An Innovative Dual Closed-Loop Control Strategy for Peak Stability of High-Frequency Fatigue Testing Machine

The high frequency fatigue testing machine employs the principle of electromagnetic resonance and is specifically designed to evaluate the tensile and compressive fatigue performance of metals under various force values. However, the main challenge faced by this tester in the later stages of the experiment is the problem of controlling the accuracy of the vibration peaks when the stiffness of the specimen varies. To solve this problem, an innovative dual closed-loop control strategy is proposed in this paper, which is based on phase and force feedback mechanisms. While utilizing the incremental PID algorithm to accurately control the force value, the excitation frequency is adjusted in real time to match the intrinsic frequency of the system by analyzing the phase angle relationship between the frequency of the excitation force and the resonance frequency using the successive approximation method suitable for the actual situation, which ensures the stability of the vibration peak value during the whole experimental process. The control scheme is modeled and simulated by MATLAB/Simulink, and the results show that the scheme can effectively track the intrinsic frequency of the system and maintain the stability of the peak value in the whole experimental process, which significantly improves the control accuracy and reliability of the testing machine and reduces the power consumption.