Research On Drive Shaft Torque Estimation For Electric Vehicles

Moving vehicle is a time-variable system with strong nonlinearity, and it is neces-sary to obtain lots of variables in order to realize a concise control on such a complex object. Therefore in the automotive control field, many parameter estimation problems are researched, and one of them is drive shaft torque estimation.Drive shaft torque knowledge always applies to controller to increase driver’s comfort. To stress the torsional vibration of driveline, active damping of engine/motor output power is an efficient approach provided drive shaft knowledge is obtained. In the shifting process, if the engagement and disengagement of clutch occrurs at improper time results in a jerk and oscillations of driveline. In order to accurately control the engagement and disengagement of the clutch, drive shaft torque estimation is necessary. Furthermore, to achieve satisfactory control effect in the regenerative braking process of electric and hybrid vehicles drive shaft torque is estimated.In this paper, the drive shaft torque estimation problem is researched. A detailed model of electric vehicle established in software AMESim (Advanced Modeling Environ-ment for performing Simulation of engineering systems) is used as a plant in place of a real vehicle in this study. A drive shaft torque estimator based on feedback linearization algorithm is designed and applied in the regenerative braking energy recovery issue of the electic vehicle.The key point in this work is the design of the drive shaft torque estimator. A longitude vehicle dynamics model is established in MATLAB/Simulink environment and a model-based estimator is designed to deal with the parameters drift problem. The estimator based on feedback linearization theory is proposed and is proved to be input-to-state stable (ISS). In addition, effectiveness of the observer is tested by simulation experiments under urban road driving cycle conditions.Based on the torque estimator mentioned above, an estimator-based control system for regenerative braking process is proposed. In the process, motor braking torque and mechanical braking cooperate to achieve the driver’s braking requirement. The drive shaft torque observer is a hinge in the close control system. Finally, it should be noted that, this paper focuses on the design and application of drive shaft torque observer. With some off-line simulation, it is verified that the effect of proposed estimator and controller basically meets the requirements. For the next step, real-time simulation should be done to further test the real-time performance, which is the next step in this research.