Vehicle System Dynamics Research Articles

A new hydraulic damper dynamics model and the availability on high speed vehicle dynamics investigation

The function of the hydraulic damper of the high-speed Multi-Electric-Units (EMUs) is to offer viscous damping to reduce the vibrations and to keep the stability of the vehicle. It is the key component and it has great effects on the high-speed EMU dynamics. A new hydraulic damper dynamics model including two clamping points stiffness, a viscous damping and two centralised masses, is presented in this paper. A high-speed vehicle–track interaction dynamics model is developed, in which the new hydraulic damper dynamics model is introduced in it to investigate the damper and vehicle dynamics. With numerical simulation, the clamping point loads and damping forces of four types of dampers of the vehicle are obtained. The reliability of the new damper dynamics model is validated with comparison between the simulation results and the field test results. The availability of the new damper dynamics model is confirmed with the comparison of the results between a simplified damper dynamics model and the new damper dynamics model for two types of high-speed EMUs in China. With the help of the new damper dynamics model, the optimised clamping point stiffness of the dampers and the effect of the damper mass on the vehicle system dynamics are discussed. The investigation results show that the vibration difference between the damper and the connected components of the vehicle could be obtained.

An innovative stepwise time-domain fatigue methodology to integrate damage tolerance into system dynamics

With the development of vehicle system dynamics, the multi-body system simulation has been proven as an effective and cost-saving way to obtain fatigue loads of high-speed railway bogies. However, the application of simulated dynamic stress spectra is usually limited to the classical damage accumulation design. Moreover, the advanced damage tolerance philosophy for railway bogies are mainly based on standard prescribed loads or measured loads. To this end, a novel time-domain stepwise fatigue assessment (TSFA) methodology was proposed to effectively bridge the vehicle system dynamics with fracture mechanics. The research results indicate that the welded butt joints of gearbox bracket are the most critical positions for bogie frames made of S355J2W steel with an estimated life of 162.7 years. This is conservative enough for the conventional safety life design. However, the residual life abruptly decreases to 26.4 years once a crack with the length of 6 mm initiates near the weld toe, and the service lifetime of 30 years cannot be covered yet. This agrees well with the practical maintenance cases and full-scale benchmark tests. Therefore, the newly-proposed TSFA approach is suggested while determining the damage tolerance and maintenance strategy of defective bogie frames under complex dynamic vibration responses.

Distributed Drive Electric Bus Handling Stability Control Based on Lyapunov Theory and Sliding Mode Control

To improve the handling stability of distributed drive electric buses, a vehicle stability control system based on direct yaw moment control (DYC) with a hierarchical control structure was designed. Considering that the vehicle dynamics system is highly nonlinear, a nonlinear controller based on Lyapunov stability theory was designed to calculate the required additional yaw moment of the vehicle in the upper controller. In the lower controller, the additional yaw moment is distributed to four wheel-side motors according to the equal proportion torque distribution method, and the direction of wheel-side motor output torque is determined based on the steering state of the vehicle. A co-simulation based on Simulink and Trucksim was conducted to verify the designed controller under two extreme conditions. Simulation results indicate that the proposed method performs feasibly and effectively in the handling stability of vehicles. Compared with traditional sliding mode control (SMC), the proposed control strategy can significantly reduce the chattering of the system, which provides a theoretical basis for the application of this yaw stability control method in engineering practice.

Setting the speed limit for highway horizontal curves: A revision of inferred design speed based on vehicle system dynamics

