Changes In Curvature Research Articles

Nonlinear dynamics of time-varying curvature balance rope coupled with time-varying length hoisting rope in friction hoisting system

Mine friction hoisting system is a typical multi-body system composed of traction sheave, conveyance, hoisting rope, and balance rope. Hoisting rope is of large-scale and flexible tension, leading to large amplitude elastic vibration and huge tension fluctuation during hoisting movement. Balance rope is of small tension amplitude and bending modulus, undergoing significant curvature changes, large displacement, and large deformation. Considering the complex coupling vibrations between the moving hoisting rope and balance rope in the ultra-kilometer-deep shaft, a coupling modeling method of the variable-length hoisting rope with the variable-curvature balance rope is proposed. Based on the absolute nodal coordinate formulation(ANCF), the balance rope is modeled by non-equal-length and variable-number elements, and the hoisting ropes on both sides are modeled by variable-length and variable-number elements. A flexible rope vibration experiment platform is built in the laboratory to verify correctness of the proposed theoretical model.The experimental results are in good agreement with those in theoretical simulation. Besides, the nonlinear coupling dynamic behaviors of hoisting rope and balance rope in an ultra-kilometer-deep well are studied. It reveals the non-stationary phenomenon of hoisting rope and balance rope with a long-time range. Both sides of flat balance rope undergo large bending deformation and non-stationary response when transient resonance occurs in hoisting ropes.

Highly sensitive temperature and curvature sensor based on seven-core fiber

A high sensitivity temperature and curvature micro-fiber Mach-Zehnder interferometer (MMZI) sensor is proposed and demonstrated. A peanut structure is fused by a section of seven-core fiber (SCF) and a section of single-mode fiber (SMF). Then the SCF is connected to another SMF and tapered. Finally, the composite structure with the tapered SCF and the SCF-SMF peanut structure is fabricated. The coupling efficiency can be significantly improved, and more high-order modes can be stimulated via the new sensor structure. The experimental results demonstrated that the maximum temperature sensitivity is 836.67 pm/ °C in the range of 35 °C to 40 °C, which is the highest temperature sensitivity of the peanut-shaped MMZI sensor to the best of our knowledge. Furthermore, the sensor can be used for curvature measurement. When the curvature changes from 0 m−1 to 0.0522449 m−1, the sensitivity can achieve 93.33664 nm/m−1. The proposed sensor not only provides a novel method to fabricate a high-sensitivity sensor by combining different types of fibers, but it also has a meaningful application prospect in the fields of biological detection and environmental monitoring.

Bending Sensing Based on Quasi Bound States in the Continuum in Flexible Terahertz Metasurface

AbstractBound states in the continuum (BIC) promote strong interaction between light and matter, which has been introduced into the metasurfaces to achieve ultra‐high Q resonance and provide a powerful tool for high‐sensitivity sensing. At present, BIC‐based sensors have been applied in biological and chemical sensing. Here, their application in bending sensing is investigated. BIC is employed to design the terahertz metallic metasurfaces and propose a feasible method for the high‐Q sensitivity detection of micro‐bending. It is demonstrated theoretically and experimentally that BIC can transform into an observable quasi‐BIC by tuning the structural parameters. More importantly, it is the first report to investigate the bending sensing performance of BIC metallic metasurfaces. The experimental results verify that both metasurfaces supporting symmetry‐protected BIC and parameter‐tuned BIC are sensitive to changes in curvatures. It indicates that the designed BIC metasurfaces can realize the bending deformation detection of some precision instruments. These results expand the application of BIC‐based sensors in the sensing field. It is expected that the design can find potential applications in wearable photonic devices, intelligent robots, and bionic machines.

Real-Time Monitoring of Human Breathing Using Wearable Tilted Fiber Grating Curvature Sensors

Respiration rate and volume are important physiological indicators of human health. They can indicate cardiovascular health status and cardiopulmonary function. Here, we demonstrate a compact breath monitoring system based on a wearable tilted fiber Bragg grating (TFBG) curvature sensor for human respiration monitoring. With the assistance of a custom designed breathing tube, TFBGs provide a very reproducible highly sensitive, real time response to curvature changes during respiration. The miniaturized and cost effective sensing system which we propose consists of a tunable laser module, a field programmable gate array acquisition control circuit module, and a sensor module. Different breathing patterns can be successfully identified from the optical amplitude and frequency output of the sensor. The robust instrument displays high repeatability and real-time tracking.

