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This paper proposes a new evaluation method of analyzing stability and design of a controller for an electric power steering (EPS) system. The main purpose of the EPS system’s control design is to ensure a comfortable driving experience of drivers, which mainly depends on the assist torque map. However, the high level of assist gain and its nonlinearity may cause oscillation, divergence and instability to the steering systems. Therefore, an EPS system needs to have an extra stability controller to eliminate the side effect of assist gain on system stability and attenuate the unpleasant vibration. In this paper, an accurate theoretical model is built and the method for evaluating system quality are suggested. The bench tests and vehicle experiments are carried out to verify the theoretical analysis.

The fully decoupled brake by wire system is a complex system consisting of mechanical components such as springs and rubber and hydraulic structural components coupled together. Compared to conventional braking systems, it is characterized by the full decoupling of the brake pedal from the brake wheel cylinders in normal braking mode, and the pressure fluctuations in the wheel cylinders do not affect the pedal feel. In order to predict brake pedal feel in a passenger car, a dynamic model was developed for both normal and backup braking modes, taking into account the variation of the volume modulus of the brake fluid and the frictional forces of the master cylinder pistons. The influence of different pedal input speeds on the pedal feel characteristic curve was analyzed using static vehicle tests and the related parameters of the braking system were identified in order to correct the design data.

A fourth-order mathematical model for I-EHB (integrated electro-hydraulic brake) system was derived from its mechanical and hydraulic subsystems. The model was linearized at equilibrium state and then was verified by AMESIM software. The friction model of the system was analyzed based on static friction and viscous friction. A bench test was designed to identify the parameters of friction model. As the I-EHB system worked at different braking conditions, a PID-based switching controller was designed to track the target servo cylinder pressure. Both simulations and experiments results showed that, the response time of pressure was less than 120ms, and there was no overshoot, which helped handling different braking conditions and improving the braking safety and comfort.

Sliding mode control with a disturbance observer (SMC-DO) is proposed for suppressing the sprung mass vibration in a quarter-car with double-wishbone active suspension system (ASS), which contains the geometry structure of the upper and lower control arms. The governing equations of double-wishbone ASS are obtained by the balance-force analysis of the sprung mass in ASS. Considering uncertainties in damping, stiffness, and external disturbance acting on the sprung mass, we design a disturbance observer based on a sliding mode control (SMC) to estimate these uncertainties under the unknown road excitation. By the Lyapunov minimax approach, the uniform boundedness and the uniform ultimate boundedness of ASS with the proposed control are rigorously proved. Through co-simulation of ADAMS software and MATLAB/Simulink software, the sprung mass acceleration of ASS can be obtained with and without the proposed control.

A road test on semi-trailers is carried out, and accelerations of some characteristic points on the braking system,axles,and truck body is measured,also brake pressure and noise around the support frame is acquired.The measured data was analyzed to determine the causes of the brake noise, and the mechanism of the noise of the drum brake of semi-trailers during low-speed braking was investigated. The following conclusions are obtained: (1) Brake noise of the drum brake of the semi-trailer at low-frequency is generated from vibrations of the brake shoes, axle, and body, and the vibration frequency is close to 2nd natural frequency of the axle. (2) Brake noise is generated from stick-slip motion between the brake shoes and the brake drum, where the relative motion between the brake drum and the brake shoes is changed alternately with sliding and sticking, resulting in sudden changes in acceleration and shock vibration.

Tuned mass dampers (TMD) are frequently used in vehicles to resolve vibration and interior booming noise issues arising from powertrain's vibration and road excitation. This paper describes a driveshaft NVH case study in which analysis and test were used to solve the NVH problem. A TMD simulation package that utilizes a database of measured elastomeric material propertied. This facilitates the designing of optimized damper systems for a wide variety of vehicle applications. The simulation software takes into account frequency effects on elastomer properties while designing dampers. And the approach has proven to accurately predict performance in vehicles prior to manufacture. Rules of thumb for TMD design are discussed including locations for placement of dampers in automotive structures, determining the needed mass, and measurements and simulations that can greatly improve the success and reducing time-cost for TMD design.

