Force Motion Research Articles

Piezo-Capacitive Flexible Pressure Sensor with Magnetically Self-Assembled Microneedle Array.

Flexible pressure sensors are pivotal in advancing artificial intelligence, the Internet of Things (IoT), and wearable technologies. While microstructuring the functional layer of these sensors effectively enhances their performance, current fabrication methods often require complex equipment and time-consuming processes. Herein, we present a novel magnetization-induced self-assembly method to develop a magnetically grown microneedle array as a dielectric layer for flexible capacitive pressure sensors. By precisely controlling the magnetic particle concentration and dynamic magnetic field strength, we achieve a tunable microneedle morphology. The resulting sensor exhibits high sensitivity (4.11 kPa-1), an ultrafast response time (20 ms), excellent cyclic stability (≈1700 cycles), and flexibility. We demonstrate real-time monitoring of various physiological signals including pulse, grip force, breathing rate, and head motion. This study introduces a promising approach for fabricating high-performance flexible sensors, potentially enabling more intuitive and effective human-machine interactions.

Design of a Freely Accessible Web Application (Instrument for the Measurement of Balance in Primary Education, IMEP) for the Assessment of Static and Dynamic Balance in Children Aged 6-9 Years Based on Force Platforms.

Background: The proper development of balance is essential in the acquisition of a correct physical condition, as well as in the evolutionary follow-up at early ages, and its periodic evaluation is very relevant in the educational environment. Objectives: The objective of this research was to design an accessible web application for static and dynamic balance assessment, based on a force platform and motion analysis software. Methods: The Single leg balance test (SLB), Tandem balance test (TBT), and Y balance test (YBT) were performed on a sample of 75 children aged 6 to 9 years. Results: The results show that static balance is more complex at an older age, greater standing height, and with eyes closed (p < 0.001). Regarding the center of pressure (COP), its variability was greater in girls owing to a lower Total Force (TF) at the time of the test (p < 0.05). Parallel observation with the Kinovea software has made it possible to elaborate a scale from 1 to 10 points for integration into an open-access web application (IMEP) to assess static and dynamic balance. Conclusions: The creation of an ad hoc application for primary school teachers and students has been possible by using validated devices obtaining a rating scale, which facilitate the monitoring of students' functional evolution and offers the possibility of scheduling physical education sessions with a preventive approach as well as a focus on improving physical condition.

Test particles in Kaluza-Klein models

Abstract Geodesics in general relativity describe the behaviour of test particles in a gravitational field. In 5D Kaluza-Klein, geodesics reproduce the Lorentz force motion of particles in an electromagnetic field. This paper studies geodesic motion on a higher-dimensional M4 × K with background metrics encoding general 4D gauge fields and Higgs-like scalars. It shows that the classical mass and charge of a test particle become variable quantities when the geodesic traverses regions of spacetime with massive gauge fields, such as the weak force field, or with non-constant Higgs scalars. This agrees with the physical fact that interactions mediated by massive bosons can change the mass and charge of particles. The variation rates of mass and charge along a geodesic are given by natural geometric formulae. In regions where mass is preserved, there are additional constants of motion, one for every abelian or simple summand in the Killing algebra of K. The last part of the paper discusses traditional difficulties of Kaluza-Klein models, such as the low q/m ratios in the 5D model. It suggests possible ways to circumvent them. It also remarks the naturalness of a model where elementary particles always travel at the speed of light in higher dimensions.&amp;#xD;

Balance Board or Motion Capture? A Meta-Analysis Exploring the Effectiveness of Commercially Available Virtual Reality Exergaming in Enhancing Balance and Functional Mobility Among the Elderly.

