Adhesion Coefficient Research Articles

Dynamic-boundary-based lateral motion synergistic control of distributed drive autonomous vehicle

To improve the path tracking accuracy and yaw stability of distributed drive autonomous vehicles (DDAVs) under extreme working conditions, a cooperative lateral motion control method based on the dynamic boundary is proposed to prevent different road adhesion conditions from affecting the motion stability of DDAVs. Based on the analysis of the DDAV lateral dynamics system coordination mechanism, a dynamic boundary considering the pavement adhesion coefficient is proposed, and the Lateral Motion Synergistic Control System (LMSCS) is designed. The LMSCS is divided into the coordination, control, and executive layers. The coordination layer divides the control domain into the stable, quasi-stable, and unstable domains by the dynamic boundary, and coordinates the control strength of the path following control and yaw stability control. In the control layer, the path following control and yaw stability control laws are designed based on the global fast terminal sliding mode. The executive layer estimates the expected steering wheel angle and expected additional wheel torque. Joint simulations under double line shifting conditions confirmed that LMSCS reflects the impact of the road attachment conditions and improves the path tracking accuracy and vehicle yaw stability. The LMSCS has better overall performance than existing lateral motion control methods.

Manufacture of Gilded Threads in the 15-17th Centuries

Since ancient times, gilded threads have been used to decorate textiles in different cultures around the world. In the article, the author examines the threads manufacturing in the 16-17th centuries in Europe and Western Asia, trying to answer two, as it seems to him, the main questions: what was the method of gilding and what was the method of cutting if width error was less than 10 μm. It is assumed that the main gilding method was the diffusion one, and the main cutting method used rollers and a sharp blade at a small angle. The first one has not been proven but the second has been proved. The article lists all marks, diffusion and adhesion coefficients, human angular resolution, and much more.

Pavement State Recognition Method Considering Slope

For the problem of road surface condition recognition, this paper proposes a real-time tracking method to estimate road surface slope and adhesion coefficient. Based on the fusion of dynamics and kinematics, the current road slope of the vehicle which correct vertical load is estimated. The effect of the noise from dynamic and kinematic methods on the estimation results is removed by designing a filter. The normalized longitudinal force and lateral force are calculated by Dugoff tire model, and the Jacobian matrix of the vector function of the process equation is obtained by combining the relevant theory of EKF algorithm. The road adhesion coefficient is estimated finally. The effectiveness of the algorithm is demonstrated by analyzing the results under different operating conditions, such as docking road and bisectional road, using a joint simulation of Matlab/Simulink and Carsim.

The adhesion force change of an experimental road vehicle

The Article deals with the controlled influence of the adhesive force in contact of the road vehicle’s wheel with the road. The first section shows how the adhesive force is reduced. The next step is the familiarization with the experimental vehicle with the Alternative SkidCar, where experimental measurements were carried out, assessment of the advantages and disadvantages of the experimental vehicle with the Alternative SkidCar and the drive on the sliding surface following the experimental test methods. The objective of the article is to determine how great the difference in vehicle behav-iour is when the adhesive force changes by modifying the radial reaction and the change in the coeffi-cient of adhesion.

Parallel Structure of Feedback Linearization and Sliding Mode Controllers to Track the Desired Velocity Profile in High-Speed Trains

High-speed railway vehicles operate much faster than traditional railway vehicles. After a four-axle high-speed railcar is modeled, an analytical solution is employed in this paper to solve dynamic equations. According to this analytical solution, the coupling of four-axle high-speed railcar equations depends strictly on the adhesion coefficient. A novel parallel control strategy is then formulated to prevent wheels from slipping and track the desired velocity profile. The proposed control strategy includes feedback linearization and sliding mode controllers to achieve the desired performance. Finally, the simulation results indicated the effectiveness of the proposed control system in the high-speed railcar such that the tracking error is less than 12%.

