【作者】 尹帅钧；

【导师】 初亮；

【作者基本信息】 吉林大学 ， 车辆工程， 2009， 硕士

【摘要】 作为汽车主动安全控制系统中最常见的一种,防抱死制动系统对提高行驶安全性具有十分重要的作用。而液压调节单元作为轿车防抱死制动系统的主要执行机构,其工作性能直接影响整个系统的控制效果。尽管液压调节单元的形式多种多样,但宗旨都是对制动系统的压力进行调节。对于轿车防抱死制动系统,如果能够精确获得车轮上当前的制动压力,就可以实现对制动压力进一步精确控制。采用压力传感器可以很好地实现这一目标,但是为了降低整个系统的制造成本,往往不用压力传感器来测量车轮上的制动压力,这就需要通过控制算法对压力进行估算从而保证制动压力调节的实时性和精确性。然而,国内对于这一方面的研究还处于起步阶段,开展液压制动系统压力预估的研究具有一定现实意义和应用价值。本文在吸收国内外防抱死制动系统压力控制研究成果的基础上,结合软件仿真深入研究了液压调节单元工作特点和控制方式,提出了轿车防抱死制动系统压力估算算法。通过在MATLAB/Simulink环境下进行建模与仿真,验证了所提出算法的可行性和有效性。更多还原

【Abstract】 As one kind of active driver assistance systems, Anti-lock Braking System plays an important part in maintaining vehicle stability and shortening brake distance. Almost all new cars are offered today with ABS. To some extend, this technology has come to perfection abroad, while the domestic research is only in its infancy. The core technology of ABS involves developments of ECU, control strategies, HCU, sensors, and evaluations for brake system-matching. As the actuator of the system, HCU directly affects the performance.ABS is used to control the force applied on the tires in an effort to optimize vehicle performance. Because the force applied on the tires is so critical to ABS, it obviously would be an advantage to know the force directly. Unfortunately, there is currently not an easy and cost-effective way to measure the force. As a secondary solution, the brake pressure could be achieved using pressure sensors whose measurements are can be used by ABS strategy; however, this approach also involves an increase in manufacturing cost of the device. The brake pressure can be estimated by the characteristics of the hydraulic modulator, which is used to perform the ABS brake pressure regulation. This paper presents a brake pressure estimation algorithm for anti-lock braking system which gives accurate and real-time pressure estimation. This paper is carried out as follows:Above all, theoretical analysis to the hydraulic control unit is carried out. The performances of high speed digital valves, including operating feature, dynamic performance and static performance, are studied firstly. On the basis of theoretical analysis to high speed digital valves, the model of hydraulic control unit for ABS is developed using AMESim. Through the simulation, several results are achieved, including the varieties of pressure, flow rate and volume of wheel cylinder. So are the variety of characteristic parameters of the accumulator, the pump, especially control valves. These results reflect dynamic characteristics of the system well.Secondly, based on the data accumulated a reduced mathematics model of the Anti-lock Braking System is developed, which consists of a brake pedal, a master cylinder, a vacuum booster, a hydraulic control unit, lines and brakes, etc. This model explicitly describes the nonlinear capacitance of the brake system. Furthermore, the model allows for brake pressure variations between wheels. The final aspect of the model, therefore, involves relating the wheel pressure to the displaced fluid volume. Finally, a concept of the hydraulic model and inversed hydraulic model is presented, which is the theoretical principle of brake pressure estimating and controlling.Thirdly, two methods of estimating the brake pressure is present on the principle of hydraulic drive and the characteristics of ABS in this paper. One approach relies on the empirical model. This kind of estimation algorithm derived from numerous of vehicle tests to determine the functions of brake pressure under kinds of work condition, which is not available under current stage. Another approach is to develop a model-based brake pressure estimation strategy. The model-based brake pressure estimation strategy is developed in terms of relating the wheel pressure to the displaced fluid volume.Finally, simulated studies of an anti-lock braking system are undertaken using Matlab/Simulink. The simulation is carried out step by step. The model of the anti-lock braking system is built to estimate the brake pressure and a simulation is performed. Then the modulation of the pressure is simulated using Stateflow. The simulation results show that the algorithm gives accurate pressure estimation.更多还原