摩擦负阻尼与伴生阻尼对低速工况下液压缸振动的耦合作用机制

Coupling Effects of Negative and Associative Friction Damping on the Vibration of Hydraulic Cylinder Running at Low Speeds

摩擦负阻尼与伴生阻尼耦合作用于低速液压缸,诱发液压缸振动、冲击,制约了液压装备的精密性能。考虑低速工况下摩擦的负阻尼与伴生阻尼效应,建立了液压缸运动非线性模型,基于摄动理论推导了液压缸速度脉动率解析表达式,分析了液压缸振动幅度与频率的变化特征,揭示了负阻尼与伴生阻尼对振动的耦合作用机制。研究结果表明:负阻尼促进系统振动,伴生阻尼抑制系统振动,负阻尼与伴生阻尼存在对立竞争关系。当系统速度低于0.61倍Stribeck速度vs时,负阻尼效应增强,伴生阻尼效应降低,振动随运行速度增大逐渐加剧;当运行速度高于0.71vs时,负阻尼效应减小,伴生阻尼效应先增大后减小,振动幅度逐渐下降直至平稳运行;当系统工作在0.61vs至0.71vs区间时,负阻尼效应达到最大,伴生阻尼效应达到最低,振动幅度急剧增大,频率下滑,形成尖脉冲冲击。研究结果揭示了摩擦对液压缸振动特征的影响机制,为精密液压装备的稳定运行与控制提供了理论参考。

The negative and associative dampings,acting on hydraulic cylinder running at low speeds,results in a complex nonlinear vibration and restricts the equipment precision performance.A nonlinear model of hydraulic cylinders is proposed by considering friction negative and associative dampings.A perturbation theory is employed for solving this nonlinear model to obtain a pulsating rate expression.And then,the coupling effects of negative and associative dampings on the cylinder vibration amplitude and frequency are studied.The results showed that:It is an opposite and competitive relationship between these two dampings because negative one promotes vibration while associative one suppresses vibration.When running velocity is below 0.61 times of Stribeck velocity vs,the vibration gradually increases because its negative effect increases while its associative effect decreases;When running velocity exceeds 0.71vs,the vibration gradually decreases until to zero because its negative effect decreases while its associative effect firstly increases and then decreases to zero;When running velocity is between 0.61vs and 0.71vs,its negative effect reach to its maximum while its associative effect reach to its minimum,resulting in diverging of vibration amplitude and decreasing of fluctuation frequency,which finally forms a spike impulse.The investigation revealed nonlinear characteristic of hydraulic cylinder under low speed condition and provided a theoretical foundation for stable operation and control of hydraulic system.