Tire Slip Research Articles

Path Following of Autonomous Vehicles in the Presence of Sliding Effects

In this paper, a new controller for the path-following problem of a car-like autonomous vehicle is proposed. This controller is based on a new transformation that, for the case of roll with no slip, transfers the model to a chain form. However, in many practical cases, due to the strong effects of tire slip angles, a roll with no slip assumption is invalid. To cope with the presence of slip, a novel controller is proposed. The new method is based on a vehicle kinematical model, where the tire slip angles are taken into account. The control design method utilizes a peak-to-peak criterion and linear matrix inequality (LMI) tools to attenuate tire slip angle effects on the closed-loop performance.

Electric Vehicle Tire Slip Identification Method Based on Self-Adaptive Kalman Filter

Based on the traits of the four-wheel drive EV, a self-adaptive Kalman filter was applied to gain the information of vehicle velocity and traction forces on four wheels. With the estimated vehicle velocity and the driving forces on four wheels, the slope k of the curves of adhesion coefficient versus slip rate could be calculated and consequently the road adhesion condition could be accurately identified. Through calculating the difference between the estimated slope k with the optimized slope k as a control reference, the output torques of the motors were adjusted instantaneously to improve the using rate of the adhesion as well as the rationality of the traction control strategy. Simulation results illustrate that whether on high adhesion or low adhesion roads the vehicle is passing, the strategy can estimate the k effectively.

Torque blending and wheel slip control in EVs with in-wheel motors

Among the many opportunities offered by electric vehicles (EVs), the design of power trains based on in-wheel electric motors represents, from the vehicle dynamics point of view, a very attractive prospect, mainly due to the torque-vectoring capabilities. However, this distributed propulsion also poses some practical challenges, owing to the constraints arising from motor installation in a confined space, to the increased unsprung mass weight and to the integration of the electric motor with the friction brakes. This last issue is the main theme of this work, which, in particular, focuses on the design of the anti-lock braking system (ABS). The proposed structure for the ABS is composed of a tyre slip controller, a wheel torque allocator and a braking supervisor. To address the slip regulation problem, an adaptive controller is devised, offering robustness to uncertainties in the tyre–road friction and featuring a gain-scheduling mechanism based on the vehicle velocity. Further, an optimisation framework is employed in the torque allocator to determine the optimal split between electric and friction brake torque based on energy performance metrics, actuator constraints and different actuators bandwidth. Finally, based on the EV working condition, the priorities of this allocation scheme are adapted by the braking supervisor unit. Simulation results obtained with the CarSim vehicle model, demonstrate the effectiveness of the overall approach.

Estimation of tyre-road friction coefficient

Tyre-road friction coefficient is hard to detect while it is important for vehicle control systems, especially the vehicle active safety control systems. This paper presents a maximum aligning moment method which requires no additional sensors if the vehicle is equipped with an electric power steering (EPS) system. A non-linear observer method is designed for the estimation of friction coefficient as well as the continual estimation of tyre slip angles. One combined estimation method is proposed to compensate for the drawbacks of the two methods above. These estimation methods are verified by computer simulations with experimental results in various conditions.

An alternative approach to automotive ESC based on measured wheel forces

Traditional electronic stability control (ESC) systems act on one or more wheels on the basis of a logic aiming at the control of variables that cannot be directly measured (vehicle sideslip angle and the tyre slip). Hence, a vehicle state estimator capable of evaluating the needed variables from the data of the input sensors is necessary. In the present paper, the authors discuss a different approach to the estimation problem, assuming that the forces acting on the wheels can be directly measured. The ESC feed-forward control logic is designed through a vehicle frequency response analysis in order to obtain a faster active system activation. The variable controlled by the logic is the tyre longitudinal force. Experimental results obtained on an ESC hardware-in-the-loop test bench prove the validity of the approach, showing enhanced dynamic performances, together with the limits due to the delays in the actuation of the ESC motor pump, which needs some time to build the pressure requested for the intervention on the selected callipers. Finally, the tests demonstrate the opportunity of closing the control loop on a variable (i.e. the force) that can be directly measured.

