Dynamic Performance Analysis And Control System Design Of MR Dampers Under Impact Load

When firing, the artillery will experience severely impact load, yielding by the high temperature and high pressure powder gas, and vibrations and beats occurs which will decrease the firing precision and stability. Although most weapon systems already have a passive recoil mechanism, the desire for building lighter weapons with increased firing power and more mission flexibility have placed new demands on the recoil mechanicsms that cannot be met with the traditional passive systems.With the development of smart material science, Magneto-rheological(MR) dampers, whose damping force can be controlled by the current applied in the damper coils, are preferd for its large output damping force, wide dynamic range, rapid response and low power supply, which have brought out new challenges for development of the recoil mechanisms and the vibration stability control of weapons.For recoil mechanisms applications, MR dampers are desired to provide optimal damping force to control the recoil dynamics, so that large peak of recoil forces can be avoided with a certain limited stroke, and the firing stillness and stability are ensured. In this dissertation, on the background of the recoil mechanisms applications, the dynamic performance of MR damper and its control system under impact load are investigated in depth. The main contributions of this dissertation are as follows:(1) The dynamic performance of the MR damper under impact is studied. By fitting the experimental data with nonlinear least square method, it's shown that the steady flow equations for parallel plates based on the non-linear Herschel-Bulkley fluid model are able to accurately describe the dynamic behavior of the MR damper under impact load, at the decreasing stage of the recoil velocities. Since the mathematical expression of the above model is complicated with different forms in high and low velocities respectively, a simplified model with uniform expression is put forward and parameters of the model are identified. The validy of the simplified model is verified by numerical simulation of the recoil cycle.(2) The controllability of MR dampers for recoil mechanisms applications is analyzed and it's concluded that the applied current of MR dampers have little effect on the peak of the recoil velocities which is decided by the amount of the imact energy, and during recoil the control region of MR dampers is at the decreasing stage of the recoil velocities. (3) The response time of the MR damper is investigated by analysis of the magnetic circuit and test of the MR damper. The results indicate that the response time of MR dampers is mainly due to the current reponse time of the magnetic circuit. By modification of the magnetic circuit, the MR damper's response time can be shortened, and the limit of the MR damper's response time for recoil mechanisms applications is solved.(4) The MR damper recoil control system is investigated. For the nonlinear characteristics, inverse system method based on the thought of feedback linearization is used, and the pseudolinear system is modified by PI controller. Considering the dynamic behavior ignored during simplified modeling and the uncertainty of the control system parameters, model reference adaptive control method is adopted. It's shown by test, that with the same recoil stroke, large peak of the recoil force is avoided and the ideal recoil dynamics is achieved by using PI controller or the adaptive control method. The validity of the MR damper recoil control system is verified, and compared with the PI controller the adaptive control method is more effective.(5) The optimal design method of MR dampers for recoil applications is discussed. The performance reqirements of MR dampers are proposed, and the optimal design of MR dampers for recoil applications is put forward by using multi-objective planning method, with parallel plates model based on the hurschel bulkley MR fluid characteristic.