Length Error Research Articles

Application of ultrasonic non-destructive testing in industrial pipeline inspection

Abstract This study focuses on applying ultrasonic non-destructive testing (UT) technology in industrial pipeline inspection, exploring the physical basis of ultrasound and its effectiveness in pipeline defect detection to improve industrial pipeline safety and reliability. We present the basic physical principles of ultrasound, including its propagation properties and reflection mechanisms. The research methodology includes the analysis of the reflection and refraction characteristics of the ultrasonic technology on different curved surfaces of the pipeline, as well as the establishment of probabilistic models to analyze the inspection data. The results show that the ultrasonic detection technology has a high degree of accuracy in detecting pipeline defects. For example, after 40 repeated inspections, the measurement errors of defect length and depth were less than 10%, of which the length measurement error of defect 2 was 7.14% and the depth error was 7.54%. The conclusion shows that ultrasonic non-destructive testing technology can be effectively applied to the safety inspection of industrial pipelines with high reliability and accuracy, which is of great significance for ensuring industrial safety.

Development stages of the geodetic network in Tashkent city

The purpose of this study is to analyze the stage of development of the geodetic network in Tashkent city, conduct satellite observations, and preprocess measurements to establish a urban frame network. The stages of development of the geodetic network in Tashkent were analyzed and evaluated. A preliminary reconnaissance was conducted at the work site to verify the suitability of selected points for satellite observations. Suitable days for field measurements were scheduled using software. Observations were carried out at 9 points of the designed frame network using 6 Chcnav i90 GNSS receivers in 2 sessions employing the Static method. The sessions were linked by 3 points, and each session lasted four hours. Measurement data from the Chcnav i90 GNSS receivers were obtained in ‘RINEX’ format for processing. Joint measurements from the two sessions were processed using Trimble Business Center software version 5.52. Initial adjustments were made to the measurements of the lengths between points, and their accuracy was verified. The maximum root mean square error of side measurements was found to be less than the specified value for the frame network. A figure closure program was utilized to accurately determine baseline length errors.

Analysis of 5G Rotman beamforming lens antenna for higher beam angle and minimum phase error

Abstract Rotman lens beamforming networks are widely used for high gain, wide bandwidth applications in 5G communication. The uniform amplitude and phase distribution along with wide angle scanning at the array ports are mostly demanded for reducing the losses. Furthermore, minimum phase error is essential requirement for lens designs. Conventionally, for wide angle scanning, the lenses are designed by using most common expression between beam angle α and focal ratio (parameter ‘g’) i.e. g = 1 + 0.5α 2. The lenses obtained by such relation are inefficient for higher beam angle such as α = 45° due to the restricted shapes of beam and array contours. Hence suffer with large path length error limitation. In this paper, the mathematical relation between beam angle and focal ratio (parameter ‘g’) has been developed. The proposed relation offers phase error reduction more than 3× than the conventional expression based lens error. The simulation of the designed lens has performed using Software MATLAB which showed close agreement with the analytical values. Furthermore, three rectangular MPA arrays at center frequency 2.35 GHz have been proposed and simulated with lens design for 5G frequency range i.e. 2.3–2.4 GHz and offer high gain, directivity and wide coverage.

Surgical outcome comparisons of multifocal IOLs of Lentis Comfort LS-313 MF15 and Tecnis Eyhance DIB00V.

To compare the surgical outcomes of a multifocal intraocular lens (IOL; Lentis Comfort LS-313 MF15) with those of an enhanced monofocal IOL (Tecnis Eyhance DIB00V). This retrospective study included patients who underwent cataract surgery with LS-313 MF15 or Eyhance IOL implantation. Data regarding patient demographics, surgical records, and ophthalmic examination before the cataract surgery and one and three months postoperatively were collected. Visual acuities, refractive values, defocus curves, contrast sensitivities and subjective symptoms were evaluated. Among the 71 eyes (47 patients) included in this study, 32 eyes (20 patients) underwent LS-313 MF15 IOL implantation, and 39 eyes (27 patients) underwent Eyhance IOL implantation. No significant differences were observed in age, axial length, or refractive error between the two groups preoperatively. Furthermore, the distance-corrected and uncorrected distance visual acuities one month postoperatively did not differ between the groups, and both groups had sufficient visual acuities at the distances of 5, 1 m, 70, 50, and 30 cm. Other ophthalmic data, including subjective symptoms based on the 14-item Visual Function Index Questionnaire, monocular defocus curves, contrast sensitivities, and halo and glare, did not differ between the groups three months postoperatively. Moreover, both groups had good outcomes. The spherical equivalent one month postoperatively was significantly myopic in the LS-313 MF15 group compared with that in the Eyhance group (P=0.033); however, this difference was not observed three months postoperatively (P=0.471). Comparison of the surgical outcomes of LS-313 MF15 with those of Eyhance with different optical properties reveal that both IOLs show good postoperative outcomes, with no significant differences being noted between the two IOLs.

