Average Angular Velocity Research Articles

Age-Related Influence on Static and Dynamic Balance Abilities: An Inertial Measurement Unit-Based Evaluation.

Balance control, a complex sensorimotor skill, declines with age. Assessing balance is crucial for identifying fall risk and implementing interventions in the older population. This study aimed to measure age-dependent changes in static and dynamic balance using inertial measurement units in a clinical setting. This study included 82 healthy participants aged 20-85 years. For the dynamic balance test, participants stood on a horizontally swaying balance board. For the static balance test, they stood on one leg. Inertial measurement units attached to their bodies recorded kinematic data, with average absolute angular velocities assessing balance capabilities. In the dynamic test, the younger participants had smaller average absolute angular velocities in most body parts than those of the middle-aged and older groups, with no significant differences between the middle-aged and older groups. Conversely, in the single-leg stance tests, the young and middle-aged groups outperformed the older group, with no significant differences between the young and middle-aged groups. Thus, dynamic and static balance decline at different stages with age. These results highlight the complementary role of inertial measurement unit-based evaluation in understanding the effect of age on postural control mechanisms, offering valuable insights for tailoring rehabilitation protocols in clinical settings.

Rotational Taylor dispersion in linear flows

The coupling between advection and diffusion in position space can often lead to enhanced mass transport compared with diffusion without flow. An important framework used to characterize the long-time diffusive transport in position space is the generalized Taylor dispersion theory. In contrast, the dynamics and transport in orientation space remains less developed. In this work we develop a rotational Taylor dispersion theory that characterizes the long-time orientational transport of a spheroidal particle in linear flows that is constrained to rotate in the velocity-gradient plane. Similar to Taylor dispersion in position space, the orientational distribution of axisymmetric particles in linear flows at long times satisfies an effective advection–diffusion equation in orientation space. Using this framework, we then calculate the long-time average angular velocity and dispersion coefficient for both simple shear and extensional flows. Analytic expressions for the transport coefficients are derived in several asymptotic limits including nearly spherical particles, weak flow and strong flow. Our analysis shows that at long times the effective rotational dispersion is enhanced in simple shear and suppressed in extensional flow. The asymptotic solutions agree with full numerical solutions of the derived macrotransport equations and results from Brownian dynamics simulations. Our results show that the interplay between flow-induced rotations and Brownian diffusion can fundamentally change the long-time transport dynamics.

Crowding accelerates the rotation of a bacterial rotor

Understanding the propulsion of a swimmer in a large group of individuals holds the key to unravelling the intriguing dynamics of active matter collective motion. Here, we develop a two-dimensional (2-D) self-assembled rotor, powered by bacterial flagella. At a water–air interface, the average direction of rotation of a rotor is fixed. When the chiral rotor is put into a 2-D bacterial suspension, we examine the average and fluctuation of the angular velocity of the rotor. Remarkably, the average angular velocity of a rotor is found to increase up to 3 times when the density of surrounding bacterial suspension increases and the increase is nonlinear. In a dense suspension of bacteria, the existence of a rotor disrupts vortices in the surrounding active turbulence, and the acceleration of the rotor is independent of the activity level of the surrounding free bacteria. The nonlinear acceleration thus results from hydrodynamic interaction with surrounding crowdedness that can be quantitatively explained by hydrodynamic simulation. The simultaneity between the acceleration of rotor and free bacteria in active turbulence suggests that crowding-induced acceleration may promote the onset of instability. The result will inspire new active-matter-based microfluidic devices with improved transport properties.

Motion planning in underactuated systems with impulsive phenomenon via dynamic shaping of virtual holonomic constraints

Rhythmic motions are traditionally achieved by developing predetermined paths for the states of the space system to follow. Since these paths are obtained offline, the dynamic behavior fails to adapt to changes in environmental conditions or user command desires. The solution we propose is a new strategy called dynamic shaping, in which the paths are formed online to allow the system to create an orbit with the characteristics we need. Hereupon, this paper focuses on applying this strategy to Dynamics with One Degree of Under-actuation and Impulsive Phenomenon (DSODUIP) to adapt the characteristics of outcomes to be in line with the demands.This research was conducted by leveraging the advantages of virtual holonomic constraints (VHCs) to establish these paths. Therefore, a novel two-level hierarchical control method is designed considering a stability criterion to avoid divergence. At the Low-Level, the controllers stabilize the output of system to follow the VHCs on the system. At the High-Level, the VHCs are modified to shape an orbit with our desired characteristic in the motion. As an illustrative example, the algorithm is implemented to adjust the average angular velocity of a devil stick and the hip velocity of a Three-Link biped robot. Their results vividly demonstrate smooth adjustments and efficient performance in achieving our desired outcomes.

