Demand High Precision Research Articles

A Planar Multi-Inertial Navigation Strategy for Autonomous Systems for Signal-Variable Environments.

The challenge of precise dynamic positioning for mobile robots is addressed through the development of a multi-inertial navigation system (M-INSs). The inherent cumulative sensor errors prevalent in traditional single inertial navigation systems (INSs) under dynamic conditions are mitigated by a novel algorithm, integrating multiple INS units in a predefined planar configuration, utilizing fixed distances between the units as invariant constraints. An extended Kalman filter (EKF) is employed to significantly enhance the positioning accuracy. Dynamic experimental validation of the proposed 3INS EKF algorithm reveals a marked improvement over individual INS units, with the positioning errors reduced and stability increased, resulting in an average accuracy enhancement rate exceeding 60%. This advancement is particularly critical for mobile robot applications that demand high precision, such as autonomous driving and disaster search and rescue. The findings from this study not only demonstrate the potential of M-INSs to improve dynamic positioning accuracy but also to provide a new research direction for future advancements in robotic navigation systems.

Preoperative application of CT and MRI registration in lumbar disc herniation endoscopic surgery could improve the postoperative rehabilitation of patients.

Percutaneous Endoscopic Lumbar Discectomy (PELD) has emerged as routine treatment for lumbar disc herniation (LDH) due to its minimal invasiveness and quick recovery. However, PELD demands high precision from the surgeon, as the risk of intraoperative complications is substantial, including potential damage to the nerve root and dura, and a higher likelihood of recurrence post-surgery. Thus, preoperative planning utilizing CT and MRI imaging is essential. In this study, the clinical data of 140 patients treated with PELD for LDH from January 2021 to December 2023 were retrospectively analyzed. Patients were categorized into two groups based on whether CT and MRI registration (CMR) was employed for surgical planning: a CMR group (n=68) and a control group (n=72). Data collected included surgery time, hospital stay duration, and scores from the Visual Analog Scale (VAS) for low back and leg pain, as well as the Japanese Orthopaedic Association Lumbar Spine Score (JOA). Differences between the two groups were assessed using the Student's t-test. No significant difference was found in hospital stay length between the groups (P=0.277). Surgery time was significantly shorter in the CMR group (P<0.001). Prior to surgery, no significant differences in VAS scores for leg and low back pain were observed between the groups (P=0.341 and P=0.131, respectively); however, at 2 months postoperatively, both scores were significantly lower in the CMR group (P<0.001 and P=0.002, respectively). Similarly, no difference in preoperative JOA scores was noted (P=0.750), but at 2 months postoperative, the CMR group exhibited significantly higher scores (P<0.001). Compared with the traditional PELD, the preoperative use of CMR has shown to reduce surgery time, alleviate leg and low back pain, and increase the lumbar JOA score at 2 months after surgery, underscoring its efficacy in enhancing surgical outcomes.

Force modeling of a reluctance motion system with multi-axial asymmetrical air gaps

Semiconductor photolithography equipment requires an actuation system that can satisfy high acceleration and precision demands on the nanoscale in order to operate with high throughput and efficiency. Reluctance actuators, which offer greater acceleration and force output than conventional Lorentz actuators, are one option. The photolithography technique uses a floating stage with air bearings to reduce friction; nonetheless, vibration transfer is not completely prevented, potentially causing misalignment and asymmetries between the actuator components. The output force can be significantly impacted by unequal offsets between the mover and stator. In the paper that follows, a technique for calculating the force of various asymmetrical instances for the C-core reluctance actuator is demonstrated. This paper looks into the effect of rotational offsets in all rotational degrees of freedom occurring simultaneously. Previously, only each degree of freedom was analyzed. Analytical models are developed and compared to Comsol Multiphysics (COMSOL) simulations, and experimental findings show accuracy to be within almost 10% for the ranges examined. The findings presented can allow for future control systems to be designed to counteract multi-axial asymmetric issues.