Performance analysis of OFDM with variations in cyclic prefix and FFT lengths

Orthogonal Frequency Division Multiplexing (OFDM) is a modern and suitable modulation strategy for commercial high-speed broadband wireless communication systems. This is because wireless services and demands have grown so quickly in recent years. While creating wireless communication, the channel environment is crucial. A square grid with identical vertical and horizontal spacing is used for the constellation points in quadrature amplitude modulation (QAM). More bits can be transferred per symbol to higher-order modulation forms. This research has looked at how Orthogonal Frequency Division Multiplexing OFDM systems perform using different modulation techniques on channels with additive white Gaussian noise (AWGN). Using MATLAB software to do an experiment with different modulation methods and parameters such as FFT length and cyclic prefix findings showed that 64-QAM modulation sends the same amount of data faster and with fewer symbols than QPSK 16-QAM. Here, the 64-QAM modulation technique performs better. An extensive literature survey has been carried out. The work done here involved working on many parameters to improve the performance of OFDM, i.e., by reducing BER, changing modulation techniques, and analyzing the trade-off between cyclic prefix length and Bit Error Rate. Compared to the existing work, the proposed system provides better performance.

Geotechnical investigation measures and techniques in construction engineering based on multi-source data fusion

Abstract Geotechnical investigation is an important aspect of construction engineering. In order to optimize this link, this paper analyzes the current status of the application of geotechnical investigation in construction engineering through the fusion of multidimensional spatial data interpolation of geotechnical geology as well as the structural design of geotechnical profiles by combining with triangular mesh search algorithm. On this basis, the parameter prediction of the fusion of multi-source parameter data in geotechnicals was carried out by determining the estimated variance and weight coefficients. In addition, the optimal interpolation algorithm was selected through the indoor test and in-situ test, and the accuracy of the modeling of the soil and the prediction of the geotechnical parameters were analyzed. The results show that the modeling width error is between [0.04,0.20], the length error is between [0.7,0.23], the planar accuracy error is around 0.2cm, the depth error is within 0.02cm, and the errors of the actual and predicted values of the rock and map parameters are within 0.1 and 0.09, respectively. Geotechnical investigation measures and techniques in construction engineering based on multi-source data fusion can optimize construction engineering.

Lower bound on operation time of composite quantum gates robust against pulse length error

Precise control of quantum systems is a cornerstone for realizing high-quality quantum technology such as quantum computing and quantum communication. The performance of control of systems often deteriorates due to systematic errors. In one-qubit control, the pulse length error (PLE) is a typical systematic error, which is often caused by deviation of the strength of the control field. A composite quantum gate (CQG) is a method for suppressing effects of such systematic errors at the cost of a long operation time. A longer operation time implies stronger decoherence, and thus a shorter CQG is preferable from the viewpoint of noise immunity. However, it has not been clear how short CQG can be implemented. This problem can be regarded as an optimization problem under constraints: optimizing the operation time while requiring the error robustness. In this paper, we find a lower bound on operation time of all CQGs with first-order robustness against the PLE, in which effects of the error are eliminated up to its first order. The derivation of this bound is based on a geometric property of robustness against the PLE. This can be used for search after high-performance CQGs.

Accuracy and Precision of New Optical Biometer Designed for Myopia Management in Measurement of Ocular Biometry.