Force platforms and motion capture are commonly used as feedback mechanisms in exergaming; nevertheless, their therapeutic effectiveness may vary. Therefore, the primary objective of this study was to evaluate the effectiveness of commercially available virtual reality (VR) exergaming systems on balance and functional mobility, with a supplementary analysis considering the administered dose of exergaming. The search was conducted in five databases. Commercially available exergaming platforms were classified into two categories: VR exergaming with a balance board (including Wii Balance Board) and motion capture (including Xbox Kinect). Two categories of control interventions (treatment as usual [TAU] and no treatment [NT]) were extracted. The meta-analysis was performed separately for static, dynamic, and proactive balance outcomes and for the aggregated results of all included outcomes with subgroup analysis of lower, moderate, and higher doses. In total, 28 studies with 1457 participants were included. Both exergaming systems were particularly effective in improving the single leg stance outcome. VR exergaming with motion capture was found to be more effective than TAU with a standardized mean difference (SMD) of 0.48 (P = 0.006) and NT (SMD = 0.86; P = 0.02). In conclusion, commercially available VR exergaming with a motion capture feedback mechanism has demonstrated effectiveness as an intervention for balance training when compared with NT. Specifically, high doses (above 134 minutes per week) appear to be more beneficial for healthy older adults. Moreover, the findings provide some weak evidence supporting the effectiveness of VR exergaming with a balance board for improving functional mobility, particularly when compared with NT.

Whole Body Control of Mobile Manipulators With Series Elastic Actuators for Cart Pushing Tasks.

Human-centered environments provide affordance for the use of two-handed mobile manipulators. Yet robots designed to function in and physically interact with such environments are not yet capable of meeting human users' requirements. This work proposes a whole body control framework of a two-handed mobile manipulator driven by series elastic actuators (SEAs) for cart pushing tasks. A whole body dynamic model for an integrated mobile platform and on-board arms is revealed, which takes into account the interaction forces with the cart. Then, the explicit force/position control of the mobile manipulator is performed. It enables the robot to interact dynamically with the environment while providing motion, i.e., the manipulators provide both output force control and motion control for pushing a cart. To cope with the highly nonlinear system dynamics and parameter variation of a SEA-driven mobile manipulator, this work proposes an adaptive robust controller based on a novel integral barrier Lyapunov function for cart pushing tasks by considering model uncertainty. The proposed controller enables the mobile manipulator to complete cart pushing tasks by regulating the position and output force of the mobile base and arms. The experimental results show the effectiveness of this approach in cart pushing tasks.

Dynamic coefficient of flexural motion of beam experiencing simple support under successive moving loads

AbstractAnalytic expressions of the dynamic coefficient (DC) factor and vibrational behavior of a uniformly elastic isotropic beam with a simple boundary condition caused by accelerating masses with varying velocities are analyzed. The motion of this problem is described by a fourth‐order partial differential equation, which governs its behavior. The weighted residual method converts the governing equation into a sequence of linked second‐order differential equations to facilitate the analysis. A rewritten version of Struble's asymptotic method further simplifies the transformed governing equation. This modification aids reduction in the complexity of the equation. The closed‐form response is contrasted across three force motions: acceleration, deceleration, and uniform motion. The study thoroughly examines how different velocities and frequencies of the moving force affect the dynamic behavior of the beam. The study also examines the influence of load velocity on the DC of the beam subjected to pinned–pinned boundary conditions.

Numerical Prediction of Two-Dimensional Coupled Galloping and Vortex-Induced Vibration of Square Cylinders Under Symmetric/Asymmetric Flow Orientations

This study presents an advanced numerical model for predicting a two-dimensional coupled galloping and vortex-induced vibration (VIV) in cross-flow and in-line directions of square cylinders under symmetric and asymmetric flow orientations. The present model combines the quasi-steady theory for the galloping with the nonlinear structure-wake oscillators simulating VIV, capturing the time-varying drag and lift hydrodynamic forces with the time-averaged and fluctuating components. By placing a flexibly mounted square cylinder in uniform flow at an initial angle of incidence, the cylinder is subject to instantaneous changes in the dynamic angle of attack accounting for relative flow-structure velocities. Modelling of such features in cross-flow and in-line directions for low and high mass ratio systems extends previous studies which have mostly focused on cross-flow responses of square cylinders with high mass ratios at a zero angle of incidence. New sets of empirical coefficients governing the drag and lift fluid forces for both the quasi-steady and wake oscillator approaches are introduced by calibrating with available experimental data in the literature, applicable to predict several flow-induced vibration phenomena under arbitrary flow-structure orientations. Mathematical criteria for the onset of two- and one-dimensional galloping instability are presented, verifying the likelihood of galloping occurrence. Parametric investigations are carried out to highlight the important effects of flow incidence angle, mass-damping ratio (Scruton number) and in-line response on the prediction of galloping and VIV in comparison with experimental results. By varying the reduced velocity parameter, the present model captures key qualitative features of the dominant galloping, interfering galloping-VIV and dominant VIV through the response amplitudes, mean drift displacements, oscillation frequencies, fluid force components and motion trajectories. Contributions from in-line responses are found to be meaningful for the interfering galloping-VIV system with a low mass-damping ratio and for an asymmetric flow orientation. The present model could be further calibrated and applied to other fluid-structure interaction applications with non-circular cross-sectional geometries under omnidirectional flow directions.