Lane Change–Intention Inference and Trajectory Prediction of Surrounding Vehicles on Highways

The behavior prediction of the surrounding vehicles is crucial when planning a minimal-risk path when realizing a collision-avoidance system. Herein, we propose a multiple model–based adaptive estimator (MMAE) that infers the lane-change intention of the surrounding vehicles and then predicts their trajectories. Specifically, first, a path is generated in the form of a cubic spline curve using the Frenet coordinate system, which is robust to changes in road curvatures. Linearized recursive least-squares estimation (LRLSE) method is used to adaptively predict a future trajectory based on the past trajectory of the target vehicle. Preview time is defined as a time-varying parameter that determines the final point of the path, and LRLSE updates it in real time. The MMAE applies LRLSEs to multiple paths and obtains the mode probability for each path, then the lane-change intention is inferred using the mode probability and preview time. The predicted future trajectory is the cubic spline curve determined based on the preview time. Further, we verify the performance of our approach using highD, a naturalistic dataset of vehicle trajectories, and compare it with those of existing methods. The proposed method does not require a large amount of data for training and has a low computational burden and high real-time performance.

Examination of surface milling performance of micro-textured ball milling cutter

To cope with the constant change of tool–work contact area caused by the constant change of workpiece surface curvature during machining surface, the tool–work contact area is evaluated, and the mathematical model of micro-texture distribution is constructed. The milling simulation is carried out by ABAQUS software. The obtained results show that the tool inclination angle is the main factor affecting the milling force, and the micro-texture diameter is the leading factor influencing the milling temperature. Subsequently, the milling experiment is carried out, and a reasonably good agreement between the observed data and the simulation results is reported. The artificial fish swarm algorithm is also exploited to optimize the parameters.

Insight on the mechanism of hexameric Pseudin-4 against bacterial membrane-mimetic environment.

As an alternative to antibiotics, Antimicrobial Peptides (AMPs) possess unique properties including cationic, amphipathic and their abundance in nature, but the exact characteristics of AMPs against bacterial membranes are still undetermined. To estimate the structural stability and functional activity of AMPs, the Pseudin AMPs (Pse-1, Pse-2, Pse-3, and Pse-4) from Hylid frog species, Pseudis paradoxa, an abundantly discovered source for AMPs were examined. We studied the intra-peptide interactions and thermal denaturation stability of peptides, as well as the geometrical parameters and secondary structure profiles of their conformational trajectories. On this basis, the peptides were screened out and the highly stable peptide, Pse-4 was subjected to membrane simulation in order to observe the changes in membrane curvature formed by Pse-4 insertion. Monomeric Pse-4 was found to initiate the membrane disruption; however, a stable multimeric form of Pse-4 might be competent to counterbalance the helix-coil transition and to resist the hydrophobic membrane environment. Eventually, hexameric Pse-4 on membrane simulation exhibited the hydrogen bond formation with E. coli bacterial membrane and thereby, leading to the formation of membrane spanning pore that allowed the entry of excess water molecules into the membrane shell, thus causing membrane deformation. Our report points out the mechanism of Pse-4 peptide against the bacterial membrane for the first time. Relatively, Pse-4 works on the barrel stave model against E. coli bacterial membrane; hence it might act as a good therapeutic scaffold in the treatment of multi-drug resistant bacterial strains.

