Realization of multiaxial load compensation mechanism capable of adjusting compensation force in any position

Abstract

This study aims at realization of multiaxial load compensation mechanism capable of adjusting compensation force in any position. By using a load compensating mechanism on an articulated manipulator, it is pointed out that the gravity of the manipulator and the object can be fully compensated regardless of those position. This mechanism reduces the energy consumption while operating and makes it possible to easily move the weightless manipulator. The purpose of this study is to clarify a design theory of a novel load compensating manipulator with the following three performance requirements. (Performance A) Since the load of the object is not uniquely determined, the compensating force can be adjusted without external energy inflow. (Performance B) Since the position of the object to be grasped is not uniquely determined, the compensation force can be adjusted in multiple positions. (Performance C) Since the picking work requires multiple degrees of freedom, it is possible to adjust the compensation force with multiple axes. For this purpose, a constant-torque spring and a transmission are used to enable adjustment of the compensation force in any position (Performance A and B), and differential gears are added to them due to enable easy multi-axis operation (Performance C). In order to evaluate the feasibility of the proposed design theory, the testing machine equipped with a constant-torque spring, a transmission for bicycles, and a differential gear for three-wheeled motorcycles are constructed to realize the theory. As a result, the error rate of the compensation force is less than 9%, and the standard deviation is less than 0.8 Nm when the compensation force is adjusted in 10 different positions. These results indicate that the proposed theory and the mechanism embody a multiaxial load compensation function that can adjust the compensation force in any position.