The Effect of Priority Assignment the Role of Evaluator and Executive in Collaborative Training on the Acquisition of Kinematic and Accuracy of Dart Throwing Skill

Background: Collaborative training can enhance individual learning, but the effect of role assignment on skill acquisition is unclear. Objectives: Therefore, this study aims to explore the influence of the evaluator and executor roles on the accuracy and kinematic indicators of dart throwing skill. Methods: Forty-eight female university students (mean age = 21.71 ± 1.14 years) participated in the study. Following dart throwing familiarization, participants were randomly assigned to individual group (IG), first-performer (FPG), and first-evaluator groups (FEG) (as a dyad condition) with alternating role orders. All groups completed a pre-test of 10 dart throws while kinematics was recorded via video camera. Practice consisted of 20 blocks of 6 trials (n = 120 physical trials for IG; n = 60 evaluation and n = 60 physical trials for FPG and FEG). Post-tests 1 and 2 directly followed after role reversals for dyads after each 60 trials in the acquisition phase. Accuracy was assessed via mean radial and variable errors. Kinematics (elbow release angle, average angular velocity, elbow range of motion) were analyzed using Kinovea software. Results: A two-way ANOVA revealed the FPG exhibited a significantly smaller release angle compared to IG. However, no significantly differences observed between FEG and IG for kinematic variables. Accuracy improved significantly from pre-to post-test at the three groups. Individual group led to higher accuracy than FPG, and frist-performer group had higher RE than the first-evaluator. Conclusions: The findings of this study support the benefits of observational learning in the early stages of learning. Also, priority assignment the role of evaluator and executive can influences motor performance in a dyadic approach.

Delayed action leads to faster turning of fish by interaction with neighbor

Schooling fish exhibit captivating biological behaviors that have garnered interest from both biologists and engineers. While the undulatory motion of fish in schools has been extensively studied, rapid turning within these schools remains underexplored. This paper presents a three-dimensional computational fluid dynamics (CFD) model of a fast-start scenario involving two fish to investigate the influence of spatial and phase differences on swimming performance. Our findings indicate that, by leveraging the wake of the upstream fish, a downstream fish can enhance its travel distance by up to 34.4% and its rotational angle by up to 41.6%. The optimal travel distance is achieved when the starting jet of the front fish aligns with the center of mass (COM) of the downstream fish. Conversely, the largest rotational angle is observed when this jet precedes the center of mass. The research further identifies a vortex phase matching phenomenon in fish schools during rapid turns. The phase difference, or the downstream fish's delayed response, allows it to harness the wake for improved transitional and rotational movement. However, this approach might decrease the average angular velocity, which represents the rotational angle divided by the total duration of turning and waiting. Our study concludes that, with a specific phase difference, this delayed action facilitates faster fish turns by utilizing the wake created by the neighboring fish.

Evaluation of Short-Term Clinical Effects of a Novel Repetitive Facilitation Exercise Training Program Using a Hemiplegic Elbow Extension Rehabilitation System

Repetitive Facilitation Exercise (RFE) is known as an effective rehabilitation method that can elicit brain plasticity. In our previous study, we developed a hemiplegic upper limb rehabilitation system that can train the elbow and shoulder based on RFE theory. The system consists of a selective Arm-DoF constrainable mechanism and a multiple facilitative stimulus timing and duration control system. The selective Arm-DoF constrainable mechanism has three DoF, making it possible to selectively restrict a DoF of the shoulder or elbow. The multiple facilitative stimulation timing and duration control system only has an electrical stimulation source and a vibrator and no large actuators to perform the training exercise. In this study, we undertook an evaluation of the short-term clinical effects of a proposed elbow training program using the hemiplegic upper limb rehabilitation system. The training method consists of two sets, each involving 50 repetitions of the elbow extension exercise programmed in our system. We evaluated the short-term training effects through clinical trials for five stroke patients using the above method. In the evaluation, 10 repetitions of pre/post-tests without any facilitative stimulus were performed before and after the two sets of training. As a result, the maximum angular velocities or the average angular velocities of the elbow extensions improved significantly in most subjects. These results indicate that the quickness or the smoothness of elbow extension movements in the hemiplegic limb improved. Therefore, our clinical experiments support the short-term clinical benefits of the proposed method as well as the practicality of quantitative evaluation using our system.

