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Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

It is very easy for a small lunar rover to slip on the regolith of the lunar surface and become stuck. Previous studies have quantitatively evaluated the effects of wheel geometry, such as elliptical or eccentric wheels, on the performance of a rover when climbing up slopes. These studies reported that the rovers were able to run on a 30-degree slope made of silica sand. In this study, a small rover was designed and created, and running tests were conducted using lunar soil simulant and silica sand to predict its performance on the lunar surface. The effects of soil differences on the performance of the rover were clarified through the running tests and the measurement of reaction force on the lug. Although the rover exhibited a greater slip ratio on the lunar soil simulant than on the silica sand, the rover with eccentric wheels was able to climb up to a 30-degree angle on the lunar soil simulant. The results for the sinkage measurement of the rover showed that the eccentric wheels prevented sinkage with their up-and-down motion, enabling the rover to climb steep slopes. Furthermore, the tests for measuring the reaction force on the lug indicated that the density change in the lunar soil simulant did not provide sufficient reaction force, and that the running performance on the lunar soil simulant was lower than that on the silica sand. [ABSTRACT FROM AUTHOR]

The influence of the external environment can reduce the braking performance of the electric vehicle (EV) with in-wheel motors (IWM). In this paper, an adaptive sliding mode wheel slip control method with a vehicle speed observer consideration is proposed, which enables the EV to accurately track the optimal slip ratio in various environments and improve braking performance. First, the braking system dynamics model is established by taking the EV with IWM as the study object. Second, a super-twisting sliding mode observer is used to estimate the vehicle speed, and a new adaptive second-order sliding mode controller is constructed to control the braking torque. Finally, co-simulation experiments are performed under different conditions based on Carsim and MATLAB/Simulink, and the proposed scheme is validated by comparison with three control methods. The experimental results show that the proposed scheme has better control performance, and both the safety and control quality of the EV is improved. [ABSTRACT FROM AUTHOR]

To provide the necessary theoretical models of sphere–soil interaction for the structural design, motion control, and simulation of spherical robots, this paper derives analytical expressions for traction force and driving torque when spherical robots slide and sink into sandy terrain, based on terramechanics and multibody dynamics. Furthermore, orthogonal experimental analysis identifies the load, joint angular acceleration, and maximum joint angular velocity of spherical robots as influencing factors, highlighting that the load significantly affects their longitudinal motion performance. Experimental results indicate that rolling friction and additional resistance on sandy terrain cannot be ignored. The corrected theoretical model effectively replicates the temporal variation of driving torque exerted by spherical robots on sandy terrain. Numerical computations and experimental analyses demonstrate that increasing the radius of the sphere shell, the load, and the slip ratio all lead to increased traction force and driving torque. However, traction force and driving torque begin to decrease once the slip ratio reaches approximately 0.5. Therefore, in the design of spherical robot structures and control laws, appropriate parameters such as load and slip ratio should be chosen based on the established sphere–soil interaction theoretical model to achieve high-quality longitudinal motion performance on sandy terrain. [ABSTRACT FROM AUTHOR]

Air can have an adverse effect on the performance of an aero-engine lubrication system. A numerical analysis was conducted to explore the influence of inlet void fraction and pipe layout on the characteristics of oil-gas two-phase flow in a 90° elbow. The pipes were arranged horizontally and vertically with inlet void fractions of 0.05-0.15. The laws governing flow velocity, void fraction, and pressure along the pipe were determined separately. The results revealed the formation of large-scale vortices with high gas volume fractions inside both types of elbows, which exacerbate oil-gas separation and cause additional head loss. The maximum pressure drop was observed at approximately one pipe diameter downstream of the elbow outlet, which initially increases with the inlet void fraction and then gradually stabilizes. Asymmetric secondary flow vortices in the horizontal elbow were found to enhance oil-gas separation and accelerate lubricating oil to greater extent than in a vertical elbow under the same conditions. Consequently, the maximum pressure drop caused by flowing through the horizontal elbow is higher than that in the vertical elbow. [ABSTRACT FROM AUTHOR]

Air can have an adverse effect on the performance of an aero-engine lubrication system. A numerical analysis was conducted to explore the influence of inlet void fraction and pipe layout on the characteristics of oil-gas two-phase flow in a 90° elbow. The pipes were arranged horizontally and vertically with inlet void fractions of 0.05-0.15. The laws governing flow velocity, void fraction, and pressure along the pipe were determined separately. The results revealed the formation of large-scale vortices with high gas volume fractions inside both types of elbows, which exacerbate oil-gas separation and cause additional head loss. The maximum pressure drop was observed at approximately one pipe diameter downstream of the elbow outlet, which initially increases with the inlet void fraction and then gradually stabilizes. Asymmetric secondary flow vortices in the horizontal elbow were found to enhance oil-gas separation and accelerate lubricating oil to greater extent than in a vertical elbow under the same conditions. Consequently, the maximum pressure drop caused by flowing through the horizontal elbow is higher than that in the vertical elbow.

