Multiple-Degree-of-Freedom Counterbalance Robot Arm Based on Slider-Crank Mechanism and Bevel Gear Units

Low-cost but high-performance robot arms are required for robot arms to come into widespread use. To provide sufficient torques to support the robot mass and payload, most arms use expensive motors and speed reducers, which are the main reasons for their high price. As a solution to these problems, a multiple-degree-of-freedom (DOF) counterbalance mechanism and robot arm were developed in our previous study, which can compensate for the gravitational torque due to the robot mass. However, there are durability and reliability problems associated with wire-based mechanisms. To solve these, in this study, we proposed a new counterbalance mechanism based on a spring and slider-crank mechanism, along with a double-parallelogram mechanism composed of bevel gear units. Moreover, a 6-DOF counterbalance robot arm was built to verify the performance of the proposed mechanism. Simulation and experimental results showed that the proposed mechanism effectively decreased the torque required to support the robot mass, thus allowing the prospective use of low-cost motors and speed reducers for high-performance robots.