Surface Tracking Research Articles

Fluid-evolving landform interaction by a surface-tracking method

This paper introduces a continuous finite element model to simulate fluid flow-bedform interaction problems. The approach utilizes a non-oscillatory finite element algorithm to compute the fluid dynamics by solving the complete Navier–Stokes equations. Additionally, it addresses the evolution of the fluid–bedform interface as a consequence of spatially non-balanced sediment fluxes through the solution of a conservation equation for the erodible layer thickness. A sign preservation algorithm is particularly relevant for landform tracking because a positive definite thickness of the erodible sediment layer is essential to model the interaction between evolving cohesionless sediment layers and rigid beds. The fluid/terrain interface is explicitly captured through a surface tracking methodology. First, new nodes fitting the interface are incorporated into the finite element mesh; then, elements beneath this interface are deactivated, while intersected elements are restructured to get a mesh composed exclusively of tetrahedral elements. Numerical experiments demonstrate capabilities of the method by exploring relevant problems related with civil engineering, such as the evolution of trenches and the scour of a submerged pile.

Surface Tracking Controls of an Unmanned Underwater Vehicle with Fixed Sonar Ray Measurements in Tunnel-Like Environments

This paper introduces 3-D surface tracking control of an Unmanned Underwater Vehicle (UUV) in tunnel-like environments. Consider the case where a sonar transducer in the UUV does not rotate, and it only emits fixed sonar ray reporting a simple distance measurement. This reduces the power consumption of the UUV, while reducing the UUV’s size and price. The UUV is controlled to proceed in tunnel-like environments, while maintaining a predefined distance from the tunnel boundaries. For maintaining a predefined distance from tunnel boundaries, the UUV uses fixed sonar rays surrounding it. As far as we know, our article is novel in developing 3-D surface tracking controls of tunnel-like environments utilizing an UUV with fixed sonar rays surrounding it. MATLAB simulations are used for demonstrating the performance of the proposed tracking controls.

Tracking control problem of nonlinear strict-feedback systems with input nonlinearity: An adaptive neural network dynamic surface control method.

In this work, the tracking control problem for a class of nonlinear strict-feedback systems with input nonlinearity is addressed. In response to the influence of input nonlinearity, an auxiliary control system is constructed to compensate for it. To process unknown nonlinear dynamics, radial basis function neural networks (RBFNNs) are introduced to approximate them, and some adaptive updating control laws are designed to estimate unknown parameters. Furthermore, during the dynamic surface control (DSC) design process, first-order low-pass filters are introduced to solve the complexity explosion problems caused by repeated differentiation. After that, an NN-based adaptive dynamic surface tracking controller is proposed to achieve the tracking control. By applying the proposed controller, it can be guaranteed that not only the output of the system can track the desired trajectory, but also that the tracking error can converge to a small neighborhood of zero, while all signals of the closed-loop system are bounded. Finally, the effectiveness of the proposed controller is verified through two examples.

The Remove-the-Mask Open-Source head and neck Surface-Guided radiation therapy system

Background and PurposeSurface Guided Radiotherapy (SGRT) for head and neck radiotherapy is challenging as obstructions are common and non-rigid facial motion can compromise surface accuracy. The purpose of this work was to develop and benchmark the Remove the Mask (RtM) SGRT system, an open-source system especially designed to address the challenges faced in radiotherapy of head and neck cancer. Materials and MethodsThe accuracy of the RtM SGRT system was benchmarked using a head phantom positioned on a robotic motion platform capable of sub-millimetre accuracy which was used to induce unidirectional shifts and to reproduce three real head motion traces. We also assessed the accuracy of the system in ten humans volunteers. The ground truth motion of the volunteers was obtained using a commercial motion capture system with an accuracy < 0.3 mm. ResultsThe mean tracking error of the RtM SGRT system for the ten volunteers was of −0.1 ± 0.4 mm −0.6 ± 0.6 mm and 0.3 ± 0.2 mm, and 0.0 ± 0.2° 0.0 ± 0.1° and 0.0 ± 0.2° for translations and rotations along the left–right, superior-inferior and anterior-posterior axes respectively and we also found similar results in measurements with the head phantom. Forced facial motion was associated with lower tracking accuracy. The RtM SGRT system achieved submillimetre accuracy. ConclusionThe RtM SGRT system is a low-cost, easy to build and open-source SGRT system that can achieve an accuracy that meets international commissioning guidelines. Its open-source and modular design allows for the development and easy translation of novel surface tracking techniques.

