Abstract
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.
Highlights
The motor brake mechanism is one of the most important parts in robot joints
Contrary to the conventional brake structure where the torque spring is embedded in the electromagnet, permanent magnet and the electromagnet are distributed on both sides of the brake armature in the proposed brake mechanism
3) After the motor brake is released, the brake mechanism will enter into a holding state, a small enough current of the electromagnet coil will be required to balance the permanent magnet force acting on the brake armature
Summary
The motor brake mechanism is one of the most important parts in robot joints. It is used to ensure that the robot joints are kept at rest after power-off or emergency braking in the event of a power failure. Contrary to the conventional brake structure where the torque spring is embedded in the electromagnet, permanent magnet and the electromagnet are distributed on both sides of the brake armature in the proposed brake mechanism. 2) When the robot system is powered on, the brake power supply circuit provides an instantaneous high current pulse in the electromagnet coil to release the brake state and keep the brake armature attached to the surface of the electromagnet, so that the motor rotor can rotate freely. 3) After the motor brake is released, the brake mechanism will enter into a holding state, a small enough current of the electromagnet coil will be required to balance the permanent magnet force acting on the brake armature. Armature will help to further understand the working mechanism of the proposed brake
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