An Output Force Control for Robotic Manipulator by Changing the Spring Stiffness

This paper presents an output control for a manipulator by changing the spring stiffness. Through the modeling and analysis of the nonlinear stiffness characteristics of the crank-rocker mechanism, and using the zero stiffness domain search method to select the appropriate spring stiffness, using different spring stiffness to establish different mechanism models, the robot can finally control the output of ideal constant force, and at the same time, the analysis results are applied to the improved design of the tire grabbing manipulator. Through this method, the tire grabbing manipulator becomes a constant grabbing force mechanism, and the mechanism is transformed from a rigid-body mechanism to a pseudo-rigid-body mechanism. The accuracy and stability of the whole system are greatly improved. In this study, the method of adding spring to each joint of the linkage mechanism is applied to the improvement design of the linkage mechanism, and the four-bar constant force mechanism is designed for the first time, which expands the application field of the nonlinear stiffness characteristics of the linkage mechanism, and has great application value to the improvement design of the mechanical system with the linkage mechanism and the control of the output force.