Xingzhong Li

Research on driving style recognition method based on driver’s dynamic demand:

Drivers usually show different driving styles in a transportation system. In analyzing the explicit linkage between driving style and driver’s dynamic demand, driving style can be classified into sports, moderate, and economical types. The sum of current driving resistance and the absolute value of its change rate is chosen as a measurement of driver’s dynamic demand. The influence of subjective and objective factors on driver’s dynamic demand has been analyzed. Single-exponential smoothing is adopted to predict the overall and staged driving style based on historical driver’s dynamic demand data. The most prominent advantage of the proposed prediction method is that there is no need to store significant historical data while considering the importance of each period data. The vehicle test scheme of driving style recognition method is designed including the test vehicle and drivers’ selection, driving route and task design. Test results show that driving style can be identified accurately with no additional sensors using the proposed method, and it can be used to quantitatively analyze the influence of different factors on driving style through statistical analysis. According to recognition results, automatic transmission shift point can be corrected to improve the adaptability of gearshift strategy for different driving styles.

Application of fuzzy logic in constant speed control of hydraulic retarder

Hydraulic retarders are extensively used in commercial vehicles because of their advantages, such as their large braking torque and long continuous operating hours. In this article, the structure and working principles of hydraulic retarders are introduced, and their dynamic characteristics are analyzed. The theoretical model of a hydraulic retarder is then established based on the dynamic analysis of a vehicle driving downhill. The braking process that involves the hydraulic retarder is divided into three stages. Moreover, the filling ratio controller of the hydraulic retarder is designed by adopting fuzzy control theory to control the braking torque of the vehicle while driving downhill. The vehicle dynamic model and constant-speed control model were then established in the MATLAB/Simulink environment. The simulation results showed that the fuzzy logic controller designed in this study has good constant-torque control and anti-inference performances, which can accurately and immediately produce braking torque to satisfy the braking requirement, thereby enabling the vehicle to drive downhill at a constant speed. As a result, the control strategy designed in this article can lead to significant improvements toward a safe road transport.

Optimal Control for Automatic Transmission in the Inertia Phase of Gear-Shift Process

In this paper, the on-coming clutch control strategy for automatic transmission in the inertia phase was developed based on the optimum output torque. Firstly, powertrain dynamic model is built, which includes planetary gear model, hydraulic actuator model, clutch transmitted torque and vehicle load model. Then weight of three shift quality evaluation indexes is distributed by Analytic Hierarchy Process; based on the weight, the three shift quality evaluation index can be normalized, so that it is convenient to compare different shift quality. Shift quality caused by different output torque curve is researched by orthogonal design; an optimum output torque with best shift quality can be got by the above analysis. The optimum output torque can be transformed into optimum turbine acceleration, and then the error value of actual turbine acceleration and optimum turbine acceleration as an input signal of the PI controller to adjust oil pressure of the on-coming clutch. Simulation tests results show that this on-coming clutch control strategy achieves an optimum output torque and optimum shift quality and proves the correctness of this control strategy based on the vehicle dynamic model.

Study on Dynamic Simulation Model of Telescopic Cylinder Based on Power Bond Graph and Simscape

The power bond graph is used to establish the dynamic model of telescopic cylinder. Simscape platform enables modeling and simulation of the hydraulic system. Analysis of the telescopic cylinder position characteristic curve and speed characteristics curve demonstrates the accuracy and reasonableness of the simulation model. All of this provides theoretical basis for the analysis and design of multistage hydraulic cylinder.