The lateral dynamics of railway vehicles are affected by not only lateral force but also traction/braking torque, resulting from the saturation effects inherent in wheel-rail creep. This research studies the creep dynamics with steady traction/braking torque based on Vermeulen–Johnson theory by linearising the creep relationship at the working point with steady tangent force. Then the influence of traction/braking torque on stable limit cycles and nonlinear critical velocity is studied analytically, and the conclusion that nonlinear critical velocity would increase with a higher creep saturation degree is drawn. Based on the analytical analysis, a control strategy involving applying traction torque and braking torque to motor vehicles and trailers, respectively, and reducing friction coefficient through rail lubrication is proposed to improve hunting stability. A dynamic model with a motor vehicle and a trailer is established in SIMPACK, and the simulation results prove the effectiveness of the control strategy on vehicle's stability on tangent tracks.

Under extreme conditions, a vehicle's handling performance and yaw stability can significantly deteriorate. This paper proposes a handling and stability decoupled control strategy for four-wheel independent drive (4WID) and four-wheel independent steering (4WIS) vehicles based on tire force vector control (TFVC). To address the conflicting objectives of handling and stability, the turning curvature is employed as the lateral reference, while the sideslip angle serves as the stability indicator, thereby decoupling handling and stability control. Additionally, a driver intention remapping method is introduced to maximise the preview turning curvature, effectively balancing longitudinal and lateral objectives. A yaw controller is developed using non-singular terminal sliding mode control (NTSMC) to maintain vehicle stability. Pentagon constraints are formulated to integrate all tire force constraints. Deviations from the driver's expectations are incorporated into the objective function to ensure the solvability of tire force allocation. The TFVC is implemented by integrating a UniTire-based inverse tire model and a saturated tire model to accurately regulate tire forces under both combined and saturated conditions. Finally, hardware-in-the-loop (HIL) and real vehicle test results confirm that the proposed handling and stability decoupled control strategy not only ensures vehicle stability but also enhances handling performance under extreme conditions.

The control accuracy of semi-active suspension systems with magnetorheological (MR) dampers is critically influenced by time delay and mechanical characteristic modelling quality. This study introduces a hierarchical time delay compensation control system, incorporating an upper system for predictive force to compensate time delay and a lower system for accurate exciting current calculation. Building on the parameter consistency of existing magic formula models, a novel asymptotic saturation model is proposed, enhancing modelling precision through parameter identification and experimental fitting. In the upper controller, a new compound H2 strategy, integrating robust control and the Taylor formula, mitigates predictive force amplification. The lower controller utilises the proposed model to calculate exciting currents. Simulation and hardware-in-the-loop experimental results corroborate the effectiveness of the semi-active suspension system featuring MR damper regulated by the specially designed hierarchical time delay compensation controller with a good suspension work effect.

An inerter stiffness damper combined with a negative stiffness (NS-ISD) in vehicle passive suspension is applied and optimized to enhance ride comfort performance. The analytical solution of the mean squared acceleration value is obtained to evaluate ride comfort when the vehicle is subjected to stochastic excitation induced by road roughness. A set of analytical solutions of stiffness and damping ratios are designed by the H2 optimization and the extreme value theory to achieve the best ride comfort. The optimal negative stiffness ratio is also presented according to the Routh-Hurwitz criterion to ensure a stable vehicle system. The influences of the vehicle parameters on the optimal values of designed parameters and the corresponding ride comfort performance are discussed in detail. Moreover, the contribution of the negative stiffness is highlighted by comparing the acceleration response between NS-ISD suspension and existing inerter stiffness damper (ISD) suspension in the frequency domain. Filtered white noise modeling road roughness demonstrates the NS-ISD suspension's ride comfort enhancement via MATLAB/Simulink simulations. The analysis reveals that the peak acceleration of the vehicle equipped with the NS-ISD suspension is 28% lower than that with the ISD suspension, demonstrating the superiority of the proposed NS-ISD suspension design.

Transportation and mobility are experiencing a significant transformation the recent years, which is evident in road (vehicles and bicycles) and rail vehicles. This transformation includes the introduction of automated vehicles (AVs), the increase of active transportation modes (e.g. cycling and walking) and the extended use of trains for commuting to work or travelling. However, despite this great transition, there are significant challenges that can hamper the wide use of these transport means, with comfort being one of them. In this paper, we explore physical comfort in these transport modes, examining ride comfort and motion sickness definitions and assessment, environmental influences, occupant postures, human body dynamics, and postural control strategies for adapting to motion. We conclude that while established comfort guidelines exist for conventional vehicles, substantial gaps persist in understanding and evaluating comfort in emerging modes like bicycles and automated vehicles with varied seating. Further research into modelling human body dynamics and the central nervous system's role in postural control, especially for cyclists and non-conventional postures, is essential for designing future transportation systems that prioritise comfort and health.