The influence of operation times of manual tamping device on ballast bed state

The manual tamping device plays an important role in the daily maintenance and repair of ballasted track. It is difficult to establish a suitable analytical model for manual operations because of their inherent flexible characteristics. There is a lack of sufficient theoretical research on daily maintenance and repair which are mainly based on the long-term field experience of workers. For guiding the field operation of manual tamping devices, a coupled simulation model of impacted manual tamping device and ballasted track was established based on the DEM-MBD coupling method. The proposed model effectively simulated the manual tamping operations. The correctness of the model was verified through field lateral resistance tests. The proposed coupling model was applied for computing the change in the support stiffness of the ballast bed under different tamping times. Further analysis was done to study the impact of manual tamping operations on the contact force and movement of the ballast. The results show that the vibration and impact of the manual tamping device have changed the original contact relationship between the ballast particles. The attenuation amplitude of the support stiffness of the ballast bed initially decreased and later increased with increase in tamping times, resulting in the ballast bed with higher initial stiffness more elastic. A similar trend and good synchronization were observed between the average contact force and angular velocity between ballast particles with manual tamping time, resulting in improved compactness and stability of the ballast bed. And it is recommended to perform tamping five times for optimal results.

Scaling a Hydraulic Motor for Minimally Invasive Medical Devices.

Aligned with the medical device industry's trend of miniaturization, academic and commercial researchers are constantly attempting to reduce device sizes. Many applications require miniature actuators (2 mm range) to perform mechanical work; however, biocompatible micromotors are not readily available. To that end, a hydraulic motor-driven cutting module that aims to combine cutting and drug delivery is presented. The hydraulic motor prototype developed has an outside diameter (OD) of ~4 mm (twice the target size) and a 1 mm drive shaft to attach a cutter. Four different designs were explored and fabricated using additive manufacturing. The benchtop experimental data of the prototypes are presented herein. For the prototype motor with fluid inlet perpendicular to the blades, the average angular velocity was 10,593 RPM at a flowrate of 3.6 mL/s and 42,597 RPM at 10.1 mL/s. This design was numerically modeled using 3D-transient simulations in ANSYS CFX (version 2022 R2) to determine the performance characteristics and the internal resistance of the motor. Simplified mathematical models were also used to compute and compare the peak torque with the simulation estimates. The viability of current design represents a crucial milestone in scaling the hydraulic motor to a 2 mm OD to power a microcutter.

RFWBS Model: Multilevel Hybrid Mapping Solution Framework for Designing Neurorehabilitation Physiotherapy Devices

Healthcare services and rehabilitation equipment have entered a phase of rapid development driven by user requirements. However, the development of corresponding design models for rehabilitation equipment is lacking. A general framework and development process are urgently needed for neurorehabilitation physiotherapy equipment. To address problems such as inadequate knowledge representation in the design process and difficulties in modeling the functional structure of the product, we combined a decomposition topology model of neurorehabilitation physiotherapy equipment with the modular design method. We proposed a general model for the design of neurorehabilitation physiotherapy equipment comprising the following modules: requirements (R), function (F), principle workspace (W), behavior (B), and structure (S), i.e., the RFWBS model. Using the neurorehabilitation robotic glove as an example for design practice, in terms of kinematics, the mechanism is analyzed by establishing a Lagrangian coordinate system for resolution. The mechanism has three degrees of freedom and can achieve the natural flexion and extension angles of each finger joint. In terms of dynamics, during the entire finger extension, the angular acceleration is almost zero, and the average angular velocity is approximately 30~50°/s. This indicates that the mechanism is suitable for wearable use, validating the scientific and effective nature of the RFWBS expanded model.

