Robust Control of Regenerative and Hydraulic Brakes for Enhancing Directional Stability of an Electric Vehicle During Straight-Line Braking

Thanks to the actuation flexibility of their systems, electric vehicles with individual powertrains, including in-wheel and on-board motors, are a very popular research topic amongst various types of electrified powertrain architectures. The introduction of the individual electric powertrain provides great capacity for improvement of the vehicle's energy efficiency and control performance. However, it also poses tremendous challenges concerning vehicle safety, due to the complex system dynamics and cooperation mechanisms between multiactuators. For an electric vehicle with independently controlled motors, because of design and manufacturing factors, the steady-state error of each motor output torque, and the flexibilities and nonlinear backlash of left and right drivetrains, can be different. This results in asymmetrical output characteristics of electric powertrain systems on the same axle. Therefore, during a normal straight-line deceleration, an unexpected yaw moment would be generated, affecting vehicle's directional stability. In this study, a novel method of directional stability enhancement through robust control of blended braking of an electric vehicle equipped with four individual on-board motors during normal straight-line deceleration are studied. System models, including the vehicle dynamics, tire, electric powertrain, and hydraulic brake models, are developed. Mechanisms of directional instability of the electric vehicle during straight-line braking are analyzed. To further improve the electric vehicle's safety and performance, robust control algorithm of blended braking is developed using nonlinear sliding mode approach. Simulations of the proposed control strategy is carried out under straight-line braking. The results demonstrate that the developed approach is advantageous over the baseline, with respect to both the directional stability and regeneration efficiency, thus validating the feasibility and effectiveness of the controller synthesis.

[1]  Chen Lv,et al.  Development of the Electrically-Controlled Regenerative Braking System for Electrified Passenger Vehicle , 2013 .

[2]  Dzmitry Savitski,et al.  Experimental Study on Continuous ABS Operation in Pure Regenerative Mode for Full Electric Vehicle , 2015 .

[3]  Chen Lv,et al.  Extended-Kalman-filter-based regenerative and friction blended braking control for electric vehicle equipped with axle motor considering damping and elastic properties of electric powertrain , 2014 .

[4]  Martin Levesley,et al.  Integrated Active Steering and Variable Torque Distribution Control for Improving Vehicle Handling and Stability , 2004 .

[5]  Chen Lv,et al.  Cooperative control of regenerative braking and hydraulic braking of an electrified passenger car , 2012 .

[6]  Ching Chuen Chan,et al.  Emerging Energy-Efficient Technologies for Hybrid Electric Vehicles , 2007, Proceedings of the IEEE.

[7]  Hans B. Pacejka,et al.  THE MAGIC FORMULA TYRE MODEL , 1991 .

[8]  Chen Lv,et al.  Mode-switching-based active control of a powertrain system with non-linear backlash and flexibility for an electric vehicle during regenerative deceleration , 2015 .

[9]  P. P. Yip,et al.  Multiple Sliding Surface Control: Theory and Application , 2000 .

[10]  J. Bocker,et al.  Active damping of drive train oscillations for an electrically driven vehicle , 2004, IEEE/ASME Transactions on Mechatronics.

[11]  Khalid Hussain,et al.  Vehicle Handling and Stability Investigation into Causes of Vehicle Drift during Straight-Line Braking , 2006 .

[12]  T.-J. Yeh,et al.  Motor control and torque coordination of an electric vehicle actuated by two in-wheel motors , 2013 .

[13]  Danwei Wang,et al.  Analysis of subsystems coordination for electric vehicle during straight-line braking and brake-in-turn , 2013, 2013 IEEE Symposium on Computational Intelligence for Engineering Solutions (CIES).

[14]  Gang Tao,et al.  Design and analysis of a hybrid control scheme for sandwich nonsmooth nonlinear systems , 2002, IEEE Trans. Autom. Control..

[15]  Mehrdad Ehsani,et al.  Electronic Braking System of EV And HEV---Integration of Regenerative Braking, Automatic Braking Force Control and ABS , 2001 .

[16]  Aldo Sorniotti,et al.  Direct yaw moment control actuated through electric drivetrains and friction brakes: Theoretical design and experimental assessment , 2015 .

[17]  J. Hedrick,et al.  Dynamic Surface Control of Uncertain Nonlinear Systems: An LMI Approach , 2011 .

[18]  A. Khajepour,et al.  Application of Adaptive Sliding Mode Control for Regenerative Braking Torque Control , 2012, IEEE/ASME Transactions on Mechatronics.

[19]  Chen Lv,et al.  Hardware-in-the-loop simulation of pressure-difference-limiting modulation of the hydraulic brake for regenerative braking control of electric vehicles , 2014 .