A model for performance enhancement in competitive cycling

A 3D cycling model is presented that combines bicycle dynamics, a tyre model, rider biomechanics and environmental factors into a single dynamic system. The system is constructed using Matlab toolboxes (SimMechanics/Simulink) with the aim of identifying mechanical mechanisms that can influence performance in a road cycling time trial. Initial conditions are specified and a variable step ODE solver numerically integrates solutions to the equations of motion. Initial validation compared rider-less self-stability presented in a published “benchmark” with model simulation and found an error of <1.5%. Model results included the weave eigenvalue becoming negative at 4.2 m/s and the capsize eigenvalue approaching a positive value at 6.1 m/s. The tyre model predicted peak front tyre slip and camber forces of 130 N and 17 N respectively which were within 0.9% of values reported in the literature. Experimental field validation compared actual and model predicted time taken by 14 experienced cyclists to complete a time trial over an undulating 2.5 mile road course. An error level of 1.4% (±1.5%) was found between actual and predicted time. This compares well with the average 1.32% error reported by existing road cycling models over simpler courses.

Investigation on the potential generation of ultrafine particles from the tire–road interface

Abstract There has been some discussion in the literature on the generation of ultrafine particles from tire abrasion of studded and non-studded tires tested in the laboratory environment. In the present study, the potential generation of ultrafine particles from the tire road interface was investigated during real driving. An instrumented Sport Utility Vehicle equipped with summer tires was used to measure particle concentrations with high temporal resolution inside the wheel housing while driving on a regular asphalt road. Different driving conditions, i.e., straight driving, acceleration, braking, and cornering were applied. For normal driving conditions no enhanced particle number concentration in the size range 6–562 nm was found. Unusual maneuvers associated with significant tire slip resulted in measurable particle concentrations. The maximum of the size distribution was between 30 and 60 nm. An exponential increase of the particle concentration with velocity was measured directly at the disc brakes for full stop brakings. A tracer gas experiment was carried out to estimate the upper limit of the emission factor during normal straight driving.

무인차량의 자동주차 알고리즘 개발

무인차량의 주행은 각종 센서를 이용한 차량제어시스템, 항법시스템, 장애물시스템, 통합시스템의 4가지 서브 시스템으로 구성 되어있다. 본 연구는 비접촉 거리측정 장치인 레이저스캐너를 이용하여 무인차량의 평행주차 및 직각주차 알고리즘 개발을 목적으로 하였다. 이 알고리즘을 검증하기 위하여 GPS와 차량에 6대의 레이저스캐너를 장착하여 이용하였고, 레이저스캐너를 이용한 위치 계산의 오차를 줄이기 위해 타이어 미끄러짐을 최소로 할 수 있도록 5km/h로 차량의 이동 속도를 제한하였다. The Unmanned Ground Vehicle is comprised of four systems of obstacle detection: The navigation system, vehicle controlling system, obstacle detecting and an integration system that use the various sensors. The research introduced utilizes 6 lasers to recognize obstacles. The system operates an avoidance system within the unmanned ground vehicle, using six lasers. The Unmanned Ground Vehicle's parallel parking and right angle parking is in development using algorithms. This algorithms' certification is intended to be installed in the encoder, in the GPS. By using the Laser Scannerfor the position's calculation, errors are both reduced and minimized, so the tire's slip minimized to the point where the vehicle had a limit of about 5Km/h.

Möglichkeiten zur Steigerung der Dieseleffizienz in der Landwirtschaft

Diesel consumption of agriculture stayed nearly constant over the last years with a 5 % share of total consumption in Germany. Actually the efficiency of traction work achieves only estimated 15 % of benefit. In other words: The tractor as a energy transforming machine transforms diesel energy nearly into 85 % of losses. The losses are composed of heat and friction losses, rolling resistance on the field and road, tire slip during field operations and bulldozing and compacting the soil. For reasons of economy and ecology farmers and contractors should aim the goal of 25 % efficiency increase. The following article examines these possibilities.

Estimation of Tire-Road Friction Coefficient Using a Novel Wireless Piezoelectric Tire Sensor

A tire-road friction coefficient estimation approach is proposed which makes use of the uncoupled lateral deflection profile of the tire carcass measured from inside the tire through the entire contact patch. The unique design of the developed wireless piezoelectric sensor enables the decoupling of the lateral carcass deformations from the radial and tangential deformations. The estimation of the tire-road friction coefficient depends on the estimation of slip angle, lateral tire force, aligning moment, and the use of a brush model. The tire slip angle is estimated as the slope of the lateral deflection curve at the leading edge of the contact patch. The portion of the deflection profile measured in the contact patch is assumed to be a superposition of three types of lateral carcass deformations, namely, shift, yaw, and bend. The force and moment acting on the tire are obtained by using the coefficients of a parabolic function which approximates the deflection profile inside the contact patch and whose terms represent each type of deformation. The estimated force, moment, and slip angle variables are then plugged into the brush model to estimate the tire-road friction coefficient. A specially constructed tire test rig is used to experimentally evaluate the performance of the developed estimation approach and the tire sensor. Experimental results show that the developed sensor can provide good estimation of both slip angle and tire-road friction coefficient.