Optimized procedure for conventional TEM sample preparation using birefringence

Specimens for quality transmission electron microscopy (TEM) analyses must fulfil a range of requirements, which demand high precision during the prior preparation process. In this work, an optimized procedure for conventional TEM specimen preparation is presented that exploits the thickness-dependence of interference colors occurring in birefringent materials. It facilitates the correct estimation of specimen thickness to avoid damage or breaking during mechanical thinning and reduces ion-milling times below 30minutes. The benefits of the approach are shown on sapphire and silicon carbide cross-section samples. The presented method is equally suitable for assessing specimen thickness during dimpling and wedge-polishing, and is particularly useful at thicknesses below 20 μm, where the accuracy of mechanical techniques is insufficient. It is precise enough to be employed for a visual thickness estimation during the thinning process, but can be additionally optimized by analyzing the RGB spectrum of the occurring interference colors.

Integrated Optical Sensing and Communication (IOSAC) System Based on Hybrid‐Waveguide Structures

AbstractAdvanced silicon photonic technologies enable integrated optical sensing and communication (IOSAC) in real time for the emerging application requirements of simultaneous sensing and communication for next‐generation networks. Herein, an IOSAC system is proposed and demonstrated on the silicon nitride (Si3N4) photonics platform. The IOSAC devices leveraging microring resonators excel in real‐time monitoring of analyte fluctuations and efficiently transmit this data to the terminal, positioning them as viable alternatives to bulk optics in applications that demand both high precision and speed. By directly integrating Si3N4 ring resonators with optical communication networks, simultaneous sensing and optical communication are demonstrated by an optical signal transmission experimental system using especially filtering amplified spontaneous emission spectra. The refractive index (RI) sensing ring with a sensitivity of 172 nm RIU−1, a figure of merit (FOM) of 1220, and a detection limit (DL) of 8.2 × 10−6 RIU is demonstrated. Simultaneously, the 1.25 Gbps optical on‐off‐keying (OOK) signal is transmitted at the concentration of different NaCl solutions, indicating the bit‐error‐ratio (BER) decreases with the increase in concentration. The novel IOSAC technology shows the potential to realize high‐performance simultaneous biosensing and communication in real time and further accelerate the development of IoT and 6G networks.

Design and Optimal Pose‐Constrained Visual Servoing of a Novel Active Flexible Endoscope Holder System for Solo Laparoscopic Surgery

Laparoscopic surgery (LS) has become an effective and widely accepted therapy for patients. However, performing LS requires advanced training and skills, as it demands high precision and dexterity due to visual feedback depending on the collaboration between the surgeon and endoscope assistant, restricted field of view, and limited dexterity inside the body. Thus, a flexible endoscope holder system with an automatic control scheme is proposed to assist LS performance, allowing the surgeon to perform solo LS. A DNA‐inspired helix‐based structure with wide‐angle and constant curvature bending is presented and made of printable nylon with selective laser sintering. The proposed flexible mechanism reduces the cost of manufacturing and assembling. Also, it has a hollow design for embedded sensing and actuation. Then, an optimization method is proposed, which provides a reference for the endoscope installation, robot placement, and pose selection. In addition, aiming at the misorientation problem, a pose‐constrained visual servoing control scheme for the endoscope system is developed. Both simulation and physical experiments are conducted to verify the effectiveness and feasibility of the proposed control scheme. Experimental results demonstrate that the proposed visual servoing scheme can maintain the optimized pose and reduce misorientation during automatic view steering.

Complex-valued matrix-vector multiplication system for a large-scale optical FFT.

Recent advancements in optical convolutional neural networks (CNNs) and radar signal processing systems have brought an increasing need for the adoption of optical fast Fourier transform (OFFT). Presently, the fast Fourier transform (FFT) is executed using electronic means within prevailing architectures. However, this electronic approach faces limitations in terms of both speed and power consumption. Concurrently, existing OFFT systems struggle to balance the demands of large-scale processing and high precision simultaneously. In response, we introduce a novel, to the best of our knowledge, solution: a complex-valued matrix-vector system harnessed through wavelength selective switches (WSSs) for the realization of a 24-input optical FFT, achieving a high-accuracy level of 5.4 bits. This study capitalizes on the abundant wavelength resources available to present a feasible solution for an optical FFT system with a large N.

