Counterbalance Mechanism Based on a Gas Spring for Ceiling-Mounted Robot Arm Carrying Heavy Payloads

In a robot arm, the actuator torques of a joint module are mostly used to compensate the gravitational torque caused by the robot ann's own weight, To deal with this problem, various counterbalance mechanisms have been developed, among which a counterbalance mechanism based on the slider-crank mechanism is generally used because of its relatively simple structure and high durability. If the counterbalance mechanism is applied to a ceiling-mounted robot arm, then the compensation torque by the device is less than that of floor-mounted one. To overcome this drawback, we propose a method to replace the coil spring, which is mainly used as an elastic body of a counterbalance mechanism, by a gas spring. After verifying the performance of the device through simulations, a single-degree-of-freedom ceiling-mounted robot was manufactured for experiments. The experimental results showed that the gravitational torque generated when the ceiling-mounted robot carried heavy payloads was effectively compensated by the proposed device.