Suspended Cable-Driven Parallel Robot with Series Elastic Actuator to Enhance the Wrench Feasibility

Abstract

Body weight support systems are used to maintain balance and compensate for the weight of patients during gait rehabilitation following neurological injuries such as stroke. Existing widely used body weight support systems are capable of providing support during over-ground walking in a relatively large workspace and can actively control multi-directional forces by using several actuators. However, with these systems, it is not possible to independently control the force in each direction. Therefore, this study proposes a new type of active body balance support system capable of independent force control in each direction in a large workspace through the integration of a Cable-Driven Parallel Robot (CDPR) with a Series Elastic Actuator (SEA). The conceptual design of the new mechanism of Series Elastic Actuator for use in the active body balance system is carried out and the system structure is optimized according to the system kinematics and Wrench Feasible Workspace (WFW) analysis. In addition, the system is designed as a result parameter of the structure optimization, and the force controller for generating the desired wrench is verified through the dynamic analysis using ADAMS® & Simulink Co-Simulation. The simulations are performed under 10 different conditions. The desired wrench generation performance of the CDPR+SEA system is compared with that of the system without a SEA. The results show that the CDPR combined with SEA has excellent wrench force generation performance compared to the CDPR system without SEA. During the simulations, most of the cables of the CDPR without SEA lost tension and thus lost control capability. On the other hand, in the case of CDPR+SEA, the number of controllable cables was always equal to or greater than the number of control degrees of freedom. Thus, the system has a high control capability. Finally, the system prototype is manufactured and the spring compression operation test for force generation and the position control operation test of the SEA connected to the end-effector of the CDPR are carried out. In the future, verification of the force controller using the real system and the design of the force & position hybrid controller will be carried out. User testing of the new active body balance system will also be carried out.