This study provides information about the repeatability of Myopia Master and its agreement with Lenstar LS900, which might be useful for the practitioners involved in myopia management. Myopia Master is a new optical biometer that measures ocular biometry and refractive error. The purpose of this study is to assess its repeatability (intra-session and short-term inter-session) and its agreement with Lenstar LS900 for the measurement of axial length and corneal curvature. A total of 304 participants including 254 children (Mean age: 13.7 ± 1.6 years) and 50 adults (24 ± 2.9 years) underwent measurements on Myopia Master and Lenstar LS900 to obtain axial length (AL), flat K (K1), and steep K (K2). On a subset of 30 participants, measurements were obtained with Myopia Master in two sessions that were spread over 10 minutes to assess the short-term inter-session repeatability. The mean standard deviation of Myopia Master in the measurement of axial length in the total sample was 0.01 mm for intra-session, when the best three measurements were considered. The short-term inter-session mean standard deviation for AL, K1, and K2 was 0.06 mm, 0.15 D, and 0.21 D respectively. There were statistically significant differences in mean values of AL (-0.04 ± 0.06 mm), K1 (-0.07 ± 0.15 D), and K2 (-0.24 ± 0.29 D) between Lenstar LS900 and Myopia Master with the Lenstar providing slightly longer axial length and steeper K values. Adults showed better repeatability with Myopia Master and better agreement between the biometers for AL measurement than children. Neither axial length nor refractive error influenced the repeatability or agreement. Myopia Master is repeatable for the measurement of axial length and corneal curvature. Considering the differences in axial length between the Myopia Master and Lenstar LS900, caution must be applied when these biometers are used interchangeably.

Profile reconstruction of irregular planar defects by mirrored composite-mode total focusing method

The direct, half-skip and full-skip modes adopt various ultrasonic reflected and mode-converted waves with different propagation paths between array elements and defects. Combining multiple modes and views is beneficial to effectively detecting regular planar defects, but it remains challenging to characterize the priori unknown irregular defects. In this paper, the mirrored composite-mode total focusing method (CTFM) is proposed by acquiring bilateral full matrix capture (FMC) datasets from irregular defects to demonstrate multi-faceted characteristics. A total of 6 effective views are selected for imaging, and the unilateral images are normalized with their Min-Max amplitude to perform mirrored CTFM, realizing the profile characterization and quantitative detection of priori unknown irregular planar defects. The 32-element linear array probes with 5 MHz central frequency and 45° wedges were employed to reconstruct a series of irregular defects composed of two branches with 4 mm length and different orientations by mirrored CTFM. The quantitative errors of length, angle and central depth for each defect were no more than 0.97 mm, 1.64° and 0.48 mm in simulation, respectively. The experimental results show that the profiles of irregular planar defects are presented by mirrored CTFM with high accuracy and have good consistency with simulated results. Finally, the effects of view selection, normalization and imaging threshold on the detection results of mirrored CTFM and its applicability are discussed by experiments.

Error Influence Simulation of the 500 m Aperture Spherical Radio Telescope Cable-Net Structure Based on Random Combinations

The reflector of a Chinese 500 m aperture spherical radio telescope is supported by a giant cable-net structure. In the actual operation process, active displacement observation is realized by connecting the actuators with the control cables to adjust the cable net, which requires high manufacturing and installation accuracy. In this study, an error sensitivity computing method based on a normal distribution is adopted to perform single-error computing and multi-error coupling computing and to investigate the effect of the length error of all the cables, tensioning force error of active surface cables, and installation error of external nodes on the cable force. The results show that the length error of the surface cables and the installation error of the external nodes are the main factors affecting the cable force, while the length error of the control cables is a secondary factor. The coupling effect of multiple errors is not the linear superposition of each error’s influence; therefore, all the error factors should be comprehensively considered for coupling computing to determine the control index. Through multi-error coupling computing, it is determined that the length error limits of the surface cables and control cables are ±1.5 mm and ±20 mm, respectively, the tensioning force error limit of the active surface cables is ±10%, and the installation error limit of the external nodes is ±50 mm.

Crushing behavior optimization of octagonal lattice‐structured thin‐walled 3D printed carbon fiber reinforced PETG (CF/PETG) composite tubes under axial loading

AbstractThin‐walled structures with good energy absorption capability can significantly use as energy absorbers in passive vehicle safety systems. The present study deals with designing and developing thin‐walled carbon fiber (CF) reinforced PETG (polyethylene terephthalate glycol) composite tubes with octagonal corrugated lattice structures on the lateral surfaces. The FFF (fused filament fabrication) factors such as layer height, nozzle temperature, printing speed, line width, and infill density were optimized. The experiment outcomes such as compressive strength and dimensional length error, are measured for the respective octagonal corrugated lattice structure incorporated in 3D printed CF/PETG composite tubes. The results proclaimed that, the optimum factors for improved compressive strength in the octagonal corrugated lattice‐structured CF/PETG composite will be 0.1 mm layer height, 220°C nozzle temperature, 20 mm/sec printing speed, 0.1 mm line width and 100% infill density. Furthermore, the R‐square value for the compressive strength and dimensional length error is within an acceptable limit of 91.25% and 93.31%. So, the developed mathematical models are in good form for practical acceptance. The optimized condition3D printed samples exhibit better compressive strength and lower dimensional length deviation, which is essential for considering it in the safety protection application in automotive components.Highlights• 3D printed octagonal shaped lattice structured PETG/CF composite tube.• Process parameters were optimized in terms of compressive strength.• Layer height has contributed a major impact on the compressive strength response.