On 6 February 2023, Türkiye experienced a pair of consecutive earthquakes with magnitudes of Mw 7.8 and 7.5, and accompanied by an intense aftershock sequence. These seismic events were particularly impactful on the segments of the East Anatolian Fault Zone (EAFZ), causing extensive damage to both human life and urban centers in Türkiye and Syria. This study explores the analysis of a dataset spanning almost one year following the Turkiye mainshocks, including 471 events with a magnitude of completeness (Mc) ≥ 4.4. We employed the maximum likelihood approach to estimate the b-value and Omori-Utsu parameters (K, c, and p-values). The estimated b-value is 1.21 ± 0.1, indicating that the mainshocks occurred in a region characterized by elevated stress levels, leading to a sequence of aftershocks of larger magnitudes due to notable irregularities in the rupture zone. The aftershock decay rate (p-value = 1.1 ± 0.04) indicates a rapid decrease in stress levels following the main shocks. However, the c-value of 0.204 ± 0.058 would indicate a relatively moderate or low initial productivity of aftershocks. Furthermore, the k-value of 76.75 ± 8.84 suggests that the decay of aftershock activity commenced within a range of approximately 68 to 86 days following the mainshocks. The fractal dimension (Dc) was assessed using the correlation integral method, yielding a value of 0.99 ± 0.03. This implies a tendency toward clustering in the aftershock seismicity and a linear configuration of the epicenters. The slip ratio during the aftershock activity was determined to be 0.75, signifying that 75% of the total slip occurred in the primary rupture, with the remaining fraction distributed among secondary faults. The methodologies and insights acquired in this research can be extended to assist in forecasting aftershock occurrences for future earthquakes, thus offering crucial data for future risk assessment. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Longitudinal slip tests of the 215/55 R17 tire were carried out using a six-component tire bench test instrument. By comparing with Abaqus simulation data, the longitudinal forces and slip ratios of the tire with a constant tire pressure under different speeds and vertical loads were analyzed. A tire finite element model was established, and the energy loss of the tire under the action of ground friction was examined using the model. It was predicted that the heat loss of the tire was mainly caused partially by the sliding of the tire against the ground and partially by rolling friction. The friction force of the tire is concentrated at the shoulder position. The results showed that the longitudinal force increased with the increase in the vertical load at the same slip ratio, but the velocity had little effect on the longitudinal force. In the braking slip stage, the heat loss due to friction was greater than that in the driving slip stage. The energy loss due to friction increased with the increase in the velocity and vertical load. In the whole sliding process, the energy release due to frictional work was the largest at 80 km/h and 6396 N. [ABSTRACT FROM AUTHOR]

A method of synthesis of an internal bevel gear by coefficients of profile shift and shaft angle is presented. Formulas for calculating qualitative rates are derived: slip ratio, specific pressure ratio and overlap ratio. It is noted that such gear in comparison with the external bevel gear is characterized by better qualitative rates. These calculated dependencies are the basis for the work of the Internal bevel gears x64 program to generate macros for modeling such gear. The internal toothed wheel can be manufactured on a three-, four-, or five-axis CNC milling machines, as well as on a 3D printer. [ABSTRACT FROM AUTHOR]

It is very easy for a small lunar rover to slip on the regolith of the lunar surface and become stuck. Previous studies have quantitatively evaluated the effects of wheel geometry, such as elliptical or eccentric wheels, on the performance of a rover when climbing up slopes. These studies reported that the rovers were able to run on a 30-degree slope made of silica sand. In this study, a small rover was designed and created, and running tests were conducted using lunar soil simulant and silica sand to predict its performance on the lunar surface. The effects of soil differences on the performance of the rover were clarified through the running tests and the measurement of reaction force on the lug. Although the rover exhibited a greater slip ratio on the lunar soil simulant than on the silica sand, the rover with eccentric wheels was able to climb up to a 30-degree angle on the lunar soil simulant. The results for the sinkage measurement of the rover showed that the eccentric wheels prevented sinkage with their up-and-down motion, enabling the rover to climb steep slopes. Furthermore, the tests for measuring the reaction force on the lug indicated that the density change in the lunar soil simulant did not provide sufficient reaction force, and that the running performance on the lunar soil simulant was lower than that on the silica sand.

