Analysis On Some Problem Of Vehicle Structue System

This dissertation studies several problems of vehicle system structure from theperspective of intelligent control, random vibration response analysis, numericalcalculation of transient temperature field, fault diagnosis, and reliability analysisthrough various theoretical methods, where models of various components of a vehiclesystem are considered. The main research contents are shown as follows:1. Intelligent control of automobile anti-skid control system. The structure of ananti-skid control system is complex and many uncertain factors influence the adhesioncoefficient between wheels and ground surface. Therefore, it is difficult to establish thecontrol model by means of traditional control theory. This research selects the slip rateand acceleration/deceleration rather than the parameter of speed difference as thecriterion of anti-skid control systems. A fuzzy neural network control model isestablished in this dissertation according to the three physical quantities above.2. Random vibration response analysis of the random parameters vehicles underrandom excitation. The question of random vibration response about nonlinear vehiclesystem with uncertainty structural parameters has been studied byfive-degree-freedom nonlinear vehicle model. The system power response analysismodel is built with respect to the following aspects:1) the mass, the damping, and thestiffness of a vehicle system are considered to be random variables,2) the nonlinearspring between tires and the body is considered,3) excitation to a vehicle caused byuneven road is thought as a white noise process. The nonlinear vehicle system isequivalently linearized by the energy difference method. Then the Lyapunov equationof the linear system is solved. Afterwards, the covariance matrix of stationary randomvibration response is obtained. Vibration response variance value of the equivalentlinear vehicle system can be got by multiple iterations, in each step of which aLyapunov equation is solved.3. Numerical analysis on transient temperature field of a braking drum withinterval parameters. The finite element calculation model on transient temperature fieldof a braking drum is built according to the theory of heat transfer and characteristics ofdrum brake structures. All parameters and boundary conditions of drum brake areconsidered as interval variables. Interval finite element analysis and perturbationmethod are combined based on finite element discrete and time difference method.Afterwards, a perturbation calculation formula of uncertain parameters transient temperature response is derived and the transient temperature field response range ofdrum brake structure is obtained.4. Vibration analysis and dynamic parameters optimization of automobilesuspension system.By using multidimensional convex model theory, the vibrationcontrol problem of automobile suspension system with uncertain parametersapproximated by a deterministic one is discussed. By using convex model theory, theuncertain parameters impacting on an automobile suspension system is analyzed basedon matrix perturbation method. In addition, the estimation of the upper and lowerbounds of both real and imaginary parts of the eigenvalue of closed-loop systems ispresented. By using four-degree-freedom automobile suspension system for models, theconcept of the variance is introduced into the gray correlation degree. In order to avoidlocal convergence phenomenon when gray particle algorithm is solving multi-objectiveproblem, and to obtain the solution of the multi-objective optimization problem ofautomobile suspension systems, the global extreme value and local extreme value ofparticle swarm algorithm are selected by reliable gray correlation degree.5. Fault diagnosis and prediction of automotive brake system. A comprehensiveassessment model is presented based on improved fuzzy gray relational analysis method,the influence of distinguishing coefficient size on relational degree is analyzed, andcommon rules and specific methods are given, which can solve the problem thatdistinguishing coefficient is difficult to be quantified. The improved correlationcoefficient is determined by a method that distinguishing coefficient is identifiedreasonably. The combination of fuzzy mathematics and generalized weighted distancetheory and performance of automobile brake system are assessed after its influencingfactors are fuzzy and grey. In addition, after combining the characteristics of fuzzymathematics and nerve network, difficult fault of automotive ABS is diagnosed byimproved BP fuzzy nerve network model. The gray relation analysis and support vectormachine model are combined to create a gray support vector machine prediction model.In order to improve the prediction accuracy, initialization parameters of gray supportvector machine was optimized by particle swarm optimization algorithm, using theoptimized parameters conduct fault diagnosis, and forecasting to automotive brakesystems.6. The reliability analysis and reliability prediction of automobile brake system andautomobile tire. The method of fuzzy synthesis evaluation is presented to implement thesystem’s reliability assignment. All elements influencing the ABS reliability aresynthesized and quantified, thus the reliability of the system is scientific and reasonable allocated. By using probability interval theory and D-S (Dempster-Shafer) theory, faulttree analysis method of automobile tires and automobile brake system is proposed. Thequestion of reliability is analyzed and studied, when automobile tires and automobilebrake system are running and the reliability of system is predicted on the basis ofsystem fault tree analysis.