Abstract: The electro-hydraulic torque load simulator is typical torque servo control systems with motion disturbance. The conventional mathematical model is too simple for the study on the high precise load simulator, especially on the description of motion disturbance. Normally the structure-invariable principle is adopted to reduce disturbance based on the simple model. There some difference between theory and practice. The complex mathematical model of the load simulator is derived, which discloses the characteristics of the system deeply. It proves the extraneous force is not only related to the actuator velocity, but also related to the actuator accelerator. Furthermore, the influence to the system performance is analyzed. The test proves complex mathematical model and indicates the validity for reducing the disturbance by speed and accelerator feedforward.

Key words: Mathematical model Structure-invariable principle, Electro-hydraulic load simulator Extraneous force