This study proposes a comprehensive coupling model that is able to accurately capture the complex nonlinear dynamics of the vehicle-turnout system. This involves developing a three-dimensional (3D) finite element model (FEM) of the wheels incorporating the centrifugal hardening effects, alongside a refined FEM of the vehicle-turnout considering the nonlinear constraints of the turnout structure. Additionally, model reduction techniques condensed the wheel model into a corresponding wheel substructure model, while a multi-time step integration (MTSI) method ensured an efficient interpolation between varying analysis step lengths of both models. The proposed approach yields a 0.35-fold reduction in computation time compared to the traditional explicit dynamic models. The mixed Eulerian-Lagrangian (MEL) method was employed to calculate the contact characteristics in the turnout area using the wheelset motion data from the co-simulation engine (CSE). A 2 MPa difference in normal contact stress was observed compared to that of CONTACT algorithm. several dynamic tests were carried out on the No. 9 turnout to verify the accuracy of the model. Since the structural damping was not considered, the simulation model overestimated results within the low-frequency range of 4-16 Hz. Despite this, the peak errors in wheel-rail force and rail displacement measurements were approximately 10%.

Subjective vehicle stability evaluation is generally conducted during closed-loop driving in which the driver controls the vehicle through transient manoeuvres and evaluate how the vehicle responds to steering inputs, especially how the slip angle builds up. To conduct such evaluation in moving base, driving simulators require that the fed vehicle response to steering inputs is representative. Limited simulator workspace often requires motion scaling, introducing errors in planar dynamics This work, therefore, investigates how the scaling of the planar motion and the slip filtering should be performed in a driving simulator, including the relative relationships between lateral acceleration, yaw rate and slip rate. Two strategies were developed based on the scaling of planar circular motion: one retaining radius information, and the other retaining velocity information. Both strategies avoided filtering the slip rate, as simulations show that the slip rate should be separated from the high-pass filtering process in cueing algorithms and that the scaling should be equal to that of the yaw rate to avoid false cues. A subjective assessment was conducted, and the results indicate advantages for retaining radius information and conclusively the advantage of unfiltered slip information in motion cueing for stability evaluation.

Railway switches are essential for ensuring efficient train operations, and efforts to improve their safety standards have driven the introduction of ‘switch rail control contact’ (TKK in Swedish) sensors in Sweden. These sensors monitor the gap between the switch and stock rail, complementing the switch rail position detection of the drives. Despite their benefits, TKK sensors are prone to faults, which in turn increase maintenance and operational costs. This study was therefore initiated to assess the utility of these devices in derailment prevention. To assess the risk of derailment caused by gauge narrowing induced by entrapped foreign objects, multibody simulation (MBS) of train switch interactions is performed. A state-of-the-art structural track model of a switch is modelled in Simpack. Simulations indicate that the train will not derail due to flange climbing when the foreign object is modelled with a failure criterion resembling crushing strength of ballast stones. An investigation featuring an unbreakable object showed that the critical gauge narrowing limit considering flange climbing is around 15 mm which is in accordance with the existing safety limit. The influence of track irregularities in combination with foreign objects is also investigated.

This paper proposes a joint estimator for the sideslip angle and road adhesion coefficient of distributed drive electric vehicles based on Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF), building upon the traditional Kalman filter algorithm. The estimator integrates a vehicle's 8-degree-of-freedom model with an improved Dugoff tyre model. By transforming the front wheel angle into lateral and longitudinal excitations, it addresses the potential issue of non-converging estimates during the collaborative estimation process. Through model simulations and real-vehicle experiments, it has been verified that the collaborative estimation system can effectively correct and predict parameters during the synchronous estimation process of the two estimators, achieving fast and accurate estimation. This proves the effectiveness of the road adhesion coefficient estimation method.

Current research on chassis-integrated control predominantly focuses on rule-based coordination of subsystems, with scant consideration given to the communication mechanisms required for optimal matching among them. In this study, a novel integrated control scheme grounded in game theory is put forward, leveraging Active Front Steering (AFS), Direct Yaw-Moment Control (DYC) and Active Suspension System (ASS). Each of the three control subsystems has distinct objectives aimed at maximising vehicle drivability. Initially, a composite model incorporating vehicle dynamics and driver behaviour is constructed. Subsequently, in accordance with Pareto-optimality theory, by minimising the linear combination of cost functions and dynamically adjusting the relative weights of each subsystem, a feasible and stable cooperative distributed model predictive control (FSC-DMPC) framework based on a hierarchical strategy is devised. This framework serves to establish communication channels and mitigate conflicts among subsystems. On this foundation, a convex iteration algorithm and safety constraints are employed to further guarantee the feasibility and stability of the designed controller. Ultimately, simulation tests are conducted on the Carsim-Simulink joint platform to validate the efficacy of the proposed controller.