Showing papers on "Slip ratio published in 2021"

Hybrid Control-Based Acceleration Slip Regulation for Four-Wheel-Independent-Actuated Electric Vehicles

Abstract: In this article, an enabling hybrid control-based acceleration slip regulation (ASR) method is proposed for four-wheel-independent-actuated electric vehicles by combining the advantages of the maximum-torque-based and slip-ratio-based ASR methods. Considering the dramatic fluctuation of tire slip ratio at low speeds caused by the poor signal-to-noise ratio (SNR) for the vehicle speed, an adaptive maximum torque search method is employed to ensure the acceleration regulation performance at low speeds. With the increasing vehicle speed, the SNR would have diminishing influence so that the tire slip ratio gradually approaches its true value. Under such scenarios, a robust sliding mode control method is proposed to regulate the real-time slip ratio to its optimal value, so as to maximize the tire-road adhesive force. In order to coordinate the driving torques and guarantee a smooth transition process in between, a finite-state machine-based control scheme is further developed. Hardware-in-Loop test results show that the proposed hybrid control-based ASR scheme exhibits good performance and high reliability under various driving conditions.

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

Abstract: 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.

Analytical consideration of the radial clearance to reduce cage slip of the turbo engine roller bearing

Abstract: Roller bearings of aircraft turbo engines are operated under high-speed conditions of over 2 million DN. If contact force between rollers and the raceway is insufficient, then relative slip between the roller and raceways occurs and speed of the cage decreases. This condition may induce skid damage in the raceway. Large operating radial clearance can cause skid damage, but their analytical correlations have rarely been studied. In this study, cage slip ratio was quantified according to clearance changes in various operating conditions and geometric parameters, and causes of cage slip were analyzed using the simplified dynamic model. The design methodology will be proposed to select the proper operating clearance in consideration of cage slip and fatigue life.

Theoretical study and experimental measurement of the gas liquid two-phase flow through a vertical Venturi meter:

Abstract: An accurate two-phase flow rate measurement is essential in many applications and industries such as; oil/gas, chemical, pipeline transportation and nuclear industry. This paper presents the findin...

Adaptive slip ratio estimation for active braking control of high-speed trains.

Abstract: Active braking control systems in high-speed trains are vital to ensure safety and are intended to reduce brake distances and prevent the wheels from locking. The slip ratio, which represents the relative difference between the wheel speed and vehicle velocity, is crucial to the design and successful implementation of active braking control systems. Slip ratio estimation and active braking control are challenging owing to the uncertainties of wheel-rail adhesion and system nonlinearities. Therefore, this paper proposes a novel adaptive slip ratio estimation approach for the active braking control based on an improved extended state observer. The extended state observer is developed through the augmentation of the system state-space to estimate the unmeasured train states as well as the model uncertainty. The accurate slip ratio is estimated using the observed extended states. Furthermore, the adaptability of the observer is improved by introducing the beetle antennae search algorithm to determine the optimal observer parameters. Finally, a feedback linearization braking control law is established to stabilize the closed-loop system due to its potential in coping with nonlinearities, which benefits the proven theoretical bounded stability. Experimental results validate the effectiveness of the proposed method.

A control strategy for efficient slip ratio regulation of a pneumatic brake system for commercial vehicles

Abstract: This paper presents a control strategy for efficient slip ratio regulation of a pneumatic brake system for commercial vehicles. A model-based estimator for brake pressure estimation has been develo...

Electrified Vehicle Wheel Slip Control Using Responsiveness of Regenerative Braking

Abstract: In vehicles, wheel locking and associated instability issues can be prevented by regulating wheel brake torque during braking In contrast with conventional vehicles, electrified vehicles have both friction and regenerative braking Typically, pneumatic friction braking is used for Wheel Slip Regulation (WSR) in Heavy Commercial Road Vehicles (HCRVs) However, the pneumatic brake system has a lower bandwidth compared to a regenerative brake system, thereby affecting the braking performance of the HCRV during WSR application This article proposes an Integral Sliding Mode Control (ISMC) based WSR to exploit the responsiveness of regenerative brakes during braking The proposed control strategy was evaluated in a hardware-in-loop experimental setup For different operating conditions, the experimental results conveyed that the proposed braking strategy incorporating regenerative braking reduced the slip ratio tracking root mean square error and stopping distance in the range of 1213% to 72% and 243% to 4% respectively compared to conventional frictional braking (without regenerative braking)

Slip Length Measurement in Rectangular Graphene Nanochannels with a 3D Flow Analysis.

