Reaction Force Model Research Articles

A ground reaction force model of speed skating based on non-contact measurement system

Accurate collection and analysis of ground reaction force (GRF) data are crucial for optimizing the technical movements of speed skaters; however, it has been a challenge for the limitations of experimental equipment and application scenarios. Therefore, we proposed a novel approach for estimating GRF based on kinematics obtained from markerless video tracking systems and achieved low errors compared with the experimental data. Our method allows for further biomechanical analysis, including muscle force and power, during speed skating competitions.

Assessment of a two-mass ground reaction force model applied to indoor overground running in adult recreational runners

Outdoor running kinetic measurements like vertical ground reaction force (vGRF) need simple and accurate models. A previous study assessed a two mass model (2MM) on an athletic adult population during treadmill running, but not recreational adults during overground running. The objectives were to compare accuracy of the overground 2MM and an optimized version to the reference study and force platform (FP) measurements. Overground vGRF, ankle position, and running speed were collected on 20 healthy subjects in a laboratory. The subjects ran at three self-selected speeds and with an opposite foot strike strategy. Reconstructed 2MM vGRF curves were calculated with the original parameter values (Model1), with parameters optimized each strike (ModelOpt), and with group-based optimal parameters (Model2). Root mean square error (RMSE), optimized parameters, and ankle kinematics were compared to the reference study; peak force and loading rate were compared to FP measurements. The original 2MM showed decreased accuracy with overground running. ModelOpt overall RMSE was lower than Model1 (p > 0.001, d = 3.4). ModelOpt overall peak force was different but most like FP signals (p < 0.01, d = 0.7) and Model1 was most different (p < 0.001, d = 1.3). ModelOpt overall loading rate was similar to FP signals and Model1 was different (p < 0.001, d = 2.1). Optimized parameters were different (p < 0.001) from the reference study. 2MM accuracy was largely attributable to curve parameter choice. These may be dependent on extrinsic factors like running surface and protocol and intrinsic factors like age and athletic caliber. Rigorous validation is needed if the 2MM is to be used in the field.

Particle dynamics governed by radiation losses in extreme-field current sheets.

Particles moving in current sheets under extreme conditions, such as those in the vicinity of pulsars or those predicted on upcoming multipetawatt laser facilities, may be subject to significant radiation losses. We present an analysis of particle motion in model fields of a relativistic neutral electron-positron current sheet in the case when radiative effects must be accounted for. In the Landau-Lifshitz radiation reaction force model, when quantum effects are negligible, an analytical solution for particle trajectories is derived. Based on this solution, for the case when quantum effects are significant an averaged quantum solution in the semiclassical approach is obtained. The applicability region of the solutions is determined and analytical trajectories are found to be in good agreement with those of numerical simulations which account for radiative effects. Based on these results we demonstrate that radiation reaction itself can provide a mechanism of pinching even within a given field consideration.

Modeling Soil Forces on a Rotary Tine Tool in Artificial Soil

HighlightsA mathematical model of soil reaction forces on a rotary tine tool was developed.Soil bin experiments using artificial soil enabled observation of soil failure due to soil-tine interaction.The model-predicted forces were similar to experimentally measured forces.Abstract. Understanding soil-tool interaction can enable better control of weeding tools to achieve higher weeding efficacy. The interaction between a vertical tine (mounted on a rotating disc) and soil was investigated using a mathematical model that estimated soil horizontal forces on the tine operating at different linear and rotational velocities. The kinematics associated with the linear and rotational velocities of the rotary tine tool were modeled, and the shearing and inertial forces were estimated. To evaluate model performance with different experimental factors, two sets of soil bin experiments were conducted using an artificial soil: with one tine to estimate model parameters and with two tines 180° apart. Experimental factors were longitudinal velocity (travel speed) at three levels (0.09, 0.29, and 0.5 m s-1) and speed ratio, i.e., the ratio of longitudinal velocity to peripheral velocity of the tines, at three levels (1, 1.5, and 2). Soil horizontal force and torque on the rotary tine tool were measured. A nonlinear least squares method was used to estimate model parameters from the experimental data, resulting in shearing force coefficients ranging from 2.9 to 37 N and inertial force coefficients ranging from 16 to 528 N s2 m-2. The variations in the shearing and inertial forces on the tine were due to differences in soil failure patterns among the treatments. The predicted longitudinal and tangential forces for two tines using the model showed trends that were similar to the forces measured in the experiment. However, the model overestimated the predicted forces because it did not account for the reduced force on a tine due to soil disturbance created by the other tine. Keywords: Soil-tine interaction, Weed control.