An inferred design speed (IS) is the maximum vehicle speed for which all critical design speed-related criteria are met at a particular location, which is widely recognized as an important speed limit on highways. However, a side friction factor is used as an index for vehicle lateral stability in the calculation of IS for horizontal curves. This condition causes inaccuracies in the value of IS due to the incapability of the index in fully characterizing the steering stability and track-holding capability of vehicles. This paper aims to fill this gap by discovering the lateral instability modes of vehicles on horizontal curves and to determine the boundary of each index beyond which the corresponding mode of instability occurs. Thus, a theoretical framework for realizing a revised IS (RIS) was established. A high-precision seven-degree-of-freedom driver–vehicle–road mathematical model was developed using MATLAB/Simulink. The state of vehicle lateral instability on highway horizontal curves was decoupled, and the boundaries of vehicle stability indices were deduced using the theory of vehicle system dynamics. Accordingly, a procedure for determining RIS was proposed. Case studies were conducted on the three horizontal curves of a two-lane rural highway in China, and existing speed limit methods were compared with RIS. With in-depth consideration of the lateral instability characteristics of vehicles, RIS provides traffic management departments with a precise maximum safe speed on horizontal curves under various pavement friction conditions. It is expected to be a restriction with respect to safety for other speed limit strategies that consider driver expectancy and efficiency.

Adaptive simulation and integration method for wheel-rail contact problems in locomotive traction studies

Knowledge of creep forces at wheel-rail interface when high power is applied to the locomotive wheels has been the subject of many recent studies. The common wheel-rail interaction methods are generally divided by two theories – Hertzian and non-Hertzian. The first method uses Hertzian contact for the normal problem and the tangential problem is divided into two algorithms – Polach’s theory and the Simplified theory-based algorithm referred to as Modified Fastsim. Kalker’s original Fastsim-based method shows a better accuracy for these two Hertzian-based algorithms. The second method is based on the non-Hertzian theory, and it uses the Exact theory also developed by Kalker and implemented in the Extended Contact library to calculate forces at the wheel-rail interface. Considering that the second method is more accurate, this paper aims to present an adaptive simulation and integration method (ASIM) which is positioned in the middle between the two common methods and is designed to introduce a transition from the non-Hertzian to Hertzian contact in the normal problem with the application of the Modified Fastsim for the calculation of contact forces at the wheel-rail interface. The proposed method is aimed to be used in vehicle system dynamics studies performed in multibody software packages. A specially developed wheel-rail coupling incorporating geometrical, normal, and tangential modules is integrated into Gensys multibody software and benchmarked with the standard Extended Contact based wheel-rail coupling by means of locomotive traction tests that use a full mechatronic model of a high adhesion locomotive. The computational performance and accuracy of the proposed method are assessed and discussed.

Numerical and Experimental Analysis of DVA on the Flexible-Rigid Rail Vehicle Carbody Resonant Vibration.

This paper examines the influence of the equipment considered as a DVA (Dynamic Vibration Absorber) upon the mode of vertical vibrations of the car body in high-speed vehicles. The car body is represented as an Euler-Bernoulli beam to minimize flexible vibration. The DVA approach is used to find the appropriate suspension frequencies for various types of equipment. A vertical mathematical model with a flexible car body and equipment is developed to investigate the effect of equipment mass, suspension stiffness, damping, and mounting location on car-body flexible vibrations. A three-dimensional, rigid-flexible coupled vehicle system dynamics model is developed to simulate the car body and equipment’s response to track irregularities. The experimental result was considered to verify the theoretical analysis and dynamic simulation. The mathematical analysis demonstrates that the DVA theory can be used to design the suspension parameters of the equipment and that it is suitable and effective in reducing the flexible vibration of the car body in which the vertical bending mode is greatly affected. Heavy equipment should be mounted as close to the car body’s center as possible to achieve significant flexible vibration reduction, whereas light equipment contributes very little flexible vibration reduction.

A survey on security challenges and protocols of electric vehicle dynamic charging system

AbstractElectric vehicle (EV) has emerged as the future of transport worldwide, with the rising need for greener and energy‐efficient transportation solutions. The adoption of EVs can accommodate a clean atmosphere, dropping conventional fuel dependence. During the charging process, the EV will have to interact with various entities that are presented in the dynamic charging station to get charged. This emerging technology grabbed the attention of several researchers to propose authentication protocols for the dynamic EV charging system to protect the information exchanged between the EVs and the dynamic charging station. Considering the complexities associated with communications among EV and other involved entities, security researchers have proposed diverse authentication protocols vital for the EV charging system to protect the information exchanged. However, several existing authentication protocols either suffer from prominent security threats or limit themselves to static charging. This review paper discusses security aspects, security threats, the typical network model, and the threat model in the EV dynamic charging system. Next, we studied and analyzed various security protocols that are needed to provide authentication, privacy preservation, secure billing, and payment among the involved entities in the EV dynamic charging system. A comparative analysis of several state‐of‐the‐art security protocols that offer authentication, privacy preservation, and secure billing and payment facilities in EV dynamic charging systems is demonstrated with their efficacy as well as security and functionality aspects. In addition, some future challenges for EV dynamic charging system security protocols are also highlighted.

