Abstract: The locking stiffness between the petal and the central part was simplified by the equivalent spring model.Using this model,the effects of the locking force and the ball diameter on the modal frequencies of the structure were analyzed.The analytical results show that the fundamental frequency of the structure connected by the kinematic couplings declines from 33.592 Hz of the fixed structure to 10~20 Hz,and it is more effective to increase the modal frequencies of the structure connected by the kinematic couplings by increasing the diameters of the location balls than by increasing the locking force.