Design of a 6-DOF collaborative robot arm with counterbalance mechanisms

Most collaborative robots use high-power motors for a good weight-to-payload ratio, thus leading to not only an increase in manufacturing cost but also possibility of injury at a collision between a human and a robot. To maintain high-performance with low-power driving units, a spring-based counterbalance mechanism (CBM) and a robot arm based on these CBMs were developed in our previous study. In this study, a 6-DOF collaborative robot equipped with a multi-DOF CBM is proposed. A double parallelogram linkage and a slider-crank mechanism are employed for a compact and durable design of a multi-DOF CBM. Unlike the previous prototypes in which some portions of CBMs were protruded out of the robot body due to their large volume, the proposed CBMs can be embedded inside the robot links. The performance of the developed CBM and collaborative robot were verified based on simulations using dynamic simulation software. Simulation results show that the proposed CBMs can effectively reduce the joint torques required to operate the robot. This reduction in the torque enables low-power motors to be used in a collaborative robot, thus significantly improving collision safety and energy efficiency.