Longitudinal Friction Force Research Articles

Theoretical and simulation study of dispersive electron cooling

In electron cooling, the transverse cooling rate is usually smaller than the longitudinal rate, especially at high energies. By introducing dispersive cooling, it is possible to redistribute the cooling rate between longitudinal and transverse planes. Theoretically, achieving dispersive electron cooling requires an ion dispersion and a transverse gradient of longitudinal friction force. The latter depends on many factors such as the relative momentum offset, transverse displacement, e-beam density distribution, and space charge effect. Therefore, several methods can be employed to achieve dispersive electron cooling based on these factors. Based on the dc electron beam, these factors and their respective impacts on the cooling rate are discussed and analyzed. For the first time, we propose a new mechanism to achieve dispersive cooling for a uniform electron beam by placing part of the ion beam outside of the electron beam. Based on a linear friction force model, we propose a simple formula to numerically estimate the cooling rate redistribution effect of these methods. The analytical results are in good agreement with Monte Carlo calculation and numerical simulation. Published by the American Physical Society 2024

A novel estimation scheme of tyre–road friction characteristics based on parameter constraints on varied-µ roads

On varied-µ roads, most of the current research on the estimation of tyre-road characteristic parameters and peak friction coefficient lack consideration of parameter constraints. To improve the estimation accuracy, in this study, a novel estimation scheme of tyre-road friction characteristics based on parameter constraints is proposed: based on estimating the longitudinal and lateral friction force, a data preprocessing method is proposed to obtain the constraint region of parameters. Then, the nonlinear least square method is used to preliminarily estimate the parameters. Finally, a constrained auxiliary particle filter algorithm is proposed to correct the estimated parameters. To verify the superiority of the proposed scheme, the estimation performances of friction characteristics of four schemes are compared on low/high speed varied-µ roads, respectively. The results demonstrate that the proposed scheme has the best estimation performance. Simultaneously, compared with the scheme without considering parameter constraints, the proposed scheme can significantly reduce the estimation error.

Force Rendering and its Evaluation of a Friction-Based Walking Sensation Display for a Seated User.

Most existing locomotion devices that represent the sensation of walking target a user who is actually performing a walking motion. Here, we attempted to represent the walking sensation, especially a kinesthetic sensation and advancing feeling (the sense of moving forward) while the user remains seated. To represent the walking sensation using a relatively simple device, we focused on the force rendering and its evaluation of the longitudinal friction force applied on the sole during walking. Based on the measurement of the friction force applied on the sole during actual walking, we developed a novel friction force display that can present the friction force without the influence of body weight. Using performance evaluation testing, we found that the proposed method can stably and rapidly display friction force. Also, we developed a virtual reality (VR) walk-through system that is able to present the friction force through the proposed device according to the avatar's walking motion in a virtual world. By evaluating the realism, we found that the proposed device can represent a more realistic advancing feeling than vibration feedback.

Novel electronic braking system design for EVS based on constrained nonlinear hierarchical control

Both environment protection and energy saving have attracted more and more attention in the electric vehicles (EVs) field. In fact, regarding control performance, electric motor has more advantages over conventional internal combustion engine. To decouple the interaction force between vehicle and various coordinating and integrating active control subsystems and estimate the real-time friction force for Advanced Emergency Braking System (AEBS), this paper’s primary intention is uniform distribution of longitudinal tire-road friction force and control strategy for a Novel Anti-lock Braking System (Nov- ABS) which is designed to estimate and track not only any tire-road friction force, but the maximum tire-road friction force, based on the Anti-Lock Braking System (ABS). The longitudinal tire-road friction force is computed through real-time measurement of breaking force and angular acceleration of wheels. The Magic Formula Tire Model can be expressed by the reference model. The evolution of the tire-road friction is described by the constrained active-set SQP algorithm with regard to wheel slip, and as a result, it is feasible to identify the key parameters of the Magic Formula Tire Model. Accordingly, Inverse Quadratic Interpolation method is a proper way to estimate the desired wheel slip in regards to the reference of tireroad friction force from the top layer. Then, this paper adapts the Nonlinear Sliding Mode Control method to construct proposed Nov-ABS. According to the simulation results, the objective control strategy turns out to be feasible and satisfactory.

