Dynamic Considerations in the Application of Hydraulic Motors 720768

Speed and pressure response of a hydraulic motor to changes in flow (stroking a directional valve) is predicted for typical mobile hydraulic circuits. A simplified approach was used to derive the equations for a system consisting of a pump, directional valve, and a motor with an inertia load. The speed and pressure response to increases in flow was studied by solving the equations on an analog computer.
Expressions for the natural frequency, ωn, and the damping ratio, ζ, were written in terms of motor displacement, load inertia, system compliance, and system leakage coefficient. The response to increases in flow is presented in terms of the damping ratio.
The response to decreases in flow is discussed for directional valves with both open and closed cylinder ports.
The effects of the simplifying assumptions of the valve stroking rate and of the valve cylinder port configuration are discussed.


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