This paper presents an adaptive H2/H∞ control strategy for a semi-active suspension system with unknown suspension parameters. The proposed strategy takes into account the damping force characteristics of continuous damping control (CDC) damper. Initially, the external characteristics of CDC damper were measured, and a forward model and a back propagation (BP) neural network inverse model of CDC damper were proposed using the measured data. Subsequently, a seven-degree-of-freedom vehicle with semi-active suspension system and H2/H∞ controller was designed. Multiple feedback control matrices corresponding to different sprung mass parameter values were determined by analyzing time and frequency domain performance. Finally, a dual observer system combining suspension state and parameter estimation based on the Kalman filter algorithm was established.

A new single-attachment air spring system with a parallel one-way tube is designed as a vibration isolation device for vehicles. The dynamics model of the new two-throttle tube air spring is established first, and the accuracy of the two-tube model is verified experimentally. Finally, the experimental results of the two-throttle tube air spring and the single-tube air spring are compared to analyze the effects of the tube diameter, tube length and additional air chamber volume on the dynamic stiffness of the two-throttle tube air spring. The results show that the combination of throttle tubes of different diameters has a great influence on the stiffness and damping characteristics of the air spring.

Because autonomous vehicles (AVs) equipped with active front steering have the features of time varying, uncertainties, high rate of fault, and high burden on the in-vehicle networks, this article studies the adaptive robust control problem for improving lateral stability in steer-by-wire (SBW) vehicles in the presence of abrupt nonlinear faults. First, an upper-level robust H∞ controller is designed to obtain the desired front-wheel steering angle for driving both the yaw rate and the sideslip angle to reach their correct values. Takagi-Sugeno (T-S) fuzzy modeling method, which has shown the extraordinary ability in coping with the issue of nonlinear, is applied to deal with the challenge of the changing longitudinal velocity. The output of the upper controller can be calculated by a parallel distributed compensation (PDC) scheme.

This paper designs the important components and structure of the integrated electro-hydraulic brake system (I-EHB). Firstly, the simplified linear system is modeled, and the transfer function without considering the nonlinear disturbance such as system friction is derived, and the correctness of the linear system is preliminarily verified by AMESim. Then set up the I-EHB system test bench, and use the Stribeck friction model to identify the friction torque parameters in the static and kinetic friction stages of the system to obtain a more accurate friction model. Finally, based on the I-EHB system model of friction disturbance, a pressure-speed-current three-loop cascade PID controller is designed, and a feedforward controller based on the system model is added to form the control structure of “pressure feedforward compensation + pressure-speed-current closed-loop cascade PID”.

The fatigue prediction model of an air spring based on the crack initiation method is established in this study. Taking a rolling lobe air spring with an aluminum casing as the studying example, a finite element model for analyzing force versus displacement is developed. The static stiffness and dimensional parameters of limit positions are calculated and analyzed. The influence of different modeling methods of air springs bellow are compared and analyzed. Static stiffness measurement of an air spring is conducted, and the calculation results and the measured results of the static stiffness are compared. It is shown that the relative error of the measured stiffness and calculated stiffness is within 1%. The Abaqus post-processing stage is redeveloped in Python language.

The characteristics of suspension elastic elements (i.e., spring, damper and anti-roll bar) are directly related to the handling and ride comfort performances, how to tune the characteristics of suspensions' elastic elements is always a big issue in developing the chassis of a vehicle. In this paper, a multi-body dynamics model of a passenger car within MSC.ADAMS® is integrated with iSight FD®, an optimization tool, to carry out a multi-objective optimization for improving the behavior of vehicle handling and ride comfort. The characteristics of suspension elastic elements (i.e., spring, damper and anti-roll bar) are considered as design variables. For handling, the objectives are defined by the measurements from multi-body dynamics simulation of typical double lane change according to ISO3888 standard. For ride comfort, the frequency-weighted RMS (Root Mean Square) value of vertical acceleration of the front seat rail according to ISO2631 standard is set as the objective.

An experiment is carried out to measure creep groan of a drum brake located in a trailer axle of a truck. The noise nearby the drum brake and accelerations on brake shoes, axle and trailer frame are collected to analyze the occurring conditions and characteristics of the creep groan. A multi-body dynamics model with 1/4 trailer chassis structures is established for analyzing brake component vibrations that generates the creep groan. In the model, the contact force between brake cam and brake shoes, the contact friction characteristics between brake linings and inner circular surface of brake drum, and the properties of chassis structure are included. Dynamic responses of brake shoes, axle and trailer frame during the braking process are estimated using the established model and the responses are compared with the measured results, which validate the model.

