Electric Vehicle Hardware-in-the-Loop System Development Based On CompactRIO

In face of the urgent situation of energy safety，environmental pollution and globalwarning, developing energy saving and new energy vehicle has been the strategic directionof Chinese Automotive industry. Additionally, the chronic and frequent haze gains electricvehicle unprecedented attention and support.VCU is the command center of an electricvehicle and it executes multi-tasks when running a vehicle, hence, whether or not thestrategy is proper directly impacts the performance and safety of a vehicle. In order to carryout an effective and comprehensive testing of VCU control strategy, HIL is widely adoptedby auto makers. In this paper, an electric vehicle is chosen as the research object，on thebasis of which, electric vehicle HIL system development is discussed using CompactRIOembedded real-time system. A general method and procedure of building electric vehicleHIL system is demonstrated both on software and software aiming at illustrating self-builtlow cost HIL system can also qualify the testing requirements with the help of resourceallocation and program optimization, thus getting rid of the huge expense and bondage ofcommercial software and devices. The main work of this paper includes:Establishment of electric vehicle forward simulation model. Based on experiment dataand theoretical formulas, electric vehicle model including battery model, motor model,chasis model, vehicle dynamic model and driver model is built in LabVIEW environment.This modular modeling method makes it easier to modify the model and have moreflexibility.Hardware function classification and software architecture establishment. Consideringthe requirements of testing, this paper chooses low cost CompactRIO9073as the real-timecontrol system. There are majorly three parts included in this platform: upper machine,real-time controller, and FPGA. The duty of each part is designated accordingly. On thebasis of hardware function classification, software architecture is established as Host VI,Target VI and FPGA VI. Among which, Host VI provides a friendly interface for HIL;Target VI runs the vehicle model in real-time and communicates with upper machine andFPGA; FPGA VI reliably acquires signals with high speed and runs the pre-charge model.Through reasonably assigning hardware and software function, the self-built HIL system is capable of responding to both fast and slow time step which increases the HIL testingscope.Research on multi-task in real-time system. In this paper, we divide the tasks runningon real-time controller into time critical task (model cycle) and non-time critical task(communication cycle). By setting a higher priority to the time critical task and using FIFOto pass data between tasks, real-time is guaranteed.Exploration of program optimization in real-time system. when program is deployedon real-time controller, the off-line simulation model need to be modified and optimizeddue to the limited resource. Through literature and experiment, program optimizationmethod is presented in this paper, including: setting cycle time step with a reasonable value;avoiding excessive usage of resource consuming variables; choosing program running placeproperly; considering the influence of displaying tasks. Moreover, the optimization methodis not merely restricted to this project, but is a general one for building HIL system andprovides a certain reference for others.Validation of simulation model and electric vehicle HIL testing. By comparingsimulation results and experimental results, the simulation model is validated hence isqualified for HIL testing. On the basis of the ensured model credibility, comprehensiveexperiments including substate-jump, control strategy under different driving scenarios andfault injection for pre-charge switches are carried out to test the VCU. With simulationmodel accuracy ensured and VCU control strategy validated, the last part in this paper teststhe dynamic performance and economy of the simulated electric vehicle which validates theVCU control strategy and confirms the self-built HIL system has a high accuracy to meetthe test requirements.