Reseach On Adaptive Robust Control For Ring Permanent Magnet Torque Motor Used In Compound Spindle Head

Compound spindle head is one of the key features used in five-axis machining center. The background of this thesis is based on the projects supported by Liaoning Province Department of Education and Liaoning Province Science and Technology Agency. The research object of the thesis is ring permanent magnet torque motor servo system that drives compound spindle head directly. According to the characteristics of the ring permanent magnet torque motor servo system, the requirements of robustness and tracking accuracy should be considered for the compound spindle head servo system. In addition, the input saturation problem at certain stage reduces the servo system performance in actual operation. Thus, adaptive robust control theory combines with backstepping design method to study those problems of the servo system, including parameters variations, external disturbances and other uncertainties. The main contents are as follows:For the uncertainties existing in the compound spindle head torque servo system, and considering that the main factors are the external disturbance and parameters variations, an appropriate mathematical model of the system is established. Then the adaptive robust control method is used to reduce the impact on system performance due to external disturbances and parameters variations to ensure the final tracking accuracy of the system. The robust control structure of adaptive robust controller designed is constructed by deterministic robust control technology proposed on the basis of Lyapunov second method, which is used to guarantee a prescribed transient performance. The adaptive control structure based on discontinuous projection algorithm is used to achieve parameters on-line identification, in order to approach to the real value of uncertainties and reduce the effect of uncertainties on the servo system. To further improve the servo performance, a desired compensation adaptive robust controller is then designed, in which the system uncertainties are off-line estimated according to reference trajectory only and the effect of measurement noise can be also reduced. The control strategies designed both have strong robustness for external disturbances and parameter variations and ensure the final tracking accuracy of the servo system.To ensure reliable operation of the servo system, especially for input saturation problem due to extremely great external disturbances and parameter variations, it will cause the instability of system. In the paper, a saturated adaptive robust controller is designed on backstepping method, which combines saturation functions with adaptive robust control strategy. A virtual control law is designed to guarantee error signal to be bounded and convergent. Non-decreasing functions are constructed to handle actuator saturation problem to limit control input, while parameter estimation based on projection algorithm is employed to achieve final tracking accuracy. The designed method enables servo system to achieve good servo system performance and final tracking accuracy in normal and input saturation situations.