Wheel Slip Ratio Research Articles

An Investigation into Wheel Sinkage on Soft Sand

ABSTRACT Sinkage is an empirically significant factor in vehicle performance as it can result in an immobile vehicle or significant environmental damage. Bernstein first proposed a pressure-sinkage relationship in 1913, and subsequent work by Janosi and Hanamoto and Hedegus concluded that longitudinal wheel slip also plays a role in sinkage. Shinone, Nakashima, Takatsu, Kasetani, and Matsukawa identified a linear relationship between slip and sinkage on a lightly loaded tire (980 N). In this study, the effects of vertical wheel load, longitudinal wheel slip ratio, and tire inflation pressure on wheel sinkage on loose sand were investigated to relate sinkage to a vehicular operating condition. The test program in this study was conducted using the Cranfield University Single Wheel Tester (SWT) on loose, desert-like sand in the Cranfield Off-Road Dynamics facility soil lane. The SWT uses a closed loop servo-controlled hydraulic actuator to actively control vertical wheel load and twin hydraulic motors to actively control wheel speed. The SWT apparatus is mounted on an independent prime mover tractor unit, which controls forward speed. True forward speed is continuously measured against a fixed reference point and used to calculate the required wheel speed in real time to give the desired slip profile. A series of controlled load tests were conducted using a Goodyear G90 tire on a dry desert sand material. Four discrete inflation pressures (0.69, 1.38, 2.07, and 2.76 bar [10, 20, 30, and 40 psi] and four vertical wheel loads (1, 2, 3, 4, and 5 kN) were chosen to represent the operating range of the tire. Each test run consisted of a continuously decreasing sweep of longitudinal wheel slip ratio (the slip ratio was controlled to decrease linearly from 85% [driven] to −15% [braked]). Although a near-linear increase in sinkage was identified for wheel slip ratios greater than 10%, as Shinone et al. also found, the overall relationship between slip ratio and sinkage was found to be nonlinear.

Improving Vehicle Lateral Stability Based on Variable Stiffness and Damping Suspension System via MR Damper

The capability of a variable stiffness and damping (VSVD) suspension system via a magnetorheological (MR) damper on improving vehicle lateral stability is investigated in this paper. First, a type of the VSVD suspension system is briefly introduced with the application of variable damping to realize the capability of VSVD. Then, variable damping via the MR damper is extended, and the characteristics of damping force are presented with the Bouc-Wen model. Then, the proposed VSVD system is inserted into a full vehicle model as a front suspension system to control tire normal forces. A control strategy composed of a fuzzy controller that the output is wheel slip ratio and a simple on/off controller to model the application of VSVD is developed to illustrate its ability in improving vehicle stability. It is shown from simulation that VSVD can increase tire normal forces and make vehicles present better performance on lateral stability.

Development of Dead Reckoning Algorithm Considering Wheel Slip Ratio for Autonomous Vehicle

최근 들어, 차량 제어 기술의 집약체라 할 수 있는 자율 주행 차량에 관한 관심이 증대되고 있다. 특히, 자율 주행 차량의 안정적인 주행과 직결되는 자기 위치 인식 기술에 관한 연구가 꾸준히 진행되어져 왔으며, GPS가 갖는 한계점을 보완하기 위한 다양한 추측항법 기술이 소개되어져왔다. 하지만 기존의 추측항법들은 추가적으로 센서를 장착해야하는 단점과 차량 거동의 급격한 변화로 인하여 자기 위치 인식 정확도가 떨어진다는 단점을 가진다. 따라서 본 논문에서는 기존의 추측항법의 단점을 보완하기 위하여 대부분의 차량에 장착되어 있는 휠속 센서(Wheel Speed Sensor)를 활용하고, 휠속 센서에서 계측된 값을 토대로 타이어 슬립율(Slip ratio)을 추정하여 차량의 급격한 거동 변화에 대응하기 위한 새로운 개념의 슬립율 기반의 추측항법 알고리즘을 개발하였다. 기존의 추측항법 알고리즘과의 성능을 비교 평가하기 위해서 차량의 거동이 급격하게 변화하는 상황이 포함된 시뮬레이션 환경을 구성하여 그 결과를 비교하였다. 【Recently, the interest in autonomous vehicle which is an aggregate of the automotive control technology is increasing. In particular, researches on the self-localization technology that is directly connected with stable driving of autonomous vehicle have been performed. Various dead reckoning technologies which are solutions for resolving the limitation of GPS have been introduced. However, the conventional dead reckoning technologies have two disadvantages to apply on the autonomous vehicle. First one is that the expensive sensors must be equipped additionally. The other one is that the accuracy of self-localization decreases caused by wheel slip when the vehicle's motion changed rapidly. Based on this background, in this paper, the wheel speed sensor which is equipped on most of vehicles was used and the dead reckoning algorithm considering wheel slip ratio was developed for autonomous vehicle. Finally, in order to evaluate the performance of developed algorithm, the various simulation were conducted and the results were compared with the conventional algorithm.】