The influence of the external environment can reduce the braking performance of the electric vehicle (EV) with in-wheel motors (IWM). In this paper, an adaptive sliding mode wheel slip control method with a vehicle speed observer consideration is proposed, which enables the EV to accurately track the optimal slip ratio in various environments and improve braking performance. First, the braking system dynamics model is established by taking the EV with IWM as the study object. Second, a super-twisting sliding mode observer is used to estimate the vehicle speed, and a new adaptive second-order sliding mode controller is constructed to control the braking torque. Finally, co-simulation experiments are performed under different conditions based on Carsim and MATLAB/Simulink, and the proposed scheme is validated by comparison with three control methods. The experimental results show that the proposed scheme has better control performance, and both the safety and control quality of the EV is improved.

A planetary exploration rover has been employed for scientific endeavors or as a precursor for upcoming manned missions. Predicting rover traversability from its wheel slip ensures safe and efficient autonomous operations of rovers on deformable planetary surfaces; path planning algorithms that reduce slips by considering wheel-soil interaction or terrain data can minimize the risk of the rover becoming immobilized. Understanding wheel-soil interaction in transient states is vital for developing a more precise slip ratio prediction model, while path planning in the past assumes that slips generated at the path is a series of slip ratio in steady state. In this paper, we focus on the transient slip, or slip rate the time derivative of slip ratio, to explicitly address it into the cost function of path planning algorithm. We elaborated a regression model that takes slip rate and traction force as inputs and outputs slip ratio, which is employed in the cost function to minimize the rover slip in path planning phase. Experiments using a single wheel testbed revealed that even with the same wheel traction force, the slip ratio varies with different slip rates; we confirmed that the smaller the absolute value of the slip rate, the larger the slip ratio for the same traction force. The statistical analysis of the regression model confirms that the model can estimate the slip ratio within an accuracy of 85% in average. The path planning simulation with the regression model confirmed a reduction of 58% slip experienced by the rover when driving through rough terrain environments. The dynamics simulation results insisted that the proposed method can reduce the slip rate in rough terrain environments. [ABSTRACT FROM AUTHOR]

The development of vehicle intelligence has driven the evolution of brake-by-wire systems, with electromechanical braking (EMB) emerging as a crucial development in intelligent vehicle braking. To enhance the braking safety of EMB-equipped vehicles, this paper proposes a slip ratio control method based on adaptive fuzzy sliding mode control (AFSMC) to more effectively achieve wheel slip ratio tracking during braking. The approach involves establishing the mathematical model of the planetary gear-type EMB system and the vehicle's longitudinal dynamics model. Additionally, a hierarchical collaborative control strategy is introduced, where the bottom layer employs the EMB clamping force control algorithm based on cascaded proportional-integral (PI), and the top layer integrates AFSMC to regulate the slip ratio. The simulation results, validated using the joint simulation platform of Simulink and Carsim under various conditions, illustrate that the AFSMC, compared to the conventional sliding mode controller (SMC), attains more precise control of wheel slip ratio while mitigating the chattering phenomenon. These findings suggest the potential of AFSMC for practical engineering applications. [ABSTRACT FROM AUTHOR]

To provide the necessary theoretical models of sphere–soil interaction for the structural design, motion control, and simulation of spherical robots, this paper derives analytical expressions for traction force and driving torque when spherical robots slide and sink into sandy terrain, based on terramechanics and multibody dynamics. Furthermore, orthogonal experimental analysis identifies the load, joint angular acceleration, and maximum joint angular velocity of spherical robots as influencing factors, highlighting that the load significantly affects their longitudinal motion performance. Experimental results indicate that rolling friction and additional resistance on sandy terrain cannot be ignored. The corrected theoretical model effectively replicates the temporal variation of driving torque exerted by spherical robots on sandy terrain. Numerical computations and experimental analyses demonstrate that increasing the radius of the sphere shell, the load, and the slip ratio all lead to increased traction force and driving torque. However, traction force and driving torque begin to decrease once the slip ratio reaches approximately 0.5. Therefore, in the design of spherical robot structures and control laws, appropriate parameters such as load and slip ratio should be chosen based on the established sphere–soil interaction theoretical model to achieve high-quality longitudinal motion performance on sandy terrain.