Vision-based detection and coordinate metrology of a spatially encoded multi-sphere artefact

New developments in vision algorithms prioritise identification and perception over accurate coordinate measurement due to the complex problem of resolving object form and pose from images. Consequently, many vision algorithms for coordinate measurements rely on known targets of primitive forms that are typically planar targets with coded patterns placed in the field of view of vision systems. Although planar targets are commonly used, they have some drawbacks, including calibration difficulties, limited viewing angles, and increased localisation uncertainties. While traditional tactile coordinate measurement systems (CMSs) adopt spherical targets as the de facto artefacts for calibration and 3D registration, the use of spheres in vision systems is limited to occasional performance verification tasks. Despite being simple to calibrate and not having orientation-dependant limitations, sphere targets are infrequently used for vision-based in-situ coordinate metrology due to the lack of efficient multi-view vision algorithms for accurate sphere measurements. Here, we propose an edge-based vision measurement system that uses a multi-sphere artefact and new measurement models to extract sphere information and derive 3D coordinate measurements. Using a spatially encoded sphere identities embedded in the artefact, a sphere matching algorithm is developed to support pose determination and tracking. The proposed algorithms are evaluated for robustness, measurement quality and computational speed to assess their performance. At the range of 500 mm to 750 mm, sphere size errors of less than 25 μm and sphere-to-sphere length errors of less than 100 μm are achievable. In addition, the proposed algorithms are shown to improve robustness by up to a factor of four and boost computational speed.

Toward Realistic 3D Human Motion Prediction With a Spatio-Temporal Cross- Transformer Approach

Human motion prediction intends to predict how humans move given a historical sequence of 3D human motions. Recent transformer-based methods have attracted increasing attentions and demonstrated their promising performance in 3D human motion prediction. However, existing methods generally decompose the input of human motion information into spatial and temporal branches in a separate way and seldom consider their inherent coherence between the two branches, hence often failing to register the dynamic spatio-temporal information during the training process. Motivated by these issues, we propose a spatio-temporal cross-transformer network (STCT) for 3D human motion predictions. Specifically, we investigate various types of interaction methods (i.e., Concatenation Interaction, Msg token interaction, and Cross-transformer) to capture the coherence of the spatial and temporal branches. According to the obtained results, the proposed cross-transformer interaction method shows its superiority over other methods. Meanwhile, considering that most existing works treat the human body as a set of 3D human joint positions, the predicted human joints are proportionally less appropriate to the realistic human body due to unreasonable bone length and non-plausible poses as time progresses. We further resort to the bone constraints of human mesh to produce more realistic human motions. By fitting a parametric body model (i.e., SMPL-X model) to the predicted human joints, a reconstruction loss function is proposed to remedy the unreasonable bone length and pose errors. Comprehensive experiments on AMASS and Human3.6M datasets have demonstrated that our method achieves superior performance over compared methods.

Binocular measurement method for a continuous casting slab based on the one-dimensional probabilistic Hough transform and local sub-pixel sifting.

Due to the low measurement accuracy of the continuous casting slab model caused by difficulty in detecting ideal corners, a binocular measurement method based on the one-dimensional probabilistic Hough transform and local sub-pixel sifting is proposed. First, the one-dimensional probabilistic Hough transform based on inclination angle voting and the Freeman chain code is used to detect the line segments of the exterior outline. Next, sub-pixel points are extracted in each region of interest (ROI) by using Zernike moments, and sifted in the overlapping area of adjacent ROIs. Then the orthogonal total least squares (TLS) method is applied to fitting sub-pixel edges. Finally, after the key points are matched, three-dimensional localization and measurement are completed according to the binocular vision measurement principle. The experimental results show that the minimum relative error and average relative error of length reach 0.3401% and 0.3945%, respectively, satisfying the measurement requirement. Compared with scale-invariant feature transform (SIFT) and the oriented FAST and rotated BRIEF (ORB), the measurement error of the proposed algorithm is reduced by 80.01% and 74.63%, respectively. Compared with another edge fitting method based on k-means clustering and least squares fitting, its measurement error is reduced by 34.11%, and the time consumption is shortened by 39.07%, verifying its excellent performance in accuracy and efficiency.

