Airborne radars are used in Aircraft interception, Air to ground, air to air, air to sea missions, Close air support and Ground target detection and tracking. Airborne Radar are also used in airborne collision avoidance system (ACAS). They can detect relative location of other aircraft. Radar servo system is designed to provide good tracking performance. In order to design a radar servo system with satisfactory response for an air defense missile, the four loops are chosen. Frequency domain and time domain methods are used for performance analysis. The design approach and criteria of the four loops radar servo system is outlined in this report. With these criteria, a servo system is designed. Then the effects of every loop are analyzed.The stability and robustness of the servo system is depends on the stability margin. Stability of the system can be determine from bode plot of individual loop by calculating the gain margin, phase margin, gain cross over frequency and phase cross over frequency. Unstable system can make stable by tuning of poles and zeros of control loops. Besides stabilizing margin, tracking precision and transient process performance, the bandwidth is an essential factor.
To make sure that the system may respond quickly, track accurately, adjust speed widely, a large bandwidth may be needed. In addition, the acceleration error decreases if the bandwidth increases. Moreover, the wind moment is proportional to the cube of the diameter of the antenna. To design an angular velocity loop with big bandwidth is to restrain the misalignment caused by the wind. However, the magnitude of the angular noise of the target and the thermal noise in radar receiver was proportional to the square root of the bandwidth. Thus the bandwidth of the system couldn't be too large, and it should be lower than the half of the frequency of the structural vibrations, otherwise there may be stability problem. It is a trade off to design a reasonable bandwidth.
Integrate design for Servo System was based on Genetic Algorithm and Matlab. After analyzing servo system model and its dynamic characteristics, research about parameter optimization and simulation was done using Matlab. Electromechanical coupling model and the optimization model which includes the integrated design of structure parameters and control parameters were built based on model of mechanism transmission system and electricity control system. Electricity control system of the airborne radar servo system has three feedback control loops. Genetic Algorithm was used to apply integrated structure and control design on the optimization model.