A planetary exploration rover has been employed for scientific endeavors or as a precursor for upcoming manned missions. Predicting rover traversability from its wheel slip ensures safe and efficient autonomous operations of rovers on deformable planetary surfaces; path planning algorithms that reduce slips by considering wheel-soil interaction or terrain data can minimize the risk of the rover becoming immobilized. Understanding wheel-soil interaction in transient states is vital for developing a more precise slip ratio prediction model, while path planning in the past assumes that slips generated at the path is a series of slip ratio in steady state. In this paper, we focus on the transient slip, or slip rate the time derivative of slip ratio, to explicitly address it into the cost function of path planning algorithm. We elaborated a regression model that takes slip rate and traction force as inputs and outputs slip ratio, which is employed in the cost function to minimize the rover slip in path planning phase. Experiments using a single wheel testbed revealed that even with the same wheel traction force, the slip ratio varies with different slip rates; we confirmed that the smaller the absolute value of the slip rate, the larger the slip ratio for the same traction force. The statistical analysis of the regression model confirms that the model can estimate the slip ratio within an accuracy of 85% in average. The path planning simulation with the regression model confirmed a reduction of 58% slip experienced by the rover when driving through rough terrain environments. The dynamics simulation results insisted that the proposed method can reduce the slip rate in rough terrain environments.

• A new model for a vehicle is developed and validated using real- experimental data from an automotive software. • The model is applied to a mobile agriculture robot to develop a coupled control law. • The coupled controller is implemented in cascade with a slip ratio controller using terramechanics law. • The results of this control law give us good results in low velocity compared to high velocity. In this paper, the coupled longitudinal and lateral control of the mobile agricultural robot "Agri-Eco-Robot" is addressed. As a first step, the Newton's law is used to develop the dynamical modeling of the mobile agricultural robot. The wheel-ground contact is modeled using the Terramechanics law called Extended-Bekker. The validation of the developed vehicle model was then conducted using an automotive simulator. The developed vehicle model is then used to derive the coupled control laws for the lateral and the longitudinal vehicle dynamics. The proposed controller is realized using two overlapping controllers, the first is dealing with coupled control of longitudinal and lateral dynamics to command the traction, and the second is the controller that minimize slipping, both are developed using the Lyapunov's theory. This controller is compared with the dynamics where the slip ratio is not controlled according to two scenarios in which one is the heigh velocity and the other is low velocity, this control law is validated using an automotive simulator applied to the mobile robot 'Agri-Eco-Robot'. The result of this control law shows the necessity of the slipping control when navigating in a rough environment such as agricultural fields, assuming a low-speed command to ensure system stability. [ABSTRACT FROM AUTHOR]

Selected 215/55 R17 radial tires for material test to obtain relevant material parameters. Used these parameters to build a finite element model and conduct longitudinal slip simulation. The relationship between longitudinal force and slip rate at different speeds and loads was determined by tire longitudinal slip tests. Then the longitudinal slip simulation results were compared with the test results to verify the feasibility of the model. The circumferential and axial rebar force of the belt layer at different speeds and the extreme value of the circumferential rebar force on the reverse-envelope of different skeleton materials were analyzed. The results show that: in the static state, the cord force of the belt layer had shown a trend consistent with the direction of the cord arrangement. As the speed increased, the belt cord force exhibited significant fluctuations and asymmetry. The rebar force of the turn-up points on the belt and ply is significantly smaller compared to the fetal crown ply. The rebar force at the fetal crown and belt wrapping points at 60 km/h was smaller than at 40 km/h and 80 km/h. The cord force of the fetal crown ply and the belt ply is much more affected by the load than that of the ply. [ABSTRACT FROM AUTHOR]

This study analyzes the quarter car braking model to determine the effect of the wheel slip ratio (λ) on the friction coefficient (µ) during the braking of the car. The friction coefficient reaches a minimum when the slip ratio λ ∼ 1; maximum friction coefficient at the optimal slip ratio value from 0.18 to 0.2. Dynamic Model of the vehicle in the ABS brake study should consider in detail the dynamic aspects of braking and the interaction between the tire and the road profile. CarSim software is used in this study to simulate the braking system of a vehicle operating in industrial plant; Simulation is performed on both cases of ABS and non-ABS braking systems. The results of braking distance, deceleration, and brake pressure are considered and analyzed to select a suitable braking system for the operating conditions of the designed truck.

