Thrust Control Method And Performance Simulation Of Pintle Controlled Solid Rocket Motor

Owing to the advantages of wide range and stepless adjustment feature,the pintle controlled technology is very promising for the thrust control of solid rocket motors(SRM).At present,the pintle controlled solid rocket motor is about to enter the application phase in the domestic.To meet the demand of missile trajectory's design,adjustable thrust motor is far from enough,but precise thrust control is even more important,which is also one of the key technologies of pintle controlled solid rocket motor's practical application.Focusing on the thrust control system of the SRM,a systematic study on its control theory and design method was carried out in this thesis.A series of simulations were conducted to test the overall performance of different thrust control methods.Listed below is the major work of this thesis.Firstly,an integrated mathematical model of the thrust control system was established,which provides theoretical basis for the design of the thrust control system.The steady and dynamic characteristics of the thrust control system were analyzed.The thrust control model included the internal ballistics model and the transfer function model,which describes the response of the combustion pressure and the thrust to the change of the equal area of the nozzle throat.Calculation formulas for steady pressure and thrust were also established.The calculation method of the equal area of the nozzle throat,including the unconstrained and the constrained optimization methods,reduced the computational time of the equal nozzle area formed by the pintle with arbitrary contour and the nozzle,and speeded up the simulation of the thrust control process.Secondly,the open-loop thrust control method was studied,including a completely open-loop thrust control method and a pressure feedback based open-loop thrust control method.The goal of direct control of the thrust was achieved.The control performance and the environmental adaptability of the two methods were compared.The completely open-loop method is easy to design and realize,but its control accuracy and environmental adaptability are not good enough to satisfy the higher control requirements.The open-loop thrust control method based on the pressure feedback had higher control accuracy and better environmental adaptability.This method can also compensate for unsteady burning surface phenomenon and erosion effect of the nozzle.A self-adaptation proportion integration differentiation(PID)control algorithm based on the radial basis function(RBF)neural network identification was used in the pressure controller,which helped to reduce the cost of the solid motor tuning.Thirdly,the close-loop thrust control method based on the overload feedback was studied.Effective feedback can be acquired by using measurable axial overload,thus the axial overload can be controlled directly.The close-loop thrust control system was finally established and the close-loop thrust control was realized indirectly.This is beneficial to simplify the design of the guidance and control system of a missile.A self-adaptation PID control algorithm based on the RBF neural network identification was also adopted to design close-loop thrust control system.But the simulation results indicate that the system is sensitive to the aerodynamic disturbance.Two schemes were employed to improve the anti-jamming ability of the system.The first one was improving the structure of the control system.By removing the equal controlled quantity caused by the change of the axial aerodynamic force,the overload controller quantity was compensated to reduce the influence of the axial aerodynamic force.The other one was using the active-disturbance-rejection algorithm to design the overload controller to restrain the axial aerodynamic force effect by taking advantage of its active-disturbance-rejection characteristic.The two methods can enhance the anti-jamming ability of the system and improve its control performance.Last,an integrative “motor-internal-ballistics and missile-external-ballistics” simulation platform was established to test the dynamic response performance,environmental adaptability and the pneumatic sensibility of all thrust control methods mentioned in this thesis for the pintle controlled SRM.The platform combined the process of the internal ballistics adjustment of the motor's thrust control system and the external ballistics of the missile's flight to simulate the whole work process of the autopilot.The simulation results indicate that the open-loop thrust control method responds faster,but the tracking error of guidance commands is bigger because of its bigger error of the thrust response and the existence of thrust undershoot,and the autopilot using this method is difficult to design because the tracking condition of guidance commands depends on the thrust transfer control algorithm of the autopilot on the missile.The close-loop thrust control method based on the overload feedback responds slower,but the tracking error of guidance commands is smaller without overload undershoot,which can effectively avoid the impact of the motor thrust undershoot on the guidance and control of missiles.Its environmental adaptability is good,and it can hardly be affected by the unsteady burning surface and erosion phenomena.In addition,the matching autopilot using this method is easier to design.In this thesis,the steady and dynamic characteristics of thrust control process of pintle controlled solid rocket motor were analyzed,the precise control of thrust and the tuning cost control of solid motor were accomplished,and a simulation platform of thrust control performance of motor was established,which will further promote the practical application process of pintle controlled solid rocket motor.