Walk-Assist Robot: A Novel Approach to Gain Selection of a Braking Controller Using Differential Flatness

Abstract

With increasing populations of the elderly in our society, robot technology will play an important role in providing functional mobility to humans. From the perspective of human safety, it is desirable that controllers for walk-assist robots be dissipative, i.e., the energy is supplied from the human to the walker, while the controller modulates this energy. The simplest form of a dissipating controller is a brake, where resistive torques are applied to the wheels proportional to their speeds. The fundamental question that we ask in this brief is how to modulate these proportional gains over time for the two wheels so that the walker can perform point-to-point motions. The unique contribution of this brief is a novel way in which the theory of differential flatness is used to plan the trajectory of these braking gains. Since the user input forces are not known a priori, the trajectory of the braking gain is computed iteratively during the motion. Simulation and experimental results show that the walkassist robot, along with the structure of this proposed control scheme, can guide the user to reach the goal.

A passive guidance system for a robotic walking assistant using brakes

“…The resulting passive walker can be guided by a differential control on the brakes, using the same idea adopted by the automotive industry for stability control (ESP). Along the same line is the work [10], which proposes a brake controller guaranteeing the dissipative nature of the overall system.…”

Added Force-Based Methods Using Load Cells to Evaluate Walking and Tumbling with a Japanese Walking Support System

“…Past scientific achievements include the execution of electric walking supporting systems (rollators); simple, non-electric systems; the tracking of characteristic points; and the drawing of stick pictures. However, limited research has examined added force on the walking supporting machine [11]- [21]. In addition, targeted achievements concerning living human bodies and non-living humanoid devices have been somewhat limited because of social and ethical issues.…”

Control algorithm and evaluation of a powered wheeled walker for tracking a user

“…[6][7][8] Some of them have capability to help users walk properly and to guide them through a safe walking path using laser and also ultrasonic sensors. Han et al 9 developed an intelligent walking-aid robot.…”