Melt pool electromagnetic force model extended to account for free surface deformation – Application to gas metal arc

Computational fluid dynamics models with free surface tracking intended to simulate the melt pool produced by an electric arc usually model the electromagnetic force ignoring the deformation of the free surface. However, with an arc heat source, the electromagnetic force is known to be among the leading-order forces, especially at high currents. In addition, the free surface can undergo significant deformations, especially in the presence of metal transfer. In the present study, a generalization of the electromagnetic force model that accounts for the deformation of the free surface is therefore proposed. Test cases with a pulsed gas-metal arc that transfers one metal drop per pulse were investigated experimentally at three different travel speeds to provide validation data. The cases were simulated with both the proposed and the earlier model to assess the influence of the new developments. The results showed that, in the regions where both models determine the force, the discrepancy between the models' results can reach up to an order of magnitude. Especially, the earlier model overestimates the electromagnetic force deep into the melt pool. On the other hand, it neglects it in the liquid metal that is located at an elevation above the original upper surface of the workpiece, while the proposed model showed that in this area the intensity of the electromagnetic force is the largest. These significant discrepancies result in non-negligible differences in the predicted melt pool thermal flow and geometry. Especially, the proposed extended model provides an improved prediction of the fingertip-shaped fusion boundary.

Feasibility and tolerability of breath-hold in liver stereotactic body radiotherapy with surface guided radiotherapy

PurposeIntrafractional motion constitutes a significant challenge in SBRT (Stereotactic Body Radiotherapy).The breath-hold (BH) technique is employed to mitigate tumor motion; however, ensuring reproducibility and consistency remains critically important. Surface tracking systems, integrated into the treatment process, facilitate motion tracking through three-dimensional camera technology. Surface guidance has been incorporated with Varian EDGE (Varian Medical Systems, Palo Alto, CA, USA) and has been utilized at multiple treatment sites within our department since 2018. Drawing on four years of experience, this study aims to publish patient experience, assess the feasibility, and evaluate the tolerability of breath-hold during SBRT with surface guided radiotherapy (SGRT), particularly focusing on a specific subgroup: patients with liver metastases. MethodsProspective evaluation was conducted on patients with liver metastases undergoing breath-hold SBRT with SGRT. A two-step survey consisting of seven questions was administered after CT simulation and treatment. Treatment duration and the number of breath-holds were recorded. Additionally, factors potentially influencing SGRT and treatment time were assessed. ResultsBetween April 2021 and May 2022, a total of 41 patients underwent 171 fractions of treatment. According to the questionnaire, prior training was found to be beneficial, and breath-holding during the procedure was tolerable. Patients reported experiencing slight stress due to their active participation in the treatment. Factors such as Karnofsky Performance Status (KPS), age, lung volume, conditions affecting lung capacity, previous breath-hold history, and being a native speaker showed no correlation with treatment time. Moreover, these factors did not correlate with the tolerability of breath-hold during SGRT. However, female patients showed better breath-holding performance in SGRT treatments compared to male patients (p: 0.02). ConclusionsThe application of breath-hold with SGRT procedures is tolerable and feasible in liver SBRT treatments. There exists no specific subgroup that cannot tolerate this method.