Self-Supervised Continual Graph Learning in Adaptive Riemannian Spaces

Continual graph learning routinely finds its role in a variety of real-world applications where the graph data with different tasks come sequentially. Despite the success of prior works, it still faces great challenges. On the one hand, existing methods work with the zero-curvature Euclidean space, and largely ignore the fact that curvature varies over the com- ing graph sequence. On the other hand, continual learners in the literature rely on abundant labels, but labeling graph in practice is particularly hard especially for the continuously emerging graphs on-the-fly. To address the aforementioned challenges, we propose to explore a challenging yet practical problem, the self-supervised continual graph learning in adaptive Riemannian spaces. In this paper, we propose a novel self-supervised Riemannian Graph Continual Learner (RieGrace). In RieGrace, we first design an Adaptive Riemannian GCN (AdaRGCN), a unified GCN coupled with a neural curvature adapter, so that Riemannian space is shaped by the learnt curvature adaptive to each graph. Then, we present a Label-free Lorentz Distillation approach, in which we create teacher-student AdaRGCN for the graph sequence. The student successively performs intra-distillation from itself and inter-distillation from the teacher so as to consolidate knowledge without catastrophic forgetting. In particular, we propose a theoretically grounded Generalized Lorentz Projection for the contrastive distillation in Riemannian space. Extensive experiments on the benchmark datasets show the superiority of RieGrace, and additionally, we investigate on how curvature changes over the graph sequence.

A Global Structure and Adaptive Weight Aware ICP Algorithm for Image Registration

As an important technology in 3D vision, point-cloud registration has broad development prospects in the fields of space-based remote sensing, photogrammetry, robotics, and so on. Of the available algorithms, the Iterative Closest Point (ICP) algorithm has been used as the classic algorithm for solving point cloud registration. However, with the point cloud data being under the influence of noise, outliers, overlapping values, and other issues, the performance of the ICP algorithm will be affected to varying degrees. This paper proposes a global structure and adaptive weight aware ICP algorithm (GSAW-ICP) for image registration. Specifically, we first proposed a global structure mathematical model based on the reconstruction of local surfaces using both the rotation of normal vectors and the change in curvature, so as to better describe the deformation of the object. The model was optimized for the convergence strategy, so that it had a wider convergence domain and a better convergence effect than either of the original point-to-point or point-to-point constrained models. Secondly, for outliers and overlapping values, the GSAW-ICP algorithm was able to assign appropriate weights, so as to optimize both the noise and outlier interference of the overall system. Our proposed algorithm was extensively tested on noisy, anomalous, and real datasets, and the proposed method was proven to have a better performance than other state-of-the-art algorithms.

Curvature monotonicity evaluation functions on rational Bézier curves

We have derived functions of the lowest possible degree that enable us to evaluate curvature monotonicity for any 2D and 3D rational Bézier curves. We proved that the degree of the function is at most 8n−12 for planar rational Bézier curves of degree n, and is at most 11n−18 for space rational Bézier curves of degree n. These functions are derived in the Bernstein basis, allowing for efficient checking of curvature monotonicity using subdivision or Bézier clipping. As an application, we present real-time visualization of the region of a particular control point that guarantees monotonic variation of curvature over the entire segment of the rational Bézier curve. This allows users to identify where to move the control point to ensure that the curvature changes monotonically.

Hügelschäffer Egg Curves as Transition Curves in Road Design

Roads and railways, as the main parts of traffic infrastructure, represent geometrically rigid elements which are hard to adapt to certain kinds of landscapes without making large changes to the terrain itself. Today, thanks to modern technology and a large number of software tools, it is possible to define new geometric curves which are easily adaptable for use as transition curves when designing roads or railways. These transition curves can be formed in such a way to make them fit in with the surrounding landscape or urban environment better, which can improve the aesthetics of the transport system. Furthermore, transition curves provide a smooth and gradual change of curvature, reducing the risk of sudden curvature changes, which can cause discomfort to passengers and create an unsafe situation, such as a loss of vehicle control or a train derailment. Accordingly, in this paper, we define the parameters for generating Hügelschäffer curves as new transition curves between two circular road segments.