Anisotropic Reaction Force Model in Two-way Coupling Simulation for a Smaller Particle Than Grid Spacing Based on Volume Averaging

In the framework of local volume-averaging for two-way coupling simulation of particle-laden flows, we have developed a force model that represents the particle reaction to the fluid. By considering the stress profile on the surface of finite size particles, our previous model was capable of representing the reaction force distribution even without fully resolving the boundary layer around the particle of comparable size to the grid spacing. In our method, the anisotropy of the surface stress is reasonably taken into account in the reaction force. To extend the applicability for particles smaller than the grid spacing, a smoothing method is developed in a consistent way with the discretization of the numerical simulation. The effectiveness of the smoothing method is demonstrated by applying to the following four fundamental fluid-particle interaction problems; a stationary particle in a uniform flow, a moving particle in a vortical flow, a rotating particle in fluid at rest and a particle suspension in a shear flow. The anisotropic contribution of the reaction force is reasonably represented by the smoothing method applied to the volume averaging technique particularly for rotating particle case. For the suspension in the shear flow, the non-physical effect of the grid size is suppressed by the smoothing method. Therefore, the developed reaction force model is effective for the case that the effects of shear and rotation are dominant.

Theoretical Study of the Mechanism of Catalytic Enanteoselective N-H and O-H Insertion Reactions.

Theoretical density functional theory (DFT) calculations were carried out to study bond insertion reactions using a copper(I)-Box-carbenoid as a bond activator. In order to understand the reaction mechanism where N-H and O-H bonds actively participate, the reaction force (RF) and activation strain model (ASM) were used. Results indicate that the first step of the reaction is barrierless for both bond insertions (N-H and O-H), and the second step of the insertion reaction in the phenol (O-H bond) is favored kinetically and thermodynamically with regard to the aniline substrate (N-H bond). The enantioselectivity is driven by the ligand of the catalyst by steric repulsion, favoring the formation of the R isomer. The analysis of the reaction force and ASM exhibited that the higher energy barrier in aniline is mainly due to a higher W2 contribution together with repulsive interactions, which hinders the insertion process.

Bucket Trajectory Optimization under the Automatic Scooping of LHD

We propose an optimal planning scheme of the bucket trajectory in the LHD (Load-Haul-Dump) automatic shoveling system to improve the effectiveness of the scooping operation. The research involves simulation of four typical shoveling methods, optimization of the scooping trajectory, establishment of a reaction force model in the scooping process and determination of optimal trajectory. Firstly, we compared the one-step, step-by-step, excavation and coordinated shoveling method by the Engineering Discrete Element Method (EDEM) simulation. The coordinated shoveling method becomes the best choice on account of its best comprehensive performance among the four methods. Based on the coordinated shoveling method, the shape of the optimized trajectory can be roughly determined. Then, we established a model of bucket force during the shoveling process by applying Coulomb’s passive earth pressure theory for the purpose of calculating energy consumption. The trajectory is finally determined through optimizing the minimum energy consumption in theory. The theoretical value is verified by the EDEM simulation.

Experimental study on the control form of fin stabilizer at zero speed.

