Acceleration Error Research Articles

Beyond the neural underpinnings of action emulation in expert athletes: an EEG study.

Athletes specializing in sports demanding rapid predictions and hand-eye coordination are highly trained in predicting the consequences of motor commands. This can be framed as highly efficient action emulation, but the neural underpinnings of this remain elusive. We examined the neural processes linked to the training effect of athletes (4,000 hours of training) by employing a continuous pursuit tracking task and EEG data. We manipulated feedback availability by intermittently occluding the cursor. As a performance measure, we used the distance between cursor and target (position error), the angle between the cursor and target movement direction (direction error) and the magnitude of cursor acceleration (acceleration error) to quantify movement strategy. In EEG data, we investigated beta, alpha, and theta frequency band oscillations. Athletes' position error is lower than non-athletes' when there is no feedback about the cursor location, but direction error is not. We found no quantitative power differences in the investigated frequency bands, but evidence that athletes and non-athletes accomplish action emulation through different functional neuroanatomical structures, especially when alpha and beta band activity is concerned. We surmise that non-athletes seemed to rely on top-down inhibitory control to predict guesses on cursor trajectories in the absence of cursor position feedback. In contrast, athletes might benefit from enhanced inhibitory gating mechanisms in the ventral stream and the integration of sensory and motor processes in the insular cortex, which could provide them with processing advantages in computing forward models. We further reflect that this advantage might be supported by alpha band activity in athletes' motor cortex, suggesting less inhibitory gating and a higher likelihood of executing integrated sensorimotor programs. We posit that current framings of neuroanatomical structures and neurophysiological processes in the action emulation framework must be revised to better capture superior motor performance.

Latency and amplitude of catch-up saccades to accelerating targets.

To track moving targets, humans move their eyes using both saccades and smooth pursuit. If pursuit eye movements fail to accurately track the moving target, catch-up saccades are initiated to rectify the tracking error. It is well known that retinal position and velocity errors determine saccade latency and amplitude, but the extent to which retinal acceleration error influences these aspects is not well quantified. To test this, 13 adult human participants performed an experiment where they pursued accelerating/decelerating targets. During the ongoing pursuit, we introduced a randomly sized target step to evoke a catch-up saccade and analyzed its latency and amplitude. We observed that retinal acceleration error (computed over a 200 ms range centered 100 ms before the saccade) was a statistically significant predictor of saccade amplitude and latency. A multiple linear regression supported our hypothesis that retinal acceleration errors influence saccade amplitude in addition to the influence of retinal position and velocity errors. We also found that saccade latencies were shorter when retinal acceleration error increased the tracking error and vice versa. In summary, our findings support a model in which retinal acceleration error is used to compute a predicted position error ∼100 ms into the future to trigger saccades and determine saccade amplitude.NEW & NOTEWORTHY When visually tracking object motion, humans combine smooth pursuit and saccadic eye movements to maintain the target image on the fovea. Retinal position and velocity errors are known to determine catch-up saccade amplitude and latency, however, it is unknown if retinal acceleration error is also used to predict future target position. This study provides evidence of a small but statistically significant contribution of retinal acceleration error in determining saccade amplitude and latency.

PLC-AWG-based FBG demodulation system for high-frequency vibration measurement.

A fiber Bragg grating (FBG) demodulation system based on arrayed waveguide gratings (AWGs) is proposed. We designed the key parameters of the AWG, prepared the AWG chip based on a silica-on-silicon planar light wave circuit (PLC) platform, and integrated the AWG with a PD array. Eight AWG output channels were selected and the output signals from the photodiode (PD) array was connected to the board with gold wire bonding. The demodulation circuitry consists of transimpedance amplifiers (TIAs), analog-to-digital converters (ADCs), and a main control chip. The signal from the PDs are synchronously captured and amplified and then transmitted at high speed through an Ethernet interface. The total volume of the demodulation system is 200 × 100 × 60 mm3. Experiments show that the wavelength demodulation accuracy of the system is 4.24 pm, the demodulation rate is more than 200 kHz, and the average error of the demodulation acceleration is better than 22.8 mg. The proposed demodulation system can be applied in the field of high-frequency vibration sensing of FBGs.

