Research On The Method Of Variable Structure Control Of Airborne Laser Communication Terminal

Line of sight tracking problem of the airborne laser communication terminal is always the emphasis and difficulty in the field of laser communication.Because of the airborne platform of strong maneuverability, speed,motion trajectory is difficult to predict, the two sides of communication need to line of sight alignment before communication,and in the process of communication,communication terminal must be constantly on the other side of tracking.Therefore,laser communication must be based on the aim,capture,tracking(Pointing,Acquisition,Tracking,PAT).in PAT process.using variable structure control is a very good strategy.The main work of this paper is to study the tracking performance of variable structure in the airborne laser communication terminal coarse tracking link,through the comparison of simulation of variable structure control before and its improvement.Experiments show that,PAT process using variable structure control has strong robustnessand meet the accuracy requirements in.First we analysis the platform performance requirements,and then determined using the composite axis control,On the basis of introducing the system structure of coarse tracking platform we established mathematical model of each link.after a detailed introduction,from the theoretical analysis on the control characteristics and design steps of variable structure,And through the theoretical verification and simulation demonstration further illustrates the contradiction between accuracy and robustness of variable structure control,and the design of control law must know the upper bound limit interference.after the introduction of fuzzy algorithm based on the principle and design idea,the switch function as input,the switching gain as output,design the fuzzy controller.through the optimization of membership function,refined inference rules simplify the design,without clear disturbance upper bound and can take into account the fuzzy controller to control accuracy and robustness.Then,according to the demand of the system characteristics and laser communication of coarse tracking system,the coarse tracking system of each ring,according to the needs and expectations of performance,use the design and correction,and takes it as a ring after controlled sectors.to achieve the PAT complex control structure simplified reasonably.finally,on the position of key ring,using theimproved fuzzy variable structure control,the controlled system can use the invariance of variable structure control to inhibition the Outside interference and the system includes each link modeling,equivalent when the merger is not accurate,its parameter perturbation.the controller overcome the adverse factors.at the same time,the fuzzy algorithm introduced in the precondition has not changing the robust of the classical variable structure,the chattering has been effectively weakened,and improves the control precision.Finally,in the Matlab simulation,using the FVSC compare with the PID control which parameters are optimized,the results showed that,FVSC has more advantages in the fast response,accuracy and robustness.even in the disturbance, FVSC can meet the requirements PAT coarse tracking system of the airborne laser communication.after comparing with the classical variable structure, we Prove that fuzzy algorithm do not need to know the he upper bound of the premise of interference and the switching gain can dynamic follow the interference changes.FVSC can get the purpose of accurate control,at the same time,the chattering will be Weaken and ensure the Invariance of classical variable structure...