Mid-Terminal Phase Guidance And Control Methods Research Of Air-Breathing Hypersonic Vehicle

Maintaining the peace and stability of the motherland,realizing the reunification of the motherland and the great rejuvenation of the nation are the responsibilities and ardent expectations of every Chinese sons and daughters,as well as the source of spiritual strength for which generations of national defense researchers have dedicated their youth.Air-breathing hypersonic vehicles not only represent the highest level of science and technology,but also a symbol of national defense and comprehensive national power.In the face of the increasingly complex environment around China’s southeastern sea,the development of air-breathing hypersonic missile weapon systems can enhance area anti-access capabilities and is a powerful guarantee of regional security and stability.In this paper,the key technologies of dynamics modeling,guidance and control system design of the air-breathing hypersonic vehicle are studied,focusing on how to estimate the aerodynamic and thrust forces of the vehicle in the design and research stages of the air-breathing hypersonic vehicle,while balancing the rapidity and accuracy of the calculation.The key problems are: how to establish a control-oriented modeling of the guidance and control system,how to design the guidance law to meet the time of flight and angle constraints under the constraints of thrust and attitude,and how to control the velocity and attitude of the vehicle under strong coupling,strong nonlinearity and uncertainty.The main research contents include.Firstly,the configuration and parameters of a typical air-breathing hypersonic vehicle are given based on relevant published test data and literature data,and then its aerodynamic and thrust and other related parameters are estimated.Because the physical nature of hypersonic flow is different from that of supersonic flow,the significant hypersonic effects make the methods used for sub/supersonic aerodynamic calculations no longer applicable.In order to estimate the hypersonic aerodynamics,the surface pressure is calculated by using the shock-expansion wave theory calculation method based on the inviscid flow,and the empirical estimation method of transition prediction is combined with the empirical estimation method of reference temperature to give the estimation method of viscous friction drag considering the effect of boundary layer laminar-transition-turbulent flow to establish the aerodynamic calculation model of the air-breathing hypersonic vehicle.Meanwhile,the thrust calculation method is given by applying the one-dimensional isentropic flow assumption,and the engine thrust model is established.Combining the aerodynamic and thrust calculation models,the dynamics model of the air-breathing hypersonic vehicle is given,which provides the theoretical basis for the subsequent guidance control system design.Based on the established aerodynamic and thrust calculation model and dynamics model,the research on the mid-flight time cooperative guidance method is carried out.Firstly,based on the analysis of the characteristics of the vehicle such as lift-to-drag ratio and thrust-to-weight ratio,a reasonable initial launch condition and shift point window design are given,and a bank-to-turn is adopted to reduce the influence of the flight attitude on the air intake and thrust.Then,considering that there is an acceleration process when the air-breathing hypersonic missile enters the mid-flight,which makes the time-to-go estimation based on the assumption of uniform speed no longer applicable,the study of the time-to-go estimation method under variable speed flight conditions is carried out for this problem,and the time-to-go error estimation is combined with the optimal feedback control to give a mid-flight time cooperative guidance method.In addition,in order to obtain a simple form of guidance law,there is no constraint on the field-of-view marginal condition of the turn-in point,so it may produce the unfavorable situation of too large field-of-view during the turn-in for terminal phase guidance,for which the design of adjusting the time-accelerated turn is carried out,which can make the turn-in point velocity direction point to the target as much as possible.Generally,in order to ensure the locking of the guidance head on the target in the final flight,the range of the field of view angle is generally constrained,and at the same time,in order to obtain a better penetration capability on the target,it is generally required to strike the target from a specific angle,i.e.,there is a constraint on the terminal strike angle.In order to solve the guidance problem of process state constraint and terminal constraint,the optimal control method of state variable constrained and terminal angle constrained is given,and combined with the proportional guidance with bias term,and the strike angle constrained guidance method is given by the reasonable segmentation and smooth connection design of the guidance law.The integrated design of the air-breathing hypersonic vehicle makes the problem of strong coupling between aerodynamics and thrust,and the hypersonic aerodynamics has the essential problem of nonlinearity,the problem of uncertainty brought by the deviation of the aerodynamics obtained from theoretical calculations,ground tests,etc.,and the control system design is needed for these problems.The influence of thrust on attitude is expressed in the form of moment in the kinetic equation,and the influence of attitude on thrust is expressed in the model of thrust calculation.The aforementioned aerodynamic calculation model as a real model has a nonlinear nature,and the linearization is fitted to it as a control system using the model,and the deviation between models shows uncertainty.To address the above problems,this paper gives an adaptive control method for an air-breathing hypersonic vehicle based on high-order sliding mode.Firstly,the command of the guidance system is converted into the body axis angular velocity command by the method of order reduction,and the problem of tracking the body axis angular velocity is used instead of the problem of attitude angle tracking to make the controlled system order reduction,then the controller is designed with the outer layer of velocity control and the inner layer of attitude control in layers,and finally the robust adaptive high-order sliding mode control method based on the finite time convergence error observer is designed to realize the tracking,and at the same time,in order to suppress the jitter brought by the sliding mode control,a differential form of control variable is used.