Single-lens dynamic z-scanning for simultaneous in situ position detection and laser processing focus control

Existing auto-focusing methods in laser processing typically include two independent modules, one for surface detection and another for z-axis adjustment. The latter is mostly implemented by mechanical z stage motion, which is up to three orders of magnitude slower than the lateral processing speed. To alleviate this processing bottleneck, we developed a single-lens approach, using only one high-speed z-scanning optical element, to accomplish both in situ surface detection and focus control quasi-simultaneously in a dual-beam setup. The probing beam scans the surface along the z-axis continuously, and its reflection is detected by a set of confocal optics. Based on the temporal response of the detected signal, we have developed and experimentally demonstrated a dynamic surface detection method at 140–350 kHz, with a controlled detection range, high repeatability, and minimum linearity error of 1.10%. Sequentially, by synchronizing at a corresponding oscillation phase of the z-scanning lens, the fabrication beam is directed to the probed z position for precise focus alignment. Overall, our approach provides instantaneous surface tracking by collecting position information and executing focal control both at 140–350 kHz, which significantly accelerates the axial alignment process and offers great potential for enhancing the speed of advanced manufacturing processes in three-dimensional space.

Features of the process of water filling the barrel of a periodic-pulse fire extinguishing installation

In the work, research was carried out, which made it possible to reveal the peculiarities of the process of filling the barrel of the periodic-impulse fire extinguishing installation with water. At the same time, a mathematical model for simulating the processes of water injection into a pipe with subsequent crushing of water by a shock wave was substantiated and proposed. To simulate the processes of water injection and water crushing in the shaft of the installation, a VOF model (volume of liquid model) is used, according to which there is no penetration of one medium into another, and which is based on the surface tracking method applied to a fixed Euler grid. On the basis of the developed mathematical model in the ANSYS software environment, numerical studies of the process of filling the barrel of a periodic-impulse fire extinguishing installation with water were carried out. According to the results of a numerical study of the process of filling the barrel of the periodic-impulse fire extinguishing installation with water, a relatively high inertia in the time of the water injection processes in relation to the gas detonation processes occurring in the periodic-impulse fire extinguishing installation was revealed. In particular, the time interval between detonation cycles in the installation operating at a frequency of 23 Hz is about 43,5 ms. If we discard the purge cycle, then we have a time interval of 21 ms, during which it is necessary to inject water into the barrel of the intermittent-impulse fire extinguishing installation. According to the results of the above studies, we have that only the time for the spread of the stream of water from one side to the other side of the barrel of the periodic-impulse fire extinguishing installation is 8 ms. The conducted research makes it possible to investigate the influence of the parameters of the fire extinguishing installation on the formation of a finely sprayed water jet, and the obtained results will significantly increase the level of operational readiness of the personnel of fire and rescue units during operational actions to extinguish internal fires.

Observer-based fixed-time dynamic surface tracking control for autonomous surface vehicles under actuator constraints and denial-of-service attacks

This paper proposes a novel trajectory tracking control strategy for autonomous surface vehicles (ASVs), subject to actuator constraints and under denial-of-service (DoS) attacks. Firstly, a fixed-time disturbance observer (FTDO) is used to estimate and compensate unknown external disturbances, which enhances the robustness of the motion system. Secondly, a novel fixed-time filter is designed by combining dynamic surface technology with fixed-time control, which avoids the problem of differential explosion, and reduces the filtering error. Lastly, in order to address the effects of actuator constraints and DoS attacks, an auxiliary system (AS) and a compensation system (CS) are included in the fixed-time dynamic surface controller based on FTDO. The proposed method improves the robustness, stability and accuracy of the closed-loop system. Additionally, the reference tracking error converges to the neighborhood of the origin within a fixed-time. The superiority of the proposed control method over traditional control strategies from the existing literature is demonstrated in simulations.

