Slip Energy Research Articles

Torque vectoring algorithm for distributed drive electric vehicle considering coordination of stability and economy

Working of in-wheel motors (IWMs) in high-efficiency areas and minimum tire slip should be considered when driving distributed drive electric vehicles (DDEVs). Therefore, a novel torque vectoring control algorithm is proposed to lower energy dissipation and ensure lateral stability, which consists of a linear quadratic regulator and a proportion integration control module in upper controller to calculate desired additional yaw moment and total driving torque, respectively, for following desired yaw rate, side slip angle, and longitudinal velocity. In addition, the stability objective function considering tire working load and the economic objective function considering working efficiency of IWMs and tire slip energy are established separately in lower controller. The fitness function of coordinating lateral stability and economy is obtained by phase plane method. Particle swarm optimization (PSO) algorithm with a superior initial population (SIP-PSO) is proposed to solve torque distribution coefficients for torque distribution of DDEVs. Finally, simulation and hardware-in-the-loop test results under double lane change and snake lane change maneuvers on lower adhesion road indicate that the proposed algorithm can effectively lower the energy loss of IWM working and tire slip while ensuring lateral stability under different working conditions.

Mitigation of Starting Transients in Slip-Energy Recovery Drives

Starting voltage and current transients in slip energy recovery drives (SERD) may damage the stator and rotor windings. The resulting torque oscillations damage the induction machine mechanical parts. In this paper three schemes for damping starting transients and torque oscillations are proposed. In the first scheme a parallel RL impedance is connected between the supply and the stator coils, in the second scheme a parallel RL impedance is added in the rotor circuit, and in the third scheme the two impedances are connected simultaneously. Transient performance is simulated and the results of the three schemes are compared. Also, the effect of each proposed scheme on the steady state values of the SERD currents, voltages, and electric torque is studied and demonstrated. Lower current and voltage transients, and lower torque oscillations resulted in all schemes, with optimum transient performance observed when adding the two impedances simultaneously.

High-Performance Flywheel Hybrid Powertrain

The high efficiency of the flywheel hybrid powertrain, as well as its power characteristics, can help to meet high energy/power conversion needs, which may prove to be promising. Moreover, the flywheel hybrid powertrain may reduce dependence on batteries. This paper presents the EC-BERS in order to capture more mechanical power than its rated power, and to reduce the charge/discharge cycles of the battery. In this new energy recovery system, maximum torque can be obtained in the higher speed zone, leading to two marked improvements in terms of improving the braking efficiency. The working point of the system changes and shifts to the high-speed zone to meet the maximum torque at higher speeds. Furthermore, this powertrain can transfer the vehicle kinetic energy into the flywheel directly in the same form. Only the slip energy needs to be dealt with in the electrical form, which is beneficial to prolonging the battery life. Two typical systems were emulated under the same conditions to verify this feature, and a small prototype was designed to prove the concept.

Discrete-element modelling of concrete behaviour under uniaxial compressive test

This paper presents a three-dimensional (3D) simulation of the concrete behaviour in a uniaxial compressive test using discrete-element modelling (DEM). The aim of this paper is to validate the numerical model developed and to study the cracking initiation and failure process in order to better understand the fracture behaviour of concrete. The particles were distributed using an algorithm that is based on sieve test analysis. The parameters were set up in order to validate the numerical model with the experimental result. It was observed that the 3D model is in line with the laboratory test in term of stress-strain response and macroscopic cracks development. Once the bond between the spheres was broken, it led to the formation of microscopic cracks, which were not visible in laboratory tests. From the observation recorded during the testing, it is clear that DEM is capable of capturing concrete behaviour both quantitatively and qualitatively. At the yielding point in the concrete the strain energy is released in the form of kinetic energy, frictional slip energy, energy of dashpot and local damping. Hence, it can be concluded that DEM can be used to study the random nature of the cracking and fracturing of concrete structures.

