Development of Four-Bar Linkage Mechanism on Chair System for Assisting Sit-to-Stand Movement

A lot of assisting system which composed of the seat, transmission mechanism (or mechanical structure) and sensor have been developed for supporting the sit-to-stand (STS) movement. However, most of these systems depend on the capability of the actuator entirely to produce enough driving power, which may cause a high load of the actuator and the high cost of the system. In order to reduce the burden of the actuator and control the cost, the transmission mechanism was considered to share the role of actuator. This paper proposed a novel design of a chair system with three four-bar linkage mechanisms, which form the transmission mechanism, and verified its performance. The key point for the design phase was to decide the specific combination between all links, so that the position of the seat can be controlled by only one actuator: the first four-bar linkage mechanism is the power source of the system, the second decided the vertical and rotational displacements of the seat, and the third strengthened the stability of the whole system. Then, the multibody dynamic software and the high-speed camera system was used to compare simulated data and measured data. The results of the comparison verified the good performance of the proposed design.