Reframing Whole-body Angular Momentum: Exploring the Impact of Low-Pass Filtered Dynamic Local Reference Frames during Straight-line and Turning Gaits.

Accurately estimating whole-body angular momentum (WBAM) during daily activities may benefit from choosing a locally-defined reference frame aligned with anatomical axes, particularly during activities involving body turns. Local reference frames, potentially defined by pelvis heading angles, horizontal center of mass velocity (vCoM), or average angular velocity (Aω), can be utilized. To minimize the impact of inherent mediolateral oscillations of these frames, such as those caused by pelvis or vCoM rotation in the transverse plane, a low-pass filter is recommended. This study investigates how differences among global, local reference frames pre- and post-filtering affect WBAM component distribution across anatomical axes during straight-line walking and various turning tasks, which is lacking in the literature. Results highlighted significant effects of reference frame choice on WBAM distribution in the anteroposterior (AP) and mediolateral (ML) axes in all tasks. Specifically, expressing WBAM in the vCoM-oriented local reference frame yielded significantly lower (or higher) WBAM in the AP (or ML) axes compared to pelvis-oriented and Aω-oriented frames. However, these significant differences disappeared after employing a low-pass filter to local reference frames. Therefore, employing low-pass filtered local reference frames is crucial to enhance their applicability in both straight-line and turning tasks, ensuring more precise WBAM estimates. In applications that require expressing anatomical axes-dependent biomechanical parameters in a local reference frame, pelvis- and vCoM-oriented frames are more practical compared to the Aω-oriented frame, as they can be determined by a reduced optical marker set or inertial sensors in future applications when the whole-body kinematics is not available.

Research on Tremor Suppression Strategies Under a Constant Current Peripheral Electrical Stimulation Device for Parkinson's Disease.

Tremor, a prevalent symptom in Parkinson's patients, is conventionally treated with medications and craniotomy. However, the associated side effects and high surgical costs pose challenges for some individuals. In this study, a lightweight constant current electrical stimulator was developed, which is driven by the FPGA to control the underlying logic and has multiple programmable stimulation parameters. Clinical experiments involving patients with Parkinson's-related resting tremor symptoms were conducted to assess the efficacy of peripheral electrical stimulation. Two Co-contraction Avoidance Stimulation (CAS) strategies targeting nerves and muscles were proposed to reduce tremors. Four Parkinson's disease (PD) patients were recruited to verify the effectiveness of these strategies. Kinematic data recorded by inertial sensors showed that the radial nerve and muscle intervention strategies reduced the average angular velocity amplitude of finger joints during resting tremor by 75.92% and 82.41%, respectively. Notably, under low-frequency pulse stimulation (100 Hz) focused on muscle interference, a low-intensity current of no more than 8 mA maintained a tremor suppression rate of 59.91% even 5 minutes post-stimulation. Based on the experimental results, it is concluded that the constant current electrical stimulator developed in this study can effectively suppress tremor under specific stimulation strategies. These findings have significant implications for the development of lightweight, wearable tremor suppression devices. The stimulator's adaptability, coupled with its precise control parameters, demonstrates promise for advancing non-invasive and cost-effective tremor management in Parkinson's patients.

Analysis and Experimental Investigation of Steering Kinematics of Driven Steering Crawler Harvester Chassis

In the context of automatic driving, the analysis of the steering motion characteristics is critical for enhancing the efficiency of crawler harvesters. To address issues such as the low transmission efficiency and the large steering radius encountered by traditional crawler harvesters featuring hydrostatic drives, a driven steering crawler harvester chassis was designed. This involved analysis of the chassis transmission system structure and its steering characteristics under several conditions, including differential steering, differential direction reversal, and unilateral braking steering. The steering parameters were determined based on real-time kinematic positioning–global navigation satellite system (RTK-GNSS) measurements, and they were compared with theoretical predictions based on the crawler harvester steering kinematics. The slip rates and modified models of the crawler chassis for various steering modes were then obtained. The results indicated that the increase in the ratio between the running input and steering input speeds led to larger track steering radii and smaller average rotational angular velocities. Remarkably, the slopes of the linear fits of the tracked chassis steering parameters varied significantly under differential direction reversal and differential steering modes. Compared with the actual results, the correlation coefficient of the tracked chassis steering parameters fitting model is close to 1. The steering parameter model was deemed suitable for actual operational requirements. The results provide a valuable reference for designing navigation and steering models of crawler harvesters operating on different road surfaces.