Study of a Companion Trajectory Kinematics Analysis Method for the Five-Blade Rotor Swing Scraper Pump

This paper proposes a five-blade rotor swing scraper pump (FRSSP) to overcome traditional volumetric pumps’ drawbacks, such as poor sealing performance, low volumetric efficiency, and complex structure. This pump employs a rotating cam-swing scraper mechanism to achieve fluid intake and discharge. The FRSSP is compact in structure, self-sealing, and highly efficient in volumetric utilization, offering promising applications. A companion trajectory kinematic analysis method of the FRSSP is proposed. The polar coordinate equation of the companion trajectory is derived from the profile equation of the five-blade rotor cam. Based on this trajectory, a kinematic model of the scraper pump is established, resulting in the kinematic equations for the swing angle of the scraper, the pressure angle of the scraper, the rotation angle of the rotor, the angular velocity of the scraper, and the angular acceleration of the scraper. The kinematics of the FRSSP were simulated and validated using ADAMS. Comparing the results of theoretical calculations and simulation reveals that the error in the scraper swing angle is 1.85%, the maximum error in the scraper angular velocity is 4.93%, and the maximum error in the scraper angular acceleration is 2.47%, confirming the accuracy of the kinematic analysis method. A sensitivity analysis was performed on the kinematic research method for companion trajectories. After modifying the dimensions of key components in the scraper pump, the discrepancies between theoretical calculations and simulation results were within 5%, confirming the accuracy and robustness of the method. Flow field simulation analysis and experimental tests on the scraper pump revealed that the deviation between the simulated and experimental outlet flow rates was less than 5%, validating the feasibility of the pump’s structural principles and the reliability of the simulations. Furthermore, these findings indirectly affirmed the correctness of the companion trajectory kinematic analysis method.

Study on the Hydrodynamic Effects of Bridge Piers Under Velocity-Type Pulse Ground Motion Based on Different Characteristic Periods

This study was based on a target spectrum (GB183062015) and synthesized different characteristic periods, pulse ground motions, and non-pulse ground motions utilizing EQsignal v1.2.1 software. It also investigated the dynamic behaviors of bridge piers in seismic motions with varying characteristic periods, pulse and non-pulse effects, and the influence of 0 m and 10 m water depths. The findings indicated that the peak acceleration and stress behaviors vary significantly under different characteristic periods of ground motion. The maximum error in peak acceleration behavior of a bridge pier under ground motions of varying characteristic periods is 19.25%, while the maximum error in peak stress response is 11.35%. The acceleration and stress behaviors of a bridge pier under pulse ground motion action are more considerable than those under non-pulse seismic motion action. When the characteristic period is 0.40 s, the maximum error in peak acceleration of the bridge pier structure under pulse seismic motion and non-pulse seismic motion action is 86.08%, with the maximum error of the peak stress reaches 80.68%. The existence of water serves to minimize the natural frequency of the bridge pier. The pulse effects result in a maximum error of 40.49% for the peak acceleration and a maximum discrepancy of 323.08% for the peak stress of the bridge pier. The hydrodynamic effects result in a maximum error of 33.51% for the acceleration peak and 12.90% for the stress peak of the bridge pier. The effect of the pulse symptoms on the dynamic behavior of the bridge pier is considerably more pronounced than that of the hydrodynamic effects, with an intricate and complex influencing mechanism. In bridge flood protection and seismic design and optimization, it is essential to consider the impact of pulse seismic motion with varying characteristic periods.

