Abstract
A nonlinear dynamic model is developed to analyze the stability of a pilot-operated valve-control hydraulic system. The dynamic model includes motion of the valve spool and fluid dynamics in the system. Characteristics such as pressure flow across the valve port and orifices, pressure, and flow rate in valve chambers are taken into consideration. Bifurcation analysis is proposed and examined by numerical simulation results when the feedback orifice diameter changes. The effects of different system parameters such as pilot-operating pressure, spring stiffness, and overlap of inlet port on the stability border of the system are studied by two-dimensional bifurcation analyses. The study identifies that bifurcation can occur in the system and lead to sustained self-excited vibration with parameters in certain region of the parameter space. It suggests that the vibration can be effectively predicted and prevented by selecting system parameters from the asymptotic stable parameter region.
Highlights
Features of a pilot-operated hydraulic actuator servo system, such as large flow rate, excellent pressure regulating, and high payload capabilities, make it suitable for actuator servo systems in various fields ranging from molding industry to automobile.[1]
The pilot-operating pressure corresponding to the minimum value of orifice diameter on stability boundary increases and the minimum orifice diameter value on the boundary increases
Bifurcation analysis is performed using a verified nonlinear dynamic model for the hydraulic system composed of a pilot-operated spool valve and a piston
Summary
Features of a pilot-operated hydraulic actuator servo system, such as large flow rate, excellent pressure regulating, and high payload capabilities, make it suitable for actuator servo systems in various fields ranging from molding industry to automobile.[1]. Acontrol Area of feedback chamber, Afb Jet angle, u1 Jet angle, u2 Valve spool diameter, dvalve Nominal orifice radius, rori[1] Nominal overlap of inlet port, L1 Nominal underlap of exhaust port, L2 Area of piston chamber, Ac Mass of piston, mpiston Damping coefficient, cp Spring rate, kp Spring pre-compression force, Fpre. The system can keep stable with 6-mm orifice under pilotoperating pressure above 0.56 MPa. To examine the calculated stability boundary and study dynamic responses of the system, numerical simulation with different parameters is performed in software MATLAB using solver ode[45], which implements a Runge–Kutta method with a variable time step for efficient computation. Effects of system parameters on stability boundary of the system under variable operating pressure are analyzed
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