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To prevent the dangerous driving behavior of cut-ins inserting into the gap between the ego car and the lead car, a vehicle control strategy for accelerating was proposed. According to the following safety distance model, considering the following characteristics of time headway and parking distance, a following safety distance model and an anti-cut-ins safety distance model were established based on three types of driver. A vehicle speed controller based on the variable safety distance control strategy was established by the Sigmoid function. When another vehicle was detected to cut-in, the anti-cut-ins safety distance model was selected, otherwise the following safety distance model was selected. The MATLAB/ Simulink and CarSim co-simulation platform was used to carry out experiments. The results show that the vehicle control strategy based on three types of driver's variable safety distance and anti-cut-ins is feasible. [ABSTRACT FROM AUTHOR]

To reduce the mass of mechanical elastic wheels, the lightweight analysis was conducted by the finite element analysis software of Abaqus. Considering the bending moment load and radial load conditions of the wheels at all times, the finite element model of mechanical elastic wheels was established, and the finite element simulation analysis was carried out. The force data of the nodes were extracted from the simulation results to determine the load of wheel hub and hinge group. The weighted variable density method was used to optimize the topology of the hub and hinge group of mechanical elastic wheel, and the 3D model was reconstructed after optimization. The results show that the mass values of the optimized mechanical elastic wheel, wheel hub and hinge assembly are reduced by 15.1%, 27.9% and 22.6%, respectively. [ABSTRACT FROM AUTHOR]

The subsystem interference problem due to chassis strong coupling characteristics of vehicles matching mechanical elastic electric wheel (MEEW) under extreme conditions was investigated. Taking active front-wheel steering (AFS) system and direct yaw moment control (DYC) system as research objects, a game coordination controller with variable subsystem weights was designed by non-cooperative feedback Nash equilibrium game theory, and the ideal output at Nash equilibrium point was obtained by coupled Riccati equation and its iterative transformation. A joint simulation platform of CarSim/Simulink was built to carry out the simulation test with the vehicle speed of 100 km·h-1 and road adhesion coefficient of 0.3 under double shift condition. The results show that the designed coordination controller can realize the real-time coordination of AFS/DYC. The stability of the vehicle matching MEEW under the action of the designed controller is better than that of the single superimposed controller, and the tracking errors of the side slip angle and yaw rate of vehicle are within 0.48°-0.81° and 0.035-0.425 (°)·s-1, respectively. [ABSTRACT FROM AUTHOR]

To improve the system stability and tracking accuracy of the four-wheel independent steering (4 WIS) unmanned vehicle during path tracking and improve the tire wear, the path tracking control algorithm was proposed based on double-layer control strategy. The upper layer was a model reference adaptive path tracking controller based on Popov hyperstability theory. Based on the two-degree-of-freedom model, the path tracking error state equation was derived. The linear quadratic optimal method was used to solve the problem that the positive linear link of the system was not strictly positive reality. The Popov integral inequality was solved to ensure the hyperstability of system. In the lower layer controller, based on Ackermann steering theorem, the angle allocation control algorithm was designed with considering tire sideslip. The simulation experiment was carried out on the CarSim/Simulink cosimulation platform. The results show that the designed path tracking controller based on double-layer control strategy can realize the path tracking task with high precision and ensure the driving stability of 4 WIS unmanned vehicle to improve the tire wear. [ABSTRACT FROM AUTHOR]

The contact stress and acceleration signal under the conditions of different speed, friction coefficient, load and the difference of acceleration signal at different position of mechanical elastic intelligent wheels were studied. The results show that the velocity and friction coefficient have little effect on the normal contact stress distribution. And the increase of friction coefficient leads to the increase of the non-uniformity of shear stress distribution; and the increase of load leads to the increase of the maximum contact stress in the contact patch area. The amplitude of acceleration peak increases and the time interval of acceleration peak decreases with the increase of wheel speed. The time interval of acceleration peak increases with the increase of load. The longitudinal friction coefficient power spectrum can distinguish the friction coefficient. The acceleration signal in the middle of flexible tire body is more suitable for the study of lateral characteristics. The lateral displacement obtained from the integration of the lateral acceleration signal can predict the lateral deflection Angle. [ABSTRACT FROM AUTHOR]