Development of a device for determining the coefficient of adhesion of a tire simulator with a flat support surface

To ensure optimal braking performance, i.e. minimum braking distance while maintaining the stability of the car at the limit of controllability, anti-lock systems are currently installed on cars. The relative fraction of the rest friction in the contact spot, which is used to form the longitudinal reaction of the support surface at the appropriate value of the slip coefficient, in relation to the total fraction of the rest friction in the contact spot is a constant value for any type and condition of the road surface. The coefficient of adhesion in physical essence is the coefficient of friction at rest. The proposed device for determining the coefficient of adhesion of a tire simulator with a flat horizontal support surface will simplify the design and increase the measurement accuracy. Keywords: coefficient of adhesion, a device for determining the coefficient of adhesion, a device

On the issue of assessing the errors in the operation of an interactive system for improving road safety outside settlements

The article presents the result of the analysis of statistical data of accidents in the Krasnoyarsk Territory on sections of roads outside settlements with their greatest concentration. The main types of vehicle collisions and their accompanying conditions were identified. A mathematical apparatus for determining the minimum safe distance between vehicles located closely in an emergency zone on a section of a road outside settlements is proposed, in which it is necessary to notify the drivers of these vehicles about the danger in conditions of insufficient and/or limited visibility in various road situations, taking into account errors in positioning and determining the speed of the vehicle, the response time of the system, the effective coefficient of adhesion of the tires to the road surface. The results of experimental studies of vehicle positioning and speed errors determined by the driver’s early warning system about hazards on the road and their impact on the operability of the designed system are presented. Keywords: road safety, interactive driver warning system, positioning error, safe distance, rest of track, braking distance

Evaluating Coordinated Cooperative Control of Three Active Car Systems Using Fuzzy-Logic

Vehicle systems automation is an inevitable process as a result of the growing safety requirements and the trend of increasing car operation autonomy by reducing driver’s influence. The paper covers the coordinated control operation of three active systems to assess the improvement of vehicle response. Direct yaw control through selective wheel braking (DYC), active front steering control (AFS) and active suspension normal force control (NFC) are included. The control method is fuzzy logic. The modelling is done in Matlab/Simulink, where 14-DOF nonlinear full vehicle model and 3-DOF reference model were introduced. Simulations were done for three manoeuvres: cornering event, single lane change and fishhook manoeuvre, at a speed of 130 km/h and dry road surface with adhesion coefficient of 0.9 was assumed. Coordination was done with adjusting scaling factors for each control. Results show improvements in the transient response behaviour of the vehicle compared with four vehicles: vehicle without any active system, vehicle with coordinated DYC and AFS, vehicle with coordinated DYC and NFC and vehicle with coordinated AFS and NFC. The biggest impact can be seen in results for sideslip angle and roll angle, coordinated cooperative control here gives lowest values in the transient period during the manoeuvre. Although it gives better results for the other variables as well. The goal of the coordinated cooperative control is fulfilled by improving the stability and handling of the vehicle, which helps the driver to maintain the feeling of manoeuvrability and the sense for the direction of movement of the vehicle. The system for direct yaw control through selective wheel braking has major impact but the coordination with the other two systems lowers the braking force per wheel. The system for active front steering control has lower impact but at lower speeds helps for maintaining better direction of vehicle movement. Considering these three active systems act simultaneously during high speeds and critical manoeuvres next step would be to define sequence of activation depending on the currently measured vehicle behaviour variables.

Bond characteristics between conventional concrete and six high-performance patching materials

Repair of damaged concrete structures with patching materials is required for a wide variety of bridge and building applications. Despite the capabilities of conventional patching materials in replacing the spalled concrete, they are often unable to restore the original structural capacity. This has motivated research investigations to develop high-performance patching materials that can help damaged concrete structures regain their strength and durability characteristics. Such characteristics, however, are not properly achieved without a satisfactory bond between the concrete substrate and the patching material applied. To investigate this critical aspect, six high-performance patching materials, i.e., proprietary and nonproprietary ultra-high performance concrete, polypropylene and alkali-resistant glass fiber-reinforced concrete, high-early strength concrete, and shrinkage-compensating cement concrete, were systematically investigated and compared in the current study. The conducted experiments included a holistic set of splitting tensile and slant shear tests performed on the samples prepared with various surface roughnesses. The experimental test results provided firsthand information about the bond characteristics between normal-strength concrete and six high-performance patching materials. With the determination of corresponding adhesion and friction coefficient factors, the outcome of this study facilitates the selection and use of high-performance patching materials, depending on the availability of materials and repair needs.

