Precise Positioning Research Articles

Addressable planar arrays of highly-luminescent 1,4-bis(5-phenyloxazol-2-yl)benzene nanowires via mask-confined graphoepitaxy for optoelectronic applications

This study introduces a facile method for the controlled growth of addressable planar arrays of highly luminescent, catalyst-free 1,4-bis(5-phenyloxazol-2-yl)benzene (POPOP) nanowires. By employing a hollow mask over a faceted sapphire substrate, simultaneous control over the position and orientation of the nanowires is achieved through a mask-confined graphoepitaxial growth, offering substantial advantages over traditional post-growth assembly techniques. High-temperature annealing creates parallel nanogrooves on the sapphire surface, inducing a graphoepitaxial effect that aligns the nanowires with a consistent [102] crystallographic axis. The hollow mask further aids in precisely localizing nanowire growth through its shadowing effect. Optoelectronic investigations reveal that these nanowires emit intense and stable blue photoluminescence at room temperature, with a broad spectrum spanning from 400 to 600 nm. This luminescence is achieved through excitation by continuous-wave ultraviolet light or two-photon absorption using femtosecond infrared light. Notably, the emission quantum efficiency of POPOP nanowires reaches 59 %, a remarkable improvement over the 12 % observed in powder counterparts when excited with 405 nm light. Transit absorption spectra indicate that ground state bleaching and excited state absorption display consistent kinetics within a 100 ps time window, suggesting the same origin from singlet excitons. The precise alignment and positioning of these nanowires make them viable for in-situ integration into photodetectors with rapid ultraviolet light responses. This study advances the controlled growth of catalyst-free nanowire arrays and enhances the understanding of the optoelectronic properties of POPOP nanowires.

Micromotor based on single fiber optical vortex tweezer

Optical micromotors are powerful tools for trapping and rotating microparticles in various fields of bio-photonics. Conventionally, optical micromotors are built using bulk optics, such as microscope objectives and SLMs. However, optical fibers provide an attractive alternative, offering a flexible photon platform for optical micromotor applications. In this paper, we present an optical micromotor designed for 3D manipulation and rotation based on a single fiber optical vortex tweezer. A tightly focused vortex beam is excited by preparing a spiral zone plate with an ultrahigh numerical aperture of up to 0.9 at the end facet of a functionalized fiber. The focused vortex beam can optically manipulate and rotate a red blood cell in 3D space far from the fiber end facet. The trapping stiffness in parallel and perpendicular orientations to the fiber axis are measured by stably trapping a standard 3-µm silica bead. The rotational performance is analyzed by rotating a trimer composed of silica beads on a glass slide, demonstrating that the rotational frequency increases with rising optical power and the rotational direction is opposite to the topological charge of the spiral zone plate. The proposed fiber micromotor with its flexible manipulation of microparticle rotation circumvents the need for the precise relative position control of multiple fiber combinations and the use of specialized fibers. The innovations hold promising potential for applications in microfluidic pumping, biopsy, micromanipulation, and other fields.

Anterior Cruciate and Anterior Oblique Ligament Reconstruction Using Hamstrings and Peroneus Longus’ Anterior Half Grafts

Objective: To describe the surgical technique for anterior cruciate ligament (ACL) and anterior oblique ligament (AOL) reconstruction using hamstring tendons and the anterior half of the peroneus longus tendon. Methods: The surgical technique involves the following key steps: 1. Tendon Harvesting: The semitendinosus and gracilis (STG) tendons are harvested from the injured limb or the contralateral limb in cases of prior ACL reconstruction. Additionally, a 3 cm longitudinal incision is made in the posterolateral region of the fibula to harvest the anterior half of the peroneus longus (PL) tendon, ensuring the fibular nerve is not injured. The harvested tendons form a quintuple graft, with the STG folded four times and the PL used as a fifth component. 2. Graft Preparation: The STG graft is folded to create a quadruple graft, and the PL is integrated into this without folding, forming a quintuple graft proximally. The distal portion remains single, extending the PL length. 3. Tunnel Positioning for ACL: The reconstruction involves precise anatomic positioning of the femoral and tibial tunnels. The femoral tunnel is created in the Anatomical Functional Position, as described by Jorge et al., using an outside-in technique with the Acufex Pinpoint guide (Smith & Nephew). The tibial tunnel is positioned on the anteromedial surface of the tibia, ensuring optimal alignment with the femoral tunnel. 4. Femoral Tunnel for AOL: The femoral tunnel for the AOL is positioned at the medial epicondyle. Fluoroscopy is used to identify the medial epicondyle in the lateral view. A guidewire is passed through the anterior portion of the medial epicondyle, creating a tunnel under radiographic visualization to ensure correct anatomical placement of the AOL. 5. Graft Passage and Fixation: The graft is passed through the tibial and femoral tunnels using a No. 5.0 Ethibond suture. The quintuple graft occupies both tunnels, and the single PL portion remains outside the tibial tunnel until fixation. Femoral fixation is achieved with an interference screw (Biosure; Smith & Nephew). After pretensioning, tibial fixation is completed with the knee in full extension. The remaining PL is passed subcutaneously on the medial side and fixed in the AOL tunnel with the knee in neutral rotation and 45 degrees of flexion. This technique ensures optimal biomechanical restoration and stability in the anterolateral and anteromedial knee compartments. Results: This technique aims to improve knee stability by addressing anterolateral and anteromedial instability, which is critical in some instances of ACL injury. Using the anterior half of the peroneus longus tendon in conjunction with hamstring tendons provides a viable, biomechanically sound option for reconstruction. Conclusion: Combined ACL and AOL reconstruction using hamstring and peroneus longus tendons is a promising technique for improving knee stability in patients with ACL injuries, particularly those with anteromedial instability. This approach may be a valuable alternative to exclusive anterolateral reinforcement in select cases.