An efficient and high-volume fraction 3D mesoscale modeling framework for concrete and cementitious composite materials

To address the cumbersome nature of mesoscale models for concrete as well as other similar materials, this paper presents an efficient and high-volume fraction mesoscale modeling framework with a novel aggregate surface tracking algorithm as well as an aggregate-cement interface interaction model to replace the interface transition zone (ITZ) in the three-dimensional space. This model could also be used in composite materials such as Fiber-reinforced polymer concrete. In this study, results are compared with the traditional 3 phases concrete models, uniaxial tension and compression models, and triaxial compression models for validation. The results show that the three-dimensional mesoscopic model can capture the detailed process of mesoscopic damage and the macroscopic behavior under different stress states while showing good agreement with the experimental results. It is demonstrated that compared with traditional methods, the new model can save up to 84 % of the preprocessing and computation time and provides a more convenient and efficient scheme for the three-dimensional mesoscopic modeling of concrete alike composite materials with good accuracy. This paper also presents several 3D mesoscale models of Fiber-reinforced polymer concrete.

Three-dimensional measurements and analysis of early-stage non-premixed flame development following spark ignition

Igniting pure fuel jets is common in aerospace propulsion systems to organize combustion. A significant issue is that the ignition process is not well understood yet due to its highly localized, transient, dynamic nature. This paper reports a study of early-stage non-premixed flame development following spark ignition based on three-dimensional (3D) measurements. These measurements are obtained by tomographic chemiluminescence, and 3D surface tracking is performed based on the level-set method to calculate the 3D distribution and evolution of flame edge speeds. Measurements are reported for different jet velocities and spark height conditions. The results show that in a typical spark ignition process, after a quick development from a wafer structure to a circular fold, the flame edge propagates along the upstream, downstream, and circular directions simultaneously to form a cylindrical flame. In low-jet-velocity cases, regardless of spark location, the flame edge speeds along the three directions have similar magnitude distributions. The downstream flame edge speeds are slightly higher than the upstream and circular speeds. In high-jet-velocity cases, the flame edge speeds have overall magnitudes larger than those in low-jet-velocity cases, and the dominance of the downstream flame edge speeds over the upstream and circular speeds becomes more obvious. The mean flame edge speeds of all tested cases are shown to be comparable to the theoretical stoichiometric laminar speed. For successful ignition, it is found that thermal convection plays a crucial role in the flame growth in low-spark-height cases, whereas in high-spark-height cases, a well-mixed condition driven by turbulence promotes flame growth. Irrespective of jet flow velocity and spark location, the early stage of flame growth after ignition can be precisely described by a logistic function (S curve), which in turn facilitates a better understanding of the process.

Multi-Object Detection for Inland Ship Situation Awareness Based on Few-Shot Learning

With the rapid development of artificial intelligence technology and unmanned surface vehicle (USV) technology, object detection and tracking have wide applications in marine monitoring and intelligent ships. However, object detection and tracking tasks on small sample datasets often face challenges due to insufficient sample data. In this paper, we propose a ship detection and tracking model with high accuracy based on a few training samples with supervised information based on the few-shot learning framework. The transfer learning strategy is designed, innovatively using an open dataset of vehicles on highways to improve object detection accuracy for inland ships. The Shuffle Attention mechanism and smaller anchor boxes are introduced in the object detection network to improve the detection accuracy of different targets in different scenes. Compared with existing methods, the proposed method is characterized by fast training speed and high accuracy with small datasets, achieving 84.9% (mAP@0.5) with only 585 training images.

Numerical investigation of structural models equipped with tuned liquid damper

Tuned liquid dampers (TLDs) are introduced in structural systems to suppress vibration of the structure due to dynamic actions. Using a grid-based Finite Volume Method-Finite Element Method (FVM/FEM), efficiency of TLDs of cylindrical and rectangular geometries was evaluated by performing a two-way Fluid-Structure Interaction (FSI) analysis. The nonlinear sloshing response of fluid was simulated by employing a three-dimensional Navier–Stokes equation as the governing equation and occurrence of wave breaking was accounted by using Volume of Fluid (VOF) method for free surface tracking. Utilizing the developed numerical model, a series of three-dimensional transient analysis were conducted on a structure with and without TLDs aiming to investigate effect of base excitation amplitude. The result show that maximum performance of TLDs at resonance is obtained when the forcing ratio is limited to 0.1, and for this case, both cylindrical and rectangular TLDs displayed comparable efficiency. Effect of excitation frequency fe was also investigated under a wide range of the forcing ratio showing that as fe increases, the natural frequency of coupled TLD-structural system approaches the natural frequency of un-damped structural system.