(163) Efficacy of Collagenase Clostridium Histolyticum in Calcified Peyronie’s Disease

Abstract Introduction Peyronie’s disease (PD) affects between 0.4% and 13% of the male population. It leads to inelastic scar tissue in the tunica albuginea which in turn leads to penile curvature, deformity, and shortening. Collagenase clostridium histolyticum (CCH) is the only FDA approved intralesional medication for PD, but its efficacy in calcified PD remains controversial. The two large, double-blind, placebo controlled randomized clinical trials, known as the IMPRESS trials, excluded men with calcified plaques, which occurs in 25-30% of all patients with PD. Objective We aimed to evaluate change in penile curvature in men with calcified PD plaques after 8 injections of CCH in a large cohort of men Methods We prospectively evaluated men with PD presenting to our clinic from October 2018 to November 2020 electing CCH treatment. All men received a pre-treatment penile duplex ultrasound with artificial erection to assess degree of calcification and curvature. We used a grading system to assess calcification: Type 1: The plaque appears as a thickening of the tunica albuginea without acoustic shadowing; Type 2: A moderately calcified plaque with a typical ultrasound shadow, and Type 3: A severely calcified plaque with complete ultrasound shadowing. All men received CCH (0.58 mg) injected directly into the primary plaque at the point of maximal penile curvature using a standardized injection technique following the manufacturer's instructions. Cycles were terminated early if the patient was satisfied with the curvature or subjects reached less than 15 degrees. We remeasured the curvature in patients 4-6 weeks after the final CCH with artificial erection. All results are presented as mean ± standard deviation (SD) Results In total, 60 patents presented with calcified PD plaques with 32 (53.3%) receiving all 8 injections and another 5 patients were satisfied with results and elected to stop treatment. The remaining 23 (38.3%) discontinued before finishing; on average they received 5.6 injections. There were no differences in baseline characteristics between men who completed treatment and those that discontinued. In patients who were satisfied there was significant (p<0.0001) mean change per subject of -21.6 ± 19.9 degrees or 37.3% (Table 1). In the discontinued there was a mean change per subject of -12.8 ± 13.9 degrees (p=0.05). There was no significance difference in change in curvature between grade 2 (-24 ± 14.9 degrees) and grade 3 (-21.3 ± 23.4 degrees) calcified plaques (p=0.71) (Table 1). Conclusions Overall, CCH appears effective in the treatment of patients with calcified PD plaques. In patients who successfully completed 8 injections or was satisfied there was a significant difference in curvature after treatment and can help inform patients about treatment benefits despite calcification. Disclosure Yes, this is sponsored by industry/sponsor: Endo Pharmaceuticals Clarification Industry funding only - investigator initiated and executed study

(375) Can Tamoxifen and a PDE5 inhibitor slow the progression of Peyronie’s Disease?

Abstract Introduction The available treatments for Peyronie’s Disease as recommended by international guidelines are either surgery or intralesional injection therapy. In recently cell and rat studies it has been shown that using a phosophdiesterase type 5 inhibitor (PDE5i) and a selective oestrogen receptor modulator (Tamoxifen) inhibited myofibroblast transformation and extracellular matrix production. Objective The aim of this study is to compare the combination of tamoxifen and a PDE5i versus no treatment or other oral medications in the progression of early Peyronie’s Disease. Methods This is a retrospective study of all patients with early Peyronie’s Disease, defined as less than 6 months duration or persistent pain presenting over a 3-year period. Patients were given Tamoxifen 20mg twice daily + Tadalafil 5mg daily for 2 months. The control group either received no treatment or simple oral medication such as Vitamin E. Data retrieved included demographics, duration of disease, change in curvature and pain, as well as further treatment modalities. Assessment of curvature was with photos or an artificial erection test. Data was analysed using the Mann-Whitney Test. Results A total of 147 patients were recruited with early Peyronie’s Disease, 102 patients given the active drug combination (median age 49, range 24-71) and 45 controls (median age 55, range 27-76). The results in each group are presented in Table 1. Overall, the patients on Tamoxifen and Tadalafil showed more improvement and less deterioration which was statistically significant (p=0.009) Conclusions The combination of Tamoxifen and Tadalafil has been shown to prevent the progression of Peyronie’s Disease in vitro and in this study in patients with early disease. Future prospective studies are warranted to confirm this finding. Disclosure No

(157) Advanced Practice Providers Deliver Equivalent Outcomes with CCH Injection for Peyronie’s Disease

