A Sensorless Control Strategy for an Active Assistive Walker: Design, Implementation, and Experimental Validation

With the increase in elderly population throughout the world, especially in the European Union, there is an utmost need for assistive technologies to help them achieving daily tasks in an independent or collaborative manner. This paper presents a novel sensorless control for an active assistive walker featuring a disturbance observer for the estimation of the force applied by the user (thus eliminating the need of external force sensors) and admittance control for smooth locomotion. The experimental validation is carried out in the ROS2 framework for data computation and analysis. The walker, driven by motorized wheels, is tested on flat and inclined surfaces. The results demonstrate accurate force estimation, efficient motion control, and stable assistance with a balanced tuning of the admittance control parameters, i.e. virtual mass and damping, thus ensuring responsive and smooth behavior of the system.