Research On Electro-hydraulic Braking Control For Electric Vehicle

Regenerative braking technology is one of the key techniques to increase themileage of electric vehicles, however, regenerative braking is so closely related toelectric vehicles’ driven layout, battery charging power and speed that makes itsubject to a variety of constraints, for security considerations, electric vehicles useelectrical-mechanical composite braking system. How to improve the accuracy ofthe hydraulic brake pressure control, and how to plan for both braking torque,making the braking process meets certain safety and energy optimization targets,but also has good maneuverability are two key technologies to improve electricvehicles’ electric-hydraulic braking performance.Firstly, this paper designed hardware in the loop simulation platform forelectro-hydraulic composite brake, including installing and testing hydraulicadjustment unit, stroke simulator, stroke sensor and other key parts of the compositebrake system. Modified the veDYNA vehicle model according to electric vehiclesstructure, and motor torque response model is established. Then designed the drivecircuit board to connect the dSPACE real-time controller with hydraulic actuators,process AD signals such as pressure signal, stroke signal, and I/O signals such asbraking, parking signals.Secondly, analyzed the work principle and structure characteristics of thehydraulic adjustment unit with flow valve, then established increase and decreasepressure mathematic models, and designed a switching PI controller based on themodel’s switch and multi-model non-linear characteristics, and analyzed the PIcontrol parameters correspond to the hydraulic pressure control performancethrough simulation, the convergence of the closed-loop system using the phaseplane method and the hardware experiments carried out based on the HIL platform.Simulation and experimental results show that the switching PI controller wouldmeet the requirements of hydraulic pressure tracking control requirement.Finally, the constraints of regenerative braking torque are analyzed. Then useda second-order to approach to the hydraulic closed-loop system model based onexperimental data. On the basis of piecewise affine model built by the motor andhydraulic model previously, using MPT toolbox designed predictive controller forhydraulic braking torque distribution. Then embedded the generated controller tothe veDYNA vehicle model for simulation, and analyzed the effects of predictionhorizon for the control effect.