This paper presents a deep neural network (DNN)-based slip ratio estimator fused with an invariant extended Kalman filter (IEKF) for lugged-wheel robot localization using an inertial sensor and an encoder. Among various sensors used in wheeled mobile robot (WMR) localization, inertial sensors and encoders are most commonly used because these sensors are inexpensive and have low computational requirements. However, inertial sensors and encoders can cause large drifts in localization due to inherent sensor characteristics and wheel slippage, respectively. Most studies on wheel slippage have primarily focused on rubber tires, and using this slip ratio model for WMRs with lugged-wheels operating in outdoor environments can result in significant estimation errors in slip ratios. This paper develops a DNN-based slip ratio estimator and IEKF for WMR localization that is robust to wheel slippage even in rugged outdoor environments. The performance of the proposed localization is demonstrated through experiments using outdoor datasets where WMRs with lugged-wheels experience various slip conditions. Experiments are conducted in wet and dry conditions on a sloped grass field. Results show that the proposed localization method reduces accumulated localization errors by 53.5% compared to integration-based localization and by 13.5% compared to IEKF-based localization.

This study presents an approach for predicting the slip ratio, a significant parameter in improving the autonomous navigation of robots. The novelty of the work is presented in two parts; first is the design of a Robot Operating System (ROS)-Physics Engine-based hybrid machine learning model with separate terrain classification and slip ratio estimation algorithms. The motivation for developing a hybrid model is presented by analyzing slip ratio-longitudinal friction coefficient characteristics in three different terrains: sand, grass, and asphalt. The longitudinal friction coefficient ( μ x ) values are distinct for the same values of slip ratio in different terrains, potentially influencing the model’s feature extraction. The features for the slip estimation model are collected from torque sensors and IMU, which measure the external forces acting on robot wheels. The slip estimation is achieved using ensembles of weak classifiers to reduce the computational load of onboard systems. An optimized model with slip ratio classes as output has been evaluated and presented for three different terrains. The model provides an accuracy of 78.1% in the sand, 77.8% in the grass, and 73.5% in asphalt in simulations. The model is compared with a strong classifier used in previous works regarding the accuracy, training time, and computational time. Second, the virtually- trained learning algorithm is tested and validated using the physical robot whose virtual model is implemented in simulations with the actual slip ratio estimated using an experimental framework. [ABSTRACT FROM AUTHOR]

The purpose of this study is to propose an effective model for predicting the slip ratio of a belt transmission mechanism during power transmission, considering the different tensile stiffness of the drive belt. The slip ratio of the belt mechanism was measured under a constant applied torque to compare it with the theoretical value based on belt elastic elongation. The apparent friction coefficient between the belt material and the pulley was measured using a laboratory-made counter-type disc-on-block friction tester under a constant fixed slip velocity condition. The test results showed that when a soft rubber belt was used, the slip ratio of the belt mechanism could be accurately predicted by considering only the elastic elongation of the belt itself. However, when a rigid metal belt was used, the experimental slip ratio of the belt mechanism was larger than the theoretical value. The observed friction coefficient between the belt material and the pulley indicated that the friction force depended on the slip velocity, with the friction force at low slip velocity being smaller than that at high slip velocity. Based on these results, a prediction model for the slip ratio was proposed, considering micro-slip due to the varied frictional coefficient, and its validity was examined.

In order to solve the adaptability problem of acceleration slip regulation for distributed drive electric vehicles, a slip ratio adaptive control strategy based on wheel angular velocity is proposed. The principle of road estimation algorithm based on the Burckhardt tire model is analyzed, and an improved estimation principle for optimal slip ratio is designed to improve the speed and accuracy of optimal slip ratio estimation. A slip ratio control strategy based on a conditional integral sliding mode control is designed, and its stability is proven. To make the slip ratio control strategy have better practicability, the slip ratio control strategy is combined with the road estimation algorithm, and the control variable of the slip ratio adaptive control strategy based on a conditional integral sliding mode control is redesigned to obtain a faster vehicle dynamic response. Finally, the effectiveness of the designed road estimation algorithm and the slip ratio adaptive control strategy is verified by simulation of acceleration on joint road and split road. Results show that the designed road estimator can obtain the road adhesion coefficient and optimal slip ratio quickly and accurately; the slip ratio adaptive controller, based on a conditional integral sliding mode control, can maintain the wheel slip ratio near the optimal slip ratio and reduce the steady-state error of the wheel slip ratio. [ABSTRACT FROM AUTHOR]