The calculation and evaluation of acceleration errors produced by position movement of acceleration sensors on the seat of a human centrifuge

Abstract With the increasing requirement for pilot anti-overload ability training, the man-machine engineering problems caused by the existing seat on a human centrifuge are becoming increasingly prominent, making it challenging to meet actual requirements and needing to be upgraded. After upgrading, the seat can be quickly adjusted in front, back, up and down. Acceleration sensors fixed on the seat will also generate displacement, which will result in errors. Three-axis acceleration values are a crucial technical index in human centrifuge systems, and their errors need to be within a certain accuracy range in order to make the system operate normally. Otherwise, the system will produce serious consequences such as alarm and shutdown. Analysis shows that the position movement of acceleration sensors on the seat has no impact on the control system, mainly affecting the safety system. This study discusses the situation when acceleration errors in seat adjustment reach the maximum values, and calculates the three-axis acceleration errors in detail. It is observed whether the values are within the set limits by the safety system in order to evaluate whether they have an impact on the safety of the entire system. The result indicates that the acceleration errors caused by the adjustment of the upgraded seat are within a controllable range and will not have any adverse effect on the safety system of the human centrifuge. Therefore, the acceleration errors will not have any adverse effect on the safety of the whole system.

Oculometric biomarkers of visuomotor deficits in clinically asymptomatic patients with systemic lupus erythematosus undergoing long-term hydroxychloroquine treatment.

This study examines a set of oculomotor measurements, or "oculometric" biomarkers, as potential early indicators of visual and visuomotor deficits due to retinal toxicity in asymptomatic Systemic Lupus Erythematosus (SLE) patients on long-term hydroxychloroquine (HCQ) treatment. The aim is to identify subclinical functional impairments that are otherwise undetectable by standard clinical tests and to link them to structural retinal changes. We measured oculomotor responses in a cohort of SLE patients on chronic HCQ therapy using a previously established behavioral task and analysis technique. We also examined the relationship between oculometrics, OCT measures of retinal thickness, and standard clinical perimetry measures of visual function in our patient group using Bivariate Pearson Correlation and a Linear Mixed-Effects Model (LMM). Significant visual and visuomotor deficits were found in 12 asymptomatic SLE patients on long-term HCQ therapy compared to a cohort of 17 age-matched healthy controls. Notably, six oculometrics were significantly different. The median initial pursuit acceleration was 22%, steady-state pursuit gain 16%, proportion smooth 7%, and target speed responsiveness 31% lower, while catch-up saccade amplitude was 46% and fixation error 46% larger. Excluding the two patients with diagnosed mild toxicity, four oculometrics, all but fixation error and proportion smooth, remained significantly impaired compared to controls. Across our population of 12 patients (24 retinae), we found that pursuit latency, initial acceleration, steady-state gain, and fixation error were linearly related to retinal thickness even when age was accounted for, while standard measures of clinical function (Mean Deviation and Pattern Standard Deviation) were not. Our data show that specific oculometrics are sensitive early biomarkers of functional deficits in SLE patients on HCQ that could be harnessed to assist in the early detection of HCQ-induced retinal toxicity and other visual pathologies, potentially providing early diagnostic value beyond standard visual field and OCT evaluations.

Biofidelity and Limitations of Instrumented Mouthguard Systems for Assessment of Rigid Body Head Kinematics.

Instrumented mouthguard systems (iMGs) are commonly used to study rigid body head kinematics across a variety of athletic environments. Previous work has found good fidelity for iMGs rigidly fixed to anthropomorphic test device (ATD) headforms when compared to reference systems, but few validation studies have focused on iMG performance in human cadaver heads. Here, we examine the performance of two boil-and-bite style iMGs in helmeted cadaver heads. Three unembalmed human cadaver heads were fitted with two instrumented boil-and-bite mouthguards [Prevent Biometrics and Diversified Technical Systems (DTS)] per manufacturer instructions. Reference sensors were rigidly fixed to each specimen. Specimens were fitted with a Riddell SpeedFlex American football helmet and impacted with a rigid impactor at three velocities and locations. All impact kinematics were compared at the head center of gravity. The Prevent iMG performed comparably to the reference system up to ~ 60g in linear acceleration, but overall had poor correlation (CCC = 0.39). Prevent iMG angular velocity and BrIC generally well correlated with the reference, while underestimating HIC and overestimating HIC duration. The DTS iMG consistently overestimated the reference across all measures, with linear acceleration error ranging from 10 to 66%, and angular acceleration errors greater than 300%. Neither iMG demonstrated consistent agreement with the reference system. While iMG validation efforts have utilized ATD testing, this study highlights the need for cadaver testing and validation of devices intended for use in-vivo, particularly when considering realistic (non-idealized) sensor-skull coupling, when accounting for interactions with the mandible and when subject-specific anatomy may affect device performance.

