The Design Of Shipborad Tracking Radar Digital Servo System With Two Degrees Of Freedom

The servo system of a tracking radar is an important portion of the radar,and its performance affects the precision of the radar directly. With the increase of the velocity and maneuvering of the moving targets such as modern missiles, aircrafts,it requires dynamic performance of the servo system more and more. The servo system of shipboard tracking radar must deal with not noly wind torque disturbance,measurement noise,and parameter changes,but also ship shaking,which require good robustness of the servo system. It is difficult to ensure the capability of reference signal tracking and the capability of disturbances attenuation simultaneously for traditional single degree of freedom controller, the tracking of reference signal and the attenuation of disturbances are adjusted separately to improve the quality of control by two degrees of freedom control structure. In order to improve the tracking performance without changing robustness of the system,two degrees of freedom controller is worth trying.In this paper,the theory of two degrees of freedom controller is applied,FOG is used as velocity sensor,a full digital servo system based on TMS320F28335 DSP is designed. A method of determining feedforward controller of two degrees of freedom system based on step response curve of single degree of freedom system is proposed. Digital closed-loop FOG is researched. Azimuth servo system is designed by using classic frequency domain analysis method, each loop mathematical model and controller transfer function are obtained by using MATLAB/Simulink. For radar tracking state, in order to reduce the dynamic lag by making the system responds to tracking error and angular velocity signal faster, two degrees of freedom control structure is established for the velocity loop, simulation results show that dynamic performance of the system is enhanced apparently by two degrees of freedom control structure. The robustness of the system is verified by sensitivity analysis. One anti-windup controller is introduced, simulation results show its effectiveness.In hardware design,servo processor design based on TMS320F28335 DSP, interfaces of the processor and sensors design,PWM power amplifier design,and RDC converter design are described in detail.In software design,High-speed asynchronous serial communication with FOG is realized by SCI hardware interrupts.Two timer interrupts is designed,one timer interrupt handles high-frequency A/D conversion of armature current signal,different rates of each loop controller regulation,and the output of PWM signals,the other timer interrupt handles synthesis of RDC codes,parallel communication with radar computer,the implementation of the work state modules of the servo system. Discretization and computer implementation of controller transfer function is researched.Digital current loop is realized.Isolation experiment and the tracking of simulated moving target experiment are carried out. Isolation experiment illustrates that the servo system has good disturbance attenuation capability, the tracking of simulated moving target experiment tests dynamic tracking accuracy of the servo system.