An Optimized Permanent Magnet Brake Mechanism in Robot Joints

This paper proposes a novel brake mechanism in robot joints, especially for space robot joints which require low power consumption and high reliability. The key point of the brake mechanism is that the torque spring is replaced with the Nd-Fe-B permanent magnet. Due to the position and force relationship between the permanent magnet and the electromagnet in the brake mechanism, the stroke of the brake armature can be extended so that the bolt type brake structure is adapted and the braking torque can be infinite theoretically. Meanwhile, the holding current in the electromagnet can be decreased to save energy and reduce heat generation. The magnetic circuit models of the electromagnet and permanent magnet in the brake mechanism are established and analyzed. In order to improve the response speed of the brake mechanism, a novel H-bridge brake power supply circuit is proposed. To verify the benefits of the design, a permanent magnet brake prototype with the H-bridge power supply circuit is set up. While the holding current is consistent with the peak current in the conventional torque spring motor brake, the proposed permanent magnet brake mechanism can decrease the holding current below 0.1 A.