Study On Integrated Chassis Control For Electric Vehicle Based On FlexRay

With the increasing popularity of electric vehicle and hybrid vehicle, research ofintegration of the vehicle control system has entered a new stage. Because control system ofpure electric vehicle is generally more than the traditional vehicle, so for vehicularcommunication, there will be more control system was added to the in-vehicle networkapplications. Therefore, signals transmitted on the bus are numerous in the integrated controlsystem for electric vehicles. This has put forward higher requirements for transmission rateand a transmission cycle and real-time performance of the systems. The busload on the busalso increases. This may affect the communication performance of the whole communicationnetwork and led to the result that control target of the control system can’t be achieved.Traditional CAN network is not fully qualified within the existing ability, the FlexRaynetwork with a high-bandwidth, dual redundant communication and trigger based on timeand events alleviate these problems. Thus, the addition of a new type of in-vehicle network-FlexRay network is extremely necessary. Based on the scientific research project of theelectric vehicles chassis dynamics control system development, in this article integratedchassis control for four-wheel steering, four-wheel drive\braking electric vehicles has beenstudied and modeled on the basis of FlexRay network platform.First, considering the effectiveness and portability of the integrated control algorithm,choose hierarchical control architecture with the aim to control the vehicle stability. Thisarchitecture including the perception layer to estimate driver’s intention, the vehicle bodymovement control layer, the tire force optimization distribution layer and the actuator controllayer. Select sliding mode controller with a certain robustness to obtain the force and torqueof vehicle body motion control layer. The optimization distribution of tire force takes intoaccount the optimization objectives and constraint conditions. By minimizing the objectivefunction to distribute the force and torque in order to get the longitudinal and lateral tireforce. At the same time, considering the actuator’s own constraints, put the response speed and saturation constraints of the actuators as the constraint conditions of the optimizationobjectives. Finally, actuator control layer is responsible for calculating the actuator controltarget by the desired tire force, and put it as the input values of the actuator controller.Then design FlexRay communication network and build the experimental platform.Take apart the integrated control algorithm model, divided into different control node, takinginto account the FlexRay bus features and signals’ requirements for integrated controlalgorithms, to establish FlexRay database meet protocol specification using NetworkDesigner software. In terms of network topology, compare the advantages and disadvantagesof all kinds of topology structure,"passive star” topology is more able to adapt to the layoutof the existing experimental platform and more in line with topology requirements of eachnode. In the building of hardware platform, the hardware of the network node controllerreplaced by rapid prototyping controller MicroAutoBox of dSPACE company, then toachieve FlexRay network development through the effective fusion withMATLAB/SIMULINK platform.Finally, choose FMVSS126, low adhesion road steering step conditions and ISO3888todo offline simulation of integrated control algorithm and hardware in the loop experimentsbased on FlexRay network platform in order to verify the validity and real-time of theintegrated control algorithm and practicability of the FlexRay network platform. Concludedfrom the experiment result, the integrated control algorithm can satisfy the vehicle’s controlrequirements for the stability under limit conditions. Meanwhile, we can find better real-timeperformance of the control algorithms by comparing the offline simulation andhardware-in-loop experiments, this shows that the formulation of the FlexRaycommunication protocol is reasonable and the hardware-in-loop platform based on FlexRaynetwork is practical and scalable.