Rolling friction and wear testing of heavy haul wheel tread was performed. The results show that a new and dominant vibration was generated owing to the surface wear, resulting in the polygonalization wear of the wheel specimen. The slip between wheel and rail specimens accelerated the formation of polygonalization wear. The pearlite and proeutectoid ferrite in the outermost layer were completely fragmented to form a fine grain layer. There was an extreme state for the deformation of the microstructure in the outermost layer, and there was a corresponding extreme value for the hardness. The slip accelerated the surface microstructure to reach the plastic hardening limit, but it had little effect on the extreme value of hardness. The stress distribution of the wheel specimen surface was simulated. The results show that there were alternating principal tensile and compressive stresses at the contact surface of the wheel specimen and shear stresses with alternating directions in the subsurface of the contact patch. The depth of the maximum shear stress from the surface was mainly related to the normal load, while the slip has no significant effect on it. A coupling modeling method of finite-element method (FEM) and smoothed particle hydrodynamics (SPH) was used to simulate the microstructure evolution of CL70 wheel steel. The simulation results show that there was mutual mechanical interaction between ferrite and cementite in pearlite. Their deformation was inconsistent owing to their different mechanical properties, resulting in large tensile stress at the boundary between them, even in the compressive stress area below the contact patch. [ABSTRACT FROM AUTHOR]

Selected 215/55 R17 radial tires for material test to obtain relevant material parameters. Used these parameters to build a finite element model and conduct longitudinal slip simulation. The relationship between longitudinal force and slip rate at different speeds and loads was determined by tire longitudinal slip tests. Then the longitudinal slip simulation results were compared with the test results to verify the feasibility of the model. The circumferential and axial rebar force of the belt layer at different speeds and the extreme value of the circumferential rebar force on the reverse-envelope of different skeleton materials were analyzed. The results show that: in the static state, the cord force of the belt layer had shown a trend consistent with the direction of the cord arrangement. As the speed increased, the belt cord force exhibited significant fluctuations and asymmetry. The rebar force of the turn-up points on the belt and ply is significantly smaller compared to the fetal crown ply. The rebar force at the fetal crown and belt wrapping points at 60 km/h was smaller than at 40 km/h and 80 km/h. The cord force of the fetal crown ply and the belt ply is much more affected by the load than that of the ply. [ABSTRACT FROM AUTHOR]

Because of the complexities of tire-road interaction, the wheels of a multi-wheel distributed electric drive vehicle can easily slip under certain working conditions. As wheel slip affects the dynamic performance and stability of the vehicle, it is crucial to control it and coordinate the driving force. With this aim, this paper presents a driving force coordination control strategy with road identification for eight-wheeled electric vehicles equipped with an in-wheel motor for each wheel. In the proposed control strategy, the road identification module estimates tire-road forces using an unscented Kalman filter algorithm and recognizes the road adhesion coefficient by employing the recursive least-square method. According to road identification, the optimal slip ratio under the current driving condition is obtained, and a controller based on sliding mode control with a conditional integrator uses this value for acceleration slip regulation. The anti-slip controller obtains the adjusting torque, which is integrated with the driver-command-based feedforward control torque to implement driving force coordination control. The results of hardware-in-loop simulation show that this control strategy can accurately estimate tire-road forces as well as the friction coefficient, and thus, can effectively fulfill the purpose of driving force coordinated control under different driving conditions.

The stability and drivability of distributed drive electric vehicles over split-friction regions and with actuator faults are studied in this paper by using control allocation. Under the integrated control architecture of high-, medium-, and low-level controllers, a slip-ratio-based synchronization approach is presented to redistribute the driving force for all the driving wheels. The synchronization of slip ratios on wheels is accomplished by autonomously regulating the distribution parameters in the design of a low-level controller. Therefore, the driving force and moment can be adjusted from the design of the regulator on distribution parameters so that the stability and driving performance are ensured when electric vehicles drive over split-friction regions. Subsequently, the concept of distribution parameters is extended to handle actuator faults in electric vehicles by regulating the driving force via the adjustment of distribution parameters. The proportional fault, additive fault, and motor saturation are considered in this paper by compensating for the loss of driving force from the force allocation approach. Numerical examples using CarSim with MATLAB/Simulink and human/hardware-in-the-loop validations are illustrated to demonstrate the efficacy and performance of the proposed control schemes. • A slip-ratio-based force allocation control is presented for DDEVs over split-friction regions. • Auto-regulation of distribution parameters ensures stability of DDEVs with actuation faults. • Integrated controller with force allocation and fault-tolerant control are validated using HIL. [ABSTRACT FROM AUTHOR]

