| The automobile is the pillar industry of our national economy,and the automobile is an industrial product integrating the latest technology.The performance of the automobile chassis is an important reflection of the intrinsic product quality of the automobile.Self-driving car technology is developing rapidly.When intelligent assisted driving technology frees the driver's hands,motion sickness in autonomous cars is also getting more and more attention.Comfortable,relaxing and natural driving experience is the eternal pursuit of the performance of the car chassis.Semi-active suspension systems have the advantages of good performance,high reliability,and low energy consumption,and have been studied by a large number of scholars,and are gradually applied to high-end cars.The semi-active suspension adjusts the damping coefficient of the shock absorber according to the road excitation condition in real time to adapt to different road excitations,and improves vehicle comfort and safety.According to the choice of different chassis driving modes,the best control strategy for different suspension control targets has become the key to the development of semi-active suspension control strategies.It is of great significance to develop semi-active control algorithms for electronically controlled suspension products.Semi-active suspension control algorithms have been developed for more than 40 years,and control algorithms have been studied under various control theory frameworks.However,the optimal control algorithm for a specific control target has not been clearly defined.This paper conducts research from this perspective,proposes the best control strategy in the full frequency domain for different suspension performance targets,and performs theoretical proof,simulation verification and experimental comparison to prove the effectiveness of the algorithm.The main research contents of this article are as follows:Firstly,the semi-active suspension of the control object is modeled,and different forms of excitation roads are established.The performance evaluation indexes and evaluation methods of the suspension are introduced,and the accuracy of the two-free model is explained.Aiming at the modeling method of the adjustable damping shock absorber,this paper takes into account the actual engineering product development needs,selects a non-parametric modeling method,and draws on the modeling ideas of the UniTire tire model,a UniDamper damper model suitable for adjustable dampers such as electromagnetic valve-controlled dampers and magnetorheological fluid dampers is proposed,have the advantages of less identification parameters and meeting physical boundary conditions.In order to accurately describe the response characteristics of the shock absorber,a dynamic model of the response characteristics of the shock absorber is established.Secondly,a comparative analysis is made on the control strategy for the ride comfort with the minimum body vibration acceleration as the control target.The related control algorithm is theoretically explained using energy transfer theory,and the different control characteristics of SH and ADD control are explained from the perspective of the control logic phase relationship.Then,the body acceleration signal is proposed at-90 ° at low frequency Phase compensation makes its control effect close to SH control at low frequencies and close to ADD control at high frequencies.This modified ADD control strategy has the control characteristics of reducing vehicle body vibration acceleration in the full frequency domain.Then the theoretical analysis of the amplitude and frequency characteristics of the transfer function model of the ideal SH and ADD control is performed,and it is confirmed that the modified ADD control does have practical advantages and theoretical foundations,and is verified by simulation.Thirdly,for the driving safety-oriented GH control algorithm,a comparative analysis is made on the two control algorithms,speed GH and displacement GH.Similarly,phase compensation is used to phase compensate the tire vibration speed.In this way,the modified GH control can effectively reduce tire movement deformation,improve driving safety.In order to comprehensively consider the performance of the suspension,the weighted factor method is used to mix the modified ADD with the GH and the modified GH,respectively,to form two kinds of the best hybrid control algorithms in the full frequency domain,and the verification is performed through simulation.Fourthly,taking the magnetorheological damper as the research object,the response characteristics were analyzed and tested,and it was found that the response time of the shock absorber was affected by factors such as movement direction,speed,drive current amplitude,and controlled bus voltage.The feedforward-proportional-integral control strategy is adopted to improve the response time of the electromagnetic system of the magnetorheological damper.In order to improve the anti-interference performance of the control algorithm,an ideal MADD reference model based on the ideal damping force element and the gravity force element is proposed.The control algorithms are simulated and compared under different damper response times.It is found that the sliding mode control using the reference model is less affected by the change of the shock absorber response time and has strong anti-interference ability.Compared with other algorithms,it has more algorithmic advantages.In terms of suspension performance,the vibration acceleration of the vehicle body is more easily affected by the response time characteristics of the shock absorber,and the dynamic deformation of the tire is less affected by the response time of the shock absorber.Finally,a absorber HiL test bench for suspension control was developed using an absorber test bench.The working principle of the absorber HiL test bench was introduced,and the follow-up characteristics of the test bench were analyzed and verified.The kinematics-dynamics model of the double wishbone suspension is presented.Use this test bench to verify the control algorithm in the previous chapter.Using the HiL test of the damper,it is further shown that the control algorithm proposed for different control targets has more advantages than other algorithms.The innovation of this article is mainly in the following aspects:(1)Aiming at the needs of engineering development for semi-active suspension control,fully considering the external characteristics and response characteristics of the shock absorber,a UniDamper absorbermodel for suspension control is proposed.(2)Theoretical analysis of the phase frequency characteristics of the control logic of SH and ADD,the modified ADD control and the modified GH control considering the phase compensation characteristics of the input signal are proposed,and finally the two optimal hybrid control strategies are proposed by means of the weighting factor(3)Using the ideal vibration suppression model under the physical force element,the sliding mode control combined with the reference model of ideal SH and ADD control is proposed,which breaks through the parameter perturbation and modeling uncertainty caused by nonlinear factors such as shock absorber response time,and improves the control effect and anti-interference of the algorithm. |
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