Wheel Slip Control System Research Articles

Amelioration of Energy Dissipation Through Robotic Evacuation Process of Solid Bulk Materials: Effectiveness of Wheel Slip Control System

Amelioration of Energy Dissipation Through Robotic Evacuation Process of Solid Bulk Materials: Effectiveness of Wheel Slip Control System

Fundamental realization of longitudinal slip efficiency of tractor wheels in a tillage practice

Longitudinal slip efficiency of driving wheels of off road vehicles is function of not only slip of all driving wheels but also their gross traction force. In this work, the slip efficiency was ascertained for a mechanical front wheel drive (MFWD) tractor in a tillage practice. Front and rear driving wheels of the MFWD tractor performed in unequal traction circumstances (size, inflation pressure, and dynamic vertical load) and soil cone indices. Obtained results indicated that the slip efficiency nonlinearly dropped from 0.94 to 0.74 as simultaneous augmentation of slip ratio of the rear wheels to that of the front wheels (0.72-0.87) along with ratio increment of gross traction force of the rear wheels to that of front wheels (1.81-4.93). These conditions occurred, when draft force requirements of implement augmented from 8.58 to 25.85 kN. Hence, it can be pointed out that the maximum slip efficiency as well as overall power efficiency of the MFWD tractor in tillage practices would be achieved at the same slip in accordance with the same gross traction force of the front and rear wheels. To do this for, specific tire type (radial or bias ply), automatic slip control of the wheels by implementing wheel slip control system would be beneficial, especially in case of lower slip than 0.2 for achievement of maximum tractive efficiency. It must be noted that adjustment of inflation pressure of the tires is also advantageous followed by ballast weight application in this realm.

Applied nonlinear control of vehicle stability with control and state constraints

For the vehicle dynamic control system, to guarantee directional stability in risky maneuvers, the side-slip angle should be restricted to the admissible range when the yaw rate tracks the proposed desired response for enhanced steerability. Meanwhile, the control input of the external yaw moment produced by asymmetric braking forces should be calculated in the practical range according to the capacity of tire forces. In the present study, a novel constrained controller with input and state constraints is developed. To this aim, a cost function consisting of predicted continuous response of yaw rate tracking error is expanded in terms of current control signal. Concurrently, the state constraint of side slip is transformed to the equivalent constraint of control signal by a novel nonlinear prediction approach. After that, the expanded performance index is analytically minimized in the presence of all input constraints to obtain the control law. The computed yaw moment is optimally distributed to asymmetric braking forces by designing a wheel slip control system. Simulation studies are conducted to evaluate the performance of proposed constrained controller compared with the unconstrained controller and a conventional nonlinear model predictive controller developed in the recent papers using a 14-degree-of-freedom vehicle model which includes suspension system dynamics. The results show that the proposed controller is much faster and easy to solve and implement.

Wheel Slip Control for Improving Traction-Ability and Energy Efficiency of a Personal Electric Vehicle

In this paper, a robust wheel slip control system based on a sliding mode controller is proposed for improving traction-ability and reducing energy consumption during sudden acceleration for a personal electric vehicle. Sliding mode control techniques have been employed widely in the development of a robust wheel slip controller of conventional internal combustion engine vehicles due to their application effectiveness in nonlinear systems and robustness against model uncertainties and disturbances. A practical slip control system which takes advantage of the features of electric motors is proposed and an algorithm for vehicle velocity estimation is also introduced. The vehicle velocity estimator was designed based on rotational wheel dynamics, measurable motor torque, and wheel velocity as well as rule-based logic. The simulations and experiments were carried out using both CarSim software and an experimental electric vehicle equipped with in-wheel-motors. Through field tests, traction performance and effectiveness in terms of energy saving were all verified. Comparative experiments with variations of control variables proved the effectiveness and practicality of the proposed control design.

