Modal and Natural Frequency Sensitivity Analysis of Electrohydraulic Stewart Platform

Abstract

Electrohydraulic Stewart platform is a multi-input and multi-output mechanical-hydraulic coupling system, which has the advantages of large power-to-weight ratio and high accuracy. It has been widely used in construction machinery, aerospace, and other fields. In the actual working process, especially in the high-speed motion, the Stewart platform movement process will produce a large impact and vibration and then affect the stability, accuracy, and service life of the platform. When the frequency of the external excitation coincides with the natural frequency of the electrohydraulic Stewart platform, it may cause the failure of the platform. Therefore, based on the relationship between the volumetric elastic modulus of the gas-bearing oil and the hydraulic stiffness of the leg, a mechanical-hydraulic coupling dynamic model of the electrohydraulic Stewart platform was established, and the natural frequencies and modal shapes of the platform were analyzed under typical conditions. The sensitivity calculation formula of the natural frequency of the system on the upper platform mass and the hydraulic stiffness of the outer leg is given by an analytical method, and the influence law of the upper platform mass and the outer leg stiffness on the natural frequency and the sensitivity of the electrohydraulic Stewart platform under typical conditions is discussed. This study can provide theoretical support for dynamic optimization of the electrohydraulic Stewart platform.