The vertical stiffness and grounding characteristics of a non-pneumatic mechanical elastic wheel under the conditions of different camber angle were studied to improve the vehicle driving safety. In considering the laminated structure of flexible tire body, a three-dimensional finite element model (FEM) of mechanical elastic wheel was established, which includes the incompressibility of rubber material, large deformation and contact nonlinearity. Static loading tests were conducted to validate the accuracy and reliability of the FEM. The simulated results of the influence of camber angle on vertical stiffness, contact patch and pressure distribution are compared with experimental results and discussed in detail. The results show that the vertical stiffness decreases with the increase in camber angle; the pressure is mainly concentrated in the shoulder of flexible tire body; and the uniformity of the pressure distribution becomes worse as the camber angle increases. The research provides a theoretical reference for the study on the camber performance, the uneven wear of tread and the structure optimization. [ABSTRACT FROM AUTHOR]

The conventional pneumatic tires have disadvantages in terms of puncture, blowout at high speed, pressure maintenance, and so on. Due to these structural inevitable weaknesses, non-pneumatic tires have been developed and are being investigated. A new non-pneumatic elastic wheel was proposed and studied to solve these problems. As an important bearing member of the non-pneumatic elastic wheel, the force of hinge group is very complex and it has a significant effect on the performance of the wheel. However, in the complex off-road driving, the hinge group has to withstand complex random load and impact load, and inevitably there will be damage failure. In order to explore the performance change of the wheel after the failure of the important bearing parts, it is necessary to study the influence of the hinge group with local damage on the performance of the non-inflated elastic wheel. In this paper, an experimental study on basic characteristics of non-pneumatic elastic wheel with local hinge group fracture damage was conducted in order to enhance the reliability. Based on tire characteristic test-bed, the tests on basic characteristics of static radical stiffness and contact behavior as well as the modal test were conducted. The wheel with local damage, one hinge group of which was disassembled, was used to simulate hinge group fracture condition in this paper. The results show that the effect of the hinge group fracture damage on the wheel load characteristics is the decrease of the radial stiffness, and it is also related to the damage position on the non-pneumatic elastic wheel. The radial stiffness of non-damaged non-pneumatic elastic wheel is 593.06 N/mm, and the corresponding values of the non-pneumatic elastic wheel with fractured hinge group on horizontal position and vertical position are 443.2 and 385.4 N/mm, respectively. Compared with non-damaged non-pneumatic elastic wheel, the numerical value of radial stiffness is reduced by 25% and 35% respectively on horizontal position and vertical position when the fractured hinge group is installed. That is to say the consistency of radial stiffness and deformation uniformity get worse for the wheel with local damage, so the poor performance of riding comfort of non-pneumatic elastic wheel appears. The influence of the hinge group fracture damage on the grounding pressure distribution is the change of grounded imprinting length and grounded area. Under the same vertical load, these 2 indicators of the non-pneumatic elastic wheel with fractured hinge group increase compared with non-damaged non-pneumatic elastic wheel. When the vertical load is 7 262 N, the imprinting length of the non-pneumatic elastic wheel with fractured hinge group on horizontal position is 138 mm, and the numerical value of non-damaged non-pneumatic elastic wheel is 120 mm. The ground imprinting length of the damaged wheel is increased by 15% compared with that of the non-damaged non-pneumatic elastic wheel. The grounded imprinting width does not change, and the value remains at 285 mm. As a result, the total grounded area of the damaged wheel also increases. The area of the non-damaged non-pneumatic elastic wheel is 34 200 mm2, and the area of damaged wheel increases to 39 330 mm2. The contact length and area of the wheel with local damage are greater than corresponding values of the non-damaged non-pneumatic elastic wheel under the same load. The influence of the hinge group fracture damage on the wheel modal test is the change of the natural frequency, the damping coefficient and the modal shape. In addition to a few orders, the natural frequency of non-damaged non-pneumatic elastic wheel is greater than that of non-pneumatic elastic wheel with local damage hinge group, and the damping coefficient of the most of non-damaged non-pneumatic elastic wheel is less than that of non-pneumatic elastic wheel with local damage hinge group. The value of the amplitude of modes gets smaller for the non-pneumatic elastic wheel with local damage hinge group. [ABSTRACT FROM AUTHOR]