Integrated tire slip energy dissipation and lateral stability control of distributed drive electric vehicle with mechanical elastic wheel

Stability and energy consumption have always been important issues in electric vehicle research. Excessive slip energy not only aggravates tire wear, but also consumes energy of electric vehicle. In order to ensure the lateral stability and to reduce the slip energy dissipation of the distributed drive electric vehicle (DDEV) equipped with Mechanical Elastic Wheel (MEW), an integrated framework considering both tire slip energy dissipation and lateral stability control is proposed. The SESC (Slip Energy and Stability Control) is a hierarchical control framework for DDEV with MEW. A PID speed tracking controller and an (Integral Terminal Slide Mode) ITSM controller are designed at the upper-level controller. The ITSM controller can improve the lateral stability of the vehicle by obtaining the desired yaw moment. Speed tracking controller can stabilize the speed of the vehicle and obtain the desired longitudinal force. At the lower-level controller, the brush model of the MEW is proposed to express tire slip energy. In order to reduce the error of the vehicle dynamics and the slip energy dissipation, a mixed objective function including a holistic corner controller (HCC) and a minimum tire slip energy characterization is proposed. The proposed control framework is verified by Carsim and Matlab/Simulink under emergency simulation conditions. The simulation results show that the SESC based method can improve the lateral stability of DDEV with MEW effectively, and has better performance compared with fuzzyPID+AD based method. Meanwhile, the SESC achieves less slip energy than conventional torque distribution method.

Torque Vectoring Control of RWID Electric Vehicle for Reducing Driving-Wheel Slippage Energy Dissipation in Cornering

The anxiety of driving range and inconvenience of battery recharging has placed high requirements on the energy efficiency of electric vehicles. To reduce driving-wheel slip energy consumption while cornering, a torque vectoring control strategy for a rear-wheel independent-drive (RWID) electric vehicle is proposed. First, the longitudinal linear stiffness of each driving wheel is estimated by using the approach of recursive least squares. Then, an initial differential torque is calculated for reducing their overall tire slippage energy dissipation. However, before the differential torque is applied to the two side of driving wheels, an acceleration slip regulation (ASR) is introduced into the overall control strategy to avoid entering into the tire adhesion saturation region resulting in excessive slip. Finally, the simulations of typical manoeuvring conditions are performed to verify the veracity of the estimated tire longitudinal linear stiffness and effectiveness of the torque vectoring control strategy. As a result, the proposed torque vectoring control leads to the largest reduction of around 17% slip power consumption for the situations carried out above.

Origin of the ω-Strengthening and Embrittlement in β-Titanium Alloys: Insight from First Principles

The ω-phase precipitates in β-Ti alloys increase the strength but significantly degrade the ductility of the alloys. In the present work, the mechanism of ω-strengthening and embrittlement is investigated by using a first principles method based on density functional theory. The generalized stacking fault energies of various slip systems in both the β and ω phases are calculated. The strengthening and embrittlement effects of the ω phase are discussed by comparing the slip energy barriers of slip systems in the β and ω phases with different orientation relationships. It is found that the slip energy barriers of slip systems in the ω phase, except for $$(\bar 2020){[0001]_\omega },$$ are much higher than those of slip systems in the β phase, which explains the ω-strengthening and embrittlement effects. The slip energy barrier of the most active slip system in the phase, $$(\bar 2020){[0001]_\omega },$$ increases with the depletion of Mo and increasing extent of structure collapse, suggesting that aging treatment enhances the -strengthening and embrittlement effects.

Torque allocation of four-wheel drive EVs considering tire slip energy

Torque allocation of four-wheel drive EVs considering tire slip energy

Design and application of a tire slip energy control scheme based on optimal guaranteed cost theory for four‐in‐wheel drive electric vehicles

AbstractIn this paper, vehicle stability with time‐varying tire cornering stiffness and tire slip energy torque distribution is investigated for four‐in‐wheel motor drive electric vehicles thanks to the control flexibility. On the issue of tire slip energy, a scheme of “semi‐empirical tire slip energy model” is proposed and analyzed. In this scheme, the hierarchical control method is used to reduce tire slip energy and improve vehicle stability. In the outer loop controller, cost control is designed based on optimal guaranteed cost theory, which is compared with the traditional linear quadratic regulator. The integrated control method of active front steering and direct yaw moment control is evaluated and studied from the cost perspective by norm‐bounded uncertainty. Finally, the simulation results verify that the control framework considering time‐varying uncertainty has significant advantages under the condition of high‐friction coefficient single‐lane change and low‐friction coefficient slalom change. Compared with the linear quadratic regulator and the minimization of tire slip energy control, the control framework with optimal guaranteed cost can achieve smaller sideslip angle; meanwhile, it can save more tire slip energy.