Simulation of Permanent Deformation in High-Modulus Asphalt Pavement with Sloped and Horizontally Curved Alignment

This study aims to evaluate the permanent deformation of high-modulus asphalt pavement in special road using viscoelastic theory. Based on the creep test, the Prony series representation of Burgers model parameters for different asphalt mixtures were obtained and used in the deformation simulation of a high-modulus asphalt pavement situated in a horizontally curved ramp. The orthogonal design method was used to show the effect of different factors on the deformation. Results reveal that rutting in curved ramp was greater than in straightaway. Further, evident upheaval was found on the downhill pavement surface and outer pavement parts of the curve due to longitudinal friction force and sideway force. In addition, the upper and middle asphalt courses in such road seemed more crucial to pavement anti-rutting performance, since inclusion of shear force changed pavement deformation characteristic and the potential rutting area tended to move up. Finally, a preliminary equation to predict rutting in sloped and curved road with widely accepted pavement structure in China was proposed.

Modeling and Simulation of the Motorcycle's Lowside Fall

The deployment of active safety systems enhancing the motorcycle stability and supporting riders in defusing critical and dangerous driving situations is a topic of major concern in the two-wheel research community. In the design and development of safety control systems, setting up an adequate model of the controlled system is a key issue since it should be able to describe adequately the motion of the vehicle in critical situations such as precarious adherence, cornering brake and acceleration, or dangerous falls. In literature, these situations are typically investigated by means of black box approaches, namely by using multibody numerical simulators in which the equations governing the vehicle dynamics are unknown. In this paper, instead, the authors propose an analytical model as alternative to black box approach for the simulation of critical and complex motorcycle's dynamics leading to falls. The model has been presented in author's earlier works, it has a minimum degree of complexity, considers the rear wheel traction/braking and takes into account the interactions between longitudinal and lateral friction forces acting on the tyres. This analytical model has allowed to investigate the lowside phenomenon and the simulation results will be presented.

The Physics of DNA in Confinement

Throughout all kingdoms of life, DNA is found to form compact structures. DNA is neatly wound inside a viral capsid, DNA forms hierarchical structures in cell nuclei, DNA could even be woven into complex 3D structures known as DNA origami. Such a ubiquitous compaction is surprising, as it contradicts, at the first look, the very basic physical properties of DNA: the high electrostatic charge and resistance to bending at the scale of 50 nm or less. Experimental work has shown that counterions surrounding DNA can considerably alter its properties, for example, turning electrostatic self-repulsion into attraction. Yet, elucidating the precise microscopic structure and mechanism of DNA-DNA interaction in confined environment remains beyond the experimental capability. Here, we report the results of all-atom molecular dynamics simulations that investigated the microscopic structure of dense DNA assemblies and the physics of interactions that makes such assemblies possible. First, we show that a refined parameterization of ion-DNA interaction [1] permits the all-atom MD method to quantitatively reproduce experimentally known properties [2,3] of dense DNA arrays. Next we characterize the microscopic structure of the arrays, elucidating their ionic atmosphere, preferred azimuthal orientation of DNA molecules, the pair-wise additivity of DNA-DNA forces, the longitudinal friction forces between DNA molecules, and the role of solvation force. Our study demonstrates the ability of all-atom molecular dynamics simulations to provide quantitative, accurate information about dense DNA systems, opening exciting opportunities for future work in the area of synthetic DNA nanostructures, DNA packaging in viral capsids and cell nuclei.[1] J Phys Chem Lett 3:45-50.[2] Proc Natl Acad Sci U S A 81:2621-2625.[3] Biophys J 94:4775-82.

Vehicle Velocity and Roll Angle Estimation with Road and Friction Adaptation for Four-Wheel Independent Drive Electric Vehicle

Vehicle velocity and roll angle are important information for active safety control systems of four-wheel independent drive electric vehicle. In order to obtain robustness estimation of vehicle velocity and roll angle, a novel method is proposed based on vehicle dynamics and the measurement information provided by the sensors equipped in modern cars. The method is robust with respect to different road and friction conditions. Firstly, the dynamic characteristics of four-wheel independent drive electric vehicle are analyzed, and a four-degree-of-freedom nonlinear dynamic model of vehicle and a tire longitudinal dynamic equation are established. The relationship between the longitudinal and lateral friction forces is derived based on Dugoff tire model. The unknown input reconstruction technique of sliding mode observer is used to achieve longitudinal tire friction force estimation. A simple observer is designed for the estimation of the roll angle of the vehicle. And then using the relationship, the estimated longitudinal friction forces and roll angle, a sliding mode observer for vehicle velocity estimation is provided, which does not need to know the tire-road friction coefficient and road angles. Finally, the proposed method is evaluated experimentally under a variety of maneuvers and road conditions.

