A Force Control Strategy for 3-PPSR Flexible Parallel Robots

An active compliance control strategy based on position impedance control is proposed to solve the problem of flexible hinges with high aspect ratio and the deformation of parallel robot caused by external environment. Based on the equivalent reaction model between a flexible parallel robot and external environment and the position-based impedance control model, this strategy adds an external environment force in its control process. The steady state error of force tracking model is considered and accurately controlled by adjusting the initial reference position based on position control. Then, the external force tracking control is analysed with the position control under accurate environment variables. Lyapunov stability model and Lyapunov energy equation are used under the condition of unknown environment variables, and the adaptive force control is achieved by directly controlling the target position through a force deviation. Experimental results show that the precision of the position-based force control and the adaptive control reaches ±0.05 N and ±0.1 N, respectively, and meets design requirement. The accuracy and effectiveness of the strategy are verified.