Low Adhesion Coefficient Research Articles

Fuzzy and Sliding Mode Variable Structure Control of Vehicle Active Steering System

Background: The safety of vehicles has been valued throughout the world, whether it is now or in the future, the automobile safety issue is the hotspot and focus of the research by experts and scholars both at home and abroad. The continuous increase of car ownership not only brings convenience to people's lives, but it also poses a threat to people's lives and security of the property. Objective: Vehicle active safety system is the hotspot of current research and development as it plays an important role in automobile safety. Through the analysis of patents and references, we aim to understand the development of an active steering system. In order to improve the development efficiency of the active steering system, the paper proposes a feedback control method of the front-wheel angle. Methods: Based on yaw velocity and center of a mass side angle, the Active Front Steering (AFS) model is established respectively by fuzzy control and sliding mode control under the establishment of seven degrees of freedom vehicle dynamics model and the Dugoff tire model. Results: The simulation results show that both the control algorithm of sliding mode control and fuzzy control can improve the handling stability of vehicle steering on high adhesion coefficient road surface. On the low adhesion coefficient road, the control effect of slide mode control is more ideal while fuzzy control caused larger oversteer. Conclusion: The simulation results show that the control effect of sliding mode is superior to fuzzy control.

Simulation of chemical composition nitrogen-argon-aluminum plasma

Plasma-chemical model of magnetron discharge is described. The model allows you to predict the densities of the main plasma components. As a result of numerical modeling, it was found that dissociation of N2 ranges from 10% to 30% with an increase in plasma power, the degree of dissociation increases. The addition of N2 to the plasma leads to a decrease in ion density due to energy consumption for non-ionizing molecular collisions. It can be assumed that aluminum nitride is deposited on the surface of a substrate with a high flow of metal ions in combination with a stream of neutral molecules N2 with a low adhesion coefficient and a relatively small flow of nitrogen ions.

Autonomous vehicle path tracking control considering the stability under lane change

Considering that when a vehicle travels on a low friction coefficient road with high speed, the path tracking ability declines. To keep the performance of path tracking and improve the stabilization under that situation, this article presents approaches to estimate the parameters and control the vehicle. First, the key states of the vehicle and the road adhesion coefficient are estimated by the unscented Kalman filter. This is followed by applying the linear time-varying model-based predictive controller to achieve path tracking control, and the initial tire steering angle control rate is obtained. Finally, the steering angle compensation controller is simultaneously designed by a simple receding horizon corrector algorithm to improve vehicle stability when the path is tracked on a low-adhesion coefficient or at high speed. The performance of the proposed approach is evaluated by software CarSim and MATLAB/Simulink. Simulation results show that an improvement in the performance of path tracking and stabilization can be achieved by the integrated controller under the variable road adhesion coefficient condition and high speed with 110 km/h.

Optimal Trajectory Planning and Control for Automatic Lane Change of in Wheel Motor Driving Vehicles on Snow and Ice Roads

In the process of vehicles changing lanes, ice and snow pavement is a very common special working condition, and the research on automatic lane change is usually based on medium and high adhesion coefficient roads. Aiming at the special situation of low adhesion coefficient of ice and snow pavement, this paper studies the process of automatic lane change of vehicles on low adhesion roads driven by the front drive automobile driven by in-wheel motor. First, a dynamic model of a front drive automobile driven by in-wheel motor is established. Then, the trajectory planning is performed based on the fifth-degree polynomial method; the lateral acceleration threshold to ensure the safety of the lane change is deduced; the optimization function of the lane change time and the longitudinal driving displacement is established; and the optimal trajectory to ensure the safety and the lane change efficiency is obtained. Finally, the controller is established based on the fuzzy adaptive PID control algorithm, and the driving torque of the hub motor is distributed through the torque distribution strategy to perform the trajectory tracking control of the vehicle. Simulation results show that the vehicle can safely and smoothly change lanes along the planned trajectory.