Clinical and Radiological Outcomes after Surgical Stabilization of Craniovertebral Junction – A Single-center Experience

Abstract Background and Objectives: Craniovertebral instability and its surgical management require a thorough knowledge of the anatomy and dynamics of the craniovertebral junction (CVJ). Due to the wide range of mobility and proximity of vital neurovascular structures, these surgeries demand high technical skill and precision. It is very difficult to suggest a single good technique for CVJ stabilization as each procedure has got its own indications and benefits. Novel techniques and gadgets like neuro navigation and robotic arms help surgeons to minimize complications, thereby improving the overall functional outcome. In this study, we are analyzing the retrospective data of CVJ instabilities surgically managed by freehand technique in our institute. Materials and Methods: We did a retrospective analysis of 33 patients operated on for craniocervical junction instability for 7 years from January 1, 2015, to December 31, 2021. We analyzed the clinical and radiological presentations and postoperative outcomes at 3 weeks, 6 months, and after 1 year. The distribution of clinical presentation in terms of neck pain, myelopathy, restricted neck movements, and lower cranial nerve palsy was evaluated and correlated with the demographic parameters. The paired “t”- test was used to correlate the clinical and radiological outcomes after surgery. Results: The paired “t” value of the clinical improvement assessed with the preoperative and postoperative Japanese Orthopedic Association (JOA) myelopathic scores was − 4.376 with P &lt; 0.001, which indicates a significant clinical improvement 6 months after surgery. Among the 33 patients evaluated, only three patients developed a slight reduction in the JOA score after surgery, which was improved within 1 year. All the patients achieved satisfactory trabecular bone formation at the graft site and decorticated joint facets without any clinical or radiological evidence of implant failure. Among the C2 pedicle screws, 3 (7.5%) were having vertebral foraminal impingement, and 2 (5%) were having medial cortical violation and spinal canal impingement. All the patients with radiological evidence of implant malposition were clinically intact and did not show any deterioration of the studied myelopathic score (JOA). Conclusions: As the bony anatomy and the vascular course of the CVJ vary from patient to patient, thorough preoperative planning is mandatory for the surgical management of CVJ instability. In our study, the clinical and radiological improvement after surgical stabilization of craniovertebral instability by freehand technique is comparable with the available data. The overall risk of screw malposition and associated lethal complications may be minimized by adding modern technologies such as neuronavigation, robotic arms, and three-dimensional C-arm in the armamentarium.

Effect of Additional Mass on Natural Frequencies of Weight-Sensing Structures.

The phenomena of variability and interference in the natural frequencies of weight-sensing structures applied in complex working conditions must solve the problem of reducing or eliminating resonance under low-frequency vibrations to maximize stability, accuracy and reliability. The influence laws of the additional mass with relevant characteristics on the natural frequencies, which include the components of mass, stiffness and center-of-mass distribution, etc. Firstly, the theoretical formulas of the mathematical model are given based on different characteristics of the weight-sensing structure, and various combinations of additional masses on the weight-sensing structures are adjusted in the X-, Y-, and Z-directions. The key factors to be specifically considered in the theoretical formulas are discussed through simulation analysis and experimental validation. Secondly, the locking strength of the fastening screws of some components was changed, and another component was placed on the experimental platform in the experiment. The results show that the mass, center-of-mass, stiffness distribution and other factors of the additional mass have different effects on the natural frequencies, which are important for the demand for high-precision, high-stability weighing measurement. The results of this research can provide an effective scientific evaluation basis for the reliable prediction of natural frequencies.

Aquaculture defects recognition via multi-scale semantic segmentation

Aquaculture net pen defects such as biofouling, vegetation, and holes are key challenges to efficient and sustainable fish production in aquaculture. These defects must be monitored to avoid problems with aquaculture net safety as well as fish growth. Recently, deep learning methods have been adopted to solve detection and classification problems in different applications. However, the conventional methods are challenging to meet the demands of high precision and real-time detection of aquaculture net defects in a complex marine environment. Towards this end, this paper proposes an autonomous net pen defect detection system that contains a novel multi-scale semantic segmentation topology for detecting the biofouling, vegetation, and hole problems in the aquaculture environment. In particular, we emphasize fusing the attention maps obtained across different decomposition levels of the network to generate rich feature distributions that enable the accurate extraction of biofouling, vegetation, and holes within aquaculture nets. Moreover, the proposed model is thoroughly tested on two private datasets and two public datasets which were acquired from a real-field fish farms. Across all four datasets, the proposed framework showed remarkable biofouling, vegetation, and hole detection performance, where it outperformed state-of-the-art methods by 6.58%, 3.69%, 6.44%, and 4.78% in terms of mean average precision across LABUST, KU, NDv1, and NDv2 datasets, respectively.

