Real-Time Force Control of Hydraulic Manipulator Arms Without Force or Pressure Feedback Using a Nonlinear Algorithm

Abstract

This study proposes a real-time control force (RCF) algorithm for precise force control of hydraulic manipulator arms (HMAs) without the need for force or pressure feedback. The algorithm utilizes the nonlinear relationship between the hydraulic manipulator arm's servo valve pressure, voltage, and dynamics to calculate joint torque in real-time, thereby accurately controlling the force applied by the manipulator's arm. We theoretically prove the convergence of the algorithm on hydraulic manipulator arms with different degrees of freedom. The advantage of RCF controller is that it does not require force or pressure sensors, which avoids the deployment of complex sensor systems, and it can adapt to hydraulic manipulator arms with different degrees of freedom without the need to redesign the force control algorithm, greatly reducing the amount of manual intervention required for control. Experimental results demonstrate that the proposed algorithm enables the hydraulic manipulator to rapidly converge to the desired force within 0.2 seconds after experiencing rigid collisions. Additionally, the algorithm achieves a positional control precision of 1.4 mm and maintains force errors within 2 N, effectively showcasing its outstanding force control performance. Therefore, we believe that this algorithm holds tremendous potential and practical value, as it can significantly reduce the cost and amount of human intervention required for force control of hydraulic manipulators.