Performances And Control Method Of Magnetorheological Shock Isolation Device

As the modern engineering equipments are getting high-speed and heavy-load, the troubles of shock and vibration become obvious. It’s very critical to mitigate shock and vibration for improving the engineering quality. The gun recoil device is a typical shock isolator which can reduce the peak force transferred to the gun carriage within the limitation of the stroke. The purpose to use recoil mechanism is to reduce the vibration of the gun. The optimal design of the conventional hydraulic device for gun recoil system is to take the area of the orifices of the hydraulic damper as an optimization variable. The area of flow orifices inside the damper is designed in a way that changes along the axial direction of the piston. The functions of the hydraulic absorber for a certain recoil system and operation conditions can’t be changed as long as the absorber is manufactured which results in a shortcoming: when the firing impact loading changes, the recoil force can’t be adjusted correspondingly.Magnetorheological (MR) fluid, the product of the development of materials science, is a kind of smart material. MR fluid dampers are the most popular devices which have continuously adjustable damping force, mechanical simplicity, low power consumption, high dynamic force range, and rapid response time.Aiming at the problem of shock isolation of the gun recoil system, this paper focuses on the properties and control method of the MR shock isolation device from system point of view. The research work starts from the control objective of the system and the optimal control theory. The theoretical analysis, numerical simulation and experimental validation are employed to study in this research work. The main contributions of this dissertation include the followings:(1) An optimal control method for the MR shock isolation device is proposed. The optimal normalized displacement, velocity and optimal control rules for the gun recoil system are derived. The solution of optimal control is useful for general situation because the dimensionless analysis method is employed.(2) A theoretical model for optimal design and control of the MR fluid damper for the shock isolation device is derived. By using Navier-Strokes equation, an axisymmetric model working in pressure-drive flow mode is developed. The viscous damping force caused by minor loss through orifice is included in the theoretical model.(3) The response properties of the MR fluid damper for gun recoil device are studied. The response models of magnetic flux density and shear yield are established respectively. The experimental results show the models work well. The response time shows the MR fluid damper has excellent response properties and is competent to work under impact loadings.(4) The dynamic model of the MR fluid damper for gun recoil device is studied. An improved polynomial model is proposed. This novel dynamic model has a correction term which can improve the accuracy of the model. The theoretical results can fit the experimental results well both at the high-acceleration and the low-acceleration part.(5) Control strategies for MR shock isolation are studied. The optimal control strategy is obtained based on the derived optimal control method. Furthermore, a fuzzy compensation-optimal control (FC-OC) strategy is proposed. Then, two kinds of performance indexes are introduced to comment the performance of the MR shock isolation system. The experimental results obtained from the full-scale gun recoil test rig show that the optimal control strategy is better than the passive control strategy and the fuzzy logic strategies. The optimal strategy presented in this paper is open-loop without any feedback system needed. That means the control process is sensor-free. It will be of great benefit for reliability and stability of the shock isolation system. The FC-OC strategy has the advantages of both fuzzy logic control and optimal control. It is partly independent on both the feedback system and theoretical model so that both the reliability and the flexibility are compromised. The experimental results show the most desired performance of the shock isolation system is obtained under the FC-OC strategy.