Research On Control Theory And Testing Of Semiactive Seat Suspention

Off-road vehicles and engineering machineries often work in harsh environment, in which the road unevenness leads to the intensive vibrations in the process of driving or operating. If the drivers or operators are exposed to a certain intensity of vibration for long time, which will affects their work effectiveness, even serious bodily injury. In order to reduce the vibration energy transmitting to the drivers or operators, the seat suspension system has been equipped for vibration isolation and improvement of the riding comfort in general. Since passive seat suspension system with limited functions in improvement of vibration isolation, can not effectively reduce the strength of vibration transmitting, especially in low frequency band. Recently, semi-active or active suspension systems become popular in effective attenuation of vibrations.Magneto-Rheological (MR) fluid, such functional material has received great attentions in recent years. Many application products utilizing the MR fluid have shown superior performance in civil engineering and mechanical engineering. In these applications, the utilizations of vibration control with MR damper are the most prominent, such as vibration isolation of high buildings and vibration damping of big bride cables. In additon, suspension system is the important application field of MR damper for vibration absorption including vehicle suspension and seat suspension, and playes a role that dissipates the main vibration energy generated by road exciting. As a result, the comfort of riding is improved.This paper studies the key technologies of semi-active seat suspension based on MR damper mentioned above. The main work includes how to build the mathematical model of MR damper with the aid of experiments by optimizing method, derive MR damper inverse model with simple structure and high precision, and design a control strategy that not only takes on robust performance for parameter uncertainties, but also reduces the using of transducer, or avoids some hard-to-access state as decision-making variable. The control strategy is reqiured to be easy to apply and reduce the realizing cost accordingly. At last, numerical simulations and experiments are used to verify these key technologies. In this dissertation, the concrete work includes the following aspects.(1) In order to establish the mathematical model of a given MR damper, the fourteen parameters of the Bouc-Wen model of MR damper are identifyed by genetic algorithm using the experimental results.(2) The inverse model is derived from the Bouc-Wen model of a given MR. This model, with only structure simple and a certain precision, is easy to be implemented. The inverse model can determine the input voltage for the MR damper by using the expected force and current speed of piston, such that a number of active suspension control algorithms can apply to the semi-active suspension control.(3) Considering the properties in the controller design process that the actual physical system is difficult to be accurately modeled, and the plant parameters changes with environmental changing, an H∞robust output feedback controller with parameter uncertainty is derived, which can enhance the robustness of the semi-active controller in control system with parameter perturbation and ensure the dynamic performance.(4)According to the requirements for acceleration power spectral density (PSD) in national standard, in which vibration experiment of engineer vehicle seat suspension system is regulated, displacement and velocity signal of excitation input in time domain can obtain through the way of inverse Fourier transform, and these signal can act as excitation input in numerical simulaion and experiment of seat suspension.(5)The dynamic performance of passive seat suspension and semi-active seat suspension are compared and studied by numerical simulation not only in time domain and frequency domain. In addition, the simulation tests the robust performance of controller for parameter uncertainties, in which a variety of parameter perturbations are added in.(6) Semi-active seat suspension controller is designed by LabVIEW program, which including data acquisition, signal condition, semi-active constraint, MR damper inverse model , control signal outputing, robust H∞output feedback controller, and other parts.(7) To verify the feasibility and robustness of the control system, an experiment is performed for semi-active seat suspension based on MR damper, which including the seat modal experiments, realization exciting of seat, seat fixture designing, driver simulation, controller designing, and so on. The experiments compare the performances of passive seat suspension and semi-active seat suspension, and verify the effectiveness of the designed control system.