The basic concept of tire safety technology was briefly introduced, and the basic connotation, the structure and main categories of non-pneumatic wheels were described in detail. Several kinds of representative products of non-pneumatic wheels were enumerated with Tweel wheel, honeycomb wheel and mechanical elastic wheel, and the current technical status of non-pneumatic wheels was analyzed. Based on the vertical mechanical properties, the longitudinal mechanical properties, the lateral mechanical characteristics and the grounding and mechanics characteristic factors, the research status at home and abroad of mechanical properties of non-pneumatic wheels was reviewed, and the main advantages and disadvantages of non-pneumatic wheels were analyzed. The technical problems of non-pneumatic wheels in current research were pointed out, and the future development trend was predicted. [ABSTRACT FROM AUTHOR]

To change the situation of the existing tire, developing run-flat and anti-puncture tire to guarantee high performance and security has become a consensus of the world's major tire manufacturers. Therefore, researchers have recently focused their attention on nonpneumatic tires with different structures. But the non-pneumatic tires have the disadvantage of excessive weight, complex processing technology or cooling difficult and so on. Furthermore, the process of manufacturing such tire is still in the stage of research and development. To solve the above problems, a mechanical elastic wheel (MEW) for the offroad vehicle is proposed which is a kind of nonpneumatic tire. The MEW could be realized the basic function of traditional pneumatic tire. In additional, the problems such as stinging, puncturing and blasting damage can be avoided. Thus, the MEW is greatly satisfied with requirements of safe service for the special vehicles, such as military vehicles, offroad vehicles, emergency service and disaster relief vehicle.In this paper, to solve the shock vibration transmission and improve vehicle ride performance when the MEW is running over uneven road, we studied the enveloping characteristics and influencing factors of MEW using the flexible roller contact (FRC) model and the method of the finite element simulation and experiments. The influence of loading and radial stiffness on the enveloping characteristics of the MEW was revealed according to the analysis of the effective road input. Moreover, the reliability of the model was verified. The amplitude of effective road input of MEW decreased with the increase of loading, and the disturbance length increased with the increase of loading. Under this circumstance, the radial stiffness was unchanged. And the amplitude of effective road input of MEW increased with the increase of radial stiffness, but the disturbance length decreased with the increase of radial stiffness under a certain loading.The analytical solution, finite element simulation and experimental results were in excellent agreement for the effective road input. The MEW swallowed the cleat completely when the obstacle was centred under the hub centre, and it behaved as if there were no cleat at all under a certain loading. The results indicated that the MEW had the remarkable characteristics of enveloping cleat, reducing the impact and prolonging the action time when the MEW was running over uneven road. Based on the established finite element model and the bench testing, the enveloping characteristics while traversing the obstacle at low speed was investigated, and the influence of loading and radial stiffness on the vertical dynamic mechanical response were illustrated. The vertical dynamic mechanical response of MEW increased with the increase of radial stiffness under a certain loading. In the lowdeflection case, the vertical force curves were similar to a parabola. With increasing deflection, in the medium deflection case, there were two maximums and between them a minimum occurred, the trend was called camel back. The MEW swallowed the cleat completely under a certain loading, which could be called typical static enveloping characteristics. The analysis results reflected the objective law of the actual enveloping characteristics of the MEW, and provided a reference for the MEW structure optimization and the vibration characteristics of the whole vehicle. [ABSTRACT FROM AUTHOR]

