Development and Control of a Cable-Driven Robotic Platform for Studying Human Balance and Gait

Aging is one of the main causes of weakness in mobility and a high risk of falling due to the degradation of neuromuscular and skeletal systems. Tremendous cable-driven robotic assistive devices have been proposed in recent years with the goal of fall risk mitigation and rehabilitation interventions. However, most of them require sophisticated structure and mechatronics design, leading to a relatively bulky nature. In this study, we developed a cable-driven robotic platform for waist perturbation. A lightweight load cell is installed between the end of the cable and a wearable waist belt to measure the pulling force in real time. A closed-loop adaptive full-state feedback control with reference input is proposed to guarantee good torque trajectory tracking performance. Preliminary benchtop and human subject testing with the proposed controller demonstrated an improved force tracking performance of sinusoidal force profiles ranging from 20 N to 80 N, with Root Mean Square Error (RMSE) values of 2.6 N to 10.6 N during fixed-object perturbations and 3.4 N ± 0.2 N to 12.7 N ± 1.0 N during standing perturbations, respectively, as compared to a RMSE of 5.6 N to 21.4 N and 7.1 N ± 0.6 N to 33.7 N ± 2.9 N with the traditional proportional-integral-derivative controller using the same force profile and magnitudes, and under the same perturbation conditions. The hardware and control development of this robotic platform will be used for balance perturbation studies during static standing and human-in-the-loop optimization control studies during dynamic walking tasks.