液压缸运动的非线性动态特征

根据非线性动力学的观点,通过理论分析和试验验证,研究非线性弹簧力和非线性摩擦力对液压缸动态特性的作用.得出三种不同节流调速回路工况下液体弹簧刚度随位移变化规律,发现不同工况各自呈现出软弹簧特性或硬弹簧特性.提出非线性弹簧力作用可以用有阻尼的Duffing方程描述,非线性摩擦力作用可以用Van Der Pol方程描述,非线性弹簧力和非线性摩擦力耦合作用可以用Lienard方程描述.指出液压缸低速爬行原因是在特定工况下软弹簧特性引起的"跳跃现象"和非线性摩擦力引起的自激振动共同作用的结果.方程的解在不同工作条件下具有不同的形态,说明液压缸非线性动态特性复杂多变.

NONLINEAR DYNAMIC CHARACTERISTICS OF MOVING HYDRAULIC CYLINDER

In terms of nonlinear dynamics, the actions of nonlinear spring force and nonlinear frictional force on dy-namic characteristics of moving hydraulic cylinder are em-phatically studied by means of theoretical analysis and experi-mental verification. Varying regularities of spring stiffness with piston displacement controlled by three types of hydraulic throttle-governing circuits are obtained. Soft spring property or hard spring property shown separately by above different working situations are found. The conclusions that the effect of nonlinear spring can be described by Duffing equation, the effect of nonlinear frictional force can be described by Van Der Pol equation, and their coupling effect can be described by Lienard equation are achieved. The reasons why hydraulic cylinder creeps in lower velocity are common acting results of the jump phenomenon caused by soft spring property and the self-excited vibration caused by nonlinear frictional force in specific working situation are expressed. Solutions of the equations are of different patterns in terms of different working conditions. All above illustrate that the nonlinear characteristics of moving hydraulic cylinder are complicated and changeable.