Abstract Introduction Independently performed procedures by well-trained advanced practice providers (APP) facilitate access to specialized care. We sought to compare outcomes between physicians and APPs with intralesional collagenase clostridium histolyticum (CCH). Objective Compare outcomes of CCH injections based on injection provider. Outcomes included curvature improvement and adverse events. Methods Men receiving CCH between 2014-2021 at our institution by four physicians and four APPs were included in an IRB-approved database. CCH was delivered as a series of 8 injections per protocol. Patient demographics, procedural-related adverse events, and curvature changes were recorded. The “APP-ratio” is defined as percentage of total injections administered by an APP per patient. Results After excluding patients who did not complete the entire CCH course or return for final assessment, 150/406 patients were analyzed. Mean baseline penile curvature was 66.2° (SD 23). Mean absolute and percent improvements in curvature were 21.7° (SD 18) and 33% (SD 27). The mean APP ratio was 69%, and 133 patients (89%) had at least 25% of their injections performed by an APP. There was no significant difference (p=0.65, p=0.39) in absolute or relative curvature improvement based on the APP-ratio [Figure 1]. There was also no difference in adverse events (pain, swelling, and hematoma). Conclusions In our high-volume CCH practice, APPs achieve the same outcomes and safety compared to physicians. Greater training efforts expand access to care for patients with PD. Disclosure No

(104) A Multicenter Evaluation of Penile Curvature Correction in Men with Peyronie’s Disease Undergoing Inflatable Penile Prosthesis Placement

Abstract Introduction Inflatable penile prosthesis (IPP) insertion is recommended for the treatment of patients with Peyronie’s Disease (PD) and significant erectile dysfunction (ED). Adjunctive procedures such as modeling, plication, or incision/excision and grafting can be used when there is residual curvature after IPP placement. Objective To evaluate the management of curvature correction in patients with PD undergoing IPP among high-volume prosthetic urologists. Methods We performed a retrospective study of 205 patients diagnosed with PD undergoing IPP by 7 high volume penile prosthetic surgeons. Demographic, intraoperative, and postoperative data were collected and analyzed. Descriptive statistics were performed using mean and standard deviation for continuous variables, while incidence and percentages were used for categorical variables. We calculated the mean change in penile curvature after IPP insertion for each of the adjunctive correction techniques. Intra- and post-operative complications were collected. Results 205 patients met inclusion criteria with a mean age of 60.7 years (SD=9.2) and a median follow-up of 6 months (0.5-58.5 months). The mean preoperative curvature was 43.4° (SD=18.9°) with dorsal curvature being the most common. Overall, 73 (35.60%) patients had IPP only with no adjunctive curvature correction procedure, 24 (11.70%) underwent plication, 10 (4.90%) underwent grafting, and 98 (47.80%) underwent modeling. Preoperatively, the mean starting curvature was 35.7° for the IPP-only group, 48.1° for the plication group, 60.6° for the grafting group, and 46.0° for the modeling group, p<0.001. Patients undergoing grafting had significantly fewer comorbidities compared to the other groups: only 1 (10%) had diabetes and none were smokers or had cardiovascular disease, p<0.001. After penile curvature correction, the mean curvature change was 25.5° for the IPP-only group, 40.0° for the plication group, 55.0° for the grafting group, and 35.0° for the modeling group, p <0.001 (Figure 1). Intraoperatively, proximal perforation occurred in 2 (0.96%) patients, managed by a rear tip extender sling. Post-operatively, there were 33 (16.10%) non-infectious and 4 (1.90%) infectious complications. There was no significant difference in complications between groups. Conclusions Although incision/excision and grafting seem to provide the greatest penile curvature correction for PD patients undergoing IPP placement, this adjunctive correction procedure is less commonly performed among high volume prosthetic urologists. Our results suggest grafting is reserved for patients with greater preoperative curvature and fewer preoperative comorbidities. Disclosure Any of the authors act as a consultant, employee or shareholder of an industry for: Antares Pharma: SpeakBoston Scientific, Clarus Therapeutics, Coloplast, Cynosure, Promescent, Sprout, Viome, Hims & Hers Health, Inc.