Modeling and analysis of the equivalent convex mandrel of the three-dimensional braiding carbon fiber composite robotic arm

The third robotic arm (drive housing) of a six-axis industrial robot often has a vertical inwardly concave surface to facilitate the installation of spatially vertical drive motors. With the inwardly concave surface of the robotic arm it is difficult to realize three-dimensional (3D) braiding directly, and based on this problem, an equivalent convex mandrel is added to the concave mandrel. The mathematical model of the concave mandrel is established, and the mathematical expression of the concave mandrel is obtained. In any cross-section perpendicular to the x-axis, the equivalent outwardly convex cross-sectional line is obtained according to the condition that the length of the outwardly convex and concave mandrel cross-sectional line is equal. All outwardly convex cross-sectional lines form a smooth surface of the equivalent convex mandrel. By the numerical calculation method, the braiding trajectory and the downward pressure trajectory are predicted for various take-up speeds. The length error of the braiding trajectory and the downward pressure trajectory are within 5%, which verifies the accuracy of the convex mandrel. The variation pattern of the braiding angle is smooth, verifying the braidability of the convex mandrel. The experimental results show that the outwardly convex carbon fiber fabric can be pressed down to fit the surface of the concave mandrel. Therefore, a carbon fiber composite arm with an inwardly concave surface can be manufactured by 3D braiding with the addition of an equivalent convex mandrel.

Spatially resolved chemiluminescence imaging of multiple combustion species using a single high-speed camera

Simultaneous chemiluminescence (CL) imaging of multiple chemical species in unsteady and/or turbulent combustion environments requires multiple high-speed camera/intensifier systems which can be cost prohibitive. This study presents a novel optical configuration for simultaneous, spatially resolved CL imaging of two species using a single high-speed camera. The superiority of the technique over existing approaches is demonstrated via a series of experiments in a methane fueled McKenna burner operated at steady and unsteady conditions. Results demonstrate capabilities of the present system to provide spatially resolved measurements of hydroxyl (OH*) and methylidyne (CH*) species without parallax or path length errors in different flame configurations.

Development of a Skeletal Mechanism of a Four-Component Diesel Surrogate Fuel Using the Decoupling Method.

Alkylcyclohexanes with a long alkyl chain account for more than 30% of diesel fuel but seldom used in the oxidation mechanism of diesel surrogate fuel due to the lack of a reduced skeletal mechanism. Hence, a four-component diesel surrogate fuel was developed with n-butylcyclohexane (NBCH) as the representative of alkylcyclohexanes with a long alkyl chain in real diesel. The surrogate fuel can reproduce the physicochemical characteristics of real diesel, especially the distillation range. The reduced mechanism of NBCH was developed, and the skeletal mechanism of the surrogate fuel was formulated including 80 species and 251 reactions based on the decoupling method. The mechanism was validated under a wide range of conditions with the experimental results of ignition delay time (IDT), laminar flame speed, and species concentrations of both pure components and diesel. The accuracy of the mechanism on the spray and ignition performance was further validated against the experimental data obtained in a constant volume combustion chamber system. The calculated results showed a satisfactory agreement, in which the maximum error of flame lift-off length is 7.82 mm and that of IDTs is 0.16 ms. It was proven that the mechanism is suitable to reproduce the physicochemical properties of diesel and further predict the diesel spray and ignition performance.

A scintillation dosimeter with real-time positional tracking information for in vivo dosimetry error detection in HDR brachytherapy.