Analysis of Force Distribution and Motion Characteristic of Hybrid-Driven Tensegrity Parallel Mechanism

Abstract Tensegrity parallel mechanisms is a novel spatial structure composed of cable-based and rigid-based chains, which is characterized by lightweight, multi-stability, high precision, good stiffness, and high load-bearing capacity. This paper focuses on the six-degree-of-freedom tensegrity parallel mechanism, analyzing its static equilibrium and presenting the force equilibrium equations. A model for cable tension distribution optimization is established, utilizing different P-norm objective functions to optimize the distribution of tension in cables and rigid links, discussing the reasons for unreasonable tensions in the system. Under given constraints on the motion pairs of the mechanism, the workspace of the mechanism is plotted, and factors influencing the size of the workspace are analyzed. Finally, the singularity of the mechanism is addressed based on the Jacobian matrix, demonstrating the feasibility of reaching the space volume by the mechanism. It has certain reference significance for the configuration theory and analysis methods of tensegrity parallel mechanisms and rigid-flexible coupling mechanisms, and provides a reference for the further promotion and application of mechanisms.

Experimental study on hydrodynamic performance of the semi-submersible vessel-shaped fish cage

Deep-sea net cages play a vital role in expanding offshore farming in modern marine fisheries. In this paper, a model-scale 1:40 tank experiment was conducted for a vessel-shaped truss-structured single-point mooring deep-sea aquaculture net cage. The study focused on the hydrodynamic characteristics, including the effect of current, wave, and net on the mooring force, heave, and pitch motion behaviors. Experimental results indicate that the mooring force increases with the current velocity, draught of the cage, and wave height, but decreases with the wave period increase. Both heave and pitch movements amplitudes increase with wave height. While heave motion amplitude initially declines and then ascends with wave periods, pitch motion shows the opposite pattern. Besides the net has an obvious damping effect on the pitch motion. These results can provide data support for the design and offshore installation of vessel-shaped truss-structured net cages in the future.

Analysis of the seismic fragility of slender piers on prestressed concrete viaducts

This research aims to study the seismic fragility evaluations of slender piers with single-column sections on prestressed concrete viaducts to investigate how pier height, prestressing force, and ground motion intensity are related, not only in terms of mean values but also in their probability density functions (PDFs), which inherently imply parameters such as dispersion indices. A detailed nonlinear numerical analysis was performed using a finite element model that incorporated the realistic response of concrete, steel, and infrm-FB element types for the columns. To this end, fragility curves were developed based on a probabilistic procedure that accounted for the variability of material properties, pier geometry, and seismic loading. The results show that the fragility function of high piers is hardly dependent on the shear span efficiency. Conversely, slender piers exhibit an increased level of fragility when the effect is confined to a constant prestressing force. This study highlights the need to account for the nonlinearity of pier members and variation in seismic loading when estimating the seismic fragility of slender piers. The conclusions of this study are beneficial for designing and retrofitting strategies for prestressed concrete viaducts in seismic regions.

