The virtual track train (VTT) is a new type of urban transit system with all-wheel active steering technology utilized to make the long combination vehicle run along the planned route (virtual track) like railway vehicles along physical track. This paper proposed a scalable cascade modular path following control strategy for the newly designed gantry virtual track train (G-VTT) based on preview & tracking controller, focusing on the lateral control for low-speed turning manoeuvre. The mathematical characteristics of the 2-norm was utilized to establish a local tracking objective function (LTOF) to find the optimal lateral acceleration (OLA) of the tracking point in the preview window and calculate the optimal wheel steering angle (WSA) to achieve the optimal local trajectory. Considering the lag time T _d , the yaw stability and path following ability of the vehicle are contradictory in some cases, so the damping adjustment factor λ was proposed to optimize the damping characteristics and the time-delay stability factor ξ was proposed to evaluate the time-delay stability. The influence of the key parameters, preview time T _p , T _d , ξ and λ , on the stability and following ability were analyzed by frequency domain analysis method, and the optimal region of ξ and λ was obtained to instruct the configuration of λ and T _p . Finally, steady-state and dynamic forward predictive models were proposed to compensate for the oscillation caused by the lag time. The effectiveness of the proposed control strategy, forward predictive models and the configuration method of λ and T _p were verified by theoretical analysis and numerical simulation.

The dynamic performance of the vehicle is improved when the bogie of a monorail vehicle passes through the curve in the radial position. This study aimed to derive the analytical relationship between the torque generated by the auxiliary guiding device and the yaw angle between the bogie and the vehicle body based on the geometric relationship between the auxiliary guiding device of the straddle monorail and the mechanical characteristics of the hydropneumatic spring. The main influencing factors were the angle of the arm and the initial pre-pressure of the hydropneumatic spring. Theoretical analysis and model simulation showed that the output torque of the auxiliary steering device had a linear relationship with the pre-pressure of the hydropneumatic spring, but a complex relationship with the angle of the rotating arm. When the reasonable pre-pressure (12.4 kN) of the hydraulic spring was selected, the output torque of the auxiliary steering device could be offset against the moment generated by the secondary suspension. At this time, the yaw angle of the running part was close to zero, and the bogie could be placed in the radial position on the circular curve, thus effectively reducing the wear of the running wheel and guiding wheel.

The anti-overturning ability of a straddle-type monorail vehicle is influenced by the contact status between the guiding and stabilizing wheels and the track beam; therefore, an initial pre-load is required for the stabilizing and guiding wheels to enhance the anti-overturning ability of the straddle-type monorail vehicle. Determining the reasonable pre-load for the stabilizing and guiding wheels is a significant problem in the operation of a straddle-type monorail vehicle. D’Alembert’s principle has been adopted to transform the dynamic problem that straddle-type monorail vehicle runs on curve segment to the statics problem. The formula describing the relationship between the critical lateral force of the vehicle and the pre-load of the stabilizing wheels is derived from the lateral roll equation of the straddle monorail vehicle and is verified using the multibody dynamics software UM. Subsequently, the reasonable pre-load for the stabilizing wheels is analyzed from the perspectives of comfort and safety based on the formula of critical lateral force. Finally, the maximum and minimum speed limits on a curve for a straddle-type monorail vehicle are discussed based on the aforementioned analysis.

Straddling monorail vehicles are a new rail transportation mode in which the bearing, running, and guiding rely on rubber tyre running gears. Since the lateral span of the running wheel is small, stabilizing wheels are added to enhance the anti-overturning capacity, which is influenced by the contact between the stability wheels and track beam. If one stabilizing wheel loses contact with the track beam, the tendency to overturn increases significantly. To ensure the straddling monorail vehicle has a stable anti-overturning capacity, an initial preload pressure is applied to the all stabilizing wheels and guiding wheels. The specific preload pressure of the stabilizing and guiding wheels is a unique issue of straddling monorail vehicles. This paper deduced a flexible coefficient formula of straddling monorail vehicles, validated the accuracy of the flexible coefficient formula based on dynamics simulations, and discussed the correlation between the flexibility coefficient and stabilizing wheel contact conditions. According to the variation regularity of the anti-overturning capacity of straddling monorail vehicles, the concept of vehicle critical roll angle was proposed. The calculation formula of the critical roll angle of straddling monorail vehicles was determined, and its accuracy was validated by dynamics simulations. Based on the above fundamentals, a functional relationship between the critical roll angle and stabilizing wheel preload pressure was derived. This paper proposed that the value of stabilizing wheel preload pressure should be reasonably determined according to the critical roll angle and discussed the maximum and minimum speed limit of curve negotiating.

Wheel–rail rolling contact is a complex tribological issue, especially the existence of a thin water film on the rail surface, which leads to low adhesion problems for the traction and braking performance of the railway trains. The objective of this paper is to propose a non-Hertzian dynamic wheel–rail adhesion model for trains passing through wet curved tracks considering wheel–rail surface roughness. A vehicle-track coupling dynamics model was first developed to output the wheel–rail dynamic contact parameters under wet conditions. These parameters were subsequently utilized as dynamic inputs for the present wheel–rail adhesion model to simulate dynamic curve passing. The present numerical model includes the normal contact model and tangential model. For the normal contact issue, an elastohydrodynamic lubrication model was used to accurately determine the normal contact stress within the contact patch along the contact traces. Based on the normal contact characteristics, the advanced extended creep force model was used to compute the tangential stress. Finally, the dynamic wheel–rail adhesion coefficient can be obtained. This model considers the effects of time variation and changes in contact geometry, resulting in sudden increases or decreases in the adhesion coefficient at certain locations. At a speed of 400 km/h, a higher spin creepage occurs, leading to an increased displacement of the third-body layer and causing the maximum tangential stress to shift from one side of the contact patch to the other. Under the combined influence of the creepages, the maximum tangential stress occurs at the trailing edge of the contact patch.