On-off Control Theory And Application In Guidance And Control

On-off type actuator is widely used in guidance and attitude control of missile,to achieve rapid maneuver of missile with hign precision in atmosphere or exoatmosphere and trajectory correction of low cost guided munition.However,it is full of challenges to design control law for the on-off actuator.This paper focuses on the key techniques in the application of on-off control on the guidance and control of flight vehiecles flying in thin air or exoatmosphere and low cost guided munition.By referring to the latest research progress on related techniques such as optimal switching control,terminal guidance law with multi-constraints,and the stability of the parasitic loop of the seeker and so on,this paper studies the key techniques systematic and in-depth on designing on-off attitude controller under disturbance,on-off guidance law with constraints,correction of the unstability of guidance loop due to the parameters mismatch between parasitic loop of the seeker and on-off controller,decoupling of rolling guidance loop.The main research results are as follows.For the attitude control of hypersonic flight vehicle flying in the thin air with external disturbance and model uncertainty,this paper designs a robust optimal on-off controller by combining disturbance observer and optimal switching control theory.Disturbance observer is used to estimate disturbance,and then aerodynamic rudder is utilized to compensate the disturbance.Based on the nominal model after compensation,model-based Approximate Dynamic Programming(ADP)is used to search the optimal switching sequence.Simulation results show that the designed optimal on-off controller can control the attitude of flight vehicle with high precision under disturbance and model uncertainty.For the performance analysis of attitude pursuit guidance law using impulse-force control which is adopted in low cost terminal correction munition,firsrtly,varying period discrete modeling of impulse force control guidance loop is completed by finding the equivalence between impulse force control guidance system and Amplitude Pulse Frequency Modulator(APF-M),and then,the impact of pulse jet impulse,pulse jet ignition waiting time and gravity on the guidance loop is obtained via analyzing the guidance loop stability using sliding-mode control theory.Moreover,bias threshold gravity compensation method is proposed to slow down the divergence speed of boresight error,which means reducing the terminal miss distance.For flight vehicle flying in exoatmosphere using impulse-force to change flight trajectory,an Optimal Pulsed Guidance Law(OPGL)with intercept angle constraint is deduced via extended maximum principle.The OPGL is eventually transformed to solve the Two-Point Boundary Value Problem(TPBVP).To decide a shooting point,an efficient adaptive algorithm is proposed to solve TPBVP by combining Particle Swarm Optimization(PSO)and Kriging surrogate model method.This method can deal with the problem that the gradient matrix of terminal state vs costate initial value.For the guidance problem using constant impulse-force as actuator,an Optimal On-off Guidance Law(OGL)with intercept angle constraint is proposed based on ADP theory.This guidance law need train Neural Networks to get the map from state to optimal cost to go.And then,this map relationship is used to obtain optimal switch command at each instant.OGL has feedback property,and it need not solve TPBVP to obtain the optimal command.Simulation results show that the aforementioned guidance laws can meet the requirement of miss distance and impact angle simultaneously.There exists a great instability risk of parasitic loop caused by seeker disturbance rejection rate when on-off control is used.The influence of seeker disturbance rejection rate on the stability of on-off guidance loop is analyzed.Firstly,a unified dynamic model is proposed for gyro-stabilized seeker and rate-gyro seeker via equivalent transformation principle of loop.And then,equivalent Lure' model of on-off guidance loop which contains isolation parasitic loop is built to analyze the stability of on-off system.Based on the constructed model,describing function is utilized to analyze the stability of parasitic loop.The influence of cable torque and friction torque on the region of parasitic loop under different flight vehicle's and modulator parameters are obtained.Finally,lag compensation method and adding disturbance observer to compensate disturbance are put forward to improve system's stability.Simulation results show that limit circle is not appeared again in the guidance loop under the attitude disturbance of flight vehicle.It avoids repeat opening.For the influence of rolling cross coupling on guidance loop,frequency method is used to analyze the factor which affects stability of guidance loop.Disturbance Observer Based(DOB)control is designed to decouple the rolling guidance loop.Five common error sources of rolling cross coupling are unified as rolling angle error.Analytical solution of the tolerance of rolling cross coupling in guidance loop is obtained when continuous actuator is used.For rolling cross coupling guidance loop which contains pulse modulator,decription function method is used to analyze the influence of rolling angle error,body dynamic parameters,and modulator parameters on guidance loop.Furthermore,frequency domain disturbance observer is designed to compensate the disturbance caused by rolling cross coupling.And then,decoupling control of rolling missile is realized.