Abstract: Although many molecular dynamics simulations have been conducted on slip flow on graphene, experimental efforts remain very limited and our understanding of the flow friction on graphene remains far from sufficient. Here, to accurately measure the slip length in rectangular nanochannels, we develop a 3D capillary flow model that fully considers the nonuniform cross-section velocity profile, slip boundary conditions, and the dynamic contact angle. We show that the 3D analysis is necessary even for a channel with a width/height ratio of 100. We fabricated graphene nanochannels with 45-nm depth and 5-{\mu}m width, and measured slip lengths of about 30 to 40 nm using this 3D flow model. We also reevaluated the slip-length data for graphene obtained from capillary filling experiments in the literature: 30 nm instead of originally claimed 45 nm for a 25-nm-deep channel, and 47 nm instead of 60 nm for an 8.5-nm-deep channel. We discover a smaller slip length than existing experimental measurements due to our full 3D flow analysis considered in our method. This work presents a rigorous analysis approach while also providing a better understanding of slip flow in graphene nanochannels, which will benefit further innovation in nanofluidic applications, including electronics cooling and biomedical chips.

Analytical modeling and DEM analysis of soil–wheel interaction under cornering and skidding conditions in off-road vehicles

Abstract: Soil–wheel interaction under cornering and slip conditions (SWICS) has a significant impact on the steering performance of off-road vehicles. In order to analyze the six-dimensional wheel forces in SWICS, a SWICS model based on the analytical method and the discrete element method (DEM) is developed in this paper. First, the modeling process of SWICS using the analytical method was detailed to predict the six-dimensional wheel forces in SWICS. The SWICS was then modeled using the DEM, which involved the following steps: (a) establishment of tire geometry, (b) selection of particle parameters, (c) parameter calibration, and (d) particle generation. Finally, DEM simulations were carried out for different slip angles and slip ratios under three loads, and the results were compared with those of the analytical model. The results show that the SWICS DEM model in this paper maintains a good fit with the analytical model, validating the efficiency of the DEM model and the parameter calibration method. The slip angle has a great influence on the lateral force, overturning moment, and aligning moment and a smaller impact on the normal force, drawbar pull, and rolling resistance moment. The slip ratio promotes an increase in the drawbar pull and rolling resistance moment but reduces the value of the lateral force and aligning moment. The research in this paper provides a DEM modeling approach and an analysis method for solving mechanical problems with different dimensions in SWICS, which will help improve the performance of off-road vehicles.

Development of Online Adaptive Traction Control for Electric Robotic Tractors

Abstract: Estimation and control of wheel slip is a critical consideration in preventing loss of traction, minimizing power consumptions, and reducing soil disturbance. An approach to wheel slip estimation and control, which is robust to sensor noises and modeling imperfection, has been investigated in this study. The proposed method uses a simplified form of wheels longitudinal dynamic and the measurement of wheel and vehicle speeds to estimate and control the optimum slip. The longitudinal wheel forces were estimated using a robust sliding mode observer. A straightforward and simple interpolation method, which involves the use of Burckhardt tire model, instantaneous values of wheel slip, and the estimate of longitudinal force, was used to determine the optimum slip ratio that guarantees maximum friction coefficient between the wheel and the road surface. An integral sliding mode control strategy was also developed to force the wheel slip to track the desired optimum value. The algorithm was tested in Matlab/Simulink environment and later implemented on an autonomous electric vehicle test platform developed by the Nanjing agricultural university. Results from simulation and field tests on surfaces with different friction coefficients (μ) have proved that the algorithm can detect an abrupt change in terrain friction coefficient; it can also estimate and track the optimum slip. More so, the result has shown that the algorithm is robust to bounded variations on the weight on the wheels and rolling resistance. During simulation and field test, the system reduced the slip from non-optimal values of about 0.8 to optimal values of less than 0.2. The algorithm achieved a reduction in slip ratio by reducing the torque delivery to the wheel, which invariably leads to a reduction in wheel velocity.