Exploring the use of wearable sensors for assessing risk factors during orthopedic surgeries: A protocol for data collection

During orthopedic surgeries, surgeons are generally exposed to prolonged periods of standing, awkward and sustained body postures, and forceful movements, which can increase the likelihood of developing work-related musculoskeletal disorders (WRMSD). Therefore, this study proposes a protocol to measure parameters related to physical risk factors contributing to lower limb WRMSD, during orthopedic surgery procedures. The protocol development was preceded by an initial phase of understanding and specifying the context of use, followed by pre-tests in laboratory environment. It integrates a motion capture system, using inertial measurement units (IMU) to collect posture data from hip, knee, and ankle, and electromyography system (EMG) to measure and record data from muscle activity of biceps femoris, rectus femoris, and gastrocnemius lateralis. Pre-tests provided insights for protocol optimization, estimating a 3-hour data collection session per surgery due to sensor battery limitations, streamlining the process by placing EMG sensors before IMU and refining thigh sensor placement strategies. The protocol presents an opportunity for a real-time and quantitative approach to monitor surgeon's exposure to risk factors contributing to lower limb WRMSD while performing surgical procedures. Two months after pre-tests, the protocol implementation began in a real work context. The study's final outcomes fall outside the paper's scope.

Dynamic analysis of six-bar tensegrity-based robot

Abstract The tensegrity-based robot is a hot research topic in the research field of robotics. The dynamics of the robot, describing the specific motion patterns under the influence of forces and torques, play an important role in the application of robotics. In addition, the dynamics should be considered when revealing the internal mechanisms of robots and predicting their dynamic behaviors. In this work, a dynamic model for a rolling six-bar tensegrity-based robot is established. In terms of kinematic representation, quaternions are chosen as the tool for attitude description, simplifying the derivation process of the complex three-dimensional rotational kinematics calculations. Quaternions play a crucial role in mathematical processing for robot attitude control and path planning due to their effective representation of three-dimensional space rotations. The classic Newton-Euler dynamic framework was adopted to conduct in-depth and detailed studies on the dynamic characteristics of the robot under various force conditions and motion states, with a particular focus on rolling dynamic analysis. Special attention was paid to the dynamic response mechanisms of each component of the robot under the combined action of internal and external forces and torques.

Effect of side ratio on the two-degrees-of-freedom vortex-induced vibrations of the rectangular cross section model

The effect of the mutative side ratio (D/B) on the vortex-induced vibration (VIV) characteristic, aerodynamic characteristics, and the surrounding time-averaged and transient flow field of a rectangular cross section model were simulated numerically. Based on Fluent 19.0 platform, overset grid technology and the fourth-order Runge–Kutta method were used at Re 22 000. First, a rectangular cross section model with D/B = 0.25 was selected, and the simulation method and parameter settings were validated against previous literatures. The subsequent analysis compared and evaluated the effect of side ratio on the VIV response by focusing on statistical values of aerodynamic force coefficients, self-spectra, amplitude ratio, motion trajectory, and phase transition changes for stream-wise and cross-flow directions. Moreover, the study examined the influence of different models at different reduced velocities (Ur) on wake vortex-shedding. The findings suggest that, within a fixed cross-sectional area, a smaller side ratio leads to a weaker VIV characteristic and notably lower aerodynamic performance compared to a larger side ratio. The vortex-shedding mode of the rectangular cross section, particularly with a large side ratio, is less sensitive to changes in Ur compared to the standard square cylinder. An examination of the Reynolds number (Re) effect on the minimum and maximum side ratio models reveals that it has a more pronounced impact on the aerodynamic performance and VIV of the cross-flow when compared to in-line flow. In general, it is noted that larger side ratio model exhibits a stronger sensitivity to the variation of Re.

Accuracy and Computational Cost Comparison of Numerical Flight Dynamics Reduced-Order Models

