# Simulation Analysis and Experimental Verification of the
## 5 Experiment
### Vibration Experiment  
Vibration experiment plays a very important role in aerospace field [19; 20; 21]. Sinusoidal vibration excitation can effectively verify the stability of the MP under vibration environment [22]. In order to verify the reliability of the locking force and eliminate faults in the normal life stage, a shake table test was adopted to simulate the mechanical environment of aerospace products and eliminate possible faults on the ground [23; 24]. According to the analysis in the previous section, the relationship between locking force and locking torque remains unchanged after the force sensor is added. Therefore, the pressure sensor and its supporting devices are removed, and the L/R mechanism motors reload the MP at the same time until the torque reaches 25 Nm. In this state, sinusoidal vibration test was carried out to verify the reliability of the locking force. The vibration verification test was carried out on the 35-ton vibration platform of Aerospace Hill as shown in Figure 14. There are three times of sinusoidal sweep vibration, and the test sequence is as follows: 0.2 g characteristic sweep, formal sinusoidal sweep, and 0.2 g characteristic sweep. The test conditions of formal sinusoidal sweep were the same as the input of the frequency response analysis described earlier, as shown in Table 1. One acceleration sensor was placed on the MP to detect the acceleration response signal. In order to prevent damage to the product caused by excessive magnitude, the response point amplitude limit of 17 g was adopted at point 8. The actual control curve of the test is shown as the black curve in Figure 15b. Figure 12: Locking force test device. Figure 13: Relationship between locking torque and locking force. (**a**) Relationship between right locking force and input torque. (**b**) Relationship between left locking force and input torque. Figure 15 shows the frequency and time domain results of the acceleration response curves of the vibration test at measuring point 8 in the X direction. It can be seen from the figure that the acceleration time history curve of response point 8 is overly smooth without obvious impact signal, so it can be concluded that there is no impact phenomenon during the test, and the L/R mechanism does not separate from the MP during the formal sinusoidal sweep test. The initial vibration response check and the final vibration response check were conducted before and after the sinusoidal vibration experiment, that is, two sinusoidal characteristic frequency sweeps in the frequency range of 0-100 Hz were conducted, respectively, and the test magnitude was 0.2 g. The input conditions, response points, and parameter settings of the two vibration tests were identical. The purpose of vibration response inspection was to determine whether the inherent characteristics of the MSHML had changed after the sinusoidal vibration experiment, and then to judge whether the structural connection state had changed or failed, so as to help analyze and determine the various faults and fatigue failures caused by the vibration experiment. The detection method was to judge by comparing the changes of resonance frequency and peak value on the acceleration response curves of the vibration at the first characteristic stage and the vibration at the second characteristic stage with the same response point. When the resonance frequency changes, it can usually indicate the change or destruction of the inherent characteristics [25]. The comparison curve of measuring point 8 before and after characteristic sweep frequency is shown in Figure 16.  
Figure 14: Vibration test. (**a**) Vibration test of the MSHML. (**b**) Measuring point layout of the MP. Figure 15: Response curve of vibration measurement point 8. (**a**) Time domain results. (**b**) Frequency domain results. It can be seen from the comparison of feature level that the first natural frequency and the peak value of the two sweep experiments do not change significantly: the change of peak frequency is 0.07 Hz, and the error is within 1%.