AN EXPERIMENTAL STUDY OF HYDRAULIC SERVO TORQUE CHARACTERISTICS AS A FUNCTION OF FREQUENCY,
JOHNS HOPKINS UNIV SILVER SPRING MD APPLIED PHYSICS LAB
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The servo torque stiffness is a decreasing function of frequency for a linear servo using a transfer valve with good low signal level performance. The limiting value of stiffness is that of a blocked actuator with only the oil and actuator compliance contributing to the servo stiffness at the high frequencies. Some of the linear valve servos had low stiffness in the low frequency region but approached the nominal limiting stiffness of the blocked actuator condition at high frequencies. The acceleration switching servo shows very high stiffness in the very low frequency region, appears slightly softer in the intermediate frequency range, and approaches the nominal limiting stiffness of the blocked actuator for the high frequency condition. Repeatability was good between two valves. The effect of dither on servo stiffness may either increase or decrease the stiffness depending on valve tolerance and frequency in question.
- Hydraulic and Pneumatic Equipment