Robust Adaptive Stabilization of Skid Steer Wheeled Mobile Robots Considering Slipping Effects

This paper represents the posture stabilization of a skid steer wheeled mobile robot (SSWMR). Although in mobile robots lateral skidding of the wheels occurs when turning at high speed, wheels of a SSWMR laterally skid in every rotational maneuver even at low speeds. Also, longitudinal slipping for wheeled mobile robots with pneumatic tires is inevitable due to tire deformation. In order to compensate for the effects of tire slippage and parameter uncertainties, an adaptive torque controller is developed based on a tunable dynamic oscillator. The globally uniformly ultimately bounded stability of the system to an arbitrarily small neighborhood of the origin is proved. The internal dynamics stability of the system is guaranteed employing a supervisory fuzzy logic-based controller. To demonstrate the performance of the proposed controller, modeling of a SSWMR was implemented through automatic dynamic analysis of mechanical systems (ADAMS).

Traction Control of Electric Vehicle by Model Predictive PID Controller

This paper proposes a new model predictive PID control method for the traction control of EV (electric vehicle). The method aims to improve the vehicle dynamics performance and the stability of EV by controlling the tire slip rate. In the proposed method, the PID controller gains are derived by off-line calculation from the optimal control input based on the model predictive control (MPC) algorithm. Numerical simulation results demonstrate the effectiveness of the proposed method.

슬립을 고려한 트랜스퍼 크레인의 주행제어에 관한 연구

Abstract: The most important thing in the container terminal is to handle the cargo effectively in the limited time. To achieve this object, many strategies have been introduced and applied to. If we consider the technical trends and environment of the automated container terminal, it is necessary that the systems for cargo handling are equipped with more intelligent control technologies. To cope with this tendency, from the middle of the 1990's, the automated RMGC (Rail-Mounted Gantry Crane) and RTGC (Rubber-Tired Gantry Crane) have been developed and widely used to handle containers in the yards. Recently, in these cranes, the many equipments like CCD cameras and sensors are mounted to cope with the automated terminal environment. If we want to obtain more efficient handling performance, the modelling, tracking control, anti-sway system design, skew motion suppressing and complicated motion control problems must be considered in the control system design and application process. Considering these problems, in this paper, the system modelling with the tire slip and a tracking control approach are proposed. Especially, we design the tracking control system based on the 2DOF servosystem design approach to cope with undesirable disturbance input. The experiment results show the desirable performance and usefulness of the designed control system. Keywords: rail-mounted gantry crane, rubber-tired gantry crane, automated container terminal, 2DOF servosystem, observer, tracking control

A New Method for Estimating Road Friction Coefficient

Road friction coefficient is a critical component in traffic safety. The estimation of tire–road friction coefficient at tires allows the control algorithm in vehicle activity system to adapt to external driving conditions. This paper develops a new tire–road friction coefficient estimation algorithm based on tire longitudinal force estimation and tire slip estimation. Vehicle tire longitudinal forces are estimated by sliding mode observer combined with Kalman filter. Based on the tire forces estimation, road friction coefficient is estimated by recursive least squares algorithm (RLS). The test conditions which contain different friction level road are established in ADAMS/Car. The conclusions validate the reliability and efficiency of the proposed method for estimating the friction coefficient in different adhesion level roads. The research also indicates the theory of slip slope can also be reappeared in virtual experiment based on ADAMS.