Adaptive motion control of wheeled mobile robot with unknown slippage

As a major representative nonholonomic system, wheeled mobile robot (WMR) is often used to travel across off-road environments that could be unstructured environments. Slippage often occurs when WMR moves in slopes or uneven terrain, and the slippage generates large accumulated position errors in the vehicle, compared with conventional wheeled mobile robots. An estimation of the wheel slip ratio is essential to improve the accuracy of locomotion control. In this paper, we propose an improved adaptive controller to allow WMR to track the desired trajectory under unknown longitudinal slip, where the stabilisation of the closed-loop tracking system is guaranteed by the Lyapunov theory. All system states use neural network online weight tuning algorithms, which ensure small tracking errors and no loss of stability in robot motion with bounded input signals. We demonstrate superior tracking results using the proposed control method in various Matlab simulations.

Development and Verification of the Tire/Road Friction Estimation Algorithm for Antilock Braking System

Road friction information is very important for vehicle active braking control systems such as ABS, ASR, or ESP. It is not easy to estimate the tire/road friction forces and coefficient accurately because of the nonlinear system, parameters uncertainties, and signal noises. In this paper, a robust and effective tire/road friction estimation algorithm for ABS is proposed, and its performance is further discussed by simulation and experiment. The tire forces were observed by the discrete Kalman filter, and the road friction coefficient was estimated by the recursive least square method consequently. Then, the proposed algorithm was analysed and verified by simulation and road test. A sliding mode based ABS with smooth wheel slip ratio control and a threshold based ABS by pulse pressure control with significant fluctuations were used for the simulation. Finally, road tests were carried out in both winter and summer by the car equipped with the same threshold based ABS, and the algorithm was evaluated on different road surfaces. The results show that the proposed algorithm can identify the variation of road conditions with considerable accuracy and response speed.

A Research on Anti-Slip Regulation for 4WD Electric Vehicle with In-Wheel Motors

This paper proposes a wheel slip control strategy for 4WD Electrical Vehicle with In-wheel Motors. In the first part of this paper, a brief introduction of sliding mode control for acceleration slip regulation is given. Consider that its control effect varies with road conditions, another algorithm which can automatically adapt to different roads is designed. This method takes advantage of the peculiarity of the longitudinal static tire force curve and regulates wheel slip ratio to the detected optimal value, aiming to maximize the traction force while preserving sufficient lateral tire force. Simulation results show that the slip rate can be regulated to a value around the optimal slip ratio, and the driving torque is very close to the maximum transmissible torque. The control strategy achieves stronger stability, shorter driving distance and hence better control performance.

