Study On Adjustment Method Associated With Statistic Of Suspension Working Space For ECAS Ride Height System

ECAS (electronically controlled air suspension) can adapt to different road conditions and riding velocity,switching and controlling the suspension height automatically.In this precedure,the core of ECAS suspension height control is generation strategy of target ,which is the based on identification of road profile and operation condition. In this paper,the subject of" Study on adjustment method associated with statistic of suspension working space for ECAS ride height system "is selected by analyzing the existing ECAS system target height adjustment mechanism and control strategy.The subject oriented the actual status and development of ECAS application in China,combined Zhejiang Province major project "Development and application research on ECAS system ".Research followed the technology route from theoretical analyzation ,simulaition ,test validation in sequence.A series of cumulative probability models have been established to identify the bumping determined by the road profile and riding velocity when vehicle riding on random road surface ,by the analyzation of the relevence of suspension working space and road profile,fully utilizing the height information acquired from the original ECU,height sensors,and other hardwares in ECAS system.Moreover,the target control patterns and controller of ECAS are designed,as the basis of the stragety generation of target control patterns in ECAS system development and application which include suspension height and damping control, switched automatically according to road profile and operation conditions.Extensive review on the literatures about ECAS automatically control pattern,height control algorithm,identification methods and algorithms of road profile have been conducted.Identification of road profile is the stdudy basis of suspension performance control stragety in controllable suspension, including through the installation of sensor signals for vehicle dynamic response, by means of an intelligent algorithm deducing level of road bump have had a wide range of research methods, or by laser radar, advanced remote sensing devices such as stereo cameras to identify in advance the road to achieve preview control. As for the suspension height control algorithm, a lot of researches have been conducted on variable structure control, and hybrid system control method.However,applying the height information available in ECAS height sensor to identify road profile ,and the generation stragety research of target control patterns,slightly less adequate.In order to generate valid standard road profile to investigae the relationship between suspension working space and road profile, a filtered white noise method has been employed to generate road profile, furthermore, problems and reasons existed in the method have been probed,some improvement on parameters selecting and setting in simulation have been presented.The accuracy of simulation has been improved by figuring out the undetermined factor between input and output of filtered white noise model through linear fitting; Analyses are performed to the gas thermodynamic process in air spring and sprung mass dynamic in leveling procedure of electronically controlled air suspension, by which equations of air spring pressure gradient, air flow rate,and sprung mass dynamics after solenoid valve action are derived. Furthermore,a vehicle dynamic model coupled height adjusted model is set up,and validated by eigen frequency test and suspension height leveling test. The overcharge and overdischarge during the course of suspension height leveling have been simulated,the cause has been analysed also.The statistical characteristics of the dynamic response of suspension affected by the rough road. In the assumption that the random input is a gaussian process with ergodic, stationary and zero mean value, the statistical characteristic value of rough road is determined. Based on the assumption of normal distribution, theoretical analyzation has performed with the relevence between suspension dynamic response and statistical characteristics of rough road in macroscope,A cumulative probability model is constructed to microscopically analyze the cumulative probability distribution of the suspension dynamic response beyond the characteristic value of rough road in a given detection period,and the relationship between the cumulative probability model and the road roughness has been determined. An event construction method for the detection of suspension working space signal in a certain observation period for rough road identification is proposed. Respectively from random road input for single wheel excitation, double wheel excitation, linear model, weak nonlinear model, soft damping and hard damping, etc. The normal distribution of the response of the suspension working space, statistical characteristic value on macroscopic, a certain observation period relative to the bumpy road characteristic value of the cumulative probability distribution on microscopic under the random road excitation are simulated and analyzed. The proposed probability model for identification of rough road is verified through road roughness test,the height sensor characteristic test,and full scale vehicle suspension working space test.According to the requirements of the ECAS system, the target height generation strategy and damping control strategy of ECAS are proposed, and acquisition process of height signal,control flow of the target height, and target damping are designed. Based on the PID algorithm, the height of the control for control system of ECAS has carried on the simulation design and implementation.