A failure of the pneumatic ABS (anti-lock braking system) weakens the braking performance of commercial vehicles. It affects the driving safety of vehicles. There are four typical failure modes that include: the failure of the pilot inlet solenoid valve and pilot exhaust solenoid valve of the pressure regulator, the failure of the series dual-chamber brake valve, and the failure of the relay valve. In order to study the braking performance and the rule of vehicles under the failure modes of the pneumatic ABS, the co-simulation model of the pneumatic ABS of the commercial vehicle was established based on AMESim and Simulink softwares. The gas path subsystem of the pneumatic ABS and the vehicle model were built based on AMESim. The controller was established based on Simulink/Stateflow. The data were transmitted between the AMESim and Simulink software by using the data interface block. The co-simulation model was validated by tests. The results showed that the maximum error of the braking deceleration is 13.51%. The model can simulate the braking process of the vehicle well. Based on this, the four typical failure modes of the pneumatic ABS were simulated, and the influences of different failure modes on the braking ability were analyzed. The influence of failure ratio on braking distance in four modes was obtained. It can be seen from the simulation results that the failure of the pilot inlet solenoid valve and the pilot exhaust solenoid valve of the pressure regulator cause the wheel lock. The failure of the lower chamber of the brake valve and the failure of the relay valve have a great influence on the braking distance.

In order to further reveal the vertical random vibration characteristics of railway vehicles, using the system engineering method, taking the passenger, the train system, and the track system (ballast track) as a unified whole, a passenger-train-track vertical coupling dynamic model is established, and the vibration differential equations of the model are derived. In the model, passengers are regarded as a single-degree-of-freedom system attached to the bottom of the carriage, the train system is represented as a 10-degree-of-freedom multi-rigid body model, the track system is regarded as the infinite long Euler beam model with three layers of continuous elastic point support, and the Hertz nonlinear elastic contact theory is applied to the wheel and rail coupling relationship. Based on this, the time-domain numerical solution of the passenger-train-track vertical coupling dynamic model is given by using Newmark-β implicit integration algorithm, and the correctness of the model is verified by the real vehicle test. This study can provide some theoretical basis for the design of railway vehicles and provide fundamentals for the coordinated control and system optimization of railway vehicle ride comfort.

The lightweight design of trucks is of great importance to enhance the load capacity and reduce the production cost. As a result, the taper-leaf spring will gradually replace the multi-leaf spring to become the main elastic element of the suspension for trucks. To reveal the changes of the handling stability after the replacement, the simulations and comparison of the taper-leaf and the multi-leaf spring suspensions with the same vertical stiffness for trucks were conducted. Firstly, to ensure the same comfort of the truck before and after the replacement, an analytical method of replacing the multi-leaf spring with the taper-leaf spring was proposed. Secondly, the effectiveness of the method was verified by the stiffness tests based on a case study. Thirdly, the dynamic models of the taper-leaf spring and the multi-leaf spring with the same vertical stiffness are established and validated, respectively. Based on this, the dynamic models of the truck before and after the replacement were established and verified by the steady static circular test, respectively. Lastly, the handling stability indexes for the truck were compared by the simulations of the drift test, the ramp steer test, and the step steer test. The results show that the yaw rate of the truck almost does not change, the steering wheel moment decreases, the vehicle roll angle obviously increases, and the vehicle side slip angle slightly increases after the replacement. Thus, the truck with the taper-leaf spring suspension has better steering portability, however, its handling stability performs worse.

The existing semi-active suspensions are very expensive and difficult to be popularized. Therefore, the search for the low-cost semi-active suspension has become a hotspot. To reduce the product cost of semi-active suspensions, this study proposed a new hydraulic semi-active suspension system based on road statistical properties and creates an identification method of road conditions. Firstly, the working process of the proposed semi-active suspension was given. Then, the formula for calculating the mean square value of the body acceleration under the running road condition was derived. Based on the formula, the road identification method was created. Finally, the road test was carried out using a test vehicle. The identified road PSD (power spectral density) values are all consistent with the real values. The test results show that the road identification method can effectively perceive the actual road grades. The identification interval with 20 s can meet the requirements of practical applications. The slight fluctuation of the running speed v has little effect on the identification results because of the statistical characteristics of road conditions.

To provide a theoretical guidance for the vibration isolation design, the vibration responses characteristics for the convalescent‐wheelchair robot with DA (dynamic absorber) undergoing the random road were revealed. Firstly, the vibration model of the convalescent‐wheelchair system with DA was created. The frequency response functions of the road excitation velocity to the convalescent acceleration, the wheelchair body acceleration, and the tire dynamic deflection were deduced. Then, the numerical calculation method of the PSD (power spectral density) and the RMS (root mean square) responses were proposed. Thirdly, the vibration isolation performances of the wheelchair robot with DA and without DA were compared. Finally, the sensitivity analysis of the vibration responses to the mass ratios, the damping ratios, and the natural frequencies was carried out to reveal the effects of the parameters on the vibration responses. The results show that the DA can partly suppress the vibration of the convalescent and the wheelchair body, especially in the resonance area of the wheelchair body. However, the DA cannot successfully improve the tire contact behavior.

To improve comfort, a nonlinear suspension system is proposed on the basis of the nonlinear vibration isolation theory and the installation space of the cab suspension system for trucks. This system is suitable for all‐floating cabs. For easy matching and design, the static and stability characteristics of the suspension system were analyzed, respectively, and the boundary condition for the stability of the system was given. Moreover, the cab simulation model was established, and the dynamic simulation was conducted. The stability analysis shows that the smaller the vibration excitation of the cab system, the higher its stability is. The dynamic simulation results show that the acceleration of the cab with the nonlinear suspension system is effectively suppressed; the dynamic deflection of the suspension is kept within a certain range, and the design space of the suspension stroke can be effectively utilized. Compared with the traditional linear suspension system, the nonlinear suspension system has better vibration isolation characteristics and can effectively improve ride comfort.