Development of a new hydraulic cylinder with built-in compound control function of displacement and thrust

A novel actuator with built-in compound control function of displacement and thrust is developed. This actuator is a kind of compact hydraulic cylinder system, which consists of a stepping motor, a control valve with a spool and a slide sleeve, a hydraulic cylinder and a mechanical feedback mechanism. In the proposed actuator, with a mechanical displacement feedback and a mechanical pressure feedback, displacement and thrust control can be realized. Also the flexible compliance control could be realized by adjusting the feedback weights in the actuator. The basic characteristics of this actuator are investigated theoretically. Through the prototype experiments, it is confirmed that the actuator is very effective in the compound control and compliance control. Furthermore, it is proved that the precision of this actuator can be improved by introducing a dither, and the system dynamic performance can be improved by adding damping orifices.