Design and Experimental Evaluations on Energy-Efficient Control for 4WIMD-EVs Considering Tire Slip Energy

Energy efficiency is extremely important for electric vehicles to improve their driving range. As the motor output energy directly acts on the tire, the tire slip energy generated by tire excessive slip will reduce the effective utilization of motor output energy, resulting in the reduction of energy efficiency, especially in the case of low friction coefficient, or even vehicle instability in some changes, such as slalom change, etc. Therefore, this paper designs an integrated chassis control and verifies the energy utilization. First, based on model predictive control (MPC), an integrated chassis controller is proposed by explicitly incorporating both motor energy and tire slip energy in the main objective function. Second, the reference control actions of the torque distribution method optimized for the motor energy, which facilitates solution-search process of MPC. Then, a semi-empirical UniTire tire slip energy model is proposed for derivation of the tire dissipation energy. Acceleration and stability tests are conducted by four in-wheel independent motor-drive electric vehicles (4WIMD-EVs) on winter proving ground, respectively. The acceleration change results show that both tire dissipation energy and motor output energy are well suppressed to achieve energy-efficient, and the energy utilization ratio of tire dissipation energy to motor output energy is only 35% to achieve stable acceleration. The slalom change verifies vehicle stability, and the results show that the slip ratio of four wheels only reaches to 0.04, and the motor output energy of four wheels is effectively utilized to generate differential yaw moment.

Road Load Based Model for Vehicle Repair and Maintenance Cost Estimation

A techno-economic model is developed based on road-load simulation results expressed in relation to slip energy (SE) at the tire–pavement interface and the repair and maintenance (R&M) cost obtained from published sources and data from state agencies. Tire SE allows for the consideration of aggressive acceleration and deceleration, high torque conditions (for instance, driving an upslope grade), and roadway curvature. Tire SE data used in this effort were generated using physics-based simulation models of different vehicle types for arrays of road conditions (e.g., grades, curvatures) and driving cycles (i.e., vehicle speed profiles). R&M costs were estimated for various vehicle categories and accumulated vehicle mileage. The approach is based on relating the probability density functions (PDFs) of SE and R&M costs. Asymptotic series expansion for an incomplete gamma function was used to approximate the gamma functions and to determine the gamma ratio function that is used as the coefficient to SE to estimate R&M costs. The average R&M cost per mile results from the model compared with the arithmetic mean R&M cost data from fleet operators and published data. The model can serve as a method for predicting R&M cost as a function of road load to vehicle fleet.

Parameter interdependence of dynamic self-similar crack with distance-weakening friction

SUMMARY In several analytical and numerical studies, the slip rate function and energy release rate for dynamic self-similar crack growth have been investigated, and the results obtained have contributed to a theoretical understanding and estimation of on-fault energetics. However, the relationships among physical parameters, including stress state, process zone size, rupture velocity, peak slip rate and energy release rate, are still unclear. Therefore, the aim of this study is to derive an analytical solution of the slip rate distribution of antiplane self-similar crack growth under distance-weakening friction that mimics slip-weakening friction. To satisfy the condition that the slip rate starts from zero at the rupture front, a trade-off relationship among rupture velocity, process zone size and breakdown stress-to-stress drop ratio is proposed. The peak slip rate, slip-weakening distance and fracture energy obtained using the proposed model provide a possible mechanism for the determination of the rupture velocity and the estimation of the fracture energy of the self-similar crack growth, based on the seismic observables.

Stress effects on the energy barrier and mechanisms of cross-slip in FCC nickel

The energy barrier for homogeneous cross-slip of a screw dislocation in face-centered cubic (FCC) nickel is calculated using atomistic simulations as a function of the Escaig stress on the glide plane, the Escaig stress on the cross-slip plane, and the Schmid stress on the cross-slip plane. Two cross-slip mechanisms, Friedel-Escaig (FE) and Fleischer, are examined and their energy barriers are calculated for a large number of stress combinations. For each mechanism, the energy barrier as a function of three stress components can be reduced into a one-dimensional function of an effective stress. The stress domains in which FE and Fleischer mechanisms operate respectively are determined. The FE mechanism dominates when the Escaig stress on the glide plane (in the direction that reduces the stacking fault width) is the largest stress component. Increasing the Schmid stress and Escaig stress (in the direction that expands the stacking fault width) on the cross slip plane promotes the Fleischer mechanism. The cross slip energy barrier functions obtained here can be used as input functions for computing cross slip rates in mesoscale dislocation dynamics simulations.

