Nonlinear adaptive robust control strategy of thrust regulation for pintle solid-propellant rocket motors

Thrust regulation of a pintle solid rocket motor (PSRM) is closely interrelated with the propellant combustion, energy release, and propulsion power. In this paper, a nonlinear adaptive robust control (NARC) strategy is developed for the accurate and fast thrust regulation of the PSRM. In order to couple the PSRM with the electric motor, functional relationships of the equivalent throat area and Mach number with respect to pintle displacement are derived. Furthermore, a state-space equation considering the friction generated during the movement of the pintle and the unknown disturbances is established for the nonlinear dynamic thrust model of the PSRM. On this basis, a robust control strategy is developed to improve the stability of the system. To reduce the system control error caused by the non-structural parameters of the thrust pintle motor, an adaptive parameter estimation method is integrated with robust control strategy. Moreover, to further raise the response speed of the thrust, an integral of the sign function is incorporated into the control factor. Finally, adaptation laws of non-structural parameters are designed based on the Lyapunov stability theory. Numerous simulations are conducted to validate the developed NARC strategy. Simulation results indicate that the undershoot can be improved by 13.6 %, 17.6 % and 40.7 % with the NARC, compared with the adaptive robust control, robust control, and PID control, respectively. Meanwhile, the response speed of thrust regulation with the NARC can also be improved by 2.8 %, 5.2 % and 28.8 %, respectively. Therefore, the developed NARC strategy performs superior performance in enhancing control accuracy and the energy release effect.