High-performance 2-D force display system using MR actuators

A force display system is a kind of human-coexistent robot systems, which share the space with people while they are working, and which directly touch and display force-senses to their users. For such a robot system, it is important to estimate safety quantitatively and to ensure mechanical safety. In this paper, it is described that using MR (magneto-rheological) actuators, which is one clutch type actuators, can ensure safety. Moreover, the characteristics of MR actuators that are low inertia, high torque/inertia ratio and high responsibility contribute to improve the performance of force display systems. In this study, we developed an MR actuator with low inertia (2.6×10^-5[kg· m²]), high torque/inertia ratio (3.8×10⁵[1/s²]) and high responsibility. Torque/inertia ratio of this MR actuator is highest among MR actuators developed so far and much higher than those of conventional servo actuators. Then, a high-performance 2-D force display system using the MR actuator was developed. Maximum force displayed is 190 [N] and rigidity of the system is 5.9 [N/mm]. Moreover, backdrivability, dynamic range and collision sense are improved by using MR actuators in comparison with a system using ER actuators.