This paper compares several approaches to model the unsteady and nonlinear longitudinal aerodynamics of a generic unmanned combat air vehicle configuration based on computational fluid dynamics (CFD). Three different reduced-order models (ROMs) are implemented through unsteady simulations to predict the evolution of forces and moments during prescribed trajectories carried out at M=0.15. The first model investigates a linear quasi-steady model based on a first-order Taylor series expansion of the aerodynamic coefficients. The second one picks up the mathematical formulation of the first model but adds a dynamic coefficient in order to take into account the unsteady effect of rotation rate variations. Finally, the third model is built on indicial functions computed from positive step changes in the angle of attack or pitch rate. The unknown parameters of the first two models and the unknown indicial functions of the third one are obtained, respectively, from the study of forced oscillations and step motions. These prescribed trajectories are performed using unsteady Reynolds-averaged Navier–Stokes simulations coupled with a grid displacement tool. Two different methods are tested and compared to carry out the CFD mesh motions: an overset method and a full moving grid (FMG) method. The indicial functions obtained using the FMG method give results equivalent to those found in the literature in half the time of the overset method. To reduce the computational costs to set up the ROMs, the FMG method is preferred to the overset method. ROMs are then applied, and their predictions are compared with CFD simulations for prescribed trajectories with different angular rates and angles of attack. A study of instantaneous and overall accuracy associated with the implementation cost of the ROMs has allowed to show their strengths and their weaknesses. Similar results are observed at low angles of attack for the ROMs studied, while a major modeling advantage of the indicial method has been identified for higher angles of attack in the nonlinear domain.

Botulinum toxin for the management of bruxism: an overview of reviews protocol

IntroductionBruxism is characterised by a repetitive activity in the masticatory muscles that involves teeth clenching or grinding and/or forceful mandibular movements. Its management is typically initiated when individuals start experiencing...

Assessing lower extremity stiffness in countermovement jumps: a critical analysis of the differences between calculation methods

ABSTRACT Introduction: Stiffness (k) describes a material’s resistance to deformation and is useful for understanding neuromuscular function, performance, and injury risk. The aim of this study is to compare the lower limb stiffness method (k LLS ), which uses only force plate data, with methods combining force plate and motion capture data to calculate stiffness during the eccentric phase of a countermovement. Material and Methods: Twelve resistance-trained males: age 24.9 (4.4) years, height 1.81 (0.05) m, weight 88.2 (14) kg) performed three maximal effort countermovement jumps (CMJ). Data were collected synchronously using three-dimensional (3D) kinematic and kinetic data (dual force plate setup). Lower limb stiffness (z), joint stiffness (x, y, and z), and leg stiffness (linear, sagittal plane, and 3D) were calculated for the eccentric phase of all CMs. Results: k LLS showed high concurrent validity with strong correlations to kinetic-kinematic methods (r = 0.90-0.97, p < 0.05). A linear mixed model revealed no significant differences in k-values between k LLS and leg stiffness, indicating high concurrent validity. Discussion: k LLS offers valid and valuable information affecting performance, injury risk, and return-to-sport decisions. Conclusion: The findings suggest that k LLS is a valid method for calculating stiffness in CMJs and equal to 3D leg stiffness.

About the improvement in Mars Polar Motion determination from radio tracking of two landers

The polar motion of Mars is defined as the movement of the rotation axis with respect to a body-fixed frame tied to the crust of the planet. It is composed of forced motion at annual and sub-annual frequencies caused by the seasonal mass redistribution, formation of the polar ice caps and angular momentum variations of the atmosphere, and of the free mode called the Chandler wobble.Radio-tracking data from landers offers the most suitable means to measure the rotation of Mars, including its polar motion. The latter, however, has not yet been achieved using lander data alone. In this study, we assess the uncertainties associated with Mars polar motion estimation using Direct-To-Earth Doppler, range and Same-Beam Interferometry (SBI) observables between multiple landers on the surface of Mars. We evaluate the improvement enabled by combining data from multiple landers with respect to one-lander scenarios, and identify the optimal mission architectures for polar motion estimation by considering the influence of respective mission parameters on the estimation uncertainty. In particular, we consider the effects of absolute and relative locations of the landers and of mission scheduling. We re-evaluate the possibility of estimating the polar motion using data from landers in proximity to the equator, and apply our considerations to simulated data consistent in number and accuracy with that collected by past Martian missions. We notice and explain a strong longitude dependence of the formal errors when the polar motion parameters are estimated concurrently with the seasonal spin variation parameters, making it impossible to properly determine all components of polar motion with a single lander regardless of its location. However, the use of two or more landers in optimal locations with respect to each other eliminates those limitations. We evaluate the influence of latitudinal and longitudinal separation on polar motion determination in such cases. In particular, we are able to determine polar motion well even in cases where the longitudes of the two landers make determination from each single lander impossible.