Nonlinear tire-road friction control based on tire model parameter identification

A hierarchical control structure is a more suitable structural scheme for integrated chassis control. Generally, this type of structure has two main functions. The upper layer manages global control and force allocation, while the bottom layer allocates realized forces with 4 independent local tire controllers. The way to properly allocate these target forces poses a difficult task for the bottom layer. There are two key problems that require attention: obtaining the nonlinear time-varying coefficient of friction between the tire and different road surfaces and accurately tracking the desired forces from the upper layer. This paper mainly focuses on longitudinal tire-road friction allocation and control strategies that are based on the antilock braking system (ABS). Although it is difficult to precisely measure longitudinal tire-road friction forces for frequently changing road surface conditions, they can be estimated with a real-time measurement of brake force and angular acceleration at the wheels. The Magic Formula model is proposed as the reference model, and its key parameters are identified online using a constrained hybrid genetic algorithm to describe the evolution of tire-road friction with respect to the wheel slip. The desired wheel slip, with respect to the reference tire-road friction force from the top layer, is estimated with the inverse quadratic interpolation method. The tire-road friction controller of the extended anti-lock braking system (Ext-ABS) is designed through use of the nonlinear sliding mode control method. Simulation results indicate that acceptable modifications to changes in road surface conditions and adequate stability can be expected from the proposed control strategy.

Adhesion and size dependent friction anisotropy in boron nitride nanotubes

The frictional properties of individual multiwalled boron nitride nanotubes (BN-NTs) synthesized by chemical vapour deposition (CVD) and deposited on a silicon substrate are investigated using an atomic force microscope tip sliding along (longitudinal sliding) and across (transverse sliding) the tube’s principal axis. Because of the tube’s transverse deformations during the tip sliding, a larger friction coefficient is found for the transverse sliding as compared to the longitudinal sliding. Here, we show that the friction anisotropy in BN-NTs, defined as the ratio between transverse and longitudinal friction forces per unit area, increases with the nanotube–substrate contact area, estimated to be proportional to (LNTRNT)1/2, where LNT and RNT are the length and the radius of the nanotube, respectively. Larger contact area denotes stronger surface adhesion, resulting in a longitudinal friction coefficient closer to the value expected in the absence of transverse deformations. Compared to carbon nanotubes (C-NTs), BN-NTs display a friction coefficient in each sliding direction with intermediate values between CVD and arc discharge C-NTs. CVD BN-NTs with improved tribological properties and higher oxidation temperature might be a better candidate than CVD C-NTs for applications in extreme environments.

Development of traction control for front-wheel drive in-wheel motor electric vehicles

This paper proposes a novel traction control for a front–wheel drive in–wheel motor electric vehicle. The presented vehicle has advantages on high fuel efficiency and cost effectiveness. In order to achieve specific control performance, this study employed a high speed microcontroller as the vehicle's electronic control unit. The anti–skid function based on a reliable traction control kernel is embedded in the system, which can guarantee the steering safety in a slippery and dangerous situation. This study verifies that the traction control based on maximum torque regulation cannot only constrain the slip to improve the longitudinal friction force and lateral friction force, but also provide some information on tyre–road conditions, which can ensure the performance and the effectiveness of two–dimensional motion control. The numerical simulation and demonstration video reveal its effectiveness and feasibility.

The Friction Force Mouse-Pad and the Forearm Muscles Efforts

The objective of the article is to evaluate the impact of the friction force mouse-pad in the contraction level of the forearm muscles M. extensor carpi ulnaris, M. extensor digitorum and M. extensor carpi radialis longus. A standard protocol of mouse movements was performed involving horizontal, vertical and diagonal mouse displacements drag-anddrop type. The operators were instructed to execute the protocol with their normal working speed. The movements protocol were performed by each subject (n=17) with three selected pairs mouse-pad, classified as low, medium and high friction force pairs. The mean time to execute the protocol with each mouse was ~138 s. Mean values of ~13%MVE (Maximum Voluntary Electromyography signal), ~17%MVE and ~10%MVE were found in the M. extensor digitorum, M. extensor carpi ulnaris and in the M. extensor carpi radialis longus respectively when performing the movements’ protocol. A 8.1% increase in %MVE was observed in the M. extensor digitorum and a 9.4% increase in %MVE was observed in the M. extensor carpi ulnaris when the high friction force pair was operated, relatively to the low friction force pair (p<0.05). The main conclusions of this study is that operating a high friction force mouse-pad (with 79 g of static longitudinal friction force measured with a compression force of 100 g on the mouse) may increase the risk to symptoms or disorders in the wrist, particularly during work with drawing applications, due to an increase in the forearm muscles contraction levels.