Cascade control method for hydraulic secondary regulation drive system based on adaptive robust control

The hydraulic secondary regulation drive system employs a hydraulic servo motor to achieve precise position tracking and zero throttling loss, but it faces challenges such as high inertia, low damping, and high system order, leading to suboptimal control accuracy. Traditional adaptive robust control methods struggle with the control challenges of such high-order systems. This paper introduces a cascaded control approach based on adaptive robust control to address these issues. A fifth-order model is developed to account for significant load inertia, dividing the system into inner and outer control loops. The outer loop applies adaptive robust control to handle uncertainties and load disturbances for accurate rotational position control, while the inner loop uses swashplate disturbance compensation robust control to manage torque disturbances and achieve precise displacement control. A cascaded Lyapunov function is designed to address the coupling effects between the errors of the inner and outer loop controllers, ensuring stability across both subsystems. Experimental results show that the proposed method’s position tracking accuracy exceeds that of cascade dual-PID control methods by 50% to 80% and traditional adaptive robust control methods by 30% to 40% under sinusoidal frequency commands of 0.1 Hz and 0.25 Hz.

Discussion on the thermal conductive network threshold of Al2O3/Co-continuous phase polymer composites

Achieving high thermal conductivity in polymer composites with micro or nanoparticle fillers are challenging. Typically, over 50 ​vol% filler loading is necessary to form a thermal conductive network. However, even with such a network in place, the increase in thermal conductivity may not be significant compared to that in electrically conductive composites. To clarify the ideal filler network structure, we endeavored to selectively disperse nano-sized Al₂O₃ nanoparticles at the interface of co-continuous SEBS/PA6 blends, with and without various filler surface modification methods. A thermal conductive network forms when all interface areas are fully covered by 2.56 ​vol% of Al2O3 nanoparticles (very close to theoretical loading content 2.29 ​vol%). In this case, the Al2O3 nanoparticle has the highest thermal conductive contribution (TCC). However, the absolute TCC values are extremely low because of the interfacial thermal resistance and it will decrease when the filler content exceeds 2.56 ​vol%, indicating that some nanoparticles are dispersed separately out of the existed thermal conductive network. These findings suggest that the construction of a connected thermal conductive network, relatively lower interfacial thermal resistance and the precise positioning of fillers within this network are essential for achieving high thermal conductivity composites.

Effect of Source-Sink Misalignment and Sink Cavity Aspect Ratio on the Thermal Performance of Gallium Heat Sinks

Herein, we numerically investigated methods to improve heat dissipation from the base of a phase-change material (PCM) heat sink exposed to high heat flux (15 W/cm2). The sink cavity exhibited a rectangular cross-section with two opposite vertical walls of high thermal conductivity. These walls serve as heat-dissipating fins. We used gallium, a metallic PCM with high thermal conductivity and a low melting point to improve heat dissipation by leveraging buoyancy-driven circulations within the molten gallium. We adopted a method to position the sink base on top of the heat source surface in such a way to augment temperature gradients within the liquid to induce imbalances in gallium density and consequent internal circulations. In this technique, one vertical wall is subjected to forced-convective heat exchange with the surroundings, while the other remains adiabatic. Subsequently, for the case which showed optimum performance, we relaxed the adiabatic thermal boundary condition applied at one of the vertical walls and replaced it with convective heat transfer condition, and assessed the sink performance based on that. Further, we analyzed the impact of various aspect ratios of the sink cavity on the induced internal circulations and base cooling. Sink cavities with aspect ratios of 1.33, 0.96, and 0.64 corresponding to sink heights of 20, 17, and 14 mm, respectively, were examined under a consistent heat flux applied across a 15-mm base length. We also investigated the precise positioning of the sink base relative to the heat source surface and explored its influence on temperature gradients and gallium density imbalances crucial for induced internal circulations. Results indicate that a sink cavity aspect ratio of 0.96 yields the optimal heat dissipation from the base. Further, aligning the left bottom edge of the sink base with the left edge of the heat source surface maximizes heat dissipation to the ambient surroundings, thereby prolonging latent-heat dumping into the sink before the gallium completely melts. Any misalignment between the sink base and the surface of the heat source may have a profound impact on the temporal evolution of induced internal circulations within the molten gallium, essentially affecting heat dissipation from the sink base.