The zero-speed fin stabilizer is used to stabilize the roll motion of the ship at full speed. It has two working modes, that is the lift-based normal anti-rolling mode and the drag-based zero-speed anti-rolling mode. Different force generation mechanisms cause different control methods, especially in the form of control. The zero-speed fin stabilizer works in a sinusoidal fashion in normal mode, the same as the conventional fin stabilizer. However, its control form at zero speed is not particularly clear. This paper aims to investigate the control form of fin stabilizer at zero speed through a composite method of theoretical analysis and experimental research. Based on the established reaction force model, the forces generated on the fin flapped in sinusoidal and trapezoidal forms are compared and analyzed. It is found that the trapezoidal form flapping with a small half-cycle ratio generates larger force than the sinusoidal flapping form when the flapping amplitude is the same. The forced rolling tank tests with the fins flapping in sinusoidal and trapezoidal forms were conducted. The test results are consistent with the theoretical analysis results, and the trapezoidal flapping form with a proper small half-cycle ratio is recommended for fin stabilizers at zero speed. The control strategy of fin stabilizer at zero speed is obtained based on the further analysis of the force characteristics of the trapezoidal flapping form and the limitations of the actual fin stabilizer actuation system. The model and full scale roll reduction tests at zero speed were conducted, achieving more than 70% and 60% of the anti-rolling effect respectively. The test results further verify the effectiveness, applicability and practicability of the obtained control form and strategy for fin stabilizers in at-anchor conditions, and can be a reference for engineering practice and other similar studies.

Numerical modelling of seabed impact effects on chain and small diameter mooring cables

Catenary mooring lines experience liftoff from and grounding on the seabed when undergoing large dynamic motions. Numerical line mooring models account for this interaction using various seabed models and it is known that the action of liftoff and grounding may lead to large dynamic tension fluctuations. These fluctuations may be spurious due to the inability of discretised mooring models to adequately account for the effect of the seabed on the mooring line. In this work, the root cause and conditions that lead to the production of the large dynamic tension fluctuations is determined. The effect of line discretisation and seabed model on the tension fluctuations is investigated using the widely used spring-mattress approach and a modified seabed reaction force model. An in-house mooring code was developed to perform these investigations. For code validation and benchmarking, and to illustrate the existence of the tension fluctuations problem due to nodal grounding in existing mooring line simulation codes, comparisons are made to a commercial software.

Molecular hydrogen formation in the interstellar medium: the role of polycyclic aromatic hydrocarbons analysed by the reaction force and activation strain model

The formation of H2 onto pyrene (from hydrogen atoms) was studied in the framework of the Eley–Rideal mechanism, which was fully analysed for all the adsorption sites of pyrene. The structural and electronic contributions to the activation energies were characterized through the reaction force and activation strain model (ASM). The reaction force indicates that the activation process of the hydrogen chemisorption is dominated by the structural rearrangements of reactants rather than by electronic reordering. Furthermore, the ASM shows that the structural rearrangements are driven by the approach of hydrogen to the pyrene surface, which generates a strong repulsive interaction. However, the changes in the geometry of the surface generate a minimal increase of the total energy, being negligible at the absorption sites at the edge of the surface. For that reason, the process is most kinetically favoured at the edge sites, which have lower activation energies (∼1–3 kcal mol–1) than the internal ones (∼6 kcal mol–1). On the other hand, the recombination of hydrogen atoms for the subsequent H2 formation is a barrier-less process, no matter the adsorption site of the carbonaceous surface. The ASM analysis shows that the attractive interactions take place at the beginning of the recombination process, they avoid that the energy barrier can be generated by structural distortions. Both the chemisorption and the abstraction of the adsorbed hydrogen atom by an incoming H atom, throughout the entire surface, are highly exoenergetic processes, with reaction energy values in the range of −12 to −36 kcal mol–1 and −84 to −60 kcal mol–1, respectively.

A New Structural Dynamic Model for Pump Mechanical Seals Vibration Analysis Incorporating Squeeze Motion of O-Ring Seals and General Dynamic Motion of the Pump Housing and the Pump Shaft

