EPS System Characteristic Setting Technique Research

As the electric power steering system(EPS) compared to hydraulic power system(HPS) has great advantages in fuel economy, speed assist characteristic, assembly, maintenance and repair, particularly in the under-intermediate passenger cars with EPS system increasingly higher proportion. For OEM(original equipment manufacturer), on the one hand due to the requirements of the new car development cycles are getting shorter and the need of different deformation of the vehicle based on the same platform, matching the performance and set-up work of EPS system are increasing; on the other hand, the EPS system with speed steering assist characteristic design influences the stiffness characteristics of the steering system, and then influences the front and rear suspension cornering stiffness matching and design; a further aspect, the advanced chassis development process requires to control the pre-performance of the electronic control system on the virtual prototype stage, these three areas need OEM and EPS suppliers to build EPS control model, vehicle model and co-simulation platform, control parameters to match the virtual calibration and release work before the trial.Combined with FAW R&D Center research project and a passenger car product development project, this paper proposes vehicle steering and handling performance evaluation standards about EPS. The evaluation technique is used for the vehicle with EPS system steering and handling performance benchmarking, EPS performance optimization, EPS virtual calibration and the actual vehicle calibration, figuring out how to evaluate the performance of EPS. Innovatively proposing a testing method of the steering system characteristics based on K & C test bench. Through disassembling and combining the steering system, the friction and stiffness of the steering system components can be got disassembly for the system performance benchmarking and performance verification. Innovatively proposing that EPS suppliers supply control logical model in the form of package file, breaks the EPS modeling problems. Setting up the machinery, electronic control virtual calibration co-simulation platform by myself, and virtual calibrating the control parameters of the EPS control model based on the co-simulation platform to achieve pre-optimized EPS system features. Establishing a complete system of EPS matching process, including the EPS system performance evaluation method of vehicle handling, test methods of the system characteristics, virtual calibration simulation platform, the release of the virtual calibration parameters, calibration and performance verification of the actual vehicle, EPS system features top-down design based on the vehicle maneuverability.Specific studies are as follows:(1) Establishing of the EPS system performance evaluation method of vehicle handlingThrough searching and reading a large number of vehicle handling and steering performance test specifications about subjective and objective evaluation from both inside and outside OEMs and EPS suppliers, classifying and summarizing the evaluation conditions in the standard. Compared to the current vehicle handling and steering criterion about subjective and objective evaluation, and considering the characteristics of the EPS control strategy, adding the evaluation conditions covering the main control functions of the EPS system in current market, and adding evaluation indicators for steering force feedback characteristics, and then forming a complete vehicle steering performance evaluation method on account of EPS performance.(2) Building a testing method of the steering system characteristics based on K&C test benchA method to test the steering system overall characteristics had been developed in K&C test rig and in the vehicle state test. different steering systems disassembly combination thereof steering friction and stiffness of the system components can be used for standard system features and performance verification. Through disassembling and combining the steering system, the friction and stiffness of the steering system components can be got disassembly for the system performance benchmarking and performance verification.(3) Building a EPS virtual calibration simulation platformWhen building an EPS system model, taking into account that the system contains both complex control logic model, also includes multiple degrees of freedom mechanical part, it is difficult to use a single software for modeling and simulation. Matlab/Simulink platform is used for EPS control logic modeling, this model is provided in the form of S-function document by the suppliers of matching passenger car EPS models of FAW. ADAMS/Car is used for mechanical parts modeling of the steering system(EPS motor system and a reduction mechanism assembly, steering linkage mechanism assembly and mechanical steering). Combining the two parts models by ADAMS/Controls, establishing precise vehicle dynamics model, and building a complete model of a virtual loop calibration simulation platform.(4) EPS control parameters virtual calibrationSelecting parking maneuver force, low speed steering forces, returnability and central road feeling as optimization target. Calibration parameters are optimized, and using the genetic algorithm through i SIGHT software to optimize, so that the above vehicle steering performance is at or near the target level, this process is EPS virtual Calibration of the control parameters based on the vehicle steering performance. EPS system control parameters of the first edition are released before the completion of the trial prototype.(5) Actual vehicle calibration and performance verificationBased on one FAW passenger car platform, actual vehicle calibration were done on the A test trial vehicles matching the suppliers' EPS system. Building on the virtual calibration parameters of the released first version of the EPS system, then the subjective evaluation engineer calibrates the control parameter of the actual vehicle based on the performance of vehicle steering. And then makes the objective evaluation of the EPS performance to verify the EPS virtual calibration results.