Vehicle validation for pressure estimation algorithms of decoupled EHB based on actuator characteristics and vehicle dynamics 2020-01-0210
In the automotive field, electro-hydraulic brake systems (EHB) has been developed to take place of the vacuum booster, having the advantage of faster pressure built-up and continuously pressure regulation. Most of the pressure control solutions are based on standard pressure-based feedback control, requiring a pressure signal. Although the pressure sensor can produce the pressure feedback signal, it will increase cost and enlarge installation space. The rotation angle of electric motor is available by the built-in sensor, so the pressure can be estimated by using the rotation angle. The pressure control is influenced intensely by the typical nonlinearities (i.e. friction, pressure-position relationship) and uncertainties (i.e. brake pads wear, temperature effect). To address these issues, this work improves an interconnected pressure estimation algorithm based on actuator characteristics [W. Han, L. Xiong, and Z. Yu, “Pressure estimation algorithms in decoupled electro-hydraulic brake system considering the friction and pressure-position relationship,” SAE Technical Paper 2019-01-0438, 2019] by introducing the vehicle dynamics and validates it via vehicle tests. The mathematical model of the motor-type EHB is built. The Gauss exponential model is selected to describe the friction phenomenon, and the friction force calculated by the Gauss model can match the real friction force with an accuracy of approximate 90%. The pressure-position relationship is fitted by a quadratic polynomial, which includes several time-varying parameters. The wheel speed feedback is used for modification via a proportional-integral (PI) observer. Superior to the estimation method based on actuator characteristics, the joint estimation method improves the accuracy by more than 10%. Most importantly, this study realized a pressure estimation without add-in sensors, which makes EHB realizable to become the actuator for automobile active safety systems, giving a promising way to achieve far better performance.
Wei Han, Lu Xiong, Zhuoping Yu, Songyun Xu
Tongji University, DIAS Automotive Electronics Co.,.Ltd.