Magneto-rheological actuator with permanent magnets for low-power activation

This research presents a new magneto-rheological brake that uses only permanent magnets to produce variable torque output. A new magnet array was developed that can be operated by a tiny motor allowing the device to apply 1.8 Nm torque using only 1.4 W of electrical power. In many applications, it is desirable to have actuators with high torque output, low volume, and low input power. In recent years, this has led to extensive study of magneto-rheological brakes since these devices can provide high torque-to-volume ratios when compared to electric motors of similar size. There have been many studies to optimize volume and torque, which usually leads to designs requiring complex internal magnetic flux paths and excessive power requirement resulting in joule heating and reduced performance in long-term use. Our brake can operate for 22 h using a small battery while cycling through full on/off torque output. It can also apply full torque output indefinitely with no power input required to keep it on. There is no joule heating since there are no coils in the design.