Development of an In-Door Tire Soil Bin Testing Facility Experimental Setup

The field testing may give the real conditions, but the uncontrolled environment may affect the results. In a soil bin, all driving conditions are controlled. Therefore a scaled soil bin was designed and established at MTC. The single wheel tester concludes the dynamic weight equal to that measured statically. Using an indoor soil bin, and measuring sensors the instantaneous wheel speed representing the theoretical speed and free wheel speed representing the actual speed were measured and recorded. Using the signals from two speed sensors, the instantaneous wheel slip is calculated. Also the dynamic sinkage due to wheel motion is measured using ultrasonic sensor. This paper presents a detailed experimental measuring of instantaneous wheel slip and dynamic sinkage on two surfaces; soft dry sand and hard surface. A theoretical control algorithm was developed and implemented. The control system using rotary valve and pressure sensor to control the tire pressure (inflation/deflation) based on the wheel slip ratio and dynamic sinkage.

Cooperative Control of Regenerative Braking and Antilock Braking for a Hybrid Electric Vehicle

A new cooperative braking control strategy (CBCS) is proposed for a parallel hybrid electric vehicle (HEV) with both a regenerative braking system and an antilock braking system (ABS) to achieve improved braking performance and energy regeneration. The braking system of the vehicle is based on a new method of HEV braking torque distribution that makes the antilock braking system work together with the regenerative braking system harmoniously. In the cooperative braking control strategy, a sliding mode controller (SMC) for ABS is designed to maintain the wheel slip within an optimal range by adjusting the hydraulic braking torque continuously; to reduce the chattering in SMC, a boundary-layer method with moderate tuning of a saturation function is also investigated; based on the wheel slip ratio, battery state of charge (SOC), and the motor speed, a fuzzy logic control strategy (FLC) is applied to adjust the regenerative braking torque dynamically. In order to evaluate the performance of the cooperative braking control strategy, the braking system model of a hybrid electric vehicle is built in MATLAB/SIMULINK. It is found from the simulation that the cooperative braking control strategy suggested in this paper provides satisfactory braking performance, passenger comfort, and high regenerative efficiency.

Slip Suppression of Electric Vehicles Using Sliding Mode Control Method

This paper presents a slip suppression controller using sliding mode control method for electric vehicles which aims to improve the control performance and the energy conservation by controlling the slip ratio of wheel. In this method, a robust sliding mode controller against the model uncertainties is designed to obtain the maximum driving force by suppressing the slip ratio. The numerical simulations for one wheel model under variations in mass of vehicle and road condition are performed and demonstrated to show the effectiveness of the proposed method.

타이어의 최적 노면 마찰력을 고려한 ABS 슬라이딩 모드 제어

This paper presents the sliding mode control methods for anti-lock brake system (ABS) with the friction force observer. Using a simplified quarter car model, the sliding mode controller for ABS is designed to track the desired wheel slip ratio. Here, new method to find the desired wheel slip ratio which produces the maximum friction force between road and tire is suggested. The desired wheel slip ratio is varying according road and tire conditions to produce maximum friction force. In order to find optimum desired wheel slip ratio, the sliding mode observer for friction force is used. The proposed sliding mode controller with observer is evaluated in simulation, and the control design is shown to have high performance on roads with constant and varying adhesion coefficients.

Basic Design of Electric Vehicle Motion Control System Using Single Antenna GPS Receiver

By integrating a single antenna GPS receiver and dynamic sensors, key states for electric vehicle motion control system can be estimated, including yaw angle, sideslip angle, longitudinal velocity, and lateral velocity. In order to achieve accurate state estimation, Kalman filter with disturbance accommodating technique considering the handling of time delay in measurements using GPS is proposed. In this paper, three motion controls of electric vehicle based on the estimated states are demonstrated. The first is attitude control using front steering angle with feedback-feedforward controller and disturbance observer. The second is a traction control based on wheel slip ratio control system using sliding mode control theory. The last is lateral stability control using estimated sideslip angle.