A fast model predictive control allocation of distributed drive electric vehicles for tire slip energy saving with stability constraints

This paper proposes a fast model predictive control allocation (MPCA) approach to minimize the tire slip power loss on contact patches for distributed drive electric vehicles (DDEV). In this strategy, two assumptions are set up from a practical focus: (1) the vehicle acceleration and yaw rate are measurable by global position system (GPS)/ inertial navigation system (INS) and inertial measurement unit (IMU), respectively; (2) the longitudinal velocity, road adhesion factor, and vehicle yaw rate are arranged to be “already known” by advanced estimators. For the strategy design, a CarSim-embedded driver model and a linear quadratic regulator (LQR) based direct yaw moment controller, are respectively applied to calculate the desired longitudinal traction and yaw moment as a virtual input first. Then, a MPCA method is proposed to reasonably distribute the virtual input among four in-wheel motors in order to optimize the tire slip power loss and vehicle stability performance. To accurately characterize tire slip power loss in MPCA, a tire slip estimator is established for tire slip information acquirement. Moreover, addressing on the heavily computational challenge in MPCA, a modified continuation/generalized minimal residual (C/GMRES) algorithm is employed. Since the traditional C/GMRES algorithm cannot directly solve the inequality constraint problem, the barrier functions are applied for transforming the inequality constraints to equivalent cost. According to Pontryagin’s minimum principle (PMP) conditions, the existence and uniqueness for solution of the modified C/GMRES algorithm are strictly proved. Subsequently, a Karush–Kuhn–Tucker​ (KKT) condition based approach is developed to fast gain the optimally initial solution in C/GMRES algorithm for extending application. Finally, numerical simulation validations are implemented and demonstrate that the proposed MPCA can ensure the compatibility between the tire slip power loss reduction and vehicle stability in a computationally efficient way.

Influence of lattice distortion on stacking fault energies of CoCrFeNi and Al-CoCrFeNi high entropy alloys

The stacking fault energy (SFE) plays an important role in the deformation mode selection and consequently the mechanical properties of high entropy alloys. In the present work, the SFEs of face-centered cubic (fcc) CoCrFeNi and Al0.57CoCrFeNi HEAs are calculated by using first-principles calculations. The influence of the local lattice distortion (LLD) on the SFE is explored. We show that the addition of Al to CoCrFeNi alloy increases the intrinsic SFE (ISFE, γisf) but decreases the unstable SFE (USFE, γusf) such that the energy barrier (γusf - γisf) for the ⟨112-⟩(111) slip decreases. The lattice distortion contributes significantly to the ISFE but has limited influence on the USFE, leading to decline of the slip energy barriers of both alloys. The ISFE and slip energy barrier differences between the two alloys are enhanced by the lattice distortion. Based on the calculated ISFE and slip energy barrier, the effects of Al alloying and lattice distortion on the mechanical properties of CoCrNiFe HEA are discussed.

High-Performance 4WD Electric Powertrain With Flywheel Kinetic Energy Recovery

Four-wheel-drive (4WD) full-electric powertrains offer great potential for vehicle performance and efficiency improvements. This study introduces a novel 4WD electric powertrain that significantly increases the overall powertrain performance and battery lifespan. The proposed powertrain benefits from a new compact and highly efficient flywheel-based kinetic energy recovery system (KERS) that enables us to overcome most of the shortcomings of the conventional battery-based KERS. The utilized KERS is capable of capturing or providing much higher mechanical power than its electrical power ratings. Meaning that, without overloading, the powertrain can capture more mechanical power than traction motors’ nominal values. Moreover, since a significant part of the energy exchange takes place in mechanical form, only a portion of the initial kinetic energy (slip energy) needs to be converted into electrical form and be processed electrically. In the proposed powertrain, there is no energy exchange necessary between the battery and the powertrain during each accelerations or braking event, thus also reducing the battery power rating. Mathematical modeling and simulations were performed using space vector modeling method for the proposed powertrain. The results prove the functionality of the proposed 4WD powertrain. Experimental results are also presented for the proof of the concept.

