Dynamic response and long-term operational performance of a ball double-screw hydraulic robotic joint actuator

Abstract

Hydraulic joint actuators are important components in robotic motion systems, where dynamic response, force transmission stability, and long-term operational reliability are critical under repeated loading. However, conventional screw-based hydraulic joints often suffer from friction-induced startup resistance, transmission nonlinearity, and performance degradation during cyclic operation. This paper investigates a ball double-screw hydraulic robotic joint actuator developed by the authors, with emphasis on its dynamic response characteristics, load transmission behavior, and long-term operational performance. A dynamic model is first derived to describe the coupled motion of the piston assembly and output shaft. Static finite element analysis and multibody dynamics simulations are then conducted to evaluate contact stress, startup behavior, rotational response, and screw-pair force transmission under representative hydraulic operating conditions. The simulation results show that the actuator achieves low startup pressure and stable motion response under different load torques. In addition, a prototype actuator is subjected to 20,000 cycles of loading and motion experiments, during which consistent motion behavior is observed without abnormal mechanical responses. Post-test scanning electron microscopy (SEM) observations reveal only mild surface features on the key contact interfaces, providing supporting evidence for stable operation under lubricated cyclic conditions. The combined results demonstrate that the proposed actuator maintains stable dynamic response and reliable long-term operational performance, indicating its potential for high-load robotic actuation systems requiring compact structure, stable force output, and repeated operation.