the performance of the proposed controller for both hip and knee joints. Results demonstrate that proposed controller has the capability to estimate the weights of the links, and the uncertain parameters while changing the assistive device dynamics.