To evaluate the performance of an electromagnetic (EM)-tracked scintillation dosimeter in detecting source positional errors of IVD in HDR brachytherapy treatment. Two different scintillator dosimeter prototypes were coupled to 5 degrees-of-freedom (DOF) EM sensors read by an Aurora V3 system. The scintillators used were a 0.3 × 0.4 × 0.4 mm3 ZnSe:O and a BCF-60 plastic scintillator of 0.5 mm diameter and 2.0 mm in length (Saint-Gobain Crystals). The sensors were placed at the dosimeter's tip at 20.0 mm from the scintillator. The EM sampling rate was 40/s while the scintillator signal was sampled at 100 000/s using two photomultiplier tubes from Hamamatsu (series H10722) connected to a data acquisition board. A high-pass filter and a low-pass filter were used to separate the light signal into two different channels. All measurements were performed with an afterloader unit (Flexitron-Elekta AB, Sweden) in full-scattered (TG43) conditions. EM tracking was further used to provide distance/angle-dependent energy correction for the ZnSe:O inorganic scintillator. For the error detection part, lateral shifts of 0.5 to 3 mm were induced by moving the source away from its planned position. Indexer length (longitudinal) errors between 0.5 to 10 mm were also introduced. The measured dose rate difference was converted to a shift distance, with and without using the positional information from the EMsensor. The inorganic scintillator had both a signal-to-noise-ratio (SNR) and signal-to-background-ratio (SBR) close to 70 times higher than those of the plastic scintillator. The mean absolute difference from the dose measurement to the dose calculated with TG-43U1 was 1.5% ±0.7%. The mean absolute error for BCF-60 detector was 1.7% when compared to TG-43 calculations formalism. With the inorganic scintillator and EM tracking, a maximum area under the curve (AUC) gain of 24.0% was obtained for a 0.5-mm lateral shift when using the EMT data with the ZnSe:O. Lower AUC gains were obtained for a 3-mm lateral shifts with both scintillators. For the plastic scintillator, the highest gain from using EM tracking information occurred for a 0.5-mm lateral shift at 20 mm from the source. The maximal gain (17.4%) for longitudinal errors was found at the smallest shifts (0.5 mm). This work demonstrates that integrating EM tracking to in vivo scintillation dosimeters enables the detection of smaller shifts, by decreasing the dosimeter positioning uncertainty. It also serves to perform position-dependent energy correction for the inorganic scintillator,providing better SNR and SBR, allowing detection of errors at greater distances from thesource.

Overground gait adaptability in older adults with type 2 diabetes in response to virtual targets and physical obstacles.

To step over an unexpected obstacle, individuals adapt gait; they adjust step length in the anterior-posterior direction prior to the obstacle and minimum toe clearance height in the vertical direction during obstacle avoidance. Inability to adapt gait may lead to falls in older adults with diabetes as the results of the effects of diabetes on the sensory-motor control system. Therefore, this study aimed to investigate gait adaptability in older adults with diabetes. Would diabetes impair gait adaptability and increase sagittal foot adjustment errors? Three cohorts of 16 people were recruited: young adults (Group I), healthy older adults (Group II), and older adults with diabetes (Group III). Participants walked in baseline at their comfortable speeds. They then walked and responded to what was presented in gait adaptability tests, which included 40 trials with four random conditions: step shortening, step lengthening, obstacle avoiding, and walking through. Virtual step length targets were 40% of the baseline step length longer or shorter than the mean baseline step length; the actual obstacle was a 5-cm height across the walkway. A Vicon three-dimensional motion capture system and four A.M.T.I force plates were used to quantify spatiotemporal parameters of a gait cycle and sagittal foot adjustment errors (differences between desired and actual responses). Analyses of variance (ANOVA) repeated measured tests were used to investigate group and condition effects on dependent gait parameters at a significance level of 0.05. Statistical analyses of Group I (n = 16), Group II (n = 14) and Group III (n = 13) revealed that gait parameters did not differ between groups in baseline. However, they were significantly different in adaptability tests. Group III significantly increased their stance and double support times in adaptability tests, but these adaptations did not reduce their sagittal foot adjustment errors. They had the greatest step length errors and lowest toe-obstacle clearance, which could cause them to touch the obstacle more. The presented gait adaptability tests may serve as entry tests for falls prevention programs.

American Society of Biomechanics Journal of Biomechanics Award 2022: Computer models do not accurately predict human muscle passive muscle force and fiber length: Evaluating subject-specific modeling impact on musculoskeletal model predictions

Musculoskeletal models are valuable for studying and understanding the human body in a variety of clinical applications that include surgical planning, injury prevention, and prosthetic design. Subject-specific models have proven to be more accurate and useful compared to generic models. Nevertheless, it is important to validate all models when possible. To this end, gracilis muscle–tendon parameters were directly measured intraoperatively and used to test model predictions. The aim of this study was to evaluate the benefits and limitations of systematically incorporating subject-specific variables into muscle models used to predict passive force and fiber length. The results showed that incorporating subject-specific values generally reduced errors, although significant errors still existed. Optimization of the modeling parameter “tendon slack length” was explored in two cases: minimizing fiber length error and minimizing passive force error. The results showed that using all subject-specific values yielded the most favorable outcome in both models and optimization cases. However, the trade-off between fiber length error and passive force error will depend on the specific circumstances and research objectives due to significant individual errors. Notably, individual fiber length and passive force errors were as high as 20% and 37% respectively. Finally, the modeling parameter “tendon slack length” did not correlate with any real-world anatomical length.