Research On The Rolling Controlled Two-dimensional Trajectory Correction Mechanism

The two-dimensional trajectory correction projectile is a sort of conventional guided ammunition, which can correct the trajectory in the direction and range for serveral times to attack the taget exactly. The trajectory correction mechanism, which is the actuator of the correction projectile, is the pivotal part whose performance could decide the ability of the trajectory correction and the accuracy. Generally, two methods of correcting trajectory are used, which are aerodynamic force corerrected and direct force corrected, and the typical actuators using the two methods are the steering gear and the jet element. For fin-stailized projectiles, both the steering gear and the jet element can achieve correcting trajectory. But for the spin-stabilized projectiles, the two types of actuators can not be the correction mechanism since the low response speed. In order to make the spin-stabilized projectiles own the ability of correcting trajectory, it is necessary to develop a new type of trajectory correction mechanism. In this paper, a fixed rudder pieces and rolling controlled two-dimensional trajectory correction mechanism for the conventional 130 mm artillery shells were developed which will make the shells own the ability of correcting trajectory in two dimensional.Firstly, the overall scheme of the two-dimensional trajectory correction mechanism was designed. The core of the correction mechanism is an energy conversion element between mechanical energy and electric energy through magnetic field, which is made up of several permanent magnets assembled inside the external case and the coil winding fixed on the inner shaft connected with the projectile body. The correction mechanism designed in this paper can work in the generator mode and motor mode and use the electromagnetic torque to chage the motion states of the external case. The external coordinates systems of the correction mechanism were defined. The measurement way of the rolling angle based on pulse comparison and the generation method of the average control force based on the difference quantity of the rotate speed of the external case were designed resolving the direction control of the aerodynamic force generated by the canards fixed on the external case of the correction mechanism. The magnetic potential of the coil winding and the magnetic flux density of the permanent magnets were analyzed and the interaction of the two mag-netic fields was also analyzed, obtaining the calculating way of the electromagnetic torque. The inner magnetic field and the structure of the correction mechanism were simulated.Secondly, the inner coordinate systems of the correction mechanism were defined and the mathematic model of the correction mechanism was also built based on the theory of energy conversion and coupling between the mechanical energy and electric energy. According to the magnetic potential equivalence principle and the theory of coordinate transformation, the mathematic model was simplified gradually. And in the model simplification process, the basic condition that the correction mechanism runs stably was obtained. In order to satisfy with the basic condition and decouple the two magnetic fields, the space vector control technology was used in the drive strategy of the correction mechanism, achiving the decoupling control of the electromagnetic torque. On this basis, the basic dynamic process of the correction mechanism was also analyzed.Thirdly, the advantages and limitations of the generator mode and the motor mode were contrasted from the controlling flexibility and influence to the stability of the projectile. According to the motion parameters of the projectile in the whole trajectory, the timesharing segment control stragety was proposed. Then, the mathematic model of the generator mode was simplified further and the mechanical characteristics curves of the different resistances were obtained. Then, the sliding mode control technology was used. For the generator mode and motor mode, the adaptive integration sliding mode controller and fuzzy sliding mode controller were designed respectively. According to the numerical simulation, the conclusion was obtained that the sliding mode controller had better robustness performance to the parameter perturbation and load torque disturbance.In order to increase the reliability and decrease the cost of the trajectory correction mechanism, the sensorless control technology was applied. The conventional sliding mode observer was designed which obtained the relative electrical angle between the external case and the inner shaft of the correction mechanism through reconstructing the winding currents and estimating the back electromotive force. Since the chattering caused by conventional sliding mode observer, the electrical angle estimated would have phase retardation and the estimation accuracy was not approving. In order to overcome the adverse influence caused by the chattering, the extended sliding mode observer was designed in this paper. Compared with the conventional sliding mode observer, the extended sliding mode observer obtained the relative electrical angle through estimating the flux linkage of the winding directly. Since the extended sliding mode observer itself could filter the high-frequency noise caused by the chattering, the extended sliding mode observer could not only keep the better robustness, but also overcome the chattering and hava a higher accuracy.Lastly, a simulation and test system for the two–dimensional trajectory correction mechanism developed in this paper was designed. On the one hand, the simulation and test system could simulate the working condition of the correction mechanism; on the other hand, the system could measure the parameters of the correction mechanism and the control method. According to the experiment results, for the spin-stablized projectile, the two-dimensional trajectory correction mechanism developed in this paper has a stable and reliable performance and a properly technology solutions, and it is appropriate to be the trajectory correction mechanism of the 130 mm artillery shells in the background project and other roll-guided munitions.