Passive micro-jitter isolation of gimbal-type antenna by using a superelastic SMA gear wheel

Spaceborne gimbal-type antenna is one of the generators of micro-jitter disturbances that substantially affect the high-resolution image quality of the observation satellite. A conventional low rotational stiffness titanium spring-blade gear wheel is effective for micro-jitter isolation of the antenna. However, this approach can result in several drawbacks such as plastic deformations on the relatively weak spring-blade of the gear under unexpected over-driving torque conditions. In order to improve the capability of the conventional spring-blade gear, this study investigated the feasibility on utilization of the superelastic characteristics of a shape memory alloy (SMA). The superelastic behavior of the SMA helps the SMA spring-blade gear to be considerably deformed without undergoing plastic deformations under excessive loading conditions and to recover its original shape upon unloading. To assess the basic characteristics of the proposed SMA spring-blade gear, rotational static loading tests were conducted. Furthermore, to evaluate the life time of the gear under various rotational angle conditions, accelerated cyclic loading tests were also carried out. The effectiveness of the proposed design was demonstrated by micro-jitter tests of the gimbal antenna.