Development of Normally Closed Type of Magnetorheological Clutch and its Application to Safe Torque Control System of Human-Collaborative Robot

Abstract

In this study, a normally closed (NC) type clutch using magnetorheological (MR) suspension and a rare-earth permanent magnet is proposed as a safety device for human-collaborative robots. This clutch can transmit an effective torque under various conditions and function as a holding brake and a changeable torque limiter. To design this clutch to achieve both good controllable characteristics and safety performance, the normally closed structure with a permanent magnet was realized by placing two facing magnetic poles asymmetrically for efficient generation of the magnetic field, and by adopting the multi-sheet rotor for the improvement of the torque output. As the analysis results show, it was confirmed that the three-sheet rotor obtained about 1.5 times torque output as much as the single-sheet rotor. When the exciting current was 0.8A, the transmitted torque marked the minimum; when the exiting current was 0A, the torque output of approx. 41 Nm was generated with the time constant of 0.15 s.

Keywords

magnetorheological suspension robot safety collaborative operation clutch normally closed type rare-earth permanent magnet.

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References

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