Abstract:Fault tree was established for the stuck fault of the signal conversion device during the test. The mechanism analysis and troubleshooting for each fault branch were carried out, and the reason of the fault was determined to be the angle between the rocker arm and the ejector rod of the signal conversion device in the locking mechanism. The lateral force was generated on the ejector rod, and the effect of lateral force has not been considered in the design of the signal conversion device. After several unlocking actions, the surface of the inner hole of the shell was abraded in the ejector rod of the signal conversion device, and the friction coefficient was abnormal, which resulted in the increase of the movement resistance of driving the ejector rod of the signal conversion device, and finally it led to the stuck fault of the signal conversion device. The problem can be solved by increasing the support length, reducing the fit clearance between the shell and the ejector rod, increasing the overlap of the shell and the ejector rod shaft end.The test proves that the measures are effective.