Experimental and numerical investigation of self-oscillations in an electrohydraulic drive

The article presents the results of experimental and theoretical studies on the self-oscillations of an electrohydraulic actuator. It is shown that the oscillation frequency is much lower than the calculated natural frequency. These low frequencies are consistently reproducible, observed across various units of actuators and in different positions on the test stand. Several hypotheses have been proposed to explain this discrepancy, and both experimental and theoretical verifications have been conducted. The findings are as follows. Rubber connecting hoses do not affect the frequency of self-oscillations. Replacing them with metal hoses does not lead to noticeable changes. The elasticity of the cylinder support reduces the effective modulus of elasticity of the fluid, which can lead to a decrease in the frequency of self-oscillations; however, this would require unrealistically low stiffness values for the cylinder support. Verification with a sufficiently rigid cylinder base is needed. The hypothesis regarding possible cavitation of the fluid in the hydraulic distributor chamber, due to certain design features, appears most plausible. This is confirmed by calculations using a model where the modulus of elasticity depends on fluid velocity. The model incorporating dry friction can fully explain the relaxation nature of the self-oscillations.
EDN: UNDUTP, https://elibrary/undutp

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