New models are developed for flexibly mounted stator (FMS) and flexibly mounted rotor (FMR) mechanical seals that incorporate the radial reaction force components produced by supporting O-rings due to relative squeezing motion across the O-rings. Supporting data come from tests done in relation to O-ring supports for ball bearing races. The reaction-force model is linear but a nonlinear function of excitation frequency. The model accounts for the axial displacement doz of the O-ring from the mass center of the seal stator (FMS configuration) or seal rotor (FMR configuration), which couples the radial and pitch–yaw motion of the model's stiffness and damping matrices. Greens' coned-face-seal model is used to define the reaction moment arising across the seal faces via stiffness and damping matrices. The damping matrix does not coincide with Green's. His is constant; the matrix developed here contains terms that are harmonic at twice theprecession frequency. When averaged over one precession cycle, the new average damping matrix coincides with Green's result. When the averaged damping matrix is used, the resultant model is linear. However, because of the viscoelastic reaction-force and reaction-moment models used for the O-ring coefficients, most of the stiffness and damping matrices are strong functions of the assumed precession frequency. The new FMR model contains a skew-symmetric stiffness matrix due to the O-ring damping terms. In rotordynamics, skew symmetric stiffness matrices due to internal damping in the rotor can lead to rotordynamic instabilities.

Anesthesia safety in progressive leukodystrophies: A retrospective study of patients with Krabbe disease and metachromatic leukodystrophy undergoing general anesthesia

Catenary mooring lines experience liftoff from and grounding on the seabed when undergoing large dynamic motions. Numerical line mooring models account for this interaction using various seabed models and it is known that the action of liftoff and grounding may lead to large dynamic tension fluctuations. These fluctuations may be spurious due to the inability of discretised mooring models to adequately account for the effect of the seabed on the mooring line. In this work, the root cause and conditions that lead to the production of the large dynamic tension fluctuations is determined. The effect of line discretisation and seabed model on the tension fluctuations is investigated using the widely used spring-mattress approach and a modified seabed reaction force model. An in-house mooring code was developed to perform these investigations. For code validation and benchmarking, and to illustrate the existence of the tension fluctuations problem due to nodal grounding in existing mooring line simulation codes, comparisons are made to a commercial software.

Analysis of trident strider robot based on a simple reaction force model

Analysis of trident strider robot based on a simple reaction force model

Uncertainty reaction force model of ship stern bearing based on random theory and improved transition matrix method

Stern bearing is a key component of marine propulsion plant. Its environment is diverse, working condition changeable, and condition severe, so that stern bearing load is of strong time variability, which directly affects the safety and reliability of the system and the normal navigation of ships. In this paper, three affecting factors of the stern bearing load such as hull deformation, propeller hydrodynamic vertical force and bearing wear are calculated and characterized by random theory. The uncertainty mathematical model of stern bearing load is established to research the relationships between factors and uncertainty load of stern bearing. The validity of calculation mathematical model and results is verified by examples and experiment yet. Therefore, the research on the uncertainty load of stern bearing has important theoretical significance and engineering practical value.

Force modeling for incisions into various tissues with MRF haptic master

This study proposes a new model to predict the reaction force that occurs in incisions during robot-assisted minimally invasive surgery. The reaction force is fed back to the manipulator by a magneto-rheological fluid (MRF) haptic master, which is featured by a bi-directional clutch actuator. The reaction force feedback provides similar sensations to laparotomy that cannot be provided by a conventional master for surgery. This advantage shortens the training period for robot-assisted minimally invasive surgery and can improve the accuracy of operations. The reaction force modeling of incisions can be utilized in a surgical simulator that provides a virtual reaction force. In this work, in order to model the reaction force during incisions, the energy aspect of the incision process is adopted and analyzed. Each mode of the incision process is classified by the tendency of the energy change, and modeled for realistic real-time application. The reaction force model uses actual reaction force information with three types of actual tissues: hard tissue, medium tissue, and soft tissue. This modeled force is realized by the MRF haptic master through an algorithm based on the position and velocity of a scalpel using two different control methods: an open-loop algorithm and a closed-loop algorithm. The reaction forces obtained from the proposed model are compared with a desired force in time domain.