The discrete element method is widely used to analyze the dynamic behavior of a wheel driving on the sandy road. The tetra clustering model for generating arbitrary shape of a particle is developed. A contact method between a wheel and numerous particles is developed to carry out simulation. A wheel testbed experimental setup is established for investigating the contact phenomenon between a wheel and sand particles. A high-speed camera is used for capturing the motion of the wheel. The technique for solving multibody dynamics and particle dynamics simultaneously is suggested. The repose angle test is carried out to obtain the contact parameter between particles. The static equilibrium test of a wheel is performed to obtain the contact parameter between a wheel and particle. The dynamic motion of the wheel according to the slip ratio is compared with experiments. According to results, simulation results show a good agreement with experiments. [ABSTRACT FROM AUTHOR]

The efficient antiskid braking control of aircraft is achieved by accurately tracking the optimal slip ratio. However, aircraft antiskid braking systems are subject to many parametric uncertainties and uncertain disturbances, and the limited sensor signals make it more difficult to design a high-performance antiskid braking system controller. To address this issue, an observer-based adaptive robust aircraft antiskid braking system controller with disturbance compensation is proposed to enhance the tracking performance and disturbance rejection of aircraft antiskid braking system. The proposed controller effectively integrates parameter identification, adaptive control, and extended state observer using the backstepping method. Parametric uncertainties and fast time-varying brake torque conversion coefficient are handled by adaptive law and least squares parameter identification method, respectively. After that, the remaining parametric uncertainties, parameter identification errors, and uncertain disturbances are observed integrally by constructing extended state observer and compensated in a feedforward way. Another feature of the designed controller is that the dynamics of the hydraulic system are considered, and the disturbances of the hydraulic system are also observed and compensated with extended state observer, thus further improving tracking accuracy. Since the burden of extended state observer is greatly reduced by adaptive law and parameter identification, the proposed controller can effectively avoid high-gain feedback while theoretically guaranteeing that the tracking error is bounded in the presence of time-variant uncertainties. The effectiveness of the proposed controller is proved by several sets of simulation tests and brake testing platform experiments. • An observer-based aircraft ABS controller with disturbance compensation is proposed. • Fast time-varying uncertain parameters in aircraft ABS are handled separately by RLS. • Disturbances in wheel and hydraulic dynamics are estimated and actively compensated. • Parameter identification, adaptive control and ESO are effectively integrated. [ABSTRACT FROM AUTHOR]

The existing energy management strategies for four-wheel-drive electric vehicles only take into account the vehicle energy consumption under static adhesion constraints. However, the front and rear axle loads transfer under dynamic conditions lead to the variations of vehicle adhesion characteristics, which results in the changes of vehicle energy consumptions. In this paper, a multi-objective optimal torque distribution strategy is proposed, taking into account the front and rear axle load transfer and the variations of adhesion characteristics. The advantages of the proposed strategy are verified through simulation studies in terms of vehicle energy consumption and wheel slip ratio, in comparison with the average torque distribution strategy and the optimal torque distribution strategy based on Sequential Quadratic Programming Algorithm. The simulation results show that the economy performance of the proposed strategy is superior to those of the competing methods. Furthermore, the proposed strategy provides good power performance and eliminates excessive wheel slip, which in turn ensures vehicle longitudinal stability and avoids energy loss resulting from frequent ASR interventions.

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.

Experiments of a sphere oblique impact with and without an initial spin have been carried out to obtain properties of the impact interface. The contact surface is recorded with a piece of thin carbon paper. The interfacial parameters measured are expressed as axis length, contact area and slip ratio. It is found that for the impact between steels the forward spin can make geometrical sizes of the contact surface increase compared with the case of no initial spin, however, just the reverse for the backward spin. The effect of the initial spin becomes more apparent for the impact with a rubber cushion. Whether the initial spin promotes or hinders the sphere sliding depends on the parameters of tangential velocity and force at the interface. [ABSTRACT FROM AUTHOR]

The bearing used to support turbopump works in ultra-low temperature environments， its cage pockets is elliptical usually. Based on the dynamics theory of the rolling bearings， the dynamics differential equations of angular contact ball bearing are established in which the pocket shape of the cage is elliptical. The influences on cage slip ratio and friction power consumption that caused by different working conditions and different structural parameters are investigated. The research show that， as the bearing speed， radial clearance and pocket axial clearance increase， the cage slip ratio increases， as the bearing load， guide clearance and pocket circumferential clearance decrease， the cage slip ratio decreases. As the bearing speed， axial load clearance increase， guide clearance， pocket circumferential clearance and axial clearance increase， friction power consumption increases， as the radial load and radial clearance increase， friction power consumption decreases.

