A novel worm gear actuated repeatable locking/unlocking device for magnetically suspended control moment gyro

Abstract

The locking/unlocking device (LUD) is crucial to protect the rotor in magnetically suspended control moment gyro (MSCMG) from vibration impacts during launch. Conventional LUDs have inevitable shortcomings in repeatability, compactness and reliability for aerospace applications. To overcome these disadvantages, this paper proposes a novel worm gear actuated repeatable locking/unlocking device (RLUD) consisting of an actuator, several transmission mechanism components and a locking nut. The configuration, working principle and design consideration are introduced in detail. Since the worm gear is a key component for torque transmission, the reliability analysis considering correlated failure modes of the tooth surface contact and tooth root bending is carried out by means of the fourth-order moment approach and copula function. The optimization design for the worm gear is subsequently implemented. The reliability analysis of the worm gear demonstrates that the assumption of independent failure modes without correlate consideration is likely to acquire conservative results, thus resulting in structural redundancy. Then, the optimization design is performed to achieve weight reduction under high reliability. The RLUDs based on optimization results are manufactured and then integrated into a prototype of MSCMG rotor system. Finally, a series of mechanics tests are conducted to evaluate the functional performance. The result of static load test shows that the strength and self-locking capacity of the RLUD are sufficient to support the compression load. The real-time response of the vibration signal indicates that the whole prototype is safe enough without any large shocks, thus satisfying the launch requirements. The relative displacements between the rotor and stator during vibrations are far less than the protective air gap, thus verifying the locking effect of the RLUD on the rotor.