Identification of Vehicle System Dynamics from the Aspect of Interaction between the Steering and the Suspension Systems

Steering and suspension systems of a motor vehicle have very important mutual connections that have direct influence on a vehicle’s steerability, stability, comfort and life expectancy. These mechanical and functional couplings cause an intensive interaction between the two mentioned vehicle systems on a geometrical, kinematical and dynamical level. This article presents a study on nonparametric identification of dynamic interaction between the steering and the suspension system of a passenger vehicle. A specific methodology for experimental research in on-road conditions was designed that was in line with the research objectives and the applied measuring system. Experimental data were acquired for a curvilinear drive, with different constant driving speeds and on different roads. A multiple input/multiple output model for identification of the vehicle dynamics system from the aspect of interaction between the steering and the suspension system was developed. The analysis of experimental data was realized with the selection of a corresponding identification model, decoupling of model inputs and conditioned spectral analysis. The results of the conditioned spectral analysis of experimentally obtained data records indicate the level of interaction between the observed input and output parameters of the steering and the suspension systems to be in the frequency range below 30 Hz.

Multi-disciplinary design optimisation considered fluid-structure interaction and life prediction applied in the lightweight carbody structure

Multi-disciplinary design optimisation based on rigid-flexible multi-body system (MBS) is presented to solve the multi-object design optimisation problems of lightweight carbody structure by considering the fluid-structure interactions at different typical load cases. A mathematical model is developed to simulate structure interactions based on the theory of finite elements. The model is integrated with a multi-object optimisation approach which utilises the Non-Sort Genetic Algorithm method. The MBS was used to understand complex vehicle system dynamics performance and obtain the structure load time histories. Through performing structural quasi-static stress analysis method, the structure dynamic stress/strain histories were obtained for fatigue life evaluation. The obtained results demonstrate the effectiveness of the proposed approach in simultaneously considering the structural vibration and the aerodynamic pressure at several vehicle speeds by proper lightweight design. This method has the advantage which can be used to understand the interaction mechanism between the vehicle dynamics characteristic and lightweight structural fatigue damage.

PI Observer-Based Fault-Tolerant Tracking Controller for Automobile Active Suspensions

The objective of this paper is to retain the desirable dynamics performances and improve ride quality for active suspensions with the actuator faults and unknown road disturbances. To that end, a novel proportional-integral observer (PIO)-based fault-tolerant tracking controller (FTTC) design is proposed for automobile active suspensions (ASSs) encountered with actuator faults and parameter uncertainties. First, the Takagi-Sugeno (T-S) fuzzy model approach is adopted to establish T-S representation of the faulty ASSs by describing vehicle dynamics system as the weighed summation of a common linear system. Afterwards, a nominal robust H∞ output feedback controller is developed to enhance the suspension performances under fault-free mode, whose output response indicators are taken as the prescribed reference trajectories. Then, a PIO-based fault estimator is designed to predict both the system states and the unmeasurable actuator faults, synchronously. On basis of this designed observer, the expected PIO-FTTC is synthesized to track the prescribed reference trajectories, and further to make up for the system performance deteriorations aroused by the actuator faults. Finally, a simulative investigation demonstrates the effectiveness and feasibility of the proposed PIO-FTTC compared to existing control approach.