Non-pneumatic safety tires have been introduced with a new type of elastomer, which functions as the air of the pneumatic tire. It appears to have advantages over the pneumatic tire in terms of flat proof and maintenance free. As the pursuing of consumer on car safety, handling stability and comfort continue to enhance, the study of the non-pneumatic tire is also growing. The mechanical elastic wheel is a kind of non-pneumatic tire. A mechanical elastic wheel with a non-pneumatic elastic outer ring which functions as the air of the pneumatic tire was presented to reduce the risk of puncturing, and its loading mode and contact behaviors were different from the pneumatic tire. In this paper, the influences of bead structure parameters on contact pressure distribution of mechanical elastic wheel were investigated to provide certain guidance for optimizing the mechanical contact characteristics of the mechanical elastic wheel. First of all, the Timoshenko circle curved beam model of the bead was established to describe the deformation characteristics of wheel bearing. Through the theoretical analysis of wheel bearing deformation, the main structural parameters affecting the mechanical elastic wheel contact behaviors were found, which contained bead section ratio, elastic ring section ratio and elastic ring distribution coefficient. Secondly, different bead structure parameters were put forward, and the three-dimensional finite element (FE) models of the corresponding mechanical elastic wheel were developed. The model of mechanical elastic wheel consisted of a thin flexible annular outer ring and hinge units that connected the outer ring with a rigid hub. To establish the FE model, various nonlinear factors, such as the geometrical nonlinearity, the material nonlinearity and the contact nonlinearity, were considered comprehensively. In order to prove the validity of the FE model, the load characteristic test of the mechanical elastic was conducted by tire test-bed. Finally, the commercial FE software ABAQUS was used to conduct static load simulation test for the mechanical elastic wheel, the test results were analyzed and the influence of bead structure parameters on the wheel contact behaviors was revealed. In addition, to scientifically evaluate the contact behaviors of the mechanical elastic wheel, evaluation indices of contact behaviors were introduced. The major findings are obtained as follows: 1) there is a positive correlation between bead section ratio and vertical stiffness of the mechanical elastic wheel, so is elastic ring section ratio; there is a negative correlation between elastic ring distribution coefficient and vertical stiffness. 2) the contact pressure distributions of the wheel with different bead structural parameters are similar, the shape of contact mark is approximately rectangle, the pressure of the center contact region is the largest and the pressure reduces gradually from center to edge, and the minimum appears on the regional edge. 3) reducing bead section ratio, elastic ring section ratio or elastic ring distribution coefficient, the wheel contact length and the contact area increase, and the average value and the skewness of contact pressure decrease, which would improve the performance of contact behaviors of the mechanical elastic wheel at different degrees, thereby improve the wheel gripping, driving and braking performance, the average abrasion performance, and so on. Through the study, we found that on the basis of meeting the requirement of vertical stiffness, the bead structure parameters could be appropriately adjusted when optimizing the structure of mechanical elastic wheel, so as to improve the wheel contact performance. [ABSTRACT FROM AUTHOR]

Abstract: Mechanical characteristics of run-flat tire under zero-pressure conditions are the basis of improving the driving performance of tire and realizing the stability control of vehicle blowout. Insert supporting run flat tire (ISRFT) is a typical safety tire based on pneumatic tire structure. As this type of safety tire has the advantages of simple structure, convenient disassembly and good zero pressure bearing capacity, it has become a new type of safety tire with great development prospect. With the improvement of vehicle performance, the performance of insert supporting run flat tire is also put forward higher requirements. The traditional insert structure is made of heavy materials such as metal and rubber, which has the problems of heat generation, shoulder cracking and so on. It can not meet the requirements of heavy load, high mobility and long-distance driving. Mechanical characteristics of inserts supporting run-flat tire is investigated in order to improve driving performance under zero pressure. Based on the tests of zero pressure load characteristics, lateral mechanical characteristics and tire grounding characteristics, the law of mechanical characteristics parameters of inserts supporting run-flat tire under different loads was studied. The mechanical characteristics parameters under zero pressure and rated tire pressure were comparatively analyzed. In addition, combined with the damage form of zero pressure driving failure, the mechanical characteristics of tire were analyzed. The results showed that the radial stiffness of the inserts supporting run-flat tire was approximately linear after the pressure loss, and the radial stiffness increased significantly after the insert takes part in the load-bearing. When there was no obvious sideslip, the lateral stiffness increases and the lateral adhesion decreases. When the load reached a certain value, the area of the tire's grounding footprint basically remained unchanged. In the center of shoulder and crown of tire, stress concentration appeared. At this time, the tread warpage was serious, and the uniformity of the ground pressure distribution was poor. When the load was less than 6000 N, the tire mainly depended on the structural load of the sidewall, and its radial stiffness was 84.76% lower than that under the rated tire pressure condition. When the load was more than 6000 N, the tire mainly depended on the insert, and the radial stiffness of the tire increased significantly, which was 283.34% higher than that under the rated tire pressure condition. The lateral stiffness characteristic curve consisted of the zone without obvious side slip, transition zone and obvious slip zone under zero pressure. In the region without obvious side slip, the relationship between lateral force and lateral displacement was approximately linear, while in the region of transition and obvious side slip, it was nonlinear. The average lateral stiffness of the tire without obvious sideslip area was 9.92% higher than that of the tire with rated tire pressure. The warpage of tire tread and the variation of uniformity of ground pressure distribution were more significant than those under rated tire pressure condition. When the load increases to 9 800 N, the length, width and area of the grounding footprint remained unchanged. The shoulder on both sides and the crown corresponding to the contact of the insert became the main bearing area of the tire. [ABSTRACT FROM AUTHOR]