A combining sliding mode control approach for electric motor anti-lock braking system of battery electric vehicle

In this paper, a combining sliding mode control (cSMC) approach of electric motor anti-lock braking system (emABS) is proposed to improve braking stability of battery electric vehicle (BEV). Two key variables, both wheel deceleration and slip ratio are utilized to design the emABS control law. Wheel deceleration directly characterizes the wheel speed, and slip ratio straightly characterizes some adhesion coefficient of ground. Based on sliding mode control (SMC) algorithm, two control laws of wheel deceleration and slip ratio are designed, the formula structures of which are very similar. At the same time, Lyapunov stability and robustness performance of the two control laws are proved, respectively. During the vehicle test, an interesting phenomenon was discovered that the SMC system of the wheel deceleration has fast transient response, and the slip ratio is more stability during stable control phase. The reason is that, the wheel deceleration can be measured accurately in the beginning, and the slip ratio can be computed accurately during stable control phase. Therefore, a SMC algorithm combined with wheel deceleration and slip ratio is designed for the control of emABS. With respect to low and high adhesion coefficient conditions, two simulation scenarios are utilized to validate the cSMC algorithm. In addition, the control strategy is verified on the test of BEV based on two road surfaces, the wet and the dry, respectively. These experimental results indicate that the proposed cSMC algorithm is a good candidate for the control of emABS.

Influence of temperature on adhesion coefficient and bonding strength of leaf films: A twin disc study

In the autumn, train operations in the UK are likely to be unstable due to the low adhesion coefficient between the wheel and rail, and fallen leaves on the line have been known as the main cause of this problem. In this study, the temperature effects on the adhesion coefficient as well as the bonding strength of the leaf film were investigated using a twin disc machine, to develop a potential prevention and mitigation method. The high surface temperature of the disc seemed to improve the adhesion when the leaf powder suspension was present, forming a linear relationship between the surface temperature and adhesion coefficient. The surface temperature around 240 °C could be enough to attain the required level of traction. The high temperature could decrease the bonding energy between the leaf film and rail, possibly decelerating the chemical reaction for the leaf film formation. Continuous drag braking in the autumn was proposed as a countermeasure. Two effects can be expected for this method: prevention of leaf contamination by removing the leaf residue on the wheel surface and improvement of the adhesion level by braking heat.

Wheel slip/Slide and low adhesion caused by fallen leaves

On the sloping section of a train service line located in mountainous areas, idling and skidding of the wheels caused by leaves that fall on the railhead in autumn often occurs, and this hinders the scheduled operation of the train. Although countermeasures such as spraying sand or ceramic particles onto the contact zone of wheel/rail are adopted, the effect is insufficient in late autumn. For clarifying the mechanism of the decrease in the adhesion between the wheel and the rail based on fallen leaves and acquiring information useful for practical implementation of countermeasures, the authors conducted a vehicle running test with driving and braking operations on a test line to investigate the occurrence of wheel slipping/sliding under various railhead states such as dry/wet leaves and dry/wet black accretion films, as well as the adhesion coefficient between the wheel and the rail when dry/wet black accretion films exist on the railhead. The results clarified that the wheel slipping/sliding was likely to occur under wet conditions, in particular frequently occur while wet black accretion films exist on the railhead, and then a low adhesion coefficient was recognized under the same conditions. Regarding the black accretion film formation process, the authors reproduced by a rail cooling device which can simulate atmospheric temperature in mountain area, and clarified that the tannin contained in the crushed fallen leaves has a reaction with steel comment of rail under wet (condensation, frost, light rain etc.) conditions and then black tannin iron was generated and adhere to the railhead. The countermeasure of wheel slip/slide should be focused on how to prevent the formation of the black accretion films or remove the black accretion films in the future work.

Optimized Handling Stability Control Strategy for a Four In-Wheel Motor Independent-Drive Electric Vehicle