Features of slopes overcoming by walking devices

For mobile robots designed to work in extreme conditions, an important characteristic is the value of the overcoming slope. For wheeled and tracked vehicles, the angle of the overcoming slope is limited by the adhesion properties of the soil. The walking device can provide overcoming of higher slopes, since the analogue of the adhesion coefficient for walking machines, with a large footprint track depth, can be significantly greater than 1. The paper discusses the results of experimental studies of the features of overcoming slopes by a walking device in weak soil conditions. When mobile robots overcoming inclines, they may overturn or slide downhill. It is shown that on soft soils the sliding of walking machines downhill is unlikely because of significant deformations of the soil under the support elements. On the other hand, the deformation of the soil worsens the resistance of the walking vehicle to overturning. A method of increasing resistance to overturning by controlling the position of the robot body by separately regulating the conditional clearance of walking mechanisms is considered. The possibility of adjusting the clearance in the propulsion unit on the basis of Umnov-Chebyshev cyclic walking mechanisms is shown. Climbing slopes requires a certain amount of traction. The values of the additional power and the force characteristics of the walking device’s drive necessary for successful overcoming of slopes have been determined. The results of the work can be demand in the development of walking machines and mobile robots. Key words Mobile robots, walking machines, interaction with the ground, traction and coupling properties, overcoming slopes, tipping resistance, mathematical modeling, field tests. Acknowledgements Research was partially supported by RFBR and the Administration of the Volgograd region, research projects no. 19-08-01180 a, 19-48-340007 p_a.

Analysis of the bond stress when using GFRP bars

For most of the structural solutions, the construction industry in Brazil is based on the use of conventional reinforced concrete elements composed of concrete and steel bars. However, problems related to this traditional structural system, such as the corrosion of metallic bars exposed to aggressiveness environments, motivate the study of new materials to be used as a replacement of conventional bars. In this context, FRP (Fiber Reinforced Polymers) bars can be viable due to their good mechanical properties and resistance to aggressive environmental agents. Thus, the main objective of this paper was the evaluation of the bond stress of GFRP bars using pullout tests. Thus, twenty specimens were analyzed with two concrete compressive strengths of 30 MPa and 60 MPa and two different GFRP bar diameters of 9.5 and 16.0 mm. According to the test results, it was verified a high variability of the adhesion between the GFRP bar and the concrete. Concerning the statistical analysis of pullout tests performed and considering the methodology proposed to analyze the quality control, the variation coefficient varied from 13.71% to 20.17%, classifying the pullout tests performed as medium or poor. These results demonstrate that the response of the GFRP bars obtained in the pullout tests was not reliable, demonstrating the need for new research to obtain adhesion coefficients and anchoring lengths for use in structural designs with such materials.

A comparative study of the recursive least squares and fuzzy logic estimation methods for the measurement of road adhesion coefficient

ABSTRACT Vehicle active safety system is the hotspot of current research and development, and the road adhesion coefficient is one of the essential parameters in the development of automobile active safety system, which plays a pivotal role in automobile safety. To improve the real-time performance and accuracy of the road adhesion coefficient, this paper proposes different control methods and compares and analyzes them. To accurately estimate the road adhesion coefficient in real-time, an eight-degree-of-freedom vehicle model was adopted in this paper. According to the tire torque and wheel speed, the adhesion coefficient was estimated based on the second-order nonlinear extended state observer. The experimental data, such as slip rate, using the improved tire model, is based on the recursive least squares method with forgetting factor and fuzzy logic algorithm real-time of tire-road friction coefficient estimation. The results show that the observer can effectively observe utilisation adhesion coefficient, and both control algorithms can estimate the road adhesion coefficient in real-time, effectively and quickly. On different roads, the use of the recursive least squares algorithm resulted in higher estimation accuracy, better robustness, and better control effect than using a fuzzy logic algorithm.

