Sliding Mode Control Method And Simulation For Scanning System Of Aerial Camera

The high precision photoelectric stabilized platform,running on Near space,has high security.Compared to the satellite platform, the instrument on it could acquire much higher resolution images.with a strong military and commercial applications and has aroused extensive research.The camera system on the platform by means of cam mechanism to coordinate the movement of the Charge-coupled Device(CCD) array in the image acquisition process,making the CCD array moving back and forth in the steady speed segments of the scanning exposure.Hardware configuration of the scan-ning system causes cycle characteristic disturbing moment on the torque motor shaft in the image acquisition process,impacting the steady speed precision of CCD array,reducing the acquired image quality of the target.To suppress disturbing moment impact on sys-tem performance in the steady speed segments,and to achieve a smooth transition in the transmission section of the CCD array movement,in this paper, variable structure control method is used to achieve load camera scanning process control.Firstly.based on the kinematics of cam and follower,acquire the simplified model of disturbance torque on the motor shaft,and factors that affect the size of the disturbance are analyzed.Joint torque motor to establish the overall model.The disturbing moment is transformed into a disturbance voltage to acuuire a block diagram of the scanning sys-tem.Then,based on the basic principles of variable structure control,taking second-order system as example,introduct the basic principles and design methods of assisted unidi-rectional sliding mode control.For solving the contradictions of chattering eliminating and speed of convergence of sliding mode controller with unidirectional auxiliary sur-faces (UAS-SMC) based on the exponential approach law,a UAS-SMC method based on improved exponential approach law is designed.Finally,the designed controller is ap-plied to physiognomy scanning system,and the effect of switching surface parameters on system performance is analyzed.Simulation results show that the designed novel UAS-SMC method can reject dis-turbances in the system scanning process and improve the scanning precision of system steady speed segment.At the same time,the amount of controller chattering has been effectively suppressed.