An optimized handling stability control strategy is put forward aiming at enhancing a four in-wheel independent-drive motors electric vehicle (4WIDEV) performance capable of handling and stability. The optimized control strategy is designed by a hierarchical control structure, which mainly includes vehicle motion controller and vehicle torque distribution controller. Lateral stability controller, in-vehicle motion controller, which yields the generalized force and generalized yaw moment required of the vehicle, is designed into two modes: an instability control mode and a continuous control mode, which mode is activated determining by stability judgment controller based on phase portraits of sideslip angle and yaw rate. When the vehicle state exceeds the stability envelope region, instability control mode based on envelope control is utilized by sliding mode control method, simultaneously controlling the two-vehicle states variables, whereas continuous control mode is performed with adaptive adjustment of the weight parameter according to pre-defined stability degree. The lateral stability controller with adaptive switching two modes exhibits excellent handling stability performance under normal driving conditions, especially under critical conditions, such as on low tire-road adhesion coefficient. The vehicle torque distribution controller assigns driving or regenerative braking torque to four wheels reasonably and efficiently to satisfy the generalized force and the generalize yaw moment acquired by the vehicle motion controller, which synchronously considers the motor output capability and tire friction ellipse constraints while maintains each wheel slip ratio within the stable range. The results in co-simulation experiments based on Carsim and MATLAB/Simulink verify the proposed control strategy, compared with other control strategies, and demonstrate the effective improvement 4WIDEV’s performance in terms of handling stability especially under critical conditions.

MPC-Based Slip Ratio Control for Electric Vehicle Considering Road Roughness

In this paper, a slip ratio controller based on model predictive control (MPC) considering road roughness is proposed for electric vehicle (EV) to improve the driving/braking performance under low adhesion coefficient road. A half vehicle dynamic model is derived in which pitching, wheel rolling, and tire vertical movement is taking into account. The influence of vertical force variation caused by road unevenness and tire load transfer is analyzed to design slip ratio controller. In order to ensure vehicle safety, wheel slip stable zone is considered as time-domain constraints of the nonlinear-MPC. Besides, the motor output torque is limited by the motor maximum torque, which is considered as system time-varying constraints. The control objectives include vehicle safety, good longitudinal acceleration and braking performance, preservation of driver comfort, and lower power consumption. The proposed slip ratio controller is verified on a 13-degree-of-freedom (13DOF) EV model in MATLAB/Simulink. Simulation results of different maneuver on roughness surfaces show the benefits of the controller.

Stability control of in-wheel motor electric vehicles under extreme conditions

To investigate the stability of in-wheel motor electric vehicles (IWMEVs) under extreme conditions, a novel control strategy including active rear steering (ARS) mode and direct yaw moment control (DYC) mode is proposed in this paper, utilizing the adaptive dynamic neural network (ADNN) algorithm to make the most of the two control modes. Firstly, a three-degree of freedom nonlinear vehicle model as well as some subsystems is established. Then, a two-layer stability control strategy is put forward, where the upper-layer calculates the desired rear steering angle as well as the differential torque of the rear wheels and the lower-layer executes commands and returns relevant signals. Besides, a stability controller based on ADNN algorithm is designed in the upper-layer so as to take advantage of the two modes under extreme conditions. Next, the impacts of initial values of the connection weights on the ability of ADNN algorithm to train and learn are revealed. Consequently, the optimal initial values can be ascertained before the following simulations. Finally, the closed loop simulations of ARS and DYC are carried out under some extreme conditions such as high velocity and low adhesion coefficient roads, and the results indicate that compared with DYC’s difficulty in playing its role, ARS mode can significantly improve the stability of IWMEVs even under extreme conditions.

The analysis of drivers' reaction time using cell phone in the case of vehicle stabilization task.

The article analyzes the driver's psychophysiological qualities such as complex reaction and individual ability to control the vehicle that has suddenly lost its stability. The comparative analysis of the duration of reaction time was performed to assess the negative influence of speaking on a phone and driving with one hand. The experimental research was carried out on special training grounds with the road surface having low adhesion coefficient, where sudden lateral vehicle destabilization was caused by the moving plate mounted on the road surface. The vehicle onboard equipment was used for identifying the difference between the destabilization moment and the responsive driver's steering wheel movement which in this research was assumed as the reaction time. Statistical methods of research applied for the analysis of results showed high probability that the driver's actions would be significantly late in controlling a vehicle. When stabilizing a vehicle movement, the complex reaction time of a vehicle driver speaking on a mobile phone is increased by 18.1% as compared with the conventional driving by a driver not speaking on a phone. The risk of using the phone depends on the driver characteristics, traits and attitudes that affect the level of their experienced dangers, and the intensity of using mobile phones and driving. Speaking on a phone while driving increases the driver's reaction time and mental workload, and changes his or her visual overview ability as well as understanding of the situation. Int J Occup Med Environ Health 2018;31(5):633-648.

