Development of Flexible Electro-Hydraulic Spherical Actuator

Voluntary rehabilitation at home helps to prevent the joint contracture after medical treatment. Our previous studies concerned a low-cost portable rehabilitation device using a flexible spherical pneumatic actuator as a passive exercise device. However, the device requires a bulky compressor to drive it. This study results in a compact fluidic driving system that is highly flexible. The system adopts a flexible electrohydraulic cylinder driven by an electric motor and a hydraulic gear pump. An empirical equation for the suitable pump rotation for the desired displacement of the system has been determined. As a result, the multiposition control of the system within the tracking error of 4 mm has been realized by using the on/off control scheme based on the obtained equation. In addition, a flexible, spherical electro-hydraulic actuator using two proposed drive systems is developed and tested. Control of the attitude of the tested spherical actuator is successfully realized.