Real-Time Interactive Parallel Visualization of Large-Scale Flow-Field Data

With the increasing demand for high precision in numerical simulations using computational fluid dynamics (CFD), the use of large-scale grids for discretized solutions has become a trend, resulting in an explosive growth of flow-field data size. To address the challenges posed by large-scale flow-field data for real-time interactive visualization, this paper proposes novel strategies for data partitioning and communication management. Firstly, we propose a data-partitioning strategy based on grid segmentation. This approach constructs metadata to create file viewports for each process and performs grid partitioning. Subsequently, it reconstructs sub-grids within each process and utilizes a coordinate-mapping algorithm to map global coordinates to local process coordinates, facilitating access to attribute variables through a lookup table. Secondly, we introduce a real-time interactive method for large-scale flow fields. This method leverages the system architecture of high-speed interconnection among compute nodes in a cluster environment and low-speed interconnection between service nodes and rendering nodes. It enables coordinated management of parallel rendering and synchronized rendering methods. The experimental results on typical flow-field data demonstrate that the proposed data-partitioning strategy improves the loading speed of millions of grid-level data by a factor of 7, surpassing ParaView’s performance by 1.5 times. Furthermore, it achieves system load balancing. Real-time interaction experiments with datasets containing 500 million and 800 million grid cells exhibit millisecond-level latencies, demonstrating the effectiveness of the proposed communication management method in meeting the real-time interactive visualization demands of large-scale flow-field data.

Enabling the Use of High-Precision Glass Wafers in a Conventional Si Fab

Glass has unique properties that make it attractive for many applications. Combining glass with Si fabrication process would create new possibilities not only in device performance and form factor, but also scale economies. Key challenges in using glass wafers in a Si fab include lack of opacity and electrical conductivity as well as metallic and particle contamination. These challenges can be overcome through a suitable coating on the glass wafer and rigorous particle removal throughput the fabrication and use process. For applications that demand high precision to support direct wafer bonding and lithography, glass wafers can be engineered to deliver the required surface smoothness and flatness.

Lossless Watermarking Algorithm for Geographic Point Cloud Data Based on Vertical Stability

With the increasing demand for high-precision and difficult-to-obtain geospatial point cloud data copyright protection in military, scientific research, and other fields, research on lossless watermarking is receiving more and more attention. However, most of the current geospatial point cloud data watermarking algorithms embed copyright information by modifying vertex coordinate values, which not only damages the data accuracy and quality but may also cause incalculable losses to data users. To maintain data fidelity and protect its copyright, in this paper, we propose a lossless embedded watermarking algorithm based on vertical stability. First, the watermark information is generated based on the binary encoding of the copyright information and the code of the traceability information. Second, the watermark index is calculated based on the length of the watermark information after compression and the vertical distribution characteristics of the data. Finally, watermark embedding is completed by modifying the relative storage order of the corresponding data according to the index and watermark value. The experimental results show that the proposed algorithm has good invisibility without damaging the data accuracy. In addition, compared with existing algorithms, this method has a higher robustness under operations such as projection transformation, precision perturbation, and vertex deletion of geospatial point cloud data.

Choice of end-state comfort is dependent upon the time spent at the beginning-state and the precision requirement of the end-state