Coordinated Longitudinal and Lateral Motion Control for Four Wheel Independent Motor-Drive Electric Vehicle

For four wheel independent motor-drive electric vehicle, the vehicle longitudinal and lateral motion can be controlled by distributing the driving and regenerative braking torques of four wheel motors. To meet the driving command of driver and keep the vehicle lateral stability, a hierarchical control system is proposed in this paper. In the upper layer, a nonlinear model predictive control is implemented to solve the nonlinear multiinput multioutput, over-actuated problem. The controller is based on a nonlinear three degree-of-freedom model with nonlinear tire model, considering wheel slips as virtual control input. In the lower layer, the wheel slips are manipulated by a PID controller for generating driving and regenerative braking torques of the independent motors. This proposed controller is tested in a hardware-in-the-loop system with four typical maneuvers, which are constant velocity, accelerating, decelerating, and low road adhesion coefficient situations to show different driver command. The results show that the driver command of longitudinal and lateral motion control are both satisfied.

Lateral stability control of vehicles based on the calculation and allocation of component forces

A vehicle lateral stability control method for real-time calculation and dynamic allocation of the longitudinal force and yaw moment of vehicle tyres is proposed. The achievable range of the longitudinal force and yaw moment of the tyre are calculated in real time through off-line numerical optimisation and nonlinear programming. The calculated values are then adjusted to within the available range and allocated dynamically. A controller for the slip rate and front wheel slip angle is used to ensure that the tyre friction can trace each component force. The proposed method avoids estimating the lateral force of vehicle rear wheels while ensuring accuracy. The results of simulations and driver-in-loop tests demonstrated that the proposed method can improve the track-holding ability while reducing the influence of a road surface with a low adhesion coefficient on vehicle stability. The method ensures high and dynamic tracking performance and lateral stability.

Research on the Traction Fuzzy Control of Articulated Vehicles Based on Matlab

In this paper, the slip rate of the articulated electric-wheel vehicles is monitored with the traction control system during running. Using fuzzy control system to control the traction force can effectively control the output torque of the motor so as to realize the effective control of the slip rate in different running roads. The full vehicle dynamic model of the articulated electric-wheel vehicles was built, and the dynamic equation of the steering process was analyzed. The motor control model and the traction fuzzy controller suitable for the system were constructed. Based on Matlab, the fuzzy controller was integrated with the full vehicle model to build the fuzzy control analysis model of full vehicle traction force. The running condition of the full vehicle on the low adhesion coefficient road and bisectional road was analyzed. The analysis results show that when vehicles run at different adhesion coefficients, the slip rate fuzzy control system can effectively reduce the skidding degree of wheels, so that the adhesive force provided by the pavement can be used to the maximum extent, so as to ensure the vehicle stability and improve the running safety, and the control has achieved good results.

Study on the vertical and lateral coupling dynamics control of the in-wheel motor-driven electric vehicles under multi-excitation

To study the coupling dynamics control in the vertical and lateral directions of the in-wheel motor (IWM)-driven electric vehicles under the steering input, road and electromagnetic excitation, a verified 16-degrees-of-freedom coupling dynamic model is given. To improve the vehicle coupling dynamics, a dynamics controller is designed based on the active suspension, active front steering (AFS) and direct yaw control (DYC) system. The dynamics controller includes a supervisory coordination layer controller and the above sub-system controller with different control algorithms, respectively. Finally, comparative analysis is carried out to verify the validity of the controller designed in this paper. The results show that, whether the road has a high or low adhesion coefficient, the controller developed in this paper is highly effective for the coupling dynamics of the IWM-driven vehicle. Especially, on a road with low adhesion coefficient, the control effect on the vehicle running stability and path track capacity is more obvious.