A measurement method of in-bore projectile motion acceleration based on bottom pressure correction

Due to factors such as high temperatures, elevated pressures, and severe high-frequency shocks in the bore, there is considerable noise interference in acceleration test signals. This makes it challenging to accurately measure projectile motion acceleration using existing methods. To address this issue, we propose an advanced measurement approach that uses bottom pressure correction. Our model suggests a significant correlation between projectile motion acceleration and thrust. By utilizing the correlations between bottom pressure and motion acceleration in both temporal and frequency domains, we can improve the accuracy of acceleration measurements. Based on these insights, we have developed a novel testing system that synchronously measures bottom pressure and acceleration, using bottom pressure as a corrective mechanism for the measured acceleration signals. Empirical results show that the maximum relative error in peak motion acceleration is only 4.86%, demonstrating the effectiveness of our proposed method.

High-accuracy determination of the beam divergence error in free-fall absolute gravimeters

We investigate the bias due to the beam divergence of the collimator in a free-fall absolute gravimeter of type FG5X. First, we measure the beam parameters with a Shack-Hartmann sensor. Then, we use the parameters to simulate the relative gravitational acceleration error of an FG5X gravimeter, which employs an unbalanced Mach-Zehnder laser interferometer. This investigation we do with four different commercial collimators, providing different divergence angles. We compare the results to real gravity measurements using the same collimators. The larger the divergence angle, and the bigger the relative length error, the bigger is the bias in the gravity measurements. A good agreement between theory and experiment is found, resulting in a relative bias of −2.77(24)⋅10−9 ( −2.72(24) μGal) for our standard collimator of type Thorlabs TC25APC, which is usually used for free-fall acceleration determinations. The outcome is also important for the realization of the SI unit kilogram via Kibble balance experiments that, on one side, employ laser interferometers for velocity measurements, and, on the other side, require accurate values of the gravitational acceleration. For example, if this divergence error is not corrected in the Kibble balance, then the mass determination would be biased by 2.77(24) μg kg−1 (numbers are valid only for our gravimeter with our collimator and fiber).

Multiple Leap Maneuver Trajectory Design and Tracking Method Based on Prescribed Performance Control during the Gliding Phase of Vehicles

A novel standard trajectory design and tracking guidance used in the multiple active leap maneuver mode for hypersonic glide vehicles (HGVs) is proposed in this paper. First, the dynamic equation and multiconstraint model are first established in the flight path coordinate system. Second, the reference drag acceleration-normalized energy (D-e) profile of the multiple active leap maneuver mode is quickly determined by the Newton iterative algorithm with a single design parameter. The range to go error is corrected by the drag acceleration profile update algorithm, and the drag acceleration error of the gliding terminal is corrected by the aerodynamic parameter estimation algorithm. Then, the reference drag acceleration tracking guidance law is designed based on the prescribed performance control method. Finally, the CAV-L vehicle model is used for numerical simulation. The results show that the proposed method can satisfy the design requirements of drag acceleration under multiple active leap maneuver modes, and the reference drag acceleration can be tracked precisely. The adaptability and robustness of the proposed method are verified by the Monte Carlo simulations under various combined deviation conditions.

An Extended Polar Format Algorithm for Joint Envelope and Phase Error Correction in Widefield Staring SAR with Maneuvering Trajectory

Polar format algorithm (PFA) is a widely used high-resolution SAR imaging algorithm that can be implemented in advanced widefield staring synthetic aperture radar (WFS-SAR). However, existing algorithms have limited analysis in wavefront curvature error (WCE) and are challenging to apply to WFS-SAR with high-resolution and large-swath scenes. This paper proposes an extended polar format algorithm for joint envelope and phase error correction in WFS-SAR imaging with maneuvering trajectory. The impact of the WCE and residual acceleration error (RAE) are analyzed in detail by deriving the specific wavenumber domain signal based on the mapping relationship between the geometry space and wavenumber space. Subsequently, this paper improves the traditional WCE compensation function and introduces a new range cell migration (RCM) recalibration function for joint envelope and phase error correction. The 2D precisely focused SAR image is acquired based on the spatially variant inverse filtering in the final. Simulation experiments validate the effectiveness of the proposed method.

