Research On Internal Model-based Control Strategy Of Operating And Aiming System For A Certain Shipborne Rocket Launcher

With the change of modern war pattern and development of military scientific technology, higher requirements of rocket launcher are put forward, i.e., higher shooting precision. The firing accuracy and response rate depend on the position servo system of the rocket launcher. In order to improve the efficiency of firing suppress and air defence in a carrier-borne rocket launcher, some high performance alternative current (AC) position servo system of rocket launcher is studied with the research and development of a certain cluster antiaircraft rocket launcher. The main work focuses on the research of high accurate tracking problem and robust control under some uncertainties by using modern control theory and feed-forward control principle. Results demonstrate that the proposed method performs well, and also has both important theoretical values and engineering meanings.Firstly, the structure features and working principle of the position servo system for the cluster rocket launcher were analyzed, and the mathematical model of the carrier-borne rocket launcher subjected to platform disturbance was established on the basis of permanent magnet synchronous motor (PMSM). The closed loops of electric current and rotational speed, which are set in the motor driver, were inserted into the controlled system model, and ultimately the mathematical rocket launcher model, in which the PMSM worked in rotational speed closed loop mode was established. Numerical simulation results and experiment results, those were similar the same, show that the mathematical model could precisely characterize the practical system and provide foundation for designing the position control module in the following text.Secondly, two key issues critical to the launcher servo system are low tracking accuracy of classical PID control strategy and high costs of executing some intelligent hybrid control strategy, therefore a feedforward-output feedback control strategy basis of invariant manifold was proposed. A high gain observer (GHO) and a state observer based on frequency analyzing were used to estimate up to3-step derivative of the target reference curve and the oscillatory motion of the board respectively, which were indispensable in the feedforward control strategy. Eigenvalues of the error system state matrix were configured to have negative real part and that made the equilibrium at the origin be exponentially stable. Moreover, some theoretical research results on friction compensation method by using positive torque load were proposed. Design specifications of the servo system could be satisfied by using the proposed feedforward-output feedback control strategy, but parameters of the controlled system and the exosystem must be exactly known. The main limitation in a practical project is that tracking error may rise if some parameters were not known.Internal model principle (IMP), which is also a feedforward control strategy based on invariant manifold, was introduced to remove the main limitation from the feedforward-output feedback control strategy. IMP shows that the exosyetem and control input could be seen as an augmented system and be immersed into a new system, which generates the control input that could drive tracking error sliding on the zero-error invariant manifold. The designing principle and numerical simulation results demonstrate that the internal model-based controller is able to cope with uncertainties on amplitude and phase of the exogenous sinusoid, but the frequency at which the internal-model oscillates must exactly match the frequency of the exogenous sinusoid, otherwise any mismatch in such frequencies results in a nonzero steady-state error.Motivated by the wish to remove such a limitation, an adaptive internal-model based control scheme in which the’natural frequencies’of the internal model are automatically tuned so as to match those of an exosystem which is totally unknown (except for an upper bound on its dimension) was addressed. Simulation results demonstrate that the proposed adaptive control scheme reduces the tracking error to its design specifications, besides, it is robust to parameters variation of the controlled system and exosystem, and is simple and easy implementation.Finally, a DSPF2812based control system consists of hardware circuit, software programming and electrical connection was built on the basis of analyzing results of the basic composition and structure characters of the experimental system. Series of experiments validating the efficiency of the feedforward-output feedback control strategy and adaptive internal model-based controller were implemented on the sample rocket launcher and experiment-bed of the simulative drive system. Through the analysis of experimental results, not only the feasibility of system design specifications achieved was confirmed, but also the correctness of theoretical analyzing and simulation research, and the effectiveness of the adaptive internal model-based strategy were proved, which provided reference for the performance improvement of servo system and the application of the internal model principle.