Dynamics and wheel's slip ratio of a wheel-legged robot in wheeled motion considering the change of height

The existing research on dynamics and slip ratio of wheeled mobile robot (WMR) are derived without considering the effect of height, and the existing models can not be used to analyze the dynamics performance of the robot with variable height while moving such as NOROS-II. The existing method of dynamics modeling is improved by adding the constraint equation between perpendicular displacement of body and horizontal displacement of wheel into the constraint conditions. The dynamic model of NOROS-II in wheel motion is built by the Lagrange method under nonholonomic constraints. The inverse dynamics is calculated in three different paths based on this model, and the results demonstrate that torques of hip pitching joints are inversely proportional to the height of robot. The relative error of calculated torques is less than 2% compared with that of ADAMS simulation, by which the validity of dynamic model is verified. Moreover, the relative horizontal motion between fore/hind wheels and body is produced when the height is changed, and thus the accurate slip ratio can not be obtained by the traditional equation. The improved slip ratio equations with the parameter of the vertical velocity of body are introduced for fore wheels and hind wheels respectively. Numerical simulations of slip ratios are conducted to reveal the effect of varied height on slip ratios of different wheels. The result shows that the slip ratios of fore/hind wheels become larger/smaller respectively as the height increases, and as the height is reduced, the reverse applies. The proposed research of dynamic model and slip ratio based on the robot height provides the effective method to analyze the dynamics of WMRs with varying height.

Coordinated vehicle traction control based on engine torque and brake pressure under complicated road conditions

Vehicle traction control system has been developed to enhance the traction capability and the direction stability of the driving wheels through the tyre slip ratio regulation. Under normal situations, if the tyre slip ratio exceeds a certain threshold, the slip ratio of the driving wheel is regulated by the coupled interaction of the engine torque and the active brake pressure. In order to obtain the best driving performance on a road under complicated friction conditions, the driving torque and the active brake pressure, need to be decoupled and adjusted to avoid penalisation of each other. In this paper, a coordinated cascade control method with two sliding-mode variable structure controllers is presented. In this control method, the driving wheel slip ratio is regulated by adjusting the engine torque and the wheel brake pressure. Through the sliding-mode controller, the engine torque is tuned to achieve the maximum driving acceleration and then the active brake pressure is applied to the slipped wheel for further modification of the wheel slip ratio. The advantage of this control method is that through proper regulation, the conflict between the two control inputs could be avoided. Finally, the simulation results validate the effectiveness of the proposed method.

Model and control for four-powered-caster vehicle: a probability-based approach

A vehicle with four powered caster wheels can provide much more motion flexibility in a constrained environment. However, the dynamic modelling and control of such system is challenging due to its high redundancy. This paper investigates the dynamic model and tracking control for a four-powered-caster vehicle (4-PCV) on complex terrain without any additional sensor. The torques applied to the wheels are dynamically redistributed based on the real-time conditions of the whole wheel–ground interactions so that the vehicle can track the desired trajectory when moving on different terrains. A dynamic model considering the wheel–ground interaction is first derived. Then a novel approach based on a probability scheme is proposed to identify the status of the vehicle and the wheel slip ratio by only observing the velocity feedback from motors encoders. Based on this real-time perception information, a tracking controller and a torque distribution scheme are applied to make sure that each wheel can be self-adapted to meet a complex wheel–ground condition to eliminate or reduce the probability of slippage. The effectiveness of the proposed estimation approach and the performance of the torque distribution schemes are verified by simulation.

Simulation Analysis of Tractor AMT Shifting Process Based on Fuzzy Optimization of Downshifting

In this paper, the fuzzy control strategy is introduced, and then it proposes a two-dimensional fuzzy control method which takes the tractor driving wheel slip ratio and the engine throttle opening as input variables, while uses gear correction as output variable. Based on these, a fuzzy controller is designed to optimize the law of downshifting of tractor AMT. Subsequently, a best tractor AMT shift rule is formed through optimal combination of resolution obtained by the law of up-shifting. At last, simulation analysis is made on the basis of the simulation model established of tractor AMT shifting process. The results show that shift cycle can be effectively avoided and shift shock will reduced in the process of shifting, which makes the quality of shifting better and greatly improve the performance of the tractor.