In order to study the effects of different factors on the static and dynamic characteristics of air springs, three models were established to calculate the static and dynamic characteristics of air springs, including modeling at the design position, modeling only considering the straight state, and modeling considering the thickness of the bellows in the straight state. Static stiffness of air springs is calculated using three different models and are compared with experiments. In the straight state model considering the thickness of the bellow, the influence of aluminum tube and bellows thickness on the static stiffness are considered, and the modeling with the straight state solved the problem of the change in cord angle after the air spring was inflated and expanded. The established model is then used to calculate static and dynamic characteristics of air springs, such as static stiffness, hysteresis loop, and dynamic stiffness.

Taking a closed airbag suspension system as studying objects, the nonlinear dynamic model of the reservoir, compressor, solenoid valve, pipeline and air spring is established. The compressor exhaust volume, solenoid valve flow rate and air spring charging and discharging rate are calculated and compared with experiment to validate the model. Taking pressure difference and height adjustment rate under different working conditions of an airbag suspension as control measures, a control strategy is developed based on the established nonlinear dynamic model. The result indicates that when the vehicle is in curb weight, design weight and GVW (gross vehicle weight), the working time of the compressor can be reduced by 13.6%, 15.1% and 46.5%, respectively, compared with the conventional mode, during a height adjustment cycle. Then a state observer is proposed to estimate the steady-height for reducing the disturbance of measured height from road excitation.

The decoupling brake-by-wire system controls the key components of the flow path and liquid flow of the whole brake system through the solenoid valve of the bottom control unit. The reference cross-sectional area value at the valve inlet is obtained by calculation, and the valve body structure model is established. The flow channel structure is extracted, and the porous media model is used to replace the fluid area of the filter screen at the entrance of the solenoid valve. The Fluent software is used to analyze the influence on the flow characteristics of the solenoid valve with or without a filter. The accuracy of the model is verified by the experimental results, which also show that the porous medium can effectively and accurately reflect the characteristics of the solenoid valve end filter.

The static characteristics of solenoid valve play an important role in the performance of brake system and can indirectly reflect the response speed of the brake system. The static characteristics of the solenoid valve reflect the electromagnetic characteristics of the solenoid valve itself, revealing the maximum potential of the solenoid valve in the system work, which is one of the important characteristics to characterize the working ability of the solenoid valve. In this paper, a numerical calculation method is used to build a finite element model of the solenoid valve electromagnetic field on the Ansoft Maxwell simulation platform. The model takes into account the nonlinear magnetization characteristics of soft magnetic materials and the air gap.

Air springs with auxiliary chambers (ASAC) are widely used in automotive suspension systems. The introducing of the auxiliary chamber and the connecting flow passage makes the system more complex, especially in which case an additional resonance peak caused by the air inertia in a connecting pipe appears. To characterize the nonlinear dynamic characteristics, this paper proposes a novel physical-neural network hybrid modeling method for ASACs. Firstly, experiments are carried out to measure the dynamic characteristics of ASACs. Then, based on the thermodynamic principle, a nonlinear dynamic characteristic model for the ASAC is developed and a linearized process is performed to obtain a linearized physical model. Due to the amplitude dependence and frequency dependence in the dynamic characteristics of ASACs, the physical model cannot accurately characterize these nonlinearities.

In order to improve the ride comfort and road friendliness of heavy commercial vehicles, a lateral interconnected air suspension system is developed. Based on the theory of thermodynamics and vehicle dynamics, a Ten-degree-of-freedom vehicle dynamics model with lateral interconnected air suspension is established. Interconnected pipeline parameters’ influence on characteristics of air suspension system in whole vehicle are calculated and analyzed. Simulation results show that the stiffness of air suspension decreases gradually with the increase of interconnected pipeline diameter. The designed interconnected air spring experiments verify the simulation results. Simulation on vehicle dynamics models is carried out by building random road models with different roughness levels in MATLAB.

The vehicle will produce certain shock and vibration during the braking process, which will affect the driving experience of the driver. Aiming at the problems of pitch vibration, longitudinal vibration and shock during the braking process, this paper proposes a planning and following control method for target longitudinal acceleration in post-braking phase, and designs control trigger strategies. Target longitudinal acceleration planning takes minimizing longitudinal shock as the design goal. The following control takes the brake pressure as the control object, and adopts the “feedforward +PID feedback” method to follow the target longitudinal acceleration. Besides, considering the safety of braking process, the trigger condition of control is designed which utilizes BP neural network method to judge whether the control has to be triggered. Based on Simulink software, the simulation model of straight-line braking is established.