Research On Angle Of Depression Control System Of Aerial Camera Based On Disturbance Observer

Aerial camera because of its advantages of high efficiency, strong purposebecame one of the main loads in the form of aerial remote sensing device. In order toextend the horizontal field of view, aerial panoramic camera uses scanning imagingmode. As the focal length increases, in order to reduce space and weight of theaircraft platform, considering the separation between shaft of the scanning systemand shaft of detector system, forming two parallel structures, namely scanningmechanism and the elimination of image rotation mechanism. In this paper thedepression angle control system is taken as the research object, in view of threekinds of structure such as single motor driving cable drive system, no mechanicalcontact dual motor drive system and dual motor driving cable drive system, studyand solve the problems of disturbance suppression for depression angle controlsystem, the vibration suppression based on the cable drive and fast and highprecision positioning and other technical problems. based on the disturbanceobserver based control strategy is applied to control the angle system, and from thetheoretical analysis, numerical simulation and application three aspects to carry onthe research on the control technology based on disturbance observer. Thedisturbance observer based control strategy is applied to depression angle controlsystem, and from the theoretical analysis, numerical simulation and application three aspects to carry on the research on the control technology based on disturbanceobserver.Around the performance index technical difficulties of the XX-CCD cameraposition angle control system, the main work and contributions are given as followsin this thesis.1. From the aspects such as the synchronization control accuracy, speed steadyprecision and positioning precision steady precision, analyzes respectively theimpact of key performance of the aerial camera depression angle control system onaerial camera imaging process. A mathematical model for velocity loop controlobject is established, which takes the current loop as the inner, the velocity loop asthe outer loop. Stiffness analysis model is established and analyzes the key factorsinfluencing the system stiffness. For both single motor drive and dual motor drivecases, a mathematical model based on the cable drive system is established,discusses the reason causes torsional vibration generated by flexible cable drive.2. In view of the complex disturbance environment under the condition ofairborne, from the point of disturbance observation and compensation, the articlestudy on the composition principle of the disturbance observer, discusses thedisturbance observer stability condition in the compensation inner loop and thefeedback loop. In the design of low pass filter, from the integer order filter designtheory and the theory of fractional order control two aspects analyzes the designmethod of low pass filter respectively, using the sliding mode control method tocompensate the observation error on the disturbance observer, improves thedisturbance observer compensation ability for high frequency, nonlinearperturbation.3. In the single motor driving cable drive control, in the view of disadvantagesthat the system resonance frequency is low and system is prone to torsional vibration,a design method that by changing the disturbance observer torque feedbackcoefficient which is equivalent to changing the resonant frequency of the system isproposed, the method can effectively inhibit the ability of the system for torsional vibration suppression. In the dual motor control, first of all, according to the controlsystem without mechanical connection, control strategies based on multi informationinteraction with and without disturbance compensation is designed respectively, andcontrol strategy with the disturbance compensation is converted into sum anddifferential mode control strategy based on the acceleration level. The two methodscan realize the independent design between the speed/position controller andsynchronous controller and are easy for practical application. Then, for the controlsystem with wire rope connection, first the torsional vibration suppression method isstudied, and take the disturbance torque deviation between the two motor controlsystem as the feedback object, a tension control method is designed, this method bymeans of the cable tension control to guarantee the stiffness of system, so that thesystem has the high resonance frequency and good control performance.4. For structural future of single motor control system and of dual motor controlsystem, the position loop adopts fuzzy control and velocity and accelerationfeed-forward control respectively, and velocity and acceleration command signals isobtained by nonlinear tracking differentiator. These two methods both can achievefast positioning for depression angle control system, and anti disturbance ability isverified by experiment.In this paper, the performance comparison in three working structure for thedepression angle control is implemented by experiments which provides a basis forthe design of aerial camera depression angle system.