Xiangdong Huang

Battery Variable Current-discharge Resistance Characteristics and State of Charge Estimation of Electric Vehicle

Through studying and characterizing variable current-discharge test data, dynamic modeling of battery used for electric vehicle or hybrid electric vehicle (EV/HEV) with the equivalent electromotive potential and resistance as essential parameters has been carried out. The resistance characteristics are analyzed and the stable condition of the equivalent resistance is discovered when the discharge current is high. A method based on this condition for batterys state of charge (SOC) estimation is detailed. Along with traditional methods, open circuit voltage method and ampere-hour integral method, the estimation of SOC is realized; its convenience and effectiveness for on-line real-time application are also proven by analyses and pilot tests

Uninterrupted Shift Transmission and Its Shift Characteristics

A novel transmission concept, the uninterrupted shift transmission (UST), is introduced in this paper, which retains most of the components common or similar to normal automated transmissions such as automated manual transmission or dual clutch transmission, but offers an uninterrupted torque from engine to wheels during the shifting process with the so-called multimode controllable shifters. An UST dynamic model is established to analyze USTs shift characteristics. The special control logic involving the engine, clutch and transmission are put forward to improve USTs shift quality, and are applied in the simulation model using MATLAB/Simulink tools. To validate the simulation model and the control logic, a proto test bench has been designed and built with corresponding data acquisition system and controlling equipment. Finally USTs torque uninterrupted functionality during shift, effectiveness of the proposed control logic and validity of the proposed dynamic model have all been verified experimentally.

Multi-stage global trajectory optimization for the overlapping shift of a seamless two-speed transmission using Legendre pseudo-spectral method

For a seamless two-speed transmission specially equipped in electric vehicles, the global trajectory optimization problem of the overlapping shift process with multiple stages and complex path/point constraints is investigated in this article. The overlapping shift principle and the dynamic models in each phase are also demonstrated in detail. The parameters to evaluate the shift quality are analyzed and then introduced into the objective function and constraints, respectively. The jerks in process and at the key moments have been distinguished and selected as the path and point constraints, respectively. Moreover, considering the joint characteristics of the torque phase and the inertia phase, the trajectory optimization problems in the above two phases are summarized as a multi-stage global trajectory optimization problem. Then, Legendre pseudo-spectral method is used to transfer the multi-stage global trajectory optimization problem into a nonlinear programming problem for numerical solutions. Finally, the effectiveness and feasibility of the multi-stage global trajectory optimization method have been verified through the comparison of the optimal shift trajectories under different conditions with that obtained by the piecewise trajectory optimization method.

Optimal coordinating control for the overlapping shift of a seamless 2-speed transmission equipped in an electric vehicle:

For a novel seamless 2-speed transmission specially equipped in the electric vehicles, the optimal coordinating control problem of the motor and the friction clutch with complex constraints on both the state and control variables during the overlapping shifts is investigated in this article. First, the shift principle and the dynamic models of the overlapping shifts between the friction clutch and the one-way clutch are analyzed. Next, the parameters for evaluating the shift quality are analyzed. The jerks in process and at the key moments (speed synchronization moments of the friction clutch or the one-way clutch) are distinguished and selected as the constraints and the objective function’s terminal items, respectively. Finally, an integral optimal coordinating controller is proposed to optimize the shift trajectories and improve the overlapping shift quality. The linear feed-forward coordinating control strategy is used in the torque phase to regulate the motor torque with the engaging or disengaging process of the friction clutch to maintain the jerk within the permissible range, and the optimal control strategy based on the principle of the minimum is used to optimize the shift trajectories with complex constraints on both the control and state variables in the inertia phase. The effectiveness of the proposed optimal coordinating controller on addressing the coordinating control problem of the motor and the friction clutch during the overlapping shifts and establishing a solid foundation for the application of the seamless 2-speed transmission in electric vehicles have been verified by the simulation and experimental test-bench results.