Development and Evaluation of a Backdrivable Vane-Type Rotary Actuator Using Magnetorheological Fluids

Robot systems with both "intrinsic safety" and "high output" are expected to be implemented in heavy-duty industries such as construction and manufacturing. But there are currently no effective solutions. In our previous work, a backdrivable piston using magnetorheological fluid (MRF) whose viscosity can vary with the applied magnetic field was developed. However, it was a passive device, and its active control scheme was not proposed. The design was complex enough to hinder its implementation to robot arms. In this article, we develop an easily implementable rotary actuator using MRF and propose a basic controller. The actuator was designed based on a vane motor and was driven by hydraulic oil (i.e., MRF), so it can generate high torque. It also has a built-in MRF valve in the vane which can change the output torque and backdrivability with the magnetic field controlled by coil current. Each component was designed to maximize the dynamic range of output torque and backdrivability based on a multiphysics coupling model of electromagnetics, MRF magnetization, and fluid dynamics. Moreover, three basic control modes including backdrivable, high-response, and power-efficiency modes were designed and tested. The experimental results showed that the proposed MRF actuator had both high output and intrinsic backdrivability, and control modes could show the advantages of the MRF actuator.