3D DEM analysis on tractive trafficability of a lunar rover wheel with bionic wheel lugs

Abstract: African ostriches are good at running in the desert, and their toenails can effectively improve the tractivetraction performance in the running process. To improve the tractivetraction trafficability of wheels on the lunar surface loose soil, a wheel with bionic wheel lugs was designed based on the bionic prototype of ostrich toenail and bionic engineering technology. Then, the rolling of the bionic wheel was simulated by using the three-dimensional (3D) discrete element method (DEM) simulation system of the interaction between irregular structure wheel and lunar soil, and the result was compared with that of the wheel with rectangular wheel lugs. Under the same working condition, the drawbar pull, torque, and sinkage of two kinds of wheels at slip ratios of 0.25, 0.375, and 0.625 were analyzed. The simulation results showed that the average drawbar pull and average torque of the bionic wheel are greater than that of the wheel with rectangular wheel lugs at three kinds of slip ratios. When the slip ratios were 0.25 and 0.375, there was almost no difference in the average sinkage of the two kinds of wheels, but the average sinkage of the bionic wheel was significantly less than that of the wheel with rectangular wheel lugs when the slip ratio was 0.625. The results show that, compared with the wheel with rectangular wheel lugs, the bionic wheel has better tractivetraction and anti-subsidence performance. This study provides a new design and research method for improving the tractive trafficability of wheels in the lunar loose surface environment.

Modified Dynamic Model for Longitudinal Motion of Ground Vehicles

Abstract: The present study aims to provide a modified model for analysing the longitudinal dynamics of ground vehicles. Bearing in mind that an inevitable tire slip occurs under the transmission of driving torque to the drive wheels, the pure rolling assumption employed in many previous works is modified in this research. This paves the way through the development of a more realistic simulation framework with promising performance when used in vehicle and powertrain related topics. The modified equation of motion is an explicit function of tire slip ratio, and as a result, by rewriting the power balance equation, a dissipation term due to tire slip appears, which is consistent with the outcome of the recent contributions. Simulation results indicate a significant difference between the modified and simplified models in the case of a relatively high tractive force. Moreover, tire slip loss is obviously large in such a case, so that its neglect would lead to a noticeable inaccuracy in the response of the traditional model. An average of 35% improvement in the accuracy of prediction of tire consumed energy is observed in 0 to 100 km/h half-throttle acceleration manoeuvre using the modified model.

Slip Estimation and Compensation Control of Omnidirectional Wheeled Automated Guided Vehicle

Abstract: To achieve Industry 4.0 solutions for the networking of mechatronic components in production plants, the use of Internet of Things (IoT) technology is the optimal way for goods transportation in the cyber-physical system (CPS). As a result, automated guided vehicles (AGVs) are networked to all other participants in the production system to accept and execute transport jobs. Accurately tracking the planned paths of AGVs is therefore essential. The omnidirectional mobile vehicle has shown its excellent characteristics in crowded environments and narrow aisle spaces. However, the slip problem of the omnidirectional mobile vehicle is more serious than that of the general wheeled mobile vehicle. This paper proposes a slip estimation and compensation control method for an omnidirectional Mecanum-wheeled automated guided vehicle (OMWAGV) and implements a control system. Based on the slip estimation and compensation control of the general wheeled mobile platform, a Microchip dsPIC30F6010A microcontroller-based system uses an MPU-9250 multi-axis accelerometer sensor to derive the longitudinal speed, transverse speed, and steering angle of the omnidirectional wheel platform. These data are then compared with those from the motor encoders. A linear regression with a recursive least squares (RLS) method is utilized to estimate real-time slip ratio variations of four driving wheels and conduct the corresponding compensation and control. As a result, the driving speeds of the four omnidirectional wheels are dynamically adjusted so that the OMWAGV can accurately follow the predetermined motion trajectory. The experimental results of diagonally moving and cross-walking motions without and with slip estimation and compensation control showed that, without calculating the errors occurred during travel, the distances between the original starting position to the stopping position are dramatically reduced from 1.52 m to 0.03 m and from 1.56 m to 0.03 m, respectively. The higher tracking accuracy of the proposed method verifies its effectiveness and validness.