Impact of Operative Room Noise on Laparoscopic Performance—A Prospective, Randomized Crossover Trial

IntroductionSurgeons are often exposed to different types of operative room (OR) noise, for instance machine alarms, phone calls, and interacting objects. The aim of this study was to evaluate the effect of OR noise on the surgeons’ laparoscopic performance. MethodsA total of 30 laparoscopic novices participated in this single-center, prospective, randomized cross-over trial after completing a standardized laparoscopic training until reaching proficiency. Afterward, all participants performed four different laparoscopic tasks (peg transfer, circle cutting, balloon resection, suture, and knot) twice, once under noise exposure (intervention group), and once without any noise (control group). Primary endpoints were the force exertion and motion analyses. To assess the psychological workload the NASA task load index score was used. ResultsThe error rates varied and were significantly different between the noise and the control group. More complex tasks like the circle cutting and suture and knot task revealed higher error rates concerning precision (circle cutting: P < 0.01; suture and knot: P < 0.01). In line with increased error rates in the circle cutting task, increased NASA task load index scores were observed in this task (P = 0.03). However, no significant differences were found in force parameters, such as the maximal force exertion (peg transfer: P = 0.43; circle cutting: P = 0.54; balloon resection: P = 0.64; suture and knot: P = 0.63) and the mean force exertion (peg transfer: P = 0.43; circle cutting: P = 0.54; balloon resection: P = 0.64; suture and knot: P = 0.63) between the groups. ConclusionsExposure to normal OR noise led to higher error rates in two of four tasks. This effect could be linked to an increased psychological workload that was present under normal OR noise exposure. However, normal OR noise does not appear to impact surgical novices' laparoscopic task performance regarding applied forces and instrument motion.

Dynamic nonparametric modeling of sail-assisted ship maneuvering motion based on GWO-KELM

Accurately predicting the state of ship motion is crucial for ship navigation control with energy efficiency optimization studies. When modeling the motion of novel ships equipped with propulsion devices such as sails, it is essential to consider the effects of sail thrust and lateral forces on the ship's motion states. Building upon the analysis of sail force and sail-assisted ship motion modeling, this paper proposes a ship motion dynamic modeling method utilizing Kernel Extreme Learning Machine (KELM) regression. By optimizing the hyperparameters of the kernel function using the Grey Wolf Optimizer (GWO) algorithm and incorporating a sliding time window for dynamic model updating, the proposed approach combines the efficient learning mechanism of KELM with the global search capability of GWO, effectively enhancing prediction accuracy and timeliness. Utilizing KVLCC2 ship model motion data, simulation data from the sail-assisted ship “New Aden” and real ship data as case studies, comparative analysis with traditional models such as SVM and ELM. The results demonstrate that the GWO-KELM modeling approach exhibits robustness and high prediction accuracy, the MAE of the proposed model in the real ship motion prediction effect is reduced by 8.89% and the RMSE is reduced by 9.44% compared with the other models, which significantly enhance the predictive performance of sail-assisted ship maneuvering motion states.

Design optimization of a snowboard performing an ollie

The ollie, a fundamental manoeuver in snowboarding, serves as a basis for various tricks requiring high altitude and extended airtime. The maximum ollie height depends on the snowboard’s geometry and structural characteristics. In this study, the influence of these properties is investigated with a flexible multibody dynamics simulation, where the snowboard is modeled by geometrically non-linear finite elements, snow contact is considered by a penetration depth and velocity proportional normal force and ollie motion is achieved by imposing measured loads to the bindings. To maximize the height, a genetic optimization procedure is presented, which yields substantial improvements. Optimizing the camber line and the bending stiffness distribution yields enhanced performance. Less damping as well as lighter boards lead to higher jumps, no noteworthy correlation between axial stiffness and damping distribution and jump height was found, and the strain energy stored in the board during takeoff is a useful indicator for estimating ollie heights. Nevertheless, further investigations should take a more advanced and realistic rider interaction into account.