Application Research of State Observer in Angle of Depression Control System of Aerial Camera
|School||Graduate Schoo,Chinese Academy of Sciences|
|Keywords||aerial camera full order state observer reduced order observer angularacceleration discrete sliding mode control acceleration feedback control multiple mode switched control fuzzy control|
Aerial camera as one primary load form of aerial remote sensor with advantages ofhigh efficiency, strong purpose and high mobility is used to obtain ground information.With the development of science technology and the promotion of aerial cameratechnological level, aerial camera of high precision positioning, long focal and dualband become a trend in future. State observer basis of modern control theory is appliedinto aerial camera for the first time in this dissertation. The control plant is the angle ofdepression control system of a long-focal CCD camera. The research on state observeris from three aspects of theoretical analysis, numerical simulation and application. Theangular acceleration observed is applied in speed control and position control of theangle of depression system. Compared with traditional control method, the dynamiccharacteristics, steady precision and disturbance rejection ability of the angle ofdepression control system are improved by modern control methods based on stateobserver.The mathematical model is given by frequency domain method firstly. Based onimplementation of state function and linear system theory, state observer is constructed.Lyapunov’s law is used to prove stability of state observer. Pole placement, phasecharacteristics and robustness of state observer are analyzed.State observers ofdifferent inertial space are studied according to feature of measuring element and the feasibility of aircraft rolling attitude angular estimated is verified by theoreticalanalysis and numerical simulation.Discrete sliding mode control theory with different reaching law is analyzed andnumerical simulation show that discrete sliding mode control method with powerfunction reaching law can not only eliminate the problem of chattering, but alsoimprove dynamic characteristics. A method of acceleration feedback control isproposed.The effect of system closed-loop bandwidth caused by acceleration feedbackgain is studied and the torque disturbance rejection principle is analyzed.The digital controller is designed used the method of multiple mode switchedcontrol based on T-S fuzzy inference which can realize combining accelerationfeedback control and discrete sliding mode control effectively. Speed control isachieved with setting time of0.128second and precision of0.875%when referenceinput is6°/s. The external disturbance with software programming and manual to provethe ability of disturbance rejection.Compared with conditional lead-leg method, themethod in paper can obtain uniform brightness image.Position control of SISO fuzzy control is achieved rapid and no overshoot locationduring working range.The photography efficiency test indicates that photographyefficiency is risen from58%to72%and more image information can be obtained. Thephotograph begin position test verified the maximum relative error of ground widthcaused by control method is only0.4%, which meets the index requirement.The work of the dissertation indicates that modern control methods based on stateobserver can attain and even exceed the control performance of traditional controller. Anew thought is presented for design of aerial camera control systems.