Estimation of Tire Slip Angle and Friction Limits Using Steering Torque

Knowledge of the vehicle's lateral handling limits is important for vehicle control systems which aim to enhance vehicle handling and passenger safety. This paper presents a model-based estimation method that utilizes pneumatic trail information in steering torque to identify a vehicle's lateral handling limits, which are defined by the tire slip angle and peak lateral force limits. This method uses measurements available on many current production vehicles. Most importantly, it takes advantage of the early friction information encoded in the tire pneumatic trail. Pneumatic trail decreases as a function of the tire parameters even in the linear handling region, enabling early detection of the limits before they are reached. Experimental results on an independent front steering steer-by-wire research vehicle demonstrate the observer's ability to provide accurate real-time estimates of tire slip angle up to the limits of handling. Testing conditions include maneuvers performed on dry, flat paved road, as well as on lower-friction, dry gravel.

Robust stabilization of a wheeled vehicle: Hybrid feedback control design and experimental validation

In this paper, the problem of robust stabilization of a wheeled vehicle is addressed. The configuration (position and orientation) set of the vehicle is divided into two parts: global and local configuration sets. The novelty of this paper is the design of a hybrid feedback controller that assigns different objectives in the vehicle’s global and local behaviors. Two Lyapunov functions for individual objectives are introduced that allow a hybrid feedback control law to pursue different objectives. In the global sense, it is important to reach the target point as quickly as possible, but once the vehicle reaches is near the goal, a precise maneuvering by rejecting disturbances including tire slippage and measurement noise becomes important. The asymptotical stability and robustness of the closed loop system are assured. The derived control law is validated by simulations and experiments using an autonomous forklift.

Identifying tyre models directly from vehicle test data using an extended Kalman filter

Individual tyre models are traditionally derived from component tests, with their parameters matched to force and slip measurements. They are imported into vehicle models which should, but do not always properly provide suspension geometry interaction. Recent advances in Global Positioning System (GPS)/inertia vehicle instrumentation now make full state measurement viable in test vehicles, so tyre slip behaviour is directly measurable. This paper uses an extended Kalman filter for system identification, to derive individual load-dependent tyre models directly from these test vehicle state measurements. The resulting model therefore implicitly compensates for suspension geometry and compliance. The paper looks at two variants of the tyre model, and also considers real-time adaptation of the model to road surface friction variations. Test vehicle results are used exclusively, and the results show successful tyre model identification, improved vehicle model state prediction – particularly in lateral velocity reproduction – and an effective real-time solution for road friction estimation.

2P1-E02 オプティカルフロー計算アルゴリズムのFPGAへの実装 : 小型全方位移動ロボットの速度推定

We developed various omni-directional mobile robots. And these robots were used for researches and competitions. It is difficult for Omni-directional mobile robots equipped with Omni wheel to perform correct dead reckoning because a tire slips. Therefore, a camera was equipped on a robot, and optical flow was calculated to estimate the speed. FPGA was used for a calculation of the optical flow. The speed of the front direction of the robot was able to be measured precisely by using optical flow.

Steady-state cornering equilibria and stabilisation for a vehicle during extreme operating conditions

In this work we study steady-state cornering conditions for a single-track vehicle model, without imposing restrictive conditions on the tyre slip. Inspired by recent progress in the understanding of advanced driving techniques, we design a sliding-mode control scheme stabilising steady-state cornering conditions, using only longitudinal control inputs, i.e., accelerating/braking torques applied at the front and/or rear wheels. The effectiveness of the control scheme is demonstrated in a variety of simulation scenarios, motivated by competitive race driving. Results are presented using both the baseline model, and an increased-fidelity model taking into account suspension dynamics.

Position Control of a Wheeled Mobile Robot Including Tire Behavior

Advanced driver assistance systems are increasingly available on road vehicles. These systems require a thorough development procedure, an important part of which consists of hardware-in-the-loop experiments in a controlled environment. To this end, a facility called vehicle hardware-in-the-loop (VeHIL) is operated, aiming at testing the entire road vehicle in an artificial environment. In VeHIL, the test vehicle is placed on a roller bench, whereas other traffic participants, i.e., vehicles in the direct neighborhood of the test vehicle, are simulated using wheeled mobile robots (WMRs). To achieve a high degree of experiment reproducibility, focus is put on the design of an accurate position control system for the robots. Due to the required types of maneuvers, these robots have independently driven and steered wheels. Consequently, the robot is overactuated. Furthermore, since the robot is capable of high-dynamic maneuvers, slip effects caused by the tires can play an important role. A position controller based on feedback linearization is presented, using the so-called multicycle approach, which regards the robot as a set of identical unicycles. As a result, the WMR is position controlled, whereas each unicycle is controlled, taking weight transfer and longitudinal and lateral tire slip into account.