In order to solve the adaptability problem of acceleration slip regulation for distributed drive electric vehicles, a slip ratio adaptive control strategy based on wheel angular velocity is proposed. The principle of road estimation algorithm based on the Burckhardt tire model is analyzed, and an improved estimation principle for optimal slip ratio is designed to improve the speed and accuracy of optimal slip ratio estimation. A slip ratio control strategy based on a conditional integral sliding mode control is designed, and its stability is proven. To make the slip ratio control strategy have better practicability, the slip ratio control strategy is combined with the road estimation algorithm, and the control variable of the slip ratio adaptive control strategy based on a conditional integral sliding mode control is redesigned to obtain a faster vehicle dynamic response. Finally, the effectiveness of the designed road estimation algorithm and the slip ratio adaptive control strategy is verified by simulation of acceleration on joint road and split road. Results show that the designed road estimator can obtain the road adhesion coefficient and optimal slip ratio quickly and accurately; the slip ratio adaptive controller, based on a conditional integral sliding mode control, can maintain the wheel slip ratio near the optimal slip ratio and reduce the steady-state error of the wheel slip ratio.

The present paper introduces a tire/road friction prediction tool based on modelling the tire/road contact as dynamic, viscoelastic, rough, and lubricated. The tool takes into account a considerable part of influent parameters related to tire, road, contaminant, and contact operating conditions: For the tire, the tool takes into account its geometry and rubber material behaviour. For the road, the texture is taken into account via the surface topography. At the contact interface, dry or wet conditions are taken into account through the lubricant depth, viscosity, and density. The operating conditions are taken into account through the normal load, speed, and slip ratio of the tire. The real novelty of this tool lies in its ability to reproduce the complete curve of the tire/road friction coefficient as a function of the slip rate. The validation of the tool is initially done through parametric studies by analyzing the trends of the results, then by performing braking tests on a passenger car at various speeds on different wet roads with different textures. The tool correctly ranks the peak friction and the sliding friction on these various road surfaces. [ABSTRACT FROM AUTHOR]

This study employs a dual deep neural network (D-DNN) to accurately estimate the absolute longitudinal speed of a vehicle. Accuracy in speed estimation is crucial for vehicle safety, because longitudinal speed is a common parameter employed as a state variable in active safety systems such as anti-lock braking system and traction control system. In this study, DNNs are applied to determine the gain of an adaptive filter to estimate vehicle speed. The used data consists of longitudinal acceleration, wheel speed, filter gain, and estimated vehicle speed. The data generated from Carsim software are collected and preprocessed using a Simulink model. To acquire data with numerous wheel slip patterns, various acceleration and deceleration conditions are applied to four different road conditions. Though, it is challenging to achieve a single DNN model that is optimally cope with the various driving situations. Thus, we adopt two DNN models that were individually trained in low and high acceleration regions. The dual DNN model results in error reductions of 74% and 65%, compared with a single DNN and classical adaptive Kalman filter approaches, respectively.

The aim of this work is to propose a new type of anti-lock braking system (ABS) using a magneto-rheological (MR) brake and validate its effectiveness by implementing a fuzzy logic sliding mode (FLSM) controller via the hardware-in-the-loop-simulation (HILS). Firstly, a quarter vehicle model integrated with the tire model is established to analyze control performance of MR brake during the braking process under different road conditions. Secondly, a disc type MR brake is designed on the basis of a mathematical model and the field-dependent braking torque is measured. Subsequently, in order to investigate the control performance of the proposed ABS, the software model is combined with the hardware configuration which is built by Matlab/Simulink. It is shown via HILS that the proposed ABS associated with the FLSM controller can provide high response speed and excellent braking control effect. In this work, control responses from the FLSM controller are also compared with those achieved from the conventional sliding mode controller in order to emphasize the significance of the control strategy to enhance ABS performances. [ABSTRACT FROM AUTHOR]

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