A quartz crystal microbalance (QCM)-based easy setup device for real-time mass change detection under high-power RF plasma.

Sensing technologies serve a crucial role in monitoring and testing surface properties in biosensors, thin films, and many other industries. Plasma treatments are routinely used in most of these technologies to modify the surfaces of materials. However, due to the high radio frequency (RF) noise in plasma processes, real-time surface tracking is still rather difficult. In this study, we aim to construct an easy-to-set up mass change detection system capable of operating under RF plasma conditions. For this purpose, we have presented a novel technique that utilizes the quartz crystal microbalance sensor to detect mass changes in different plasma environments. The constructed device was then tested under 13.56MHz, 100W plasma atmosphere. The results showed that the resonance frequency of a crystal was successfully measured with 1.0Hz resolution under the impact of plasma-induced high power of RF noise. Moreover, as a preliminary study, we used ethylenediamine (EDA) to track changes in resonance frequency under plasma conditions and observed noise-free signals in frequency-voltage curves. Furthermore, the system's sensitivity was found to be 3.8 ng/Hz, with a test molecule (EDA) deposition of about 380 ng in the RF plasma atmosphere. Overall, this study focused on creating a relatively new approach for detecting the real-time mass change in a strong RF environment, which we believe could be an improved and easy-to-set up technique for plasma-based processes such as surface coating, etching, and activation.

Research on Surface Tracking and Constant Force Control of a Grinding Robot

To improve the quality and efficiency of robot grinding, a design and a control algorithm for a robot used for grinding the surfaces of large, curved workpieces with unknown parameters, such as wind turbine blades, are proposed herein. Firstly, the structure and motion mode of the grinding robot are determined. Secondly, in order to solve the problem of complexity and poor adaptability of the algorithm in the grinding process, a force/position hybrid control strategy based on fuzzy PID is proposed which greatly improves the response speed and reduces the error of the static control strategy. Compared with normal PID, fuzzy PID has the advantages of variable parameters and strong adaptability; the hydraulic cylinder used to adjust the angle of the manipulator can control the speed offset within 0.27 rad/s, and the grinding process can be carried out directly without obtaining the specific model of the surface to be machined. Finally, the experiments are carried out, the grinding force and feed speed are maintained within the allowable error range of the expected value, and the results verify the feasibility and effectiveness of the position tracking and constant force control strategy in this paper. The surface roughness of the blade is maintained within Ra = 2~3 μm after grinding, which proves that the grinding quality meets the requirements of the best surface roughness required for the subsequent process.

A CFD model with free surface tracking: predicting fill level and residence time in a starve-fed single-screw extruder

Mixing in extrusion is a vital part of achieving consistent and high-quality extrudates, with residence time being an elucidative measure of the mixing performance. Recent studies around numerical modeling of residence time distributions in single-screw extruders appear to consider flooded extruders mainly. This paper introduces a new and general CFD model to characterize the extruder fill length and residence time distribution for a viscoplastic ceramic material in a starve-fed extruder, including free surface tracking. The CFD model simulates a pulse-injection test, where a fluid parcel is injected at the inlet, with subsequent outlet concentration measured over time. The study includes material characterization and model validation based on laboratory tests. Results quantify the impact of accounting for the partially filled extruder instead of assuming it to be flooded, addressing the potential error when only considering simple analytical approximations to calculate system average residence times. Results further show the ability to fit simulation results to more simple analytical models. This underlines the importance of including the entire extrusion system and forming the basis for further work toward enabling real-time model predictions in starve-fed extrusion systems.

