| Gyro stabilized pod is a comprehensive photoelectric detection equipment combining light,mechanism and electricity.It possesses advantages such as high tracking precision,good instantaneity,clear image display and strong anti-jamming capability,and has extensive application in military and civil engineering fields.LOS stabilization accuracy is a key indicator for measurement of its performance.The higher the LOS stabilization accuracy,the clearer the imagery of photoelectric detection equipment is and the more accurate the information acquisition is.However,in actual working environment of pod,factors such as changing of flying attitude of carrier,mechanical vibration,flow disturbance as well as friction moment,line disturbance moment,mass unbalanced moment and so on inside the pod may affect definition of imagery,positional accuracy of target and detecting distance.Therefore,how to improve system's inhibition capability on these internal and external non-linear and uncertain disturbances is one of the key technologies to improve LOS stabilization accuracy of gyro stabilized pod.This paper,starting from improvement of stabilization accuracy and disturbance inhibition capability of gyro stabilized pod,taking developed prototype model for two-axle two-frame gyro stabilized pod as research object,carries out deep researches on aspects including working principle and composition of gyro stabilized pod,system parameter identification and modeling,fiber-optic gyro signal analysis and filter,disturbance signal inhibition and compensation,etc.Main works and innovations finished in this paper are as following:1.Firstly,it introduces general structure,main functions,software/hardware composition of gyro stabilized pod,based on which four working modes of gyro stabilized pod are researched.It analyzes linear,non-linear,uncertain factors and disturbances affecting LOS stabilization accuracy systematically based on the principle of angular motion of isolating carrier of two-axle gyro stabilized pod,and divides them into model disturbance,moment,angular velocity disturbance and sensor noise according to mode of disturbance actions.Based on this,mechanism modeling,disturbance transmission characteristic analysis and flow ring characteristic analysis are carried out for gyro stabilized pod to bring forward method combining system identification and mechanism modeling for establishment of mathematical model for gyro stabilized pod,so as to lay foundation for research of disturbance inhibition method.2.Aiming at the problem that measurement errors for noise,drifting and outliers in output signals of fiber-optic gyro affect LOS accuracy,fiber-optic gyro filter algorithm research is carried out.Based on detailed analysis of working principle for fiber-optic gyro,Allan variance method is adopted to carry out time domain analysis for null drift signals of fiber-optic gyro.Several random errors of fiber-optic gyro are identified and isolated according to the Allan variance and power spectral density relationship of null drift signals and noise of fiber-optic gyro.Then,Kalman filtering,wavelet transform threshold filteringand tracking differentiator prediction filtering methods are researched according to characteristics of noise in fiber-optic gyro signals.With the overall consideration on calculated quantity,instantaneity and filtering effect of the three filtering algorithms,it is finally deemed that in signal processing for gyro stabilized pod,the tracking differentiator filtering based on prediction method is more proper.3.Aiming at performance requirements of quick response speed and high stabilization accuracy for gyro stabilized pod,researches on robust fractional order control strategy are further carried out.Firstly,definition and character of fractional calculus are described.Aiming at that fractional calculus possesses the characteristic of infinite dimension,the numeralized implementation method for fractional controller based on Oustaloup discretization method and its improved algorithm are researched,based on which fractional controller is designed and influence caused by fractional calculus on system performance is researched.Aiming at the problem of complicate solution process and big calculation quantity for parameters of traditional fractional controller,a fractional controller parameter setting method based on vector method is brought forward.Uniqueness of robust fractional controller parameters based on vector is certified and the calculation process for solution of fractional controller parameters is simplified.Designed fractional controller and integer-order controller is adopted for simulation and test study.Results of tests for step function response characteristics,sine tracking performance,disturbance isolation capability and model robust shows that systems adopting fractional controller has advantages such as quick response speed,small overshoot and strong disturbance isolating capability.4.Aiming at performance requirement of strong disturbance resistance for gyro stabilized pod,research on disturbance observation method for gyro stabilized pod is further carried out.Starting from disturbance inhibition principles of “active disturbance rejection”and “positive disturbance rejection”,structural composition and disturbance rejection performance of disturbance observer and self disturbance rejection controller are analyzed,with their structural composition and control rate given;aiming at the problem that high order observer may easily cause phase lag and affect stabilization of the system,order-reduced self disturbance rejection controller design method is brought forward;aiming at the problem of noise containing in measured signals,self disturbance rejection controller method based on tracking differentiator filtering is brought forward.According to disturbance observation principle,designed disturbance observer and self disturbance rejection controller is adopted for stimulation and test study.Results of tests for step function response characteristics,sine tracking performance,disturbance isolation capability and model robust shows that systems adopting disturbance observation has better inhibition on external and internal disturbances.5.Aiming at control requirements of high accuracy and strong robust for gyro stabilized pod,a kind of fractional disturbance observation control method is brought forward innovatively.The method absorbs advantages of quick response speed and high stabilization accuracy of fractional order control rate,and is able to satisfy the requirement of highprecision stabilization control of gyro stabilized pod;meanwhile,it absorbs the advantage of strong disturbance rejection capability of disturbance observer,and is able to overcome influence caused on system working performance by external disturbance and uncertain factors of the system.According to fractional disturbance observation principle,it brings forward a kind of fractional order self disturbance rejection controller innovatively.The controller is composed by three parts: fractional tracking differentiator arranged with transient process;fractional extended state observer extracting fractional order state information and overall disturbance information of the system;fractional order controller generating control quantity according to error information.Aiming at the problem of high-order observer's phase lag and measurement noise,fractional order reduced self disturbance rejection controller design method and self disturbance rejection controller method based on fractional order tracking differentiator filtering are brought forward.Finally,simulation analysis and tests are carried out to verify that the above mentioned method,when applied in pod system,can effectively improve dynamic performance and disturbance inhibition capability of the system. |
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