Water flow simulation in a pelton turbine bucket with variable bucket dimensions using computational fluid dynamic

Today, especially among industrialized and developing nations, the usage of renewable energy sources is growing in popularity as a means of supplying energy needs. One of the renewable energy sources that is now being heavily exploited in Indonesia is the potential of water that may be used as a source of electrical energy by establishing a hydroelectric power plant (PLTA). One of the turbines that is frequently used in hydropower plants as a part that may transform water's kinetic energy into mechanical energy is the Pelton turbine. There is not a lot of literature on the design of Pelton turbine buckets. In order to determine the most ideal bucket dimensions that can be used with Pelton turbines, this study presents the conceptual and experimental components of the design and analysis of Pelton turbines based on bucket variations. AutoCAD was used to model the bucket and Pelton turbine, and ANSYS Fluent was used to perform the simulation so that results could be analyzed later. By comparing the simulated data of the blade variants 1 and 2, the ideal blade dimension variation is identified by the blade simulation of variant 1. The blade variation 2 with average torque of 5.859 Nm, average angular velocity of 40.822 rad/s, and average power of 242,970 watts is the most ideal blade. With an average torque of 4,735 Nm, an average corner speed of 40,404 rad/s, and an average power of 196,794 W, the blade 3 model has lower values

Exploring the issue of ‘functionality’ in isokinetic dynamometry

ABSTRACT Strength is a primary and modifiable contributor to performance, injury risk, and rehabilitative success. The gold standard measure of strength is the isokinetic dynamometer, providing the clinician with the opportunity to manipulate contraction modality, range, and speed about a joint. However, criticism has highlighted a lack of functional relevance, with arbitrary selection of speed across the full range. To better understand function, biomechanical analysis of movement can inform a bespoke isokinetic data collection protocol. In this case, we use walking gait, a function goal for daily living and clinically assessed following knee replacement surgery for example. Concentric knee flexor and extensor demand was evident at an average angular velocity of 70°·s−1, whilst eccentric knee flexor and extensor demands were evident at speeds of 192°·s−1 and 165°·s−1, respectively. The efficacy of isokinetic dynamometry can be enhanced with bespoke data collection protocols, which better reflect the functional demands of the clinical movement objective.

Translational and angular velocities statistics of inertial prolate ellipsoids in a turbulent channel flow up to Re τ = 1000

Direct numerical simulations of the turbulent flow in a channel are conducted up to $Re_{\tau }=1000$ to examine the influence of the friction Reynolds number on the translational and angular velocities of inertial, prolate ellipsoids. The quadrant distribution of the turbulent events seen by the particles is not significantly affected by the value of $Re_{\tau }$ , but subtle modifications take place, depending on the position in the channel and on the particle relaxation time. Overall, the influence of $Re_{\tau }$ on the first and second statistical moments of the ellipsoids translational velocity is the same as that observed for the fluid velocity. The weak dependence of these statistics to the particle shape previously observed at low Reynolds number remains at higher values of $Re_{\tau }$ . Similarly, the mean and root mean square (r.m.s.) of the angular velocity of the fluid seen by the particles weakly depend on particle shape and they have the same dependence to $Re_{\tau }$ as the angular velocity statistics of the carrier fluid. Particle angular velocity statistics are more strongly affected by the flow Reynolds number due to the evolution of the complex shape and inertia dependent rotation orbits with $Re_{\tau }$ . In the near-wall region the average angular velocity of weakly inertial ellipsoids increases with $Re_{\tau }$ due to their stronger alignment with the mean fluid vorticity. Furthermore, the r.m.s. of the wall-normal component of the angular velocity of more inertial ellipsoids increases with $Re_{\tau }$ owing to the larger fluctuations of the angle between the particle major axis and the velocity-gradient plane.