Resource-aware cooperative level surface tracking control in 3D time-varying scalar field

Resource-aware cooperative level surface tracking control in 3D time-varying scalar field

Development and Discharge Characteristics of Surface Tracking on the Interface Between the PD Suppression Coatings Outside of Stator Winding Slots

During the operation of high voltage (HV) motors, the end-winding surface can be contaminated by oil or dust, resulting in a type of intense discharge: surface tracking, which gradually develops into phase-to-phase or phase-to-ground faults. To improve our understanding of the development process and characteristics of surface tracking on the end-winding, an accelerated aging test was performed on 10-kV stator coils to induce surface tracking under electrical and oil contamination stresses. To understand the evolution of surface tracking, the partial discharge (PD) was collected and the characteristics of the corresponding phase-resolved PD (PRPD) patterns and pulse sequence analysis (PSA) patterns were analyzed. Combined with finite element analysis (FEA) simulations, the development process of surface tracking was interpreted. It is established that the electrical field of a dry band with high resistivity on the contamination is much higher than other contaminated areas via FEA simulation, causing the electrical breakdown of the adjacent air and discharge. Such continuous and intense discharges finally leave on the end-winding surface a carbonized channel, forming a tree-like structure. This article presents the results of changes in PRPD patterns and PSA patterns during different stages, together with the surface potential distribution after tracking generation. The research of this article is devoted to providing a reference for PD monitoring and fault diagnosis of HV motors.

Deformable cardiac surface tracking by adaptive estimation algorithms

This study presents a particle filter based framework to track cardiac surface from a time sequence of single magnetic resonance imaging (MRI) slices with the future goal of utilizing the presented framework for interventional cardiovascular magnetic resonance procedures, which rely on the accurate and online tracking of the cardiac surface from MRI data. The framework exploits a low-order parametric deformable model of the cardiac surface. A stochastic dynamic system represents the cardiac surface motion. Deformable models are employed to introduce shape prior to control the degree of the deformations. Adaptive filters are used to model complex cardiac motion in the dynamic model of the system. Particle filters are utilized to recursively estimate the current state of the system over time. The proposed method is applied to recover biventricular deformations and validated with a numerical phantom and multiple real cardiac MRI datasets. The algorithm is evaluated with multiple experiments using fixed and varying image slice planes at each time step. For the real cardiac MRI datasets, the average root-mean-square tracking errors of 2.61 mm and 3.42 mm are reported respectively for the fixed and varying image slice planes. This work serves as a proof-of-concept study for modeling and tracking the cardiac surface deformations via a low-order probabilistic model with the future goal of utilizing this method for the targeted interventional cardiac procedures under MR image guidance. For the real cardiac MRI datasets, the presented method was able to track the points-of-interests located on different sections of the cardiac surface within a precision of 3 pixels. The analyses show that the use of deformable cardiac surface tracking algorithm can pave the way for performing precise targeted intracardiac ablation procedures under MRI guidance. The main contributions of this work are twofold. First, it presents a framework for the tracking of whole cardiac surface from a time sequence of single image slices. Second, it employs adaptive filters to incorporate motion information in the tracking of nonrigid cardiac surface motion for temporal coherence.

Design of a Compliant Robotic End-Effector Tool for Normal Contact Estimation

The use of industrial robots for machining operations such as polishing is gaining popularity these days. However, maintaining constant normal contact on unknown geometrical surfaces still remains a challenge. In order to cope with the issue, this research has developed a unique compliant robotic end-effector that can measure the depth and angles deviation of the robot from the normal complex surfaces in real-time without any prior geometric model of the workpiece. The indigenously developed compliant robotic end-effector is made up of three main components: a novel three-axis force/torque sensor, a compliant contact pin, and a data acquisition (DAQ) board. Initially, the three-axis force/torque sensor has been validated with both simulation and testing. The advantage of being able to take measurements in real-time is provided by the DAQ’s automatic weight compensation feature. Additionally, the pose correction algorithm receives the estimated contact force as feedback during robot surface tracking in order to assess depth and angles and determine the proper distance and perpendicular relationship between the surface and the end-effector. The proposed scheme is then evaluated using a six-axis industrial robot. The experimental results show that the maximum average depth and angle errors are 0.13 mm and 0.64°, respectively. The developed system has achieved significant improvement in contact-based robot surface measuring.