Estimation of tire–road friction coefficient and its application in chassis control systems

Knowledge of tire–road friction conditions is indispensable for many vehicle control systems. In particular, friction information can be used to enhance the performance of wheel slip control systems, for example, knowledge of the current maximum coefficient of friction would allow an anti-lock brake system (ABS) controller to start braking with the optimal brake pressure, meaning the early cycles of operation are more efficient, resulting in shorter stopping distances. Also, from a passive safety perspective, it may be useful to present the driver with friction information so they can adjust their driving style to the road conditions. Hence, it is highly desirable to estimate friction using existing onboard vehicle sensor information. Many approaches for estimating tire–road friction estimation have been proposed in the literature with different sensor requirements and relative excitation levels. This paper aims at estimating the tire–road friction coefficient by using a well-defined model of the tire behavior. The model adopted for this purpose is the physically based brush tire model. In its simplest formulation, the brush model describes the relationship between the tire force and the slip as a function of two parameters, namely, tire stiffness and the tire–road friction coefficient. Knowledge of the shape of the force–slip characteristics of the tire, possibly obtained through the estimation of both friction and tire stiffness using the brush model, provides information about the slip values at which maximum friction is obtained. This information could be used to generate a target slip set point value for controllers, such as an ABS or a traction control system. It is also important to realize that a model-based approach is inherently limited to providing road surface friction information when the tire is exposed to an excitation with high utilization levels (i.e. under high-slip conditions). To be of greatest use to active safety control systems, an estimation method needs to offer earlier knowledge of the limits. In order to achieve the aforementioned objective, an integrated approach using an intelligent tire-based friction estimator and the brush tire model-based estimator is presented. An integrated approach gives us the capability to reliably estimate friction for a wider range of excitations (both low-slip and high-slip conditions).

Automatic wheel slip control system in field operations for 2WD tractors

A microcontroller based automatic wheel slip control system was designed and developed for 2WD tractors. The system continuously measures wheel slip under field conditions and generates commands for depth adjustment if the wheel slip falls outside the desired range. Wheel slip was calculated using the actual and theoretical speeds of the tractor obtained by measuring the rotational speed (rpm) of front and rear wheels, respectively. The developed system was installed on a test tractor and the performance was evaluated with different implements under varying field conditions. The performance data indicated a significant reduction in fuel consumption per hectare (20–30%), increase in field capacity (7–38%), and gain in tractive efficiency (4–10%) with slip control system versus the existing draft control system. The slip control system is also expected to reduce the operator’s effort as it adjusts the depth control lever automatically in response to variation in the soil conditions within the field.

Development of a Vehicle Stability Control System Using Brake-by-Wire Actuators

The wheel slip control systems are able to control the braking force more accurately and can be adapted to different vehicles more easily than conventional braking control systems. In order to achieve the superior braking performance through the wheel slip control, real-time information such as tire braking force at each wheel is required. In addition, the optimal target slip values need to be determined depending on the braking objectives such as minimum braking distance, stability enhancement, etc. In this paper, a vehicle stability control system is developed based on the braking monitor, wheel slip controller, and optimal target slip assignment algorithm. The braking monitor estimates the tire braking force, lateral tire force, and brake disk-pad friction coefficient utilizing the extended Kalman filter. The wheel slip controller is designed based on the sliding mode control method. The target slip assignment algorithm is proposed to maintain the vehicle stability based on the direct yaw-moment controller and fuzzy logic. A hardware-in-the-loop simulator (HILS) is built including electrohydraulic brake hardware and vehicle dynamics software. The effectiveness of the proposed stability control system is demonstrated through the HILS experiment.

휠 슬립 제어기 및 최적 슬립 결정 알고리즘을 이용한 차량의 최대 제동력 제어

The wheel slip control systems are able to control the braking force more accurately and can be adapted to different vehicles more easily than conventional ABS systems. In order to achieve the superior braking performance through the wheel-slip control, real-time information such as the tire braking force at each wheel is required. In addition, the optimal target slip values need to be determined depending on the braking objectives such as minimum braking distance, stability enhancement, etc. In this paper, a robust wheel slip controller is developed based on the adaptive sliding mode control method and an optimal target slip assignment algorithm. An adaptive law is formulated to estimate the longitudinal braking force in real-time. The wheel slip controller is designed using the Lyapunov stability theory and considering the error bounds in estimating the braking force and the brake disk-pad friction coefficient. The target slip assignment algorithm is developed for the maximum braking force and searches the optimal target slip value based on the estimated braking force. The performance of the proposed wheel-slip control system is verified in simulations and demonstrates the effectiveness of the wheel slip control in various road conditions.

The Increase of Cornering Force and Traction by a Wheel Slip Control System

The Increase of Cornering Force and Traction by a Wheel Slip Control System