Search Results

The joint forces and moments applied to the joints in an air suspension system in truck are important input loads for lightweight and fatigue analysis of bushings, air spring brackets, torque arms and trailing arms. In order to derive a reliable solution of joint forces and moments, engineers will generally use Multi Body Dynamics (MBD) simulation software, like ADAMS, which can save time in product development cycle. Taking an air suspension in truck as a study example, a 2-dimensional quasi-static model of an air suspension, whose stiffness of air spring and bushing is nonlinear, is established in ADAMS environment. After that, simulations are performed at the typical and extreme working condition respectively, and the results are compared with another three cases. Case I assumes that the stiffness of air spring is linear but the stiffness of bushings, including torsion and radial stiffness, are nonlinear.

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.

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.

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.

The trajectory planning and the accurate path tracking are the two key technologies to realize the intelligent driving. The research of the steering wheel angle plays an important role in the path tracking. The purpose of this study is to optimize the steering wheel angle input during the automated lane changing. A dynamic programming approach to trajectory planning is proposed in this study, which is expected to not only achieve a quick reaction to the changing driving environment, but also optimize the balance between vehicle performance and driving efficiency. First of all, the lane changing trajectory is planned based on the positive and negative trapezoidal lateral acceleration method. In addition, the multi-objective optimization function is built which includes such indexes: lateral acceleration, lateral acceleration rate, yaw rate, lane changing time and lane changing distance.

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.

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.

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.

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”.

Roll stability is an important attribute which must be accounted for in heavy trucks. In order to analyze the anti-roll performance of the suspension in the early period of development, engineers will generally use Multi Body Dynamics (MBD) simulation software which can save time in the product development cycle. However, air suspension employs levelling valves to adjust the height by charging and discharging air springs. The air spring is typically modeled as a closed container in the simulation; the stiffness change of the air spring caused by the levelling valve is not considered. In this paper, an air suspension with levelling valves model integrated into the multi-body dynamic model of a 6�4 heavy truck is built with a co-simulation technique to investigate the influence of three types of levelling valves arrangement on the roll performance of the suspension under two typical conditions.

An Inline 4-cylinder engine is equipped with second-order balance shafts. When the engine is running under no-load acceleration conditions, the gear system of the balance shaft generated whine noise. In this paper, an analysis and experiment method for reducing the whine noise is presented. First, a flexible multi-body dynamic model of the engine is established, which includes shaft and casing deformation, micro-modification of the gears. Taking the measured cylinder pressure as input, the load on each gear of balance shaft gear system is calculated. In addition, the influence of tooth surface micro-modification on the meshed noise was analyzed. The results show that the dynamic meshing force between the crank gear and the shim gear is large under the original tooth surface micro-modification parameters, which is the main reason of the whine noise.

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.

For the improvement of the vehicle yaw stability, this paper studies the control problem of the active front steering (AFS) system with actuator input delay. A novel sliding mode predictive control method to handle actuator input delay is proposed for the AFS system. Firstly, considering the nonlinearities of the vehicle system, a linear parameter varying vehicle system model with two-level structure is proposed to capture the vehicle dynamic behaviors. Secondly, to deal with the issues of actuator input delay and system constraints, a novel sliding mode predictive control method is put forward. In the process of controller design, a sliding mode control algorithm is employed for the improvement of the robustness of the control system, and then a model predictive control algorithm is employed to deal with system constraints.

Electronic expansion valve as a throttle element is widely used in heat pump systems and flow characteristics are its most important parameter. The flow characteristics of the electronic expansion valve (EXV) with a valve port diameter of 3mm are studied, when the refrigerant R134a is used as the working fluid. The main factors affecting the flow characteristics are researched by adopting the orthogonal experiment method and single factor control method, for example, inlet pressure, inlet temperature, outlet pressure and valve opening. The results show that the expansion valve opening degree has the greatest influence on mass flow rate. In view of the complicated phase change of the refrigerant passing through electronic expansion valve, it is difficult to model the flow characteristics accurately.

The silicone oil clutch is a device that uses the viscous shear force of silicone oil to transmit torque. Due to the difference in the rotational speed of the driving and driven parts, the silicone oil inside the clutch generates much heat, and the silicone oil temperature increases, resulting in a decrease in viscosity. Therefore, excellent thermal performance is necessary for silicone oil clutch to ensure torque transmission ability. This paper proposes a modeling method for analyzing the thermal performance of a silicone oil clutch. Firstly, the temperature measurement test for the silicone oil clutch is carried out by using wireless temperature measurement equipment. The driven speed, silicone oil temperature, and the temperature of different areas of the clutch shell are measured under different driving speeds.

Uniaxial fatigue tests of rubber dumbbell specimens under different mean and amplitude of strain are carried out. An Extreme Learning Machine (ELM) model optimized by Dragonfly Algorithm (DA) is proposed to predict the fatigue life of rubber based on measured rubber fatigue life data. Mean and amplitude of strain and measured rubber fatigue life are taken as input variables and output variables respectively in DA-ELM model. For comparison, genetic algorithm (GA) and particle swarm optimization (PSO) are used to optimize ELM parameters, and GA-ELM and PSO-ELM models are established. The comparison results show that DA-ELM model performs better in predicting the fatigue life of rubber with least dispersion. The coefficients of determination for the training set and test set are 99.47% and 99.12%, respectively. In addition, a life prediction model equivalent strain amplitude as damage parameter is introduced to further highlight the superiority of DA-ELM model.

If a car is braked frequently or at high speed, the thermal decay of brake system performance appears, which reduces the braking performance of the car. To compensate brake moment reduction during braking at thermal decay of brake system, a compensation strategy of brake moment is designed by using “feedforward +PID feedback” to pressure at wheel braking cylinder. The trigger and exit conditions of the strategy for the wheel cylinder pressure are proposed based on the threshold. A vehicle model consisting braking system is established if a vehicle runs at straight line, and the braking distance and braking acceleration are estimated, the results shown that the thermal decay compensation control strategy proposed in this paper can reduce the braking distance and braking time.

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.

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.