Analysis of deformation behavior and microscopic characteristics of asphalt mixture based on interface contact-slip test

To analyze the slip deformation behavior of asphalt mixture, an interface contact-slip tester of asphalt mixture was developed in this investigation. Four evaluation indicators, including the maximum slip shear stress τsl, the slip shear strain εS, the slip failure modulusES and the interface slip energy index ET, were proposed. According to the correlation and sensitivity analysis, the optimum evaluation indicator was determined. By analyzing the variation coefficient of test results, the key experiment parameters were recommended. The gray binarization method of MATLAB software was adopted to process the slip failure surface of specimen, and the bonding ratio Bn was calculated to analyze the effect of asphalt bonding on strength formation. Based on the deformation curve, the slip deformation behavior of asphalt mixture and the influence factors were analyzed from the microscopic perspective. Results obtained indicated that the optimum test conditions are the loading head of 28.5 mm, the diameter of the support ring of 80 mm, and the loading rate of 5 mm/min. The τsl was selected as the evaluation indicator of slip deformation behavior due to the best correlation with RD, good stability and sensitivity. The bonding effect of asphalt binder is greater than particle contact effect for suspended-dense asphalt mixture. The slip deformation of asphalt mixture can be divided into five stages, including densification, elastic deformation, viscoelastic deformation, initial cracking and plasticity slip deformation. The contact from coarse aggregates and bonding from asphalt binder can enhance the slip deformation resistibility. While the interference of fine particles and the lubrication of asphalt can accelerate the slip deformation of asphalt mixture.

Multi-motor drive with common inverter for pumping unites

This paper presents the results of a research of a multi-motor drive with the electric coupling and a common grid-controlled inverter for pumping facilities of pumping irrigation systems. This system is the most preferable in compliance with the requirements for a controlled electric drive of water-lifting pumping facilities, in which a group of water-pumping sets works in parallel in a common hydraulic pressure circuit. In addition, this electric drive system can be used in multi-motor electric drives of the general purpose industrial grades that do not require absolutely strict coordination of the rotational speeds of their drive of the wound-rotor induction motor, depending on the requirements of the process conditions. In addition, a clear advantage of this system is that it is characterized by a high efficiency compared to other known systems of controlled electric drive, since it only converts the slip energy of the drive motors.

Energy absorption and response speed of composite/aluminium alloy coupling bumper beam in compact electric cars

Composite materials could be applied to the bumper beam in order to enhance the structure performance and provide a light weight solution. This article assessed the impact performance of automobile bumper beams produced from composite material. First, the structural models of the bumper beams with different cross-sections were established in CAE software, and then the impact simulation was carried out. The sum of internal energy and slip energy in the bumper beams of A, B and C-type section were 140.1, 28.331 and 129.533 J, respectively. It can be concluded that the energy absorption of the collision beams with three cross-section shapes is: A-type > C-type > B-type. The simulation results are analysed from the aspects of energy absorption performance and response speed. Then, it can be seen from the simulation results that the integral crash box and separated crash box have influence on the energy absorption performance. Finally, composite specimens were produced and tested by the three-point bending test. The results showed that the specific energy absorption of 6061 aluminium alloy sample is 348.37 J. The specific energy absorption of the composite/aluminium alloy coupling sample is 359.67 J. The results showed that the energy absorption performance of the composite anti-crash beam was more satisfactory.

Energy saving system of cascade variable frequency induction electric drive

This paper discusses the wound rotor induction motor and variable-frequency drive (VFD) that regulates the stator voltage frequency. The stator and rotor windings are connected to a common electrical circuit. The slip energy of the motor goes to the DC link and feeds the stator winding of the motor. The block diagram of the electric drive, the equivalent circuit and the basic characteristic of the cascade VFD are considered. It is shown that the energy-saving mode with a minimum ratio “stator current/torque” is achieved at an angle between vectors of the stator current and the excitation current at the level of 45 degrees. The experimental static mechanical characteristics of the electric drive were obtained. These characteristics provide a limitation of the starting torque.