Analysis of reliability of the drill pipe in the clamping mechanism

In oilfield equipment, a significant place is occupied by clamping mechanisms used to grip pipes during tripping operations. They are mainly divided into 2 groups. The first includes mechanisms with a forced clamping of the part. The second group includes self-clamping devices with a wedge mechanism. Here, the clamping force increases in proportion to the axial shear force. In these clamping devices, clamping jaws serve as a common element. In addition to smooth jaws, there may be jaws with notches on the inner cylindrical surface. Such notches contribute to an increase in the coefficient of adhesion when clamping cylindrical parts, in particular pipes. During the operation of clamping devices with corrugated jaws, the teeth of the notch are introduced into the pipe walls under the action of the clamping force. The shearing force can then displace the pipe relative to the jaws. The adhesion coefficient µ is the ratio of the shear force P to the clamping force Q, i.e. P/Q. Exceeding the shear force P of the limit value causes the pipe to be clamped to move. The correct choice of the place of load application is also of great importance.
 Optimum clamping performance can be achieved by clamping workpieces without slipping from shear forces. At the same time, it is necessary to ensure reliability, efficiency, productivity. Therefore, all factors that determine the holding capacity of clamping mechanisms should be considered. These factors include the coefficient of adhesion, the design of the working surfaces of the clamping elements, the type of notch of the corrugated jaws and the place of application of the clamping force

Research on Decoupled Optimal Control of Straight-Line Driving Stability of Electric Vehicles Driven by Four-Wheel Hub Motors

The optimal control strategy for the decoupling of drive torque is proposed for the problems of runaway and driving stability in straight-line driving of electric vehicles driven by four-wheel hub motors. The strategy uses a hierarchical control logic, with the upper control logic layer being responsible for additional transverse moment calculation and driving anti-slip control; the middle control logic layer is responsible for the spatial motion decoupling for the underlying coordinated distribution of the four-wheel drive torque, on the basis of which the drive anti-skid control of a wheel motor-driven electric vehicle that takes into account the transverse motion of the whole vehicle is realized; the lower control logic layer is responsible for the optimal distribution of the driving torque of the vehicle speed following control. Based on the vehicle dynamics software Carsim2019.0 and MATLAB/Simulink, a simulation model of a four-wheel hub motor-driven electric vehicle control system was built and simulated under typical operating conditions such as high coefficient of adhesion, low coefficient of adhesion and opposing road surfaces. The research shows that the wheel motor drive has the ability to control the stability of the whole vehicle with large intensity that the conventional half-axle drive does not have. Using the proposed joint decoupling control of the transverse pendulum motion and slip rate as well as the optimal distribution of the drive force with speed following, the transverse pendulum angular speed and slip rate can be effectively controlled with the premise of ensuring the vehicle speed, thus greatly improving the straight-line driving stability of the vehicle.

Robust Control Design of Active Front-Wheel Steering on Low-Adhesion Road Surfaces

In order to improve the stability of vehicle steering on low-adhesion road surfaces, this paper designed a hybrid robust control strategy, H2/H∞, for active front-wheel steering (AFS) based on robust control theory. Firstly, we analyzed the influence of the sidewall stiffness and road adhesion coefficient of the tires on vehicle stability, through which we can study the wheel deflection characteristics of low-adhesion roads. Secondly, the reference yaw velocity of the vehicle was calculated using the three-degrees-of-freedom model as the reference model, through which, taking the norm H∞ as the objective function and the norm H2 as the limit to control the output, the hybrid robust control strategy H2/H∞ of the AFS system on a low-adhesion road surface was developed. Finally, the simulation experiment was carried out by the Simulink/CarSim co-simulation platform and a hardware-in-the-loop (HIL) experiment. In this paper, the results show that the AFS control strategy can improve the vehicle handling stability on low-adhesion road surfaces, and the controller has good path tracking performance and robustness.

Analysis on the Dynamic Performance of Vehicles

The current accelerated developments within the automotive sector have triggered a series of performance, comfort, safety and design-related issues. Hence, oftentimes manufacturers are challenged to combine various elements so as to achieve an attractive design, without diminishing the vehicle’s dynamic performance. In order to determine the vehicle dynamic performances we carried out an analysis by two methods. In the first part of the paper, we have used the analytical method to establish the dynamic performances of a vehicle. The second part of our study addresses another method to determine the star performances of the vehicle by means of computerized simulations. The first test aimed to determine vehicle starting performances for two vehicle models, with similar technical configuration, but with the same initial data. In the second test, we aimed at determining the start performance for the same car model, with the same initial data, but for different adhesion coefficients

Evaluation of Failure Probability in Series System of Three-Axle Trucks under Strong Crosswind