MAS-Based Slip Ratio Fault-Tolerant Control in Finite Time for EV

Abstract: The driving torques of all four wheels of distributed drive electric vehicles are independently controllable, and acceleration slip regulation (ASR) can be realized through the coordinated effort of torque actuators Considering the multiple actuator coupling, nonlinearity, uncertainty and actuator faults in an ASR system, an adaptive nonsingular terminal sliding mode (NTSM) fault-tolerant control method-based multi-agent system (MAS) is proposed to address the above problems of an ASR system in this paper First, based on multi-agent theory, a four- wheel independent drive ASR system is decomposed into four separate driving wheel agent systems to reduce the model dimension and transform the design of the ASR system controller into the design of a single driving wheel agent controller to reduce the computational complexity Second, to address the unknown uncertainty of an actuator fault in an ASR system, an adaptive NTSM controller for a single driving wheel agent is designed to make the actual slip ratio track the ideal slip ratio for the ASR system in finite time The controller switch item gains are selected by using an adaptive estimation mechanism for a single driving wheel agent controller to address the gain overestimation problem This approach ensures that the actual control signal is smooth and that chattering phenomena and energy consumption are reduced For actuator faults, a Lyapunov function based on multiagent theory is designed for a single driving wheel agent to avoid the impact of the coupling subsystem fault Third, the Simulink and CarSim cosimulation results show that the proposed method improves the fault tolerance and robustness The system can realize the actual slip ratio, track the optimal slip ratio in a finite time under different road adhesion conditions and effectively avoid the wheel slippage problem

A Fuzzy Sliding-Mode Control for Regenerative Braking System of Electric Vehicle

Abstract: This paper presents a novel sliding-mode control scheme with fuzzy logic control approach for the energy management of electric vehicles subject to a regenerative braking system. Based on the μ−slip curve, the road friction coefficient can be estimated. A fuzzy logic controller is designed to adjust the sliding mode parameters according to the slip ratio tracking error between the optimal slip ratio and the actual slip ratio. The proposed torque distribution strategy can integrate the best battery condition and energy recovery efficiency through this control method by determining the hydraulic braking torque and regenerative braking torque, which consider related constraints. The simulations have been conducted in the Simulink environment based on an electric vehicle model to verify the proposed controller.

Localization of Wheeled Mobile Robots from Slip Ratio Estimation with Simple Model

Abstract: This paper proposes a localization method by estimating the slip ratio of wheeled mobile robots. The slip ratio estimator is designed based on the equations of motion. Input torque and encoders data are used, and driving force, vehicle velocity, and slip rate are estimated. This method can estimate the robot's position accurately without visual odometry (VO) when the driving resistance is obtained. When VO is available, even if the obtained driving resistance is different from its true value, instantaneous speed observer updates the resistance and the robot's velocity. The sampling time of torque is very short, which allows us to obtain position estimation much faster than VO. The experiments were conducted with a robot on alumina balls, and the proposed methods showed improvements in the accuracy of localization compared to wheel odometry.

Slip Estimation for Autonomous Tracked Vehicles via Machine Learning

Abstract: Slip is a crucial parameter in the kinematic and dynamic models of tracked vehicles, which also exercises considerable influence over the track-ground interactions. The methods based on machine learning for slip estimation only employ proprioceptive sensor signals and obtain models by learning from numerous data, but they still have some limitations. This paper explores the applicability of such methods to autonomous tracked vehicles, which considers wider speed range, bends and difference between two tracks slip. First, a tremendous amount of data are collected with a tracked vehicle. Then road types identification is realized based on convolutional neural networks because the road types and slip are closely related. Lastly the piecewise regression method is employed to estimate slip. The performance of proposed approach is evaluated on test set. The results indicate that it can accurately identify the road(success rate, > 96%) and estimate the slip ratio(root mean square error, < 0.7%). The contrast experiment and analysis also show that classification before regression improves the accuracy and reduces the computational burden. Further, sparse Gaussian process regression is applied to return the distribution of slip, which can reflect the uncertainty of estimation.