Research on micro-influence mechanism of fine particles on dynamic characteristics of graded macadam materials in heavy-haul railway subgrade beds

Fine particle content is an important physical state parameter of graded macadam materials used in heavy-haul railway subgrade beds. Understanding the micro-influence mechanism of the fine particle content on the filler’s dynamical characteristics is of great significance. In this study, the granular system generation logic in PFC3D software was modified to enhance efficiency and quality, and the three-dimensional discrete element numerical model of graded macadam materials dynamic triaxial specimen was established. The servo program was used to simulate the dynamic triaxial numerical test confining pressure and dynamic loading conditions. A series of laboratory tests were performed using a GCTS large-scale cyclic triaxial test system to calibrate and verify the numerical model. Finally, dynamic triaxial numerical tests were conducted for graded macadam materials with different fine particle contents. These tests had the aim of determining the variation law for the contact force chain distribution, mechanical coordination number, average rotational angular velocity, and energy dissipation of the specimens under cyclic loading with the increase of fine particles and then revealing the influence mechanism of fine particles on the dynamic characteristics of graded macadam materials used in heavy-haul railway subgrade beds from a microscopic perspective. The study’s findings serve as a framework for describing the mechanism of subgrade bed disease occurrence and proposing effective remediation measures.

Lower-limb wearable resistance overloads joint angular velocity during early acceleration sprint running

ABSTRACT Lower-limb wearable resistance (WR) facilitates targeted resistance-based training during sports-specific movement tasks. The purpose of this study was to determine the effect of two different WR placements (thigh and shank) on joint kinematics during the acceleration phase of sprint running. Eighteen participants completed maximal effort sprints while unloaded and with 2% body mass thigh- or shank-placed WR. The main findings were as follows: 1) the increase to 10 m sprint time was small with thigh WR (effect size [ES] = 0.24), and with shank WR, the increase was also small but significant (ES = 0.33); 2) significant differences in peak joint angles between the unloaded and WR conditions were small (ES = 0.23–0.38), limited to the hip and knee joints, and <2° on average; 3) aside from peak hip flexion angles, no clear trends were observed in individual difference scores; and, 4) thigh and shank WR produced similar reductions in average hip flexion and extension angular velocities. The significant overload to hip flexion and extension velocity with both thigh- and shank-placed WR may be beneficial to target the flexion and extension actions associated with fast sprint running.

Numerical simulation of vortex flow evolution during droplet formation in T-inlet microchannel

The formation of microdroplets in T-inlet microchannel device was numerically simulated based on the conservation level set method. The strength of the swirling flow is evaluated by defining the average rotational angular velocity of the fluid inside the microdroplet under the condition of no shear. The differences in the evolution of swirling flow caused by the alteration of viscosity ratio at low capillary number (Ca≤0.01) were analyzed, and the influence of two-phase interfacial tension on the vortex evolution is also discussed. Numerical simulation results show that the evolution process of swirling flow in the squeezing droplets can be divided into five phases. The increase of capillary number will lead to an improvement of internal swirling intensity during the development of microdroplet. However, raising the viscosity ratio will inhibit the swirling strength. The variation of the interfacial tension between the two-phase fluids has a significant effect on the swirling intensity, the swirling intensity inside the droplet increases with increasing interfacial tension.

Tandem control method of two axes with different reduction ratios (Comparison of three methods to equalize the transmission torque for a load)

Tandem control is the control to drive one load with multiple motors. We compare three tandem control methods to suppress the natural vibration of the system: 1) a common torque method, 2) an average rate feedback method, 3) an individual rate feedback method. The common torque method is to feedback the position signal and rate signal from the motor 1 to obtain the torque reference of the motor 1, and give the torque reference to the motor 2 with the correction calculation to equalize the torque. We found that the difference in reduction ratio affects the suppression effect of the natural vibration. The average rate feedback method feedbacks the average position, the average angular velocity, and the rate difference of the motors to execute the tandem control. In addition, it is a method to equalize the torque by calculating a torque correction signal of the same value with a different sign, from the average rate and average current of the motors. The rate difference signal feedbacks through a high-pass filter that passes the natural vibration of the system, so the natural vibration is suppressed in the transient state. The individual rate feedback method feedbacks the angular velocity individually. In addition, it is a method to equalize the torque by calculating its torque correction signal from the rate of the each motor. We could equalize the torque and suppress the natural vibration through this simulation and experiment, in all three methods. We result the individual feedback method is the best, because the common torque method is not able to tune the natural vibration with the control gain, and the average rate feedback method is complicated to tune the control gain.