Choice of posture while grasping an object typically depends upon several factors including the time spent in that posture, what postures were held prior to choosing that posture, and the precision required by the posture. The purpose of this study was to test choice of end-state thumb-up posture based on time spent at the beginning-state and the precision requirement of the end-state. To determine choice of thumb-up based on time or precision, we varied how long a subject had to hold the beginning state before moving an object to an end location. We made end-state precision either small or large and eliminated the precision needed to stand the object up at the end of the movement. A choice between “comfort” at the beginning or precision at the end-state would be demanded by the conditions with long beginning-state hold times and high precision demands. We aimed to determine which aspect of movement was of greater importance to individuals, overall “comfort” or precision. When the requirement was to hold the initial grasp longer, and the end-target was large, we predicted that we would see more thumb-up postures adopted at the beginning state. When the final placement was small and the initial posture was not constrained, we predicted we would see thumb-up postures adopted at the end state. On average, we found that, as beginning-state grasp time increased, more individuals chose beginning-state thumb-up postures. Perhaps, not surprisingly, we found distinct individual differences within our sample. Some individuals seemed to choose beginning-state thumb-up postures nearly 100% of the time, while other individuals chose end-state thumb-up postures nearly 100% of the time. Both the time spent in a posture and its precision requirements influenced planning, but not necessarily in a systematic way.

A Multi-Scale Tool Orientation Generation Method for Freeform Surface Machining with Bull-Nose Tool.

Free-form surface parts are widely used in industries, and they consist of intricate 3D surfaces such as molds, impellers, and turbine blades that possess complex geometrical contours and demand high precision. Proper tool orientation is crucial for ensuring the efficiency and accuracy of five-axis computer numerical control (CNC) machining. Multi-scale methods have received much attention and have been widely used in various fields. They have been proven to be instrumental and can obtain fruitful outcomes. Ongoing research on multi-scale tool orientation generation methods, which aim to acquire tool orientations that satisfy both macro- and micro-scale requirements, is significantly important for improving the machining quality of workpiece surfaces. This paper proposes a multi-scale tool orientation generation method that considers both the machining strip width and roughness scales. This method also ensures a smooth tool orientation and avoids interference in the machining process. First, the correlation between the tool orientation and rotational axis is analyzed, and feasible area calculation and tool orientation adjustment methods are introduced. Then, the paper introduces the calculation method for machining strip widths on the macro-scale and the roughness calculation method on the micro-scale. Besides, tool orientation adjustment methods for both scales are proposed. Next, a multi-scale tool orientation generation method is developed to generate tool orientations that meet the macro- and micro-scale requirements. Finally, to verify the effectiveness of the proposed multi-scale tool orientation generation method, it is applied to the machining of a free-form surface. Experimental verification results have shown that the tool orientation generated by the proposed method can obtain the expected machining strip width and roughness, meeting both macro- and micro-scale requirements. Therefore, this method has significant potential for engineering applications.

Sheath &amp; Dilator 카테터 내 폴리머 튜브의 원형도 및 표면 개선에 관한 연구

As the market for minimally invasive procedures developed rapidly, there was an increase in the demand for high-precision, high-performance catheter fabrication technology. Sheath and dilator tubes are essential intervention devices for procedures, in which catheters are used and require precise dimensional accuracy, and uniform roundness and surface roughness. Polyethylene is used in sheath and dilator limitation for processability, which causes low melt flow index and side effects. Therefore, in the extrusion process using polyethylene, it is important to study the manufacturing of tubes with improved roundness and surface roughness. In this study, we proposed a calibrator for precise production with an aim to manufacture 5Fr micro-puncture tubes, and studied the changes in the roundness and surface roughness of tubes by changing the cooling water temperature and water disk thickness. As a result, it was found that the cooling water temperature and wafer disk thickness had an effect on the roundness and surface roughness, and the roundness had an effect on the formation of the wall thickness. Therefore, these experimental results were used as a study for the production of improved Sheath and Dilator tubes.

Real-time GNSS multiple cycle slip detection and repair based on a controllable geometry-based method in relative positioning

The demand for high-precision and high-reliability positioning has expanded as a result of the proliferation of Global Navigation Satellite System (GNSS) applications. A tough issue for accurate positioning, particularly in kinematic circumstances, is the repair and detection of multiple cycle slips, where more large and small cycle slips are often mixed. Compared with the geometry-free (GF) model, the geometry-based (GB) model has unique advantages in multi-GNSS. However, the conventional GB model cannot work well in highly multiple cycle slips because of excessive parameters. This paper proposes a new multiple cycle slip detection and repair method based on the controllable GB model. Specifically, the method mixes state-domain plus measurement-domain strategy. The relatively large cycle slips are first processed by a polynomial fitting aided GF strategy. As the sampling interval increases, the magnitude of minimal detectable cycle slips increases. The processing will make the number and amplitude of cycle slips reduced. Based on this, a partial GB model containing the clean measurements and polluted measurements with cycle slip is conducted, which is especially suitable for the relatively small cycle slips. The partial GB model's strength is successfully enhanced through partitioned processing. Finally, the multiple cycle slips are detected and repaired with fixed solutions. By conducting the simulated experiments and field tests, the effectiveness of the proposed method is compared and demonstrated comprehensively. The results show that the proposed method is superior to conventional methods in terms of detection and repair rates in typical and complex conditions.

