Research On The Closed-loop Control Method Of Automobile Steering Motion For Motion Quality

In recent years,the automobile industry has developed rapidly,and consumers have put forward higher requirements for the motion quality of automobiles.Regarding steering motion,consumers are mainly concerned about the stability of the motion,the steering feel,the return speed after releasing the steering wheel(or partially holding the steering wheel),and the consistency of the above performance after long-term use.There are still some urgent issues that need to be addressed in improving the quality of steering motion.Firstly,at the current stage,it mainly relies on the field test at the late stage of development and the subjective experience of test drivers to iteratively adjust the control parameters of the steering system,which is aimed at improving the steering feel and return performance.However,this approach is challenging and does not always meet the driver’s expectations.It is also difficult to ensure consistent style among vehicles of the same brand.Secondly,to ensure the consistency of performance of mass-produced vehicles,OEMS have been increasing the requirements for the manufacturing,assembly of steering system components,and wheel alignment precision,which raises manufacturing costs.Additionally,the performance decline of functional components or changes in wheel alignment can decrease steering motion quality.The existing steering system control strategies are primarily based on assistance,utilizing either torque closed-loop or angle closed-loop control methods.Due to the absence of motion closed-loop control,it is impossible to control and adjust the steering feel and return speed directly,and they can’t ensure the consistency of their performance and stability of motion,which increases the difficulty of engineering calibration in the later stage of development and the demand for precision manufacturing.In addition,due to insufficient consideration of road surface information,there are problems with poor steering feel and return performance when driving on wet roads.Ensuring that mass-production vehicles have good motion stability and consistent,controllable,and road-adapted steering feel and return performance in the whole life cycle has become one of the development problems of the automobile industry.To solve the above problems,this paper proposes an automotive steering motion closedloop control method for motion quality.The driver’s steering torque is directly analyzed as motion demand.Through the closed-loop control of steering motion intensity,the mass-production vehicles have good motion stability and consistent and controllable steering feel and return performance in the whole life cycle.It also considers the impact of road conditions on determining motion intent and implementing control,and the steering motion quality on different road surfaces is improved.The main research contents of this paper are as follows.First,research on the theory and method of vehicle steering dynamics modeling.In this paper,the modeling methods of vehicle critical systems and assemblies are studied,which directly affect steering motion and steering feel.And a dynamic model that can meet the development needs of driving motion quality is established.The model’s accuracy is verified by comparing virtual and on-road field test results,providing a testing and verification platform for subsequent control strategy development.Second,research on psychological methods of driver’s torque intention.Existing steering system control strategies often directly interpret the driver’s steering torque as assist demand or steering system position demand without establishing a direct relationship between steering torque and steering motion intensity.This leads to difficulty tuning and aligning the steering feel with the driver’s expectations.To solve the above problems,a method is proposed that represents the driver’s torque intention using steering motion intensity.By establishing an ideal relationship between steering torque and steering motion intensity based on Stevens’ law,a theoretical basis is provided for designing and adjusting steering feel,which effectively addresses the challenge of tuning steering feel.Third,research on the steering motion quality control method based on motion closed loop.Existing steering system control strategies,which often use torque or angle closed-loop control methods,fail to guarantee motion stability and cannot directly adjust steering feel and returning speed or address performance decline of the above performance after long-term use.To solve the above problems,a steering motion quality control method based on motion closed-loop is proposed.First of all,the desired steering feel and return performance is set.On this basis,the steering feel and the return speed after releasing the steering wheel(or partially holding the steering wheel)are achieved through the motion closed-loop.The straight-line driving stability is improved,and the difficulty of engineering calibration in the later stage of development is reduced.In addition,the demand for precision manufacturing is reduced.It ensures that the mass-production vehicles have good motion stability,consistent and controllable steering feel,and return performance in the whole life cycle,which makes it possible for low-cost vehicles to have high motion quality.Fourth,research on the road adaptive method for steering motion quality.Aimed at the pool steering feel and return performance when driving on wet roads,a road adaptive method for steering motion quality is proposed.The road friction coefficient is identified based on typical road data and considering the influence of vehicle load and slope change.The steering style,torque hysteresis characteristics,return time,and the inverse vehicle dynamics characteristics used in the control are adjusted based on the identification results.This allows for modifying the driver’s motion intention and improves vehicle steering motion control accuracy.It ensures that the steering feel and return performance align with the road conditions,which significantly enhances the steering motion quality when driving on different road surfaces.Finally,a driver-in-the-loop simulation test verification platform based on d SPACE is established,and the proposed closed-loop control method for improving steering motion quality proposed in this paper is validated in a driving simulator environment.The results indicate that the research in this paper significantly improves the steering motion quality of vehicles.It can ensure mass-produced vehicles have good motion stability and return performance throughout their entire lifecycle.It can also ensure mass-produced vehicles have a consistent,controllable,and road-adapted steering feel.It significantly reduces the difficulty of calibration in the later stages of development and the demand for precision manufacturing,which makes it possible for low-cost vehicles to have high motion quality.