The probability of wind-induced failure accidents in three-axle trucks under pulsating strong crosswinds and the corresponding critical safe speed are investigated in this study. Reliability theory and random fuzzy methods are utilized to establish the membership function of the failure probability in the series system (FPSS) composed of rollover, side-slip, and rotation failure accidents. The Kaman spectrum is used to realistically simulate the fluctuating wind time history curves of different average speeds. Four factors affecting the six-component force coefficient of the three-axle truck and the crosswind load are considered: fluctuating average wind speed, wind direction (angle), truck driving speed, and road adhesion coefficient. A three-axle truck nonlinear model is established accordingly. The model is used to obtain the dynamic response of the three-axle truck under strong crosswind conditions as per the time-varying curves of the vertical load of the truck, the time-varying curves of the lateral displacement of the center of mass, and the time-varying curves of the heading angle. An advanced Monte Carlo simulation algorithm based on importance sampling is used to determine the probability of a three-axle truck with FPSS under strong crosswinds; the given acceptable probability of failure (accident) is used to obtain the critical safety speed. The sensitivity analysis of random variables reveals that the possibility of three truck failures of the three-axle truck in strong crosswinds is, from largest to smallest, rollover, side-slip, and rotation. This research may provide useful guidance for exploring the probability of wind-induced accidents and the critical safety speeds of vehicles, as well as useful general information for road transportation management departments.

Prevention of injuries in concurrent collision of vehicles in AIC technological pro-cesses

The results of research on the prevention of road accidents when carrying out cargo transportation of agro-industrial products as a result of collisions of vehicles moving in the same direction or hitting a standing vehicle or an obstacle are given. It is noted that this situation occurs due to the density of traffic on general roads, as well as on field and country roads characteristic of agricultural production for reasons of low adhesion coefficient in rainy weather, snowfall, ice. In such conditions, a vehicle moving in a stream behind the leader (especially low-clearance ones, such as cars) collides with the rear of the upcoming high-sized transport. The consequences of these collisions are the destruction of the front of the transport moving behind the leader and the injury to the driver and passengers (especially those sitting in the front seat). In order to avoid such situations, an innovative solution is proposed that automatically eliminates the possibility of injury and damage to the rear of the leader and the front of the vehicle colliding with him moving behind the leader.

Preview Control with Dynamic Constraints for Autonomous Vehicles.

In this paper, a preview theory-based steering control approach considering vehicle dynamic constraints is presented. The constrained variables are predicted by an error states system and utilized to adjust the control law once the established dynamic constraints are violated. The simulated annealing optimization algorithm for preview length is conducted to improve the adaptability of the controller to varying velocities and road adhesion coefficients. The theoretical stability of a closed-loop system is guaranteed using Lyapunov theory, and further analysis of the system response in time domain and frequency domain is discussed. The results of simulations implemented on Carsim–Simulink demonstrate the favorable performance of the proposed control in tracking accuracy and system stability under extreme conditions.

Laser Processing of Hard and Ultra-Hard Materials for Micro-Machining and Surface Engineering Applications.

Polycrystalline diamonds, polycrystalline cubic boron nitrides and tungsten carbides are considered difficult to process due to their superior mechanical (hardness, toughness) and wear properties. This paper aims to review the recent progress in the use of lasers to texture hard and ultra-hard materials to a high and reproducible quality. The effect of wavelength, beam type, pulse duration, fluence, and scanning speed is extensively reviewed, and the resulting laser mechanisms, induced damage, surface integrity, and existing challenges discussed. The cutting performance of different textures in real applications is examined, and the key influence of texture size, texture geometry, area ratio, area density, orientation, and solid lubricants is highlighted. Pulsed laser ablation (PLA) is an established method for surface texturing. Defects include melt debris, unwanted allotropic phase transitions, recast layer, porosity, and cracking, leading to non-uniform mechanical properties and surface roughness in fabricated textures. An evaluation of the main laser parameters indicates that shorter pulse durations (ns—fs), fluences greater than the ablation threshold, and optimised multi-pass scanning speeds can deliver sufficient energy to create textures to the required depth and profile with minimal defects. Surface texturing improves the tribological performance of cutting tools in dry conditions, reducing coefficient of friction (COF), cutting forces, wear, machining temperature, and adhesion. It is evident that cutting conditions (feed speed, workpiece material) have a primary role in the performance of textured tools. The identified gaps in laser surface texturing and texture performance are detailed to provide future trends and research directions in the field.