Reasearch On Attitude Measurement And Control Strategy Of Stabilized Platform For Shipborne Weapon Aiming System

Water-borne carriers are easy to be influenced by wind waves when operating on the water. Passive isolator can reduce the effects of high-frequency and low-amplitude vibration, but is not so good to low-frequency swing. Hence stabilized platform technology is proposed to guarantee the stabilization of shipborne weapon aiming systems in the dissertation. Stabilized platform is the device which can keep the stabilized objects in a stable attitude under the actions of external disturbances, or make the stabilized objects work following the given orders in inertial space. The dissertation focuses on the two-axis parallel platform, studies the effect rules of error sources, attitude measurement and intelligent control, means to develop a shipborne stabilized platform which has the characteristics of quick reaction and strong anti-disturbance capability.The overall structure of shipborne stabilized aiming system is described firstly, the working modes of aiming system and stabilized platform are introduced meanwhile. Stabilized platform is a high precision equipment which composes of mechanism and electronics, and the precision influencing factors are numerous. In the dissertation, error sources are sorted and some hard unquenchable ones are dicussed in detail. In the stabilized aiming system, digital magnetoresistive compass and Attitude and Heading Reference System (AHRS) are used to feed back the states of aiming system and stabilized platform respectively. Outputs of digital magnetoresistive compass are easy to be influenced by magnetic environment. To solve the problem, a two-step integrated compensation method is proposed which uses least squared method to compensate firstly and uses BP network method to compensate the remaining errors. For micro-mechanical gyro in AHRS, Singer model is applied in direct modeling of gyro signal, and a gyro signal filtering method based on Interacting Multiple Models (IMM) is proposed.The PIOGRAM diagram method can describe coordinate conversion simply and intuitively. With PIOGRAM diagram, conversion relationships of different coordinate systems are established, and kinematics analysis of executive mechanism and disturbance-isolation theory analysis are finished. To realize high precision control, the three-loop control structure of stabilized platform which includes current loop, speed loop and position loop is modeled. Disturbance Observer (DOB) is applied in the speed stabilization loop, the dissertation indicates that classical DOB can suppress external disturbance well, but has non-ideal performances of suppressing measurement noise and model perturbation. In view of the problems, a novel improved DOB is proposed which uses an additional control signal to compensate system outputs in feedback channel. In the position tracking loop, a compound controller combined with feedback and disturbance forward is designed, and Grey Prediction Control method is used in feedback channel to reduce the influence of delay link. The critical qualification of grey prediction step is discussed in detail, and a grey prediction controller with variable steps is designed. In forward channel, the prediction method of carrier motion attitude is studied. After finishing the chaos identification of attitude series, the L1norm change laws of reconstructed phase points are studied with residual GM(1,1) model, and predicted values of time series are obtained with L1norm inverse solution. In the end, the theories and technologies discussed in this dissertation are tested with numerical simulations and experiments, results indicate that the designed platform system is feasible.