Study on Power Train of Two Axles Four Wheel Drive Electric Vehicle

This paper is focused on design of a power train for two-axle four-wheel-drive (4WD) electric vehicle (EV). The purpose is to improve the energy efficiency, driving stability for an Utility Vehicle (UV) that is original equipped with a 500cc internal combustion engine. The designed power train is consisted of two 5kw brushless DC motors (BLDC) with the associated motor drivers, automatic manual transmission (AMT), AMT controllers, and 288V16AH Lithium-ion battery pack. The works include power train specification design, mechanism and controller design for the clutchless AMT, optimal transmissions gear-shifting strategy design, and finally, power split strategy design for the 4WD in terms of wheel slip ratio control. To guarantee AMT gear-shifting quality, the gear-shifting maps was applied in gear change process. The power split strategy design for the 4WD EV was based on sliding mode algorithm, it was shown through numerical simulation that slip ratio on each wheel can be controlled within an optimal value in ECE40 drive pattern.

Driving Control of Planetary Rover Based on Slip Ratio Estimation

Slip-sinkage is one of the main factors influencing the driving safety of planetary rover in soft terrain. In the environment of scarce features, based on the stereo visual sensors, the visual odometry algorithm is firstly developed to calculate the position changes of planetary rover with six degrees of freedom, which combine with the wheel speed sensor achieve the estimation of wheel slip ratios. Then, on the basis of mechanical analysis of soft terrain, choosing the slip ratio as the state variable, the coordinated driving control algorithm is designed. Simulation and experiment results demonstrate the effectiveness of the proposed control algorithm.

The Research of Driving Force Distribution under Identical-State-Control while 4WID-EV Driving Straight

The strategy of 4-wheel-identical-state-control is proposed on the designed 4-wheel-independent-driven electric vehicle (briefed as 4WID-EV), the working states of each wheel are adjusted to be the same through controlling the ratio of drive-force and vertical-load on them as equal as possible, the co-simulation of ADAMS and Matlab/Simulink is done about the 4WID-EV driving on the straight flat road and slopes. The real vehicle test is performed. The result indicates that the strategy of identical-state-control can control each wheel slip ratio to be equal, make each wheel working in phase, reduce the power loss, improve the vehicle power property, and achieve the aim of good driving force distribution.

Efficient Antilock Braking by Direct Maximization of Tire–Road Frictions

Antilock braking systems (ABSs) are usually designed based on controlling the wheel slip ratio so as to maintain each wheel in a presumed stable region. Since the optimal slip ratio (which results in maximum tire-road friction) varies with the type of road, current methods are not efficient in the sense of achieving the shortest possible stopping distance. This paper introduces an efficient ABS, in which the brake commands directly maximize the longitudinal component of tire-road friction at each wheel of the vehicle independently. The tire-road friction is estimated using a torque balance equation at each wheel, and within those equations, real-time estimates of the effective radius of tire are used. A step-by-step algorithm for computing the brake commands that maximize the tire-road friction is also presented. Three challenging braking scenarios were tested using the comprehensive CarSim simulation environment. The results show that, in comparison to conventional ABS, our method significantly reduces the stopping distance and improves the vehicle stability.

Wheel slip-sinkage and its prediction model of lunar rover

In order to investigate wheel slip-sinkage problem, which is important for the design, control and simulation of lunar rovers, experiments were carried out with a wheel-soil interaction test system to measure the sinkage of three types of wheels in dimension with wheel lugs of different heights and numbers under a series of slip ratios (0-0.6). The curves of wheel sinkage versus slip ratio were obtained and it was found that the sinkage with slip ratio of 0.6 is 3-7 times of the static sinkage. Based on the experimental results, the slip-sinkage principle of lunar’s rover lugged wheels (including the sinkage caused by longitudinal flow and side flow of soil, and soil digging of wheel lugs) was analyzed, and corresponding calculation equations were derived. All the factors that can cause slip sinkage were considered to improve the conventional wheel-soil interaction model, and a formula of changing the sinkage exponent with the slip ratio was established. Mathematical model for calculating the sinkage of wheel according to vertical load and slip ratio was developed. Calculation results show that this model can predict the slip-sinkage of wheel with high precision, making up the deficiency of Wong-Reece model that mainly reflects longitudinal slip-sinkage.