Advanced active suspension control: A three-input fuzzy logic approach with jerk feedback for enhanced performance and robustness

Active suspension systems aim to increase ride comfort by reducing body acceleration due to road disturbances. This research proposes a new fuzzy logic controller (FLC) for such systems which includes acceleration error as third input. The objective of the proposed 3-inputs FLC is to improve vehicle comfort and ensure passenger safety. To assess the performances of the newly introduced controller, a theorical study is conducted on a quarter-car system with a four-wheel independent suspension design. Simulation results demonstrate high performances of the proposed 3-inputs FLC compared with conventional PID and 2-inputs FLC. The acceleration error as an additional FLC input was, to the best of our knowledge, not explored yet. Hence, this contribution offers a new method for the design of more effective active suspension systems.

Current Sensor-Free Output-Feedback Voltage Control for DC/DC Converters via Critical Damping Injection Technique for Converter-Fed Servo System Applications

This study proposes an observer-based multi-loop output-feedback system that regulates the output DC-link voltage of DC/DC converters to the desired value to lower the system model dependence level. There are a few features: (a) the outer loop injecting the nonlinear active damping to ensure the critically damped output voltage response, (b) a model-independent output voltage derivative observer facilitates the inner loop and eliminates the need for complex matrix calculations for tuning the estimation performance, and (c) the use of a pole-zero cancellation acceleration error stabilizer for the inner loop helps maintain the targeted closed-loop performance. The experimental study adopts a 420 W brushless DC motor dynamo system as the load for the prototype 600 W bi-directional converter controlled using the proposed solution.

Modelling and simulation of suspension system based on topological structure

The traditional approach of longitudinal cutting in suspension system simplification introduces redundant degrees of freedom, leading to increased system errors. This study focused on a seven degrees of freedom (7DOF) car model and constructed a suspension system topology model based on an across-cutting approach. To emulate road surface excitation, the filtered white noise method was employed. MATLAB/Simulink was used to create simulation models for the across-cutting, traditional longitudinal cutting and the whole car structure. Comparative analysis of these three topologies was conducted in both the time and frequency domains. Simulation results demonstrated that the performance curve of the across-cutting simplified suspension system closely matched that of the whole car model, validating the accuracy of the proposed across-cutting topology. Furthermore, when compared to traditional longitudinal cutting, the across-cutting simplification method reduced the natural frequency error of body pitch vibration by 25% and decreased the root mean square error of body acceleration by 27%. The suspension topology based on across-cutting more closely resembled the actual car structure, offering a theoretical foundation for enhancing overall ride comfort in automobiles.

Комбинированное управление следящего электропривода с компенсацией ошибки по ускорению

This article presents the technical implementation of a second-order corrective device for combined control of a tracking electric drive with adjustment of the speed contour to a symmetrical optimum with a filter and the position contour to a modular optimum. The effect of current limitation and limitation on the control signal at the input of the power converter is taken into account. A formula for determining the optimal gear ratio of the gearbox is presented, which ensures achievement of the maximum angle of rotation with a zero-acceleration error and the maximum permissible engine torque. A formula for calculating the required power of an electric motor is given. Tracking systems with acceleration error compensation are relevant in the field of robotics, where it is necessary to move along a complex trajectory of wheels or grips, as well as for guidance locators.

Constitutive modeling and simulation of polyethylene foam under quasi-static and impact loading

In this paper, quasi-static and dynamic compression experiments were carried out on polyethylene foam by a universal material testing machine and a drop tower impact device. The mechanical response characteristics and energy absorption capacity of polyethylene foam under quasi-static and moderate strain rate (4 × 10−3–102s−1) loading conditions were obtained. An improved constitutive model of strain-rate term coupling strain and strain rate was established based on the Sherwood–Frost phenomenological constitutive model and Johnson–Cook constitutive model. Low Density Foam model combined in the finite element software ABAQUS with the improved constitutive model was used as the parameter definition of polyethylene foam material in the simulation. The drop-tower impact tests at different heights were simulated, and the simulation results were compared with the actual drop tower impact test results. The results showed that the peak acceleration errors between simulation and experiment were less than 7.1%, verifying the accuracy of the constitutive model. This study provides a method of constitutive models and finite element simulation to the performance of polymer foams.

