中文摘要：

利用磁流体在外加磁场作用下具有较高饱和磁化强度和较大粘度的特点，提出了采用磁流体改善伺服阀力矩马达动态特性的方法。通过把磁流体添加到伺服阀力矩马达的工作气隙，来增加力矩马达的阻尼，改变力矩马达的动态响应特性，提高力矩马达及伺服阀的稳定性，从而有助于抑制和消除伺服阀自激振荡及噪声。通过对磁流体作用机理及力矩马达磁回路的分析，给出了磁流体作用力数学模型，以及添加磁流体和不添加磁流体的力矩马达动态数学模型，采用MATLAB／Simulink对添加磁流体和不添加磁流体的伺服阀力矩马达动态响应特性进行了分析，给出了分析结果，并通过激光位移传感器对伺服阀力矩马达动态响应特性进行了试验研究。仿真及试验结果表明，磁流体可增加伺服阀力矩马达的阻尼比，从而提高伺服阀力矩马达的稳定性和抗干扰能力。

英文摘要：

As magnetic fluids show a higher saturation magnetization and larger viscosity when they are exposed to a magnetic field, a new method using magnetic fluids to improve the dynamic characteristics of a hydraulic servo-valve torque motor is presented. If magnetic fluid is filled into the working gaps of a torque motor, the forces owing to the magnetic fluid on the torque motor armature can increase the damping of the motor and the servo-valve. Therefore, the stability and dynamic performance of the torque motor can he improved. The self-excited oscillations and noise frequently appearing in a hydraulic servo-valve can be reduced. After the working mechanism of magnetic fluids and the magnetic circuit of the torque motor are studied, the mathematical models of the forces owing to the magnetic fluid on the torque motor armature and the dynamic mathematical model of the torque motor are given. By using MATLAB/Simulink software, the dynamic characteristics of a hydraulic servo-valve torque motor are simulated in the frequency domain when the magnetic fluid is applied or not in the motor. Experiments are carded out to test the dynamic characteristics of the torque motor with or without magnetic fluids by using a laser displacement transducer. The simulation and experimental results show that magnetic fluids can be used to increase the damping ratio of a servo-valve torque motor, so that the stability and anti-disturbing capability of a hydraulic servo-valve can be improved.