Model Predictive Controller Design for Vehicle Motion Control at Handling Limits in Multiple Equilibria on Varying Road Surfaces

Electronic vehicle dynamics systems are expected to evolve in the future as more and more automobile manufacturers mark fully automated vehicles as their main path of development. State-of-the-art electronic stability control programs aim to limit the vehicle motion within the stable region of the vehicle dynamics, thereby preventing drifting. On the contrary, in this paper, the authors suggest its use as an optimal cornering technique in emergency situations and on certain road conditions. Achieving the automated initiation and stabilization of vehicle drift motion (also known as powerslide) on varying road surfaces means a high level of controllability over the vehicle. This article proposes a novel approach to realize automated vehicle drifting in multiple operation points on different road surfaces. A three-state nonlinear vehicle and tire model was selected for control-oriented purposes. Model predictive control (MPC) was chosen with an online updating strategy to initiate and maintain the drift even in changing conditions. Parameter identification was conducted on a test vehicle. Equilibrium analysis was a key tool to identify steady-state drift states, and successive linearization was used as an updating strategy. The authors show that the proposed controller is capable of initiating and maintaining steady-state drifting. In the first test scenario, the reaching of a single drifting equilibrium point with −27.5° sideslip angle and 10 m/s longitudinal speed is presented, which resulted in −20° roadwheel angle. In the second demonstration, the setpoints were altered across three different operating points with sideslip angles ranging from −27.5° to −35°. In the third test case, a wet to dry road transition is presented with 0.8 and 0.95 road grip values, respectively.

Robust Fault Estimation of Vehicular Yaw Rate Sensor Using a Type-2 Fuzzy Approach

In this article, a proportional integral (PI) fault observer is introduced due to its accuracy and expeditiousness. Considering the time-varying vehicle speed and other uncertain parameters in vehicle dynamics system, a type-2 fuzzy model is proposed to describe the system nonlinearity. Moreover, it could also address the problem of uncertainty in the membership function, which resulted from the parameter uncertainty. In addition, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathcal {H}_{\infty }$</tex-math></inline-formula> technique is studied to attenuate the effect of disturbance on the estimation performance and a set of linear matrices inequalities are obtained. The particle swarm optimization (PSO) approach is then adopted to find solutions to the PI fault observer. Finally, a simulation test is carried out based on the experimental data, which are collected from an electric vehicle. The simulation results demonstrate the effectiveness of the proposed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathcal {H}_{\infty }/PSO$</tex-math></inline-formula> method.

The effect of high-speed train meet on wheel wear at different speeds

PurposeConsidering that a meet between high-speed trains can generate aerodynamic loads, this study aims to investigate the effect of high-speed train meet on wheel wear at different speeds to provide a more accurate wheel wear model and a new idea for reducing wheel wear.Design/methodology/approachThe train speed was set at 250, 300, 350 and 400 km/h separately, and a vehicle system dynamics model was constructed using the parameters of an actual high-speed train on a line. The aerodynamic forces arising from constant-speed train meet were then applied as additional excitation. Semi-Hertzian theory and Kalker’s simplified theory were used to solve the wheel/rail contact problems. The wheel wear was calculated using Archard wear model. The effect of train meet on wheel wear was analyzed for the whole train, different cars and different axles.FindingsAccording to the results, all wheels show a wear increase in the case of one train meet, compared to the case of no train meet. At 250, 300, 350 and 400 km/h, the total wheel wear increases by 4.45%, 4.91%, 7.57% and 5.71%, respectively, over the entire operational period. The change in speed has a greater impact on wheel wear increase in the head and tail cars than in the middle car. Moreover, the average wear increase in front-axle wheels is 1.04–2.09 times that in rear-axle wheels on the same bogie.Practical implicationsThe results will help to analyze wheel wear more accurately and provide theoretical guidance for wheel repair and maintenance from the perspective of high-speed train meet.Originality/valueAt present, there is a lot of focus on the impact of high-speed train meet on the dynamic performance of vehicles. However, little research is available on the influence of train meet on wheel wear. In this study, a vehicle dynamics model was constructed and the aerodynamic forces generated during high-speed train meet were applied as additional excitation. The effect of train meet on wheel wear was analyzed for the whole train, different cars and different axles. The proposed method can provide a more accurate basis for wear prediction and wheel repair.