Investigation of Process Parameters of a Novel Magnetorheological Finishing Process for External Cylindrical Surfaces

The recent rise in the demand for high precision, close tolerances, and super surface finish quality of components and part assembly modules in the competitive manufacturing industrial environment for the enhanced working life and functional requirements of machines globally. Three revolving curved tip tools based magnetorheological process is designed and developed to fine finish the external cylindrical surfaces of soft and hard materials. The effect of the key operational machining parameters on the surface roughness of a newly developed magnetorheological process was carried out using a one factor at a time method. The magnetizing current, the revolving speed of the tools, the rotational speed of the workpiece, workpiece traverse speed are the parameters that have been considered for this purpose. The experimentation has been performed on the aluminium workpiece because of its broad applicability, such as manufacturing shafts, rods, pistons, and other circular components. The primary purpose of this study was to determine the range of essential control parameters for the newly developed finishing process. The percentage reduction in Ra, Rq, and Rz values are 69.64%, 58.21%, and 54.48%, respectively, after 60 minutes of finishing at magnetizing current 2A, the revolving speed of the tools 30 RPM, the rotation speed of the workpiece 600 RPM and feed 10 cm/min.

Research on the joint timekeeping of pulsars and atomic clocks based on Vondrak–Cepek filtering

ABSTRACTThere is a wide demand for high-precision and high-stability time-scales, which are mainly established by atomic clocks. The short-term stability of atomic clocks is good, while the long-term stability is poor. Meanwhile, millisecond pulsars have good long-term stability. It is expected to produce time-scales with high-stability performance by combining pulsars and atomic clocks to keep time. In this paper, a novel joint timekeeping algorithm based on Vondrak–Cepek filtering is proposed. The filter makes a compromise between the fidelity of the observation data and their first derivatives and the smoothness of the filtering results. Also, it can give full play to the long-term stability of pulsars and the short-term stability of atomic clocks. Experiments and results show that the joint timekeeping algorithm improved σz of 7.58 × 10−13 on 6.5-d time interval with respect to that obtained from the pulsar ensemble time-scale algorithm. Also, the joint timekeeping algorithm improved σz of 6.94 × 10−15 on 9.1-yr time interval with respect to that obtained from the atomic ensemble time-scale algorithm. The algorithm proposed in this paper can be applied to scenes requiring high-stability time-scales.

A novel adaptive PD-type iterative learning control of the PMSM servo system with the friction uncertainty in low speeds.

High precision demands in a large number of emerging robotic applications strengthened the role of the modern control laws in the position control of the Permanent Magnet Synchronous Motor (PMSM) servo system. This paper proposes a learning-based adaptive control approach to improve the PMSM position tracking in the presence of the friction uncertainty. In contrast to most of the reported works considering the servos operating at high speeds, this paper focuses on low speeds in which the friction stemmed deteriorations become more obvious. In this paper firstly, a servo model involving the Stribeck friction dynamics is formulated, and the unknown friction parameters are identified by a genetic algorithm from the offline data. Then, a feedforward controller is designed to inject the friction information into the loop and eliminate it before causing performance degradations. Since the friction is a kind of disturbance and leads to uncertainties having time-varying characters, an Adaptive Proportional Derivative (APD) type Iterative Learning Controller (ILC) named as the APD-ILC is designed to mitigate the friction effects. Finally, the proposed control approach is simulated in MATLAB/Simulink environment and it is compared with the conventional Proportional Integral Derivative (PID) controller, Proportional ILC (P-ILC), and Proportional Derivative ILC (PD-ILC) algorithms. The results confirm that the proposed APD-ILC significantly lessens the effects of the friction and thus noticeably improves the control performance in the low speeds of the PMSM.