Research On Coarse And Fine Dual Stability Control Of Aviation Photoelectric Stabilized Platform

Aviation optoelectronic stabilization platform is widely used in reconnaissance,tracking,target positioning and other fields.For ultra long range reconnaissance of tens or even hundreds of kilometers,the Los of the platform must be stable enough to get clear images and realize tracking.Due to the imperfection of motor body,mechanical resonance,sensor noise and other hardware problems,and the influence of mass imbalance,airframe vibration,atmospheric turbulence and other real-time disturbances on the system,it is difficult for the platform Los to accurately track the given value.At present,under the condition of 2°/2Hz swing,only relying on the frame system can achieve the maximum LOS stabilization accuracy of 25μrad,which is difficult to meet the requirements of ultra long range imaging tracking.In order to make up for the defects of low bandwidth and poor anti-interference ability of the framework system,it is necessary to introduce a second stability system on the premise of the first level stability of the frame system to compensate the residual error after the first level stability.The control accuracy of the first level stabilization system is restricted by many factors.It is necessary to consider and optimize the servo system from three aspects:structure design,hardware design and efficient algorithm,so that the residual error after the first level stabilization is within the compensation range of the second level stabilization.In order to reduce the volume and weight of the platform and ensure that the output torque of the motor is large enough,the permanent magnet synchronous motor with higher power density is used as the direct drive motor of the framework.However,compared with DC torque motor,permanent magnet synchronous motor(PMSM)has some disadvantages,such as cogging torque disturbance and "dead time effect" of the driver,which makes it difficult to control,especially for low-speed servo stabilized platform.Fast steering mirror(FSM)used to adjust the optical path is widely used in the long-distance photoelectric reconnaissance platform as a secondary stabilization system.Mechanical resonance is a common problem in fast steering mirrors supported by flexure hinges.Mechanical resonance seriously limits the closed-loop bandwidth of the fast mirror system,and may cause chattering or even instability of the system.Due to the limited bandwidth and anti-interference ability of the first level stability,the medium and high frequency part of the body vibration will be transferred to the fast mirror system,and the existence of real-time disturbances such as the mass imbalance torque of the fast mirror itself and the change of the system model caused by the change of the working environment,it is difficult for the fast steering mirror system to maintain high stability accuracy,so high performance control strategy must be designed according to the specific characteristics of the system.Based on the above background,this paper makes a detailed analysis and algorithm research.The main work is as follows:1.The basic theoretical background of framework system is introduced.Aiming at the cogging effect of permanent magnet synchronous motor(PMSM),an off-line iterative learning controller(ILC)in space domain is designed to suppress it.For the motor moving at any time,according to its mechanical angular position,the current cogging torque is estimated by linear interpolation method and compensated by feedforward.Aiming at the problem of strong chattering in traditional sliding mode controller(SMC),a sliding mode controller based on a new reaching law is designed.Compared with PI control and traditional sliding mode control,the speed tracking experiment shows that it is a more effective control method.An extended state observer(ESO)is designed to compensate and suppress the real-time disturbances of the frame system.2.In order to verify the effectiveness of the proposed off-line ILC + SMC + ESO compound control scheme for the frame system,a comparative control scheme of offline ILC + PI + disturbance observer(DOB)is designed,and the uniform speed,sine wave and triangular wave speed tracking experiments are designed to prove the superiority of the proposed control scheme.3.This paper introduces the basic principle of the fast mirror driven by voice coil motor,deduces its mathematical model,and obtains its actual frequency response by frequency sweep method.According to the mathematical model,the nominal model is obtained by fitting the actual model with the second-order oscillation link.Aiming at the common problem of "resonance" in fast mirror system,"speed feedback method" is used to suppress it.The influence of differentiator type in "speed feedback method" on the new system is analyzed in detail,which points out the direction for the follow-up research.The influence of the feedback coefficient on the noise introduction and the closed-loop bandwidth of the new system is clarified from the theoretical analysis and the actual system experiment,and the setting method of the feedback coefficient is determined.For the disturbance residual after mechanical damper and first-order stabilization,an adaptive robust controller is designed to suppress the external disturbance,and its superiority is proved by the comparative experiment on the shaking table.In order to improve the response speed of the fast reaction system,a zero phase difference controller is designed.Through the closed-loop sweep and step response of the system,it is proved that the zero phase difference controller greatly improves the bandwidth and response speed of the system.4.The stability experiments of the photoelectric stabilization platform are carried out on the shaking table and the vibration table,and the stability effects of the frame system with different control strategies are compared,which proves the superiority of the composite control scheme proposed in this paper.In the 2 ° / 2Hz shaking experiment,the frame system stability accuracy of the system reaches 23.6μrad.The stability accuracy of the system before and after the fast mirror was compared.Through the actual collimator experiment and resolution plate imaging experiment,the final stability effect is demonstrated.