A Study On Working Trait And Advanced Measurement & Control Method Of Seeker Servo Mechanism

Seekers are core parts of accurate guide weapons, used to search, recognise and track targets automatically. A seeker servo equipment is executive mechanism to provide stabilization of LOS and track targets, thus its performance has a direct effect on the seeker. As complicated optics-mechanism-electronics incorporate production, the design of the equipment relates to several subjects such as optics, inertia technique, mechanism and control engineering, and its capability is affected by many error factors. The current study on the mechanism lacks in view of the whole homing system, because it regards the equipment as independent mechanism, and the design method is mostly the traditional control technique which is difficult to obtain good performance.With the development of accurate guide weapons, it is demanded to apply modern advanced control algorithms to improve the performance of the equipment. Concerning that, this paper starts with the method of system modeling and simulation to study on working process of the equipment. According to the influence of the main error factors, the paper has a deep research on four aspects including the restraint of gyro's random error, robust optimization of stabilization loop, matching control of the tracker and the restrain of disturbance respectively.The writer's research is mainly focused on the following 6 sections:1. For the sake of reflecting the effect of error factors and performance of the servo equipment on the seeker's and the missile's guide accuracy, the working process of the equipment is modeled and simulated, which provides references for the choosing of its main indexes and the subsequent measurement and control problems. Besides, the dynamics equations of the equipment are deduced with space kinematics and Newtonian mechanics, and the mathematical models of the equipment are also established.2. Owing to the equipment's trend of miniaturization, the paper has carried out an investigation into the application of MEMS gyro in the mechanism. The effect of gyro's random error on stabilization accuracy is analyzed, which proves the feasibility of applying the MEMS gyro in the equipment. In order to restrain the effect of gyro's random error, several advanced filtering algorithms are applied to process the gyro's signal, the performance of which are verified and compared through experiments.3. Considering the uncertainty of the system model, the paper puts forward a kind of two-degree-freedom internal model controller for stabilization loop that has good performance in attenuating disturbance as well as tracking command. In order to endow the designed internal model controller with stronger robustness when dealing with model mismatch, the controller's design is transformed into typical optimization of H∞robust. The H∞Controller of stabilization loop is designed by means of the techniques of multi-rate sampled control theory, such as Jump alternation and Lifting operation, by which the control system can obtain good dynamic response between two points of consecutive sampling time. Compared with traditional controllers, the presented controller can reduce the effect of disturbance, model mismatch and multirate sample, therefore, it can distinctly improve the precision and robustness of the equipment's stabilization loop.4. Concerning the influence of the tracker's error factors on the equipment's tracking performance, research is carried out to match the tracking loop with the tracker. Based on the model of grey cloud system, the model of tracker is established. By means of filtering and prediction with grey model, the influence of noise and lag on the control system can be reduced distinctly. Regarding to the effect of low sampling output of tracker, a kind of s multi-rate input atisfactory PID controller is presented, which can increase the control input within fixed time and enhance the stabilization margin. The choosing of parameters of multi-rate PID controller is transformed into the optimization constrained by poles and variance, so the tracking control loop reaches the promised dynamic and precision indexes. The presented control method can reduce the influence of tracker's error factors on tracking loop, and improve the performance of the equipment's precision, dynamic and robustness to track targets.5. As disturbance is the main factor to reduce the equipment's control precision, the method based on multi-rate output feedback is studied to attenuate disturbance. With time delay estimation algorithm, a kind of multi-rate output disturbance observer is brought forward, which improves the capability of control system to attenuate disturbance without reducing the system's stabilization. According to the equivalence between the feedback of the multi-rate output and the states, a multi-rate output variable structure sliding mode controller with disturbance observer is put forward, which needs neither sensors to measure the states of the system, nor any other state observer. Besides, the control algorithm has less switching ripple, compared with VSS control algorithm.With its advantages of simplicity and strong anti-disturbance, the presented method is promising in high precision servo systems such as seeker servo mechanism which is restrained strictly on volume and mass.6. The control algorithms presented in this paper have been verified through experiments. The command characteristics of tracker and the disturb torque are simulated, and a virtual working condition of seeker servo equipment is thereby constructed. Finally, the presented control algorithms are realized by dSPACE, and the experiments are made to validate the superiority of the method studied in this paper.