Strength calculation considering structural stiffness coupling of shaft bracket

In this paper, the current specification concerning strength computing theory of shaft bracket is analyzed, and it is seen that structural stiffness coupling is not considered in this theory. In the view of the shaft bracket structural and mechanical features, the reaction force model of shaft brackets considering structural stiffness coupling is established, and the calculation formulas for the internal forces of the shaft brackets are derived, and the parameters of the generalized stiffness ratio describing the structure stiffness coupling effects is defined. Taking shaft brackets of a certain boat as an example, the quantitative calculation on FEM simulation, the computing theory presented in this paper, and the conventional computing theory without considering structural stiffness coupling are applied, respectively. In addition, the computing method on torsional rigidity of shaft brackets is also put forward. The results show that the computing theory of this paper agrees well with the FEM simulation, while the conventional theory deviates far from the FEM simulation performance. Moreover, the conventional theory yields larger result, which further worsens with the enlargement of the generalized stiffness ratio, causing the overly design of the shaft bracket structure strength. In brief, the computing theory proposed in this paper serves as great guidance to the optimization in the strength design of the shaft bracket structure.

Locomotion of a Running Quadruped Robotic System

Very little is known about the locomotion of quadruped robotic systems. In Latin, the term quadruped means 'having four feet'. The robotic system analyzed in this project was a software simulation program modeled after a horse. Simulation data was recorded to resolve the relationship between foot position and impulses required to accelerate or to decelerate the system while trotting. These sets of data were then analyzed in MATLAB to produce graphical representations which allowed for a better understanding of the robot's motion in the simulation environment. A function was fit to the graph of discrete data values measured in the simulation. This function provided a model of the necessary ground reaction forces and foot position at touchdown of the system.

Efficient Scooping of Rocks by Autonomous Controlled Wheel Loader

We propose a method for the efficient scooping of sediment by a wheel loader. We performed experiments to verify the effectiveness of the proposed method. First, in order to calculate the energy required for the scooping operation, we derived a model of the reaction force that is generated on the bucket. We verified the validity of the model by experiments. We then used the reaction force model to determine the optimal trajectory for the bucket. A mechanical simulator was used to verify the trajectory. Although experimental results showed the unexpected effects of sediment that settled inside the bucket, we obtained results that reflect theoretical values.

Development of a method for quantifying the midsole reaction model parameters

Midsole force–deformation pattern has important implications in determining the kinematics and kinetics of foot during locomotion. Furthermore, the midsole stiffness and viscosity determine the midsole's force–deformation behaviour. Despite the importance of stiffness and damping components of the midsole reaction, which determines the shoe-specific ground reaction forces during locomotion, there is still a lack of methodology to quantify them separately. The purpose of this study was to develop a method of extracting the shoe-specific midsole stiffness and damping components during uniaxial compression testing. For this purpose, the force–deformation behaviour of the sole was modelled as a system consisting of a nonlinear spring and a nonlinear damper. Based on the fact that the stiffness and damping component of the midsole reaction force acts in favour during loading, and work against each other during unloading, the stiffness and damping components were separated. Utilising a curve-fitting technique, a parametric curve represented by the stiffness and damping components of the midsole reaction force model was fitted to each components of force-deformation data to extract the parameters. Statistical tests indicated that the proposed method is reliable for extracting the midsole reaction model parameters with the stiffness and damping components producing favorable results (R2 0.998 ± 0.000 and 0.984 ± 0.018/root mean squared error of 5.550 ± 0.954 and 3.286 ± 2.504, respectively).

Calculation of Settlement of Composite Foundation with Rigid Piles under Flexible Ground

According to the character of the interaction of the pile, soil and cushion in composite foundation by fitting the vertical relative displacement distribution function of pile-soil element and introducing an elastic-plastic load transfer model, and deformation form of the pile-soil relative displacement, friction variation of pile, and pile-side soil reaction force model were simplified to a certain degree, and a basic differential equation of settlement calculation of the rigid pile composite foundation was established with consideration of both upward and downward penetration displacements of piles and the coordination of deformation of neutral point and the pile-soil interface. Then, a new method of calculating the settlement of the rigid pile composite foundation considering the interaction of pile-soil-cushion system was developed. At last, this new method was applied to the analysis of a model experiment and a project example, and the results show that (1) there exist great difference between the deformation mode and pile-soil stress ratio of rigid pile composite foundation under flexible ground and those under rigid ground; (2) the calculated results are close to the measured values. This method can reduce the calculation and provide a reference for the settlement calculation of rigid pile composite foundation.