Recovering tractor stability from an intensive rollover with a momentum flywheel and active steering: System formulation and scale-model verification

As a representative type of off-road vehicle, agricultural wheeled tractors are driven under varied and complicated road conditions such as plowed and hilly fields. Active control is the essential technique to solve tractor rollover accidents which have been identified as the most fatal incident along with agricultural mechanization. The aim of this study is to provide active correction of tractor attitude in emergency cases by combing a single-axis momentum flywheel system and active steering system. In this study, the time-varying structural nonlinear vehicle dynamic system and its subsystems are formulated during transitions among tractor states under road stimulation. By exploring the phased mutation mechanism of tractor stability, the corresponding stability criteria are proposed. The coordinated tractor safety control strategy was verified using parametric studies in a simulation and scale-model experiments. The results indicated the effective and robust control of tractor safety regarding the independent and integrated active control systems. The proposed approach is expected to provide a theoretical basis and technical support for advanced driver assistance systems applied to future intelligent agricultural vehicles.

Modelling and stability analysis of a longitudinal wheel dynamics control loop with feedback delay

Vehicle safety is an important field of today's engineering practice and the scientific research as well. One of the basics of the modern vehicle system dynamics control systems is braking or driving torque control. Ensuring proper connection between the tyre and the road surface is essential for safety and good handling behaviour. Fundamental questions may arise about the details of the model, such as feedback delay, sampling effect, numerical differentiation in the control algorithm or the dynamical characteristics of the tyre model. In this article, a connected dynamical system is presented which contains a wheel model and a PID type traction controller. Steady state and dynamical brush type tyre models are presented and compared. Two different ways are described to model the feedback delay. The fully continuous time model contains constant time delay, while there is another case, where the sampling effect and the numerical differentiation methods of the control algorithm are presented. Finally, stability analysis of the delayed system is performed. The stability and performance characteristics and different bifurcations are presented using stability charts. The type of the tyre model has significant effect on the stability characteristics.

Optimization on the Crosswind Stability of Trains Using Neural Network Surrogate Model

Under the influence of crosswinds, the running safety of trains will decrease sharply, so it is necessary to optimize the suspension parameters of trains. This paper studies the dynamic performance of high-speed trains under crosswind conditions, and optimizes the running safety of train. A computational fluid dynamics simulation was used to determine the aerodynamic loads and moments experienced by a train. A series of dynamic models of a train, with different dynamic parameters were constructed, and analyzed, with safety metrics for these being determined. Finally, a surrogate model was built and an optimization algorithm was used upon this surrogate model, to find the minimum possible values for: derailment coefficient, vertical wheel-rail contact force, wheel load reduction ratio, wheel lateral force and overturning coefficient. There were 9 design variables, all associated with the dynamic parameters of the bogie. When the train was running with the speed of 350 km/h, under a crosswind speed of 15 m/s, the benchmark dynamic model performed poorly. The derailment coefficient was 1.31. The vertical wheel-rail contact force was 133.30 kN. The wheel load reduction rate was 0.643. The wheel lateral force was 85.67 kN, and the overturning coefficient was 0.425. After optimization, under the same running conditions, the metrics of the train were 0.268, 100.44 kN, 0.474, 34.36 kN, and 0.421, respectively. This paper show that by combining train aerodynamics, vehicle system dynamics and many-objective optimization theory, a train’s stability can be more comprehensively analyzed, with more safety metrics being considered.