Bifurcation of Lane Change and Control on Highway for Tractor-Semitrailer under Rainy Weather

A new method is proposed for analyzing the nonlinear dynamics and stability in lane changes on highways for tractor-semitrailer under rainy weather. Unlike most of the literature associated with a simulated linear dynamic model for tractor-semitrailers steady steering on dry road, a verified 5DOF mechanical model with nonlinear tire based on vehicle test was used in the lane change simulation on low adhesion coefficient road. According to Jacobian matrix eigenvalues of the vehicle model, bifurcations of steady steering and sinusoidal steering on highways under rainy weather were investigated using a numerical method. Furthermore, based on feedback linearization theory, taking the tractor yaw rate and joint angle as control objects, a feedback linearization controller combined with AFS and DYC was established. The numerical simulation results reveal that Hopf bifurcations are identified in steady and sinusoidal steering conditions, which translate into an oscillatory behavior leading to instability. And simulations of urgent step and single-lane change in high velocity show that the designed controller has good effects on eliminating bifurcations and improving lateral stability of tractor-semitrailer, during lane changing on highway under rainy weather. It is a valuable reference for safety design of tractor-semitrailers to improve the traffic safety with driver-vehicle-road closed-loop system.

Coaxial-coupling traction control for a four-wheel-independent-drive electric vehicle on a complex road

An independent-wheel-drive electric vehicle has the advantage of better implementation of precise motion and stability control. However, when the vehicle is moving on a road that has complex slopes and various adhesion coefficients and is subjected to the structural limitations of the independent-wheel-drive systems, the driving performance will deteriorate. In order to make full use of the drive torque of every motor to improve the vehicle’s climbing and accelerating abilities, on the basis of the designs of a dual-motor coaxial-coupling independent-wheel-drive system and a sliding-mode controller, a coaxial-coupling traction control system was developed. Simulations on coaxial-coupling traction control for a four-wheel-independent-drive electric vehicle were completed. With the innovative coaxial-coupling equipment, the drive torque can be satisfactorily transferred between the wheels at the two sides of one drive shaft. When one of the driving wheels begins to slip, the torque transmission will increase rapidly, the probability that wheel slipping occurs will be reduced and the vehicle’s driving force can be enhanced. Also, the chatter of the traction control system can be quietened effectively, and the dynamicity and trafficability can be improved. In addition, with the additional yaw moment generated by the torque coupling, the system also has the auxiliary effect of improving the high-velocity lateral stability of the vehicle on a road which has a low adhesion coefficient.

Research on Electronic Differential Control Method of Electric Vehicle with Motorized Wheels Based on Adhesion Coefficient

This paper presents an electronic differential control strategy based on equal adhesion coefficient, it makes electric vehicle (EV) with two dual-motorized-wheels achieve differential by distributing and controlling the driving torque. First, six degree-of-freedom (6-DOF) vehicle dynamic model was set up and electronic differential system based on permanent magnet synchronous motor (PMSM) vector control was designed, then the simulation of differential control method with Matlab/Simulink was performed. The results show that when the high-speed vehicle steering in the low road adhesion coefficient, the electronic differential control method based on the principle of equal adhesion coefficient can keep two driving wheels’ adhesion coefficient utilization ratio the same, avoiding single wheel skid and improving the steering stability.

Evaluation Method about Braking Force Utilization

For the braking performance investigated when vehicle was on the road of different road adhesion coefficient, the match of ideal braking force distribution curves of front and rear wheels and front and rear arresters was studied. The concept of braking performance to reflect "braking force utilization" was introduced.The braking force utilization algorithm came out depending on the different matches. A light bus was chosen as an example. Vehicle braking performance under different road adhesion coefficient was studied in detail.At the same time, vehicle braking performance under different matches was studied with braking force distribution value changed. The results indicate that, braking force utilization appears first increased and then decreased with the increase of road adhesion coefficient.Along with the increase of braking force distribution value,the braking force utilization decreased on low adhesion coefficient road,then increased on high adhesion coefficient road.The method could evaluate the braking performance on the road of different road adhesion coefficient efficiently.

Modeling and Controlling of Anti-Slip Regulation Based on Limited-Slip Differential

The dynamic models of whole rear-wheel drive vehicle, limited-slip differential, hydraulic control system and electronic throttle were established. Simulations of acceleration course on split-µ road, checkerboard-µ road, low-µ road and step-µ road were carried out combining electronic throttle PI controller and limited-slip differential fuzzy controller. The results show that the Anti-slip Regulation quickly works according to the road adhesion coefficient, effectively inhibits the slip of driving wheels on low adhesion coefficient road, the acceleration performance driving on bad roads was improved obviously, and show a good adaptability.