Design and Evaluation of an Integrated Active and Passive Body Weight Support System for Variable Gravity and Inertia Compensation

The body weight support system has been widely used to reduce the physical and psychological burden of rehabilitation walking training for patients with dyskinesia. However, it is challenging for current systems to reduce the weight and dynamic load of the patient simultaneously during high-performance rehabilitation training tasks. This article presents an integrated active and passive body weight support system based on a wire-driven spring-loaded parallelogram mechanism, which provides variable gravity and inertia compensation during treadmill training, depending on the patient's condition. Coupling the elastic preloaded spring with the linkage allows for greater flexibility and stability to achieve balancing conditions. As the core technology of the proposed system, the control strategy consists of three stages, the impedance-based auxiliary force generation, the quasistatic force/position conversion, and the model-based wire tension control. With the proposed controller, the effects of time delay and load inertia on the impedance performance of the system are thoroughly analyzed. The experimental results show that the system can provide effective and stable auxiliary forces with a maximum error of 5.3% and significantly reduce weight and inertia during human walking, with an average unloading error of 7.6% obtained by comparing ground reaction forces.