Dynamical Analysis of Motorcycle by Multibody Dynamics Approach

In this paper, a dynamical model of a motorcycle, which consists of four rigid bodies with nine degrees of freedom, is presented. In this model, the cross-sectional shape of the tire is described as a half-circle and its deformation is taken into account. By taking account of the tire slip condition or the tire nonslip condition in the longitudinal direction of the wheels, each equation of motion is derived. Also, by carrying out simulations, it is verified that the responses to the front steering impulsive torque are in good agreement with the results obtained using commercial software. Moreover, the longitudinal friction force and the lateral force in a turning maneuver are analyzed.

Dynamical Analysis of Motorcycle by Using Multibody Dynamics Theory

In this paper, we present an equation of motion for a motorcycle based on the multibody dynamics analysis assuming that the motorcycle consists of four rigid parts with nine degrees of freedom. In this model the cross-sectional shape of the tire is described as a half circle and its deformation is taken into account. Also by taking account of the slip condition or the nonslip condition of tires in longitudinal direction of wheels, the each equation of motion is derived. By carrying out simulations it is verified that the responses to the front-steering impulsive torque are in good agreement with those of a marketed software. Also longitudinal friction force and side force in the turning maneuver are shown.

Development of a Peristaltic Crawling Robot Based on Earthworm Locomotion

Earthworm locomotion, called peristaltic crawling, requires less space than other types of movement, making it practical across irregular ground and inside narrow areas such as pipes and a thus a candidate for use with rescue and exploration robots. We developed a multiple-segment peristaltic crawling robot that uses servomotors. We discuss the basics of locomotion patterns, e.g., the length of longitudinal waves, period, friction force, and number of segments. We confirmed that robot movement resembled that of an actual earthworm and found in experiments that an appropriate period exists for the robot’s peristaltic crawling and that speed tends to decrease with decreasing friction force.

A 3D Brush-type Dynamic Tire Friction Model

The use of advanced dynamic friction models can improve the brush-type tire friction models. This paper presents a 3D dynamic brush model based on the LuGre friction model. The model describes the dynamics of longitudinal and lateral tire friction forces, as well as the self aligning torque dynamics. It has been originally derived in a distributed-parameter form, and then transformed to a simpler lumped-parameter form with only three internal states. Both uniform and non-uniform normal pressure distributions are considered. The model has analytical solution for steady-state conditions. The steady-state behavior is validated with respect to “magic” formula static model, which served as an “ideal” benchmark. The lumped model dynamic behavior is validated by comparing its time-responses with original distributed model responses. The model parameterization with respect to normal force and other tire/road parameters is considered as well.

Applying the contact element for simulation of interaction between drillstring and holewall

The purpose of research is to create a contact element in order to simulate the dynamics contact phenomenon of drillstring and drillhole. The contact element is located at some selected node along the drillstring. In the contact element, not only transverse friction force but also the longitudinal friction forces are taken into account. The element stiffness and damping matrices are derived explicitly. This element is implemented in general and powerful multi-body dynamics analysis software, namely Mecano module of Samcef. Therefore, many computational aspects of the Mecano software, for example the nonlinear beam element, the implicit time integration method, can be directly applied.

Further results and evaluation of electron cooling experiments at LEAR

First electron cooling experiments were performed with 10 7 to 2×10 9 stored antiprotons of 50, 21 and 6 MeV at the Low Energy Antiproton Ring (LEAR) at CERN. Most effort was put into the study of the longitudinal cooling. Schottky pick-up signals were used to measure the equilibrium momentum spread and the longitudinal cooling time. From the equilibrium between stochastic heating and electron cooling the longitudinal friction force in the low 10 3 m/s relative velocity range could be deduced. This method was used also to increase the cooling force by improving the alignment between the antiproton and the electron beam. Some of the experimental data are compared with results of a simulation program for electron cooling (SPEC).

On the deceleration of ions in a magnetized electron stream

Within the framework of the logarithmic approximation the longitudinal friction force for positively and negatively charged ions inside a magnetized electron beam has been calculated. Limitations on the magnitude of the friction force caused by the space charge of the cooling beam is discussed.