Investigation of ocular biometry in 4– to 9-year-old Chinese children

PurposeTo investigate the distribution and changes in ocular biometry in 4-to to 9-year-old Chinese children and to compare the differences between age and genders in these parameters.MethodsThis was a school-based cross-sectional study. A total of 1,528 Chinese children, aged 4–9 years, from one primary school and 12 kindergartens, were included in the study. Axial length, corneal curvature, anterior chamber depth, and corneal diameter were measured for each child.ResultsAL and anterior chamber depth gradually increased with age in both genders. No significant changes in corneal curvature or corneal diameter were detected at different ages in either genders group. The mean ALs of males and females were 22.94 ± 0.80 mm and 22.38 ± 0.79 mm, respectively. The mean corneal curvatures of males and females were 43.05 ± 1.37 D and 43.75 ± 1.48 D, respectively. The mean anterior chamber depth of males and females were 3.47 ± 0.24 mm and 3.38 ± 0.25 mm, respectively. The mean corneal diameter of males and females were 12.08 ± 0.43 mm and 11.94 ± 0.44 mm, respectively. Females had consistently shorter ALs, shorter anterior chamber depth, smaller corneal diameter, and steeper corneal curvatures than males at any age.ConclusionsBoys had larger dimensions than girls for all ocular parameters except corneal curvature (flatter). Boys and girls showed similar trends for all parameters. Axial length and anterior chamber depth increased from 4 to 9 years of age, whereas corneal diameter and curvature did not change with age in either genders.

Mechanical strength and nature of lithospheric deformation beneath the rifted sedimentary basins of the east India passive margin

The study of gravity signatures corresponding to sediment load over the passive margins is helpful to constrain the mechanical properties of continental rift systems as well as the adjacent ocean basins. Seismic reflection, free-air gravity and well information from the East India Passive Margin (EIPM) are investigated through spectral approach and 2D process-oriented gravity modelling for quantifying effective elastic plate thickness (Te) to understand the rift mechanisms and the sedimentary basins evolution. The characteristics of lithosphere within the major structural domains along the margin are quite variable. A narrow necking zone (40 km) in the southern segment, and approximately a 70 km hyper-thinned and exhumed domains are inferred in the central segment, while a narrow hyper-thinned domain (30–35 km) is observed in the northern segment of the margin. The southern segment of EIPM, adjacent to Southern Granulite Terrain has low Te values ranging from 5 to 10 km. The segment in the central margin, offshore Dharwar Craton has moderate Te values of 15–20 km. And the northern segment adjacent to onshore Eastern Ghats Mobile Belt has relatively high mechanical strength with Te values ranging from 25 to 35 km. The pattern of Te values and extent of major structural domains along the margin indicates that the southern, central and northern segments evolved as three different modes of rifting such as transform, hyperextended and hypoextended, respectively. In the oceanic domain, the lithospheric strength broadly increases with age following the thermal induced cooling plate model (600 °C isotherm). The thick sedimentary basin of the Bay of Bengal had attained the high value of elastic thickness (Te > 45 km) in the last 23 Myrs. The significant rheological strengthening of the oceanic lithosphere may be attribute to the following reasons: 1) increase in shear-wave velocity anomaly at a depth of 150 km and upper mantle density, 2) change in plate curvature caused by excessive deposition of Bengal Fan sediments in the deep ocean basins and subduction of oceanic plate under the Eurasian plate near the Bengal Fan and 3) modification of stress state of the lithosphere as a convergent interaction of the Indian plate with SE Asia.

Curvature and shape relaxation in surface-viscous domains.

