Research On Integrated Control Of Steering System And Suspension System Of Multi-axle Vehicle

In modern construction, more and more multi-axis vehicles are used, du e to their strong off-road ability, high-intensity rough road passing ability, st eering flexibility, and strong driving force. Multi-axle vehicle have these cap abilities thanks to its multi-axle steering technology and oil and gas suspens ion technology. With the rapid development of construction, the driving envi ronment is more and more badly and changing, and the existing performanc e of multi-axle vehicles is limited. So more advanced multi-axle technology and oil and gas suspension technology are required urgently, what's more a good match between them. Faced with this situation, more and more dom estic and foreign enterprises and research institutes focus on electronic contr ol of hydraulic multi-axle steering technology and active oil and gas suspen sion. In addition, since the multi-axle vehicle itself has a powerful hydraulic power source, which provides a good platform for the installation of electr onically controlled hydraulic steering and active oil and gas suspension, sho wing that using electro-hydraulic active control to the steering and suspensio n of multi-axle vehicle has been the general trend. Considering the facts ab ove, multi-axle steering, suspension and integrated control of both technologi es are researched in this paper. First, the analysis of drawbacks in design a nd optimization of multi-axle steering mechanical linkage system is done, m ade quadratic optimization steering linkage necessity. In order to fundamenta lly solve the tire wear, and improve vehicle stability, multi-axle steering con troller is designed. Second, the analysis of the status of active suspension is done, and the necessity of using active suspension in multi-axle vehicle is proposed. Finally, the mutual relevant of these two technologies is studied, and the integrated control methods are given.Study of multi-axle steering technology is based on precise mathematical models. For ease of study, most researchers only built linear models of vehi cles, but establishing a system linear model is not enough for the actual hi ghly nonlinear multiple-axis vehicle. With this deeply in mind, on the basis of the multi-axle steering linear model established, a non-linear model of v ehicle systems is established in this paper.Suspension models include one-fourth model, half-vehicle model and the whole vehicle model. The first two cannot demonstrate the property of the suspension. Due to the high mass and the heavy load of the vehicles invol ved in this article, and the vehicle roll angle particularly concerned about, a whole vehicle suspension system model of multi-axle vehicle is established in this paper. By associating vehicle suspension model with steering model, 5+2n linear model and non-linear models are composited, and the correctne ss of the model was proved by MATLAB/Simulink simulation of vehicle m odel.Tire nonlinear is the main source of vehicle nonlinear and the core pro blems of vehicle dynamic analysis. This article proved the rationality with f inite element method by tire finite element calculation and comparison of c alculated and experimental data. The paper proposed a quadratic equation as expression of the tire model, fitted curve with evaluation data by using M ATLAB, gave imitative parameters, and got the tire model finally. By concl uding above work, a new establishment method of tire model was proposed, By above method, to establish the appropriate tire models used in this arti cle and to be compared with test proved the accuracy of the model, also p aved for later study.This article designed multi-axle steering controller and active suspension controller respectively. When multi-axle steering is researched, the existing situation of serious tire wear caused by the machinery multi-axle steering sy stem was analyzed. By making rigid rods used in optimization design flexib le, the result shows that the steering angles of each tire after simulation is different with the angle before flexibility, instead of relatively close to the a ctual angle. Showing that making the linkage system flexible is very import ant. Through the above analysis, showing that making the steering linkage s ystem flexible is necessary, and two corresponding optimization methods are given. But mechanical steering linkage can not fundamentally solve the pro blem of tire wear and improve the handing and stability of multi-axle vehic le. Considering the above questions, multi-axle steering controller is designe d in this paper, taking the actual lateral deflection angle of vehicle mass ce nter, body-side-angle and problems that the angle of roll speed was difficult to measured in mind at the same time, designed the Luenberger dimension reduction observer to estimate the value, and illustrated the superiority of c ontrollers through the analysis of simulation results, by using State feedback control method for multi-axle steering control.Contrary to the design of active suspension controller, the performance of H2 controller, H∞controller and H2/H∞controller are comparative an alyzed. The analysis shows that the active suspension H2 controller have g ood optimal performance of suspension, it could enable indicators performan ce of suspension to optimal, but this design of indicators is based on the in put of white noise random road, its ability to inhibit the external disturbanc e is not strong, considering the special operating environment of multi-axle vehicle, Just use the H2 controller could not make the need of multi-axle vehicle. For the purposes of the active suspension H∞controller, it had rob ust performance and has strongly interference inhibition, but its optimal perf ormance was worse than the H2 controller. In summary, the active suspensi on H2/H∞controller in this paper had the advantage of the H2 controlle r and H∞controller, it is not only make the performance of suspension to the optimal, but also it has good robust performance. the superiority of the H2/H∞controller is proved by comparative simulation, and H2/H∞contro Her is finally employed in this paper.The integrated control of multi-axle steering control system and active s uspension control system is the key issue in this paper. Firstly, by studying the steady-state model of multi-axle vehicle, the impact of vehicle basic pa rameters to the performance is found. Secondly, the problems to the vehicle under the separately control of the multi-axle steering controller and the ac tive suspension controller is studied, finding that the multi-axle steering cont roller has good handling and stability, could ensure driving safety, but this i s to the cost of the expense yaw rate of the vehicle. Active suspension cou Id inhibit the change of vehicle roll angle well, but it reduced the lateral fo rce of the vehicle, changed the steady-state performance of vehicle, it is ad verse to the safety of the vehicle. Through the above analysis, get that use the control strategy of active suspension coordinately of multi-axle to contr ol vehicle. The idea is that use the additional steering angle of each wheel to compensate loss of lateral force because of active suspension control to i mprove the control performance. Based on this, added the control strategy o f suspension coordinately to control the vehicle, and then by changing the c ontrol force of each suspension to change indirectly the suspension stiffness, lead to the change of the yaw rate of vehicle. By tracking ideal yaw rate, compensated the corresponding lack of yaw rate. The result of simulation analysis proved the superiority of integrated controllers.By researching in this paper, more reasonable technology which integrate d multi-axle steering system and active suspension system is finally obtaine d, it make the performance of vehicle chassis more substantial improvement and could reference and guide the relate research.