Optimization of Motion Parameters and Structural Stiffness of Spatial Four-Bar Weft Insertion Mechanism of Rapier Loom

In view of the problems of poor stability and low precision of rapier belt motion of spatial four-bar weft insertion mechanism, the mechanism was optimized from two aspects, i.e., motion parameters and structural stiffness. Firstly, the motion law of the rapier belt was analyzed based on the spatial mechanism theory, and its correctness was verified by software simulation, so as to provide a theoretical basis for the optimization design. Then, minimize the maximum acceleration of the rapier belt and the constraint condition of meeting the requirements of weft insertion technology and performance, the mechanism was optimized and analyzed using ADAMS parametric modeling. Considering the non-negligible flexibility of the weft insertion mechanism working at high speed, a rigid-flexible coupling model was established and simulated. Finally, with the connecting rod as an example, aiming at reducing the acceleration error of the rapier belt, a method was proposed to reduce the influence of the flexible deformation of the component by increasing the section size and improving the structural stiffness. The results showed that the maximum acceleration of the rapier belt after optimizing the motion parameters was reduced by 35.7%, and the motion stability was improved; After the structural stiffness was optimized, the acceleration error of the rapier belt was significantly reduced, and the motion accuracy was improved.

The validity of raw custom-processed global navigation satellite systems data during straight-line sprinting across multiple days

Objectives(1) Determine the validity of instantaneous speed and acceleration and (2) the variation in validity over time (multiple sessions) for global navigation satellite systems (GNSS) devices. DesignRepeated measures. Methods10-Hz GNSS devices from Statsports (n = 2, Apex Pro) and Catapult (n = 2, Vector S7) were examined, whilst a speed laser manufactured by MuscleLab (n = 1, LaserSpeed) was the criterion measure, sampling at 2.56 kHz, with data exported at 1000 Hz. Ten participants completed 40 m sprinting and changes of pace on three separate days. Root mean square error (RMSE) was used to assess the magnitude and direction of the difference between GNSS and criterion measures (instantaneous speed, instantaneous acceleration). Linear mixed models were built to assess the difference in validity across days. ResultsRMSE ranged from 0.14 to 0.21 m·s−1 and 0.22 to 0.47 m·s−2 for speed and acceleration, respectively showing strong agreement. There were small variations in the agreement to criterion between days for both devices for speed (Catapult RMSE = 0.12 to 21 m·s−1; Statsports RMSE = 0.14 to 0.17 m·s−1) and for acceleration (Catapult RMSE = 0.26 to 0.47 m·s−2; Statsports RMSE = 0.22 to 0.43 m·s−2) across all movements. There was a negative linear relationship between speed and acceleration error as speed increased. ConclusionsWearable microtechnology devices from Catapult (Vector S7) and Statsports (Apex Pro) have suitable validity when measuring instantaneous speed and acceleration across multiple days. There may be small variations during different sessions and over the speed spectrum.

Initial Identification of Thrust and Orbit Elements for Continuous Thrust Spacecraft in Circular Orbit

Continuous thrust spacecraft in circular orbits have had a great influence on the identification and cataloging of space targets. Gaussian-type orbital element variational equations are simplified and approximated. Ground-based radar observation datasets are transformed into orbit elements datasets. The initial thrust and orbit elements are obtained by optimally solving the spatial parameter error sum of squares minimization problem with the Levenberg–Marquardt method. The simulation analysis is carried out under the high-precision orbit model, and the solution error of tangential acceleration is around 5 × 10−7 m/s2, and that of normal acceleration is around 3 × 10−6 m/s2; the accuracy of the semi-major axis is 350 m, and the accuracy of inclination is 0.095°. The method is applicable to the preliminary identification of thrust and orbit elements for circular orbit continuous thrust spacecraft and can provide reliable initial values for the subsequent precision orbit determination of such spacecraft.