Intelligent-Tire-Based Slip Ratio Estimation Using Machine Learning

Abstract: Autonomous vehicles are most concerned about safety control issues, and the slip ratio is critical to the safety of the vehicle control system. In this paper, different machine learning algorithms (Neural Networks, Gradient Boosting Machine, Random Forest, and Support Vector Machine) are used to train the slip ratio estimation model based on the acceleration signals ($a_x$, $a_y$, and $a_z$) from the tri-axial Micro-Electro Mechanical System (MEMS) accelerometer utilized in the intelligent tire system, where the acceleration signals are divided into four sets ($a_x/a_y/a_z$, $a_x/a_z$, $a_y/a_z$, and $a_z$) as algorithm inputs. The experimental data used in this study are collected through the MTS Flat-Trac tire test platform. Performance of different slip ratio estimation models is compared using the NRMS errors in 10-fold cross-validation (CV). The results indicate that NN and GBM have more promising accuracy, and the $a_z$ input type has a better performance compared to other input types, with the best result being the estimation model of the NN algorithm with $a_z$ as input, which results is 4.88\%. The present study with the fusion of intelligent tire system and machine learning paves the way for the accurate estimation of tire slip ratio under different driving conditions, which will open up a new way of Autonomous vehicles, intelligent tires, and tire slip ratio estimation.

Design and Stability Analysis of High-Speed Unmanned Aerial Vehicle Electric Anti-Skid Braking System

Abstract: A new combined electric anti-skid braking system of a high-speed unmanned aerial vehicle is designed to improve the stability and to reduce the system sensor noise. An electric anti-skid braking mechanism model considering the sensor noise effect is built in MATLAB/Simulink. The stability of a slip ratio braking system and a deceleration braking system is analyzed using the Routh criterion and Lyapunov stability method. Then the UAV ground taxiing dynamic model is built in LMS Virtual. Lab Motion. The braking performance and dynamic responses are studied under the control of the designed braking system using a co-simulation method. Conclusions show that the designed braking control system can solve the sensor noise problem effectively and the stability and robustness are both ensured under this control law.

LBM Investigation of the Droplet Displacement and Rubbing on a Vertical Wall by a Modified Pseudopotential Model

Abstract: In this paper, the displacement and deformation of a two-dimensional droplet on a vertical wall are examined using a modified pseudopotential model and imposing the multi-relaxation time into the collision term. The selected model guarantees the thermodynamic consistency adjusting proper values for the constant of the potential function k and the weighting factor for the force term, A. Also, it is possible to add adhesion forces and create different contact angles defining the index function for the solid points. Accordingly, non-dimensional parameters of Reynolds number, Weber number, Froude number, and density ratio are defined under the influence of the gravitational force and the uniform vapor flow. Results show that the change of the each dimensionless numbers affects the slip ratio between the droplet and vapor. It is also observed that in addition to the effects of viscous and gravitational forces, the change of the contact angle plays a significant role in the displacement and velocity of the droplet. The results show that reducing the contact angle increases the surface wettability and decreases the droplet velocity. It is seen that by decreasing the intermolecular forces at the Weber number of 62.36 and contact angle of 150°, the droplet begins to decay. Also, it is concluded that the droplet rubbing on the solid surface weakens the slip ratio in all cases.

Design of Lyapunov-Based Discrete-Time Adaptive Sliding Mode Control for Slip Control of Hybrid Electric Vehicle

Abstract: This paper has developed discrete-time Fuzzy Adaptive sliding mode control algorithm for controlling the slip ratio of a hybrid electric vehicle. Fuzzy logic algorithm is used to develop controller for controlling slip ratio so as to handle different road conditions. A discrete-time Sliding Mode Observer is designed to observe the vehicle velocity. Furthermore, an adaptive SMC has been designed by employing Lyapunov theory in order to adapt with slip dynamic change for varying or changing road conditions. The performances of designed controller such as ASMC, SMO, FLC, and Fuzzy PID for controlling slip ratio are compared using MATLAB simulation and it is proved that the discrete-time fuzzy ASMC perform most impressively and effectively.