An Adaptive Nonsingular Fast Terminal Sliding Mode Control for Yaw Stability Control of Bus Based on STI Tire Model

Due to the bus characteristics of large quality, high center of gravity and narrow wheelbase, the research of its yaw stability control (YSC) system has become the focus in the field of vehicle system dynamics. However, the tire nonlinear mechanical properties and the effectiveness of the YSC control system are not considered carefully in the current research. In this paper, a novel adaptive nonsingular fast terminal sliding mode (ANFTSM) control scheme for YSC is proposed to improve the bus curve driving stability and safety on slippery roads. Firstly, the STI (Systems Technologies Inc.) tire model, which can effectively reflect the nonlinear coupling relationship between the tire longitudinal force and lateral force, is established based on experimental data and firstly adopted in the bus YSC system design. On this basis, a more accurate bus lateral dynamics model is built and a novel YSC strategy based on ANFTSM, which has the merits of fast transient response, finite time convergence and high robustness against uncertainties and external disturbances, is designed. Thirdly, to solve the optimal allocation problem of the tire forces, whose objective is to achieve the desired direct yaw moment through the effective distribution of the brake force of each tire, the robust least-squares allocation method is adopted. To verify the feasibility, effectiveness and practicality of the proposed bus YSC approach, the TruckSim-Simulink co-simulation results are finally provided. The co-simulation results show that the lateral stability of bus under special driving conditions has been significantly improved. This research proposes a more effective design method for bus YSC system based on a more accurate tire model.

Distributed Expansion Planning of Electric Vehicle Dynamic Wireless Charging System in Coupled Power-Traffic Networks

In this paper, a distributed planning method for EV dynamic wireless charging system (DWCS) is proposed, which determines the locations and the scales of DWCS to maximize the economic effects of wireless charging while meeting EV charging demands. The Nesterov's model with multiple traffic patterns is adopted in the traffic network (TN) to solve the traffic assignment problem and the traffic wave theory is used to analyze the distribution of road traffic density. In power distribution network (PN), the effect of EV connection modes on the expansion cost of power lines is considered. A mixed-integer linear programming (MILP) model for the proposed planning problem of DWCS in coupled power-traffic networks (PTN) with PN and TN constraints is formulated and solved with MATLAB/CPLEX. The DWCS case studies are carried out to verify the effectiveness of the proposed distributed planning method in PTN.

The effect of 3D wear state of wheel polygon on wheel–rail system dynamics

Wheel wear is a natural phenomenon of wheel–rail rolling contact during vehicle operation. The non-uniform wear in lateral and circumferential directions is normally occurred on wheels. The lateral non-uniform wear will lead to the unexpected hollow wear which can cause flange to flange vibration at low-frequency band, and the circumferential non-uniform wear will result in the vertical vibration which is the originate from the polygon phenomenon. These two forms of wear are coupled to each other on wheels and affect the dynamic behaviours of wheel–rail system. In this paper, a wheel–rail contact dynamics model which includes the 3D geometric shape of wheel profile is established and employed to vehicle system dynamics. The results show that the contact mechanical properties of wheel–rail are greatly affected by the 3D wheel profile. The low-frequency vibration of wheelset caused by hollow wear and the high-frequency vibration by polygonised wear are coupled, which increase the vibrational acceleration of wheel–rail system and even made for the main problem of the periodic separation of wheel and rail and aggravate the wear of wheel polygon.

Numerical and experimental investigation of the wheel/rail interaction and dynamics for a high-speed gauge-changeable railway vehicle

For a high-speed rail vehicle with gauge-changeable wheelsets, wheel/rail interactions and vehicle dynamics were numerically and experimentally studied within 600 km/h. Matching among four treads, three rail profiles, two gauges, and two rail cants are analysed by examining the wheelset conicity, contact points distribution, and stress. It shows that the conicities of the S1002 and LMA become smaller than the permitted minimum when rail cant 1/20 is used instead of 1/40 when matching with any of the three rail profiles. The conicity of S1002 decreases by up to 95% while that of LMA drops by about 30%. Whereas the RUS and LMB10 are compatible with two cants. Worn treads are more sensitive to the rail cant than new ones. Wheelback distance error leads to a conicity change, especially for worn profiles. A multi-body vehicle system dynamics analysis indicates that a 0.6 mm wheel-axle clearance leads to running instability at low speeds, but will not have an obvious effect on running safety and ride comfort. The vehicle dynamics behaviour on the standard- and broad-gauge tracks shows a slight difference. This has been validated through lab tests performed on a full-scale roller rig.