The mechanics of curved, heterogeneous, surfactant-laden surfaces and interfaces are important to a variety of engineering and biological applications. To date, most models of rheologically complex interfaces have focused on homogeneous systems of planar or fixed curvature. In this study, we investigate a simple, dynamical model of a two-phase surface fluid on a curved interface: a condensed, surface-viscous domain embedded within a surface-inviscid, spherical interface of time-varying radius of curvature. Our aim is to understand how changes in surface curvature generate two-dimensional Stokes flows inside the domain, thereby resisting curvature deformation and distorting the domain shape. We model the surface stress within the domain using the classical Boussinesq-Scriven constitutive equation, simplified for a near-spherical cap undergoing a small-amplitude curvature deformation. We then analyze the frequency-dependent dynamics of the surface stress and curvature within the domain when the pressure difference across the surface is sinusoidally oscillated. We find that the curvature relaxes diffusively, and thus define a Peclet number (Pe) relating the rate of diffusion to the oscillation frequency. At small enough Pe, the surface deforms quasi-statically, whereas at high Pe, the curvature varies sharply within a thin boundary layer adjacent to the domain border. Consequently, the curvature of the domain appears discontinuous from the rest of the surface under rapid oscillation. We then examine the linear stability of the domain shape to small, non-axisymmetric perturbations when the surface is steadily compressed (i.e., the pressure difference across it is increased). While the line tension at the domain border tends to maintain circular symmetry, surface-viscous stresses generated by surface compression tend to destabilize the perimeter. A shape instability arises above a critical surface capillary number (Ca) relating surface-viscous stresses to line tension. Moreover, we show that the mechanism of instability is distinct from that of the famous Saffman-Taylor fingering instability. Various extensions of our model are discussed, including materials with finite dilatational surface viscosity, linear and nonlinear (visco)elasticity, and large-amplitude deformations.

Theoretical and experimental study on FBG bending sensor for quantitative monitoring of bolt looseness

A quantitative monitoring method for bolt looseness using an elastic substrate fiber Bragg grating (FBG) bending sensor is presented in this paper, which is achieved by measuring the wavelength shift of the FBG sensor response to the bending curvature change induced by bolt loose angle variation. The theoretical sensing principle is established based on the deformation model of an inextensible elastic beam under prescribed end rotations. The influence parameters on the FBG bending sensor are investigated numerically under the bolt loose angle variation from 0° to 15°, and the position on the sensor with maximum curvature difference varying linearly to bolt loose angle variation is obtained and selected to arrange the FBG. Based on the theoretical and numerical analysis, a general solution of the wavelength shifts of the FBG bending sensor versus bolt loose angle under an optimal initial installation condition (i.e., d/l=0.9, and s/l = 0.85) is established for quantitative monitoring bolt looseness. The feasibility and performance of the proposed method are experimentally verified and the maximum error between numerical and experimental results is less than 6.19%. The results indicate that the proposed method can quantitatively monitor bolt loose angle with high resolution (about 0.005°), also prove that the theoretical derivation in this paper and the proposed design criteria can theoretically guide the monitoring of bolt looseness using FBG bending sensor.

Investigating the Path Tracking Algorithm Based on BP Neural Network.

In this paper, we propose an adaptive path tracking algorithm based on the BP (back propagation) neural network to increase the performance of vehicle path tracking in different paths. Specifically, based on the kinematic model of the vehicle, the front wheel steering angle of the vehicle was derived with the PP (Pure Pursuit) algorithm, and related parameters affecting path tracking accuracy were analyzed. In the next step, BP neural networks were introduced and vehicle speed, radius of path curvature, and lateral error were used as inputs to train models. The output of the model was used as the control coefficient of the PP algorithm to improve the accuracy of the calculation of the front wheel steering angle, which is referred to as the BP-PP algorithm in this paper. As a final step, simulation experiments and real vehicle experiments are performed to verify the algorithm's performance. Simulation experiments show that compared with the traditional path tracking algorithm, the average tracking error of BP-PP algorithm is reduced by 0.025 m when traveling at a speed of 3 m/s on a straight path, and the average tracking error is reduced by 0.27 m, 0.42 m, and 0.67 m, respectively, at a speed of 1.5 m/s with a curvature radius of 6.8 m, 5.5 m, and 4.5 m, respectively. In the real vehicle experiment, an electric patrol vehicle with an autonomous tracking function was used as the experimental platform. The average tracking error was reduced by 0.1 m and 0.086 m on a rectangular road and a large curvature road, respectively. Experimental results show that the proposed algorithm performs well in both simulation and actual scenarios, improves the accuracy of path tracking, and enhances the robustness of the system. Moreover, facing paths with changes in road curvature, the BP-PP algorithm achieved significant improvement and demonstrated great robustness. In conclusion, the proposed BP-PP algorithm reduced the interference of nonlinear factors on the system and did not require complex calculations. Furthermore, the proposed algorithm has been applied to the autonomous driving patrol vehicle in the park and achieved good results.