电液疲劳试验系统的变谐振控制技术研究

随着激振频率的增加，电液疲劳试验机激振输出幅值急剧衰减，激振频率和激振输出幅值两者之间存在相互矛盾的关系，因此提出了利用谐振能量来提高激振输出幅值的方案。该方案通过改变阀控单出杆液压缸无杆腔容积的方法来改变系统的谐振频率，使得谐振频率与激振频率重合，在谐振点进行激振。在对液压动力机构的运动过程进行分析的基础上，建立系统的数学模型，运用四阶龙格库塔的数值方法对其进行求解，并对仿真结果进行理论分析；理论分析表明可以通过改变无杆腔容积来改变系统的谐振频率，且在谐振点处的激振输出幅值有较大幅度的提升；从负载流量曲线上看，由于谐振能量的输出使得在谐振点处的负载流量急剧降低。最后建立实验系统对以上仿真结果进行实验验证。实验结果表明：在谐振点出的激振输出幅值为饱和输出幅值的25%左右，负载流量反而减小了90%左右；通过改变无杆腔的容积能有效改变谐振频率，拓宽电液疲劳试验机应用范围。

Study on Variable Resonant Technology of Electro-hydraulic Fatigue Test System

The amplitude of the exciting output force in electro-hydraulic fatigue testing machining will attenuate with the increasing exciting frequency. There is a confliction between amplitude and exciting frequency. Therefore, a novel scheme using the resonant power is proposed to enhance the amplitude in high exciting frequency. A single rod cylinder control by 2D exciting valve is used and the resonant frequency of system varies with the volume of no-rod chamber cylinder. The resonant power can be excited and enhance the amplitude while the resonant frequency matches the exciting frequency. The hydraulic power mechanism is simplified based on the analysis of system structural and motion. A mathematical model of the hydraulic power mechanism for the proposed vibration exciter was established to investigate the relationship between the volume of no-rod chamber and resonant frequency, as well as the amplitude at various frequencies. An experimental system was built to validate the theoretical analysis. It is verified that the resonant frequency can be controlled by no-rod chamber’s volume in cylinder. The amplitude is 25% of the maximum amplitude in low exciting frequency while the system excited in resonant frequency, and the flow rate from oil source reduces to 10% of the maximum flow rate. Therefore, the application scope of the electro-hydraulic fatigue test can be broaden and the exciting frequency can be broaden in electro-hydraulic fatigue test used in high load test and save energy by using the resonant energy.