Non-singular sliding mode control-based attitude control analysis of ELITE satellite with flywheel failures

Abstract This paper addresses the challenge of maintaining the attitude control of the ELITE satellite in the event of flywheel failures. Given the critical need for highly stable and precise attitude control during Time-Delay Integration (TDI) Imaging missions, a failure in any flywheels poses a significant threat to the satellite’s attitude control stability and accuracy. To tackle this issue, a Non-singular Sliding Mode Control (NSMC) method was proposed to ensure ELITE’s continued performance under flywheel failure conditions. The research involves a thorough analysis of ELITE’s attitude dynamics, followed by designing an NSMC tailored to its specifications. Theoretical validation of the NSMC’s finite-time stability was achieved using the Lyapunov function. Numerical simulations conducted demonstrate that the proposed NSMC method enables ELITE to maintain its attitude control stability and precision even in the presence of flywheel failures, thereby ensuring mission continuity and reliability.

Review Paper on Agricultural Terrain Traversal Rocker Bogie Mechanism

Abstract: This paper details the design and implementation of a terrain traversal system leveraging the rocker-bogie mechanism, specifically tailored for agricultural applications where uneven terrain presents significant challenges. The rocker-bogie suspension system, renowned for its application in planetary rovers, is innovatively adapted to navigate the complexities of agricultural fields. The primary objective of this research is to create a prototype that minimizes soil disturbance while effectively maneuvering over obstacles such as rocks, furrows, and varying soil conditions. Through this approach, the prototype aims to enhance operational efficiency in critical agricultural tasks, including planting, monitoring, and maintaining crops. The system's design incorporates advanced navigation capabilities, potentially integrating sensors for obstacle detection and GPS for precise positioning. This research addresses the pressing need for low-cost, scalable solutions in the realm of agricultural mechanization, ultimately contributing to improved productivity and reduced labor costs in farming operations. The findings from this study are anticipated to provide significant insights into the future of agricultural technology, paving the way for further innovations in automated systems that can adapt to the dynamic challenges of modern agriculture. The successful deployment of this prototype not only underscores the feasibility of the rocker-bogie mechanism in agricultural settings but also highlights its potential to revolutionize practices in the industry.

Image tampering detection based on RDS-YOLOv5 feature enhancement transformation

Malicious image tampering has gradually become another way to threaten social stability and personal safety. Timely detection and precise positioning can help reduce the occurrence of risks and improve the overall safety of society. Due to the limitations of highly targeted dataset training and low-level feature extraction efficiency, the generalization and actual performance of the recent tampered detection technology have not yet reached expectations. In this study, we propose a tampered image detection method based on RDS-YOLOv5 feature enhancement transformation. Firstly, a multi-channel feature enhancement fusion algorithm is proposed to enhance the tampering traces in tampered images. Then, an improved deep learning model named RDS-YOLOv5 is proposed for the recognition of tampered images, and a nonlinear loss metric of aspect ratio was introduced into the original SIOU loss function to better optimize the training process of the model. Finally, RDS-YOLOv5 is trained by combining the features of the original image and the enhancement image to improve the robustness of the detection model. A total of 6187 images containing three forms of tampering: splice, remove, and copy-move were used to comprehensively evaluate the proposed algorithm. In ablation test, compared with the original YOLOv5 model, RDS-YOLOv5 achieved a performance improvement of 6.46%, 5.13%, and 3.15% on F1-Score, mAP50 and mAP95, respectively. In comparative experiments, using SRIOU as the loss function significantly improved the model’s ability to search for the real tampered regions by 2.54%. And the RDS-YOLOv5 model trained by the fusion dataset further improved the comprehensive detection performance by about 1%.

A millisecond pulsar position determined to 0.2 mas precision with VLBI

Context. Precise millisecond pulsar (MSP) positions determined with very long baseline interferometry (VLBI) hold the key to building the connection between the kinematic and dynamic reference frames respectively used for VLBI and pulsar timing. A frame connection would provide an important pathway to examining the planetary ephemerides used in pulsar timing, and would potentially enhance the sensitivities of the pulsar timing arrays used to detect stochastic gravitational-wave background in the nano-Hz regime. Aims. We aim to significantly improve the precision of the VLBI-based MSP position (from >1 mas at present) by reducing the two dominant components in the positional uncertainty – the propagation-related uncertainty and the uncertainty resulting from the frequency-dependent core shifts of the reference sources. Methods. We introduce a new differential astrometry strategy called PINPT (Phase-screen Interpolation plus frequeNcy-dePendent core shifT correction; pronounced “pinpoint”), which entails the use of multiple calibrators observed at several widely separated frequencies. The strategy allows determination of the core shift and mitigates the impact of residual delay in the atmosphere. We implemented the strategy on PSR J2222-0137, an MSP that is well constrained astrometrically with VLBI and pulsar timing. Results. Using the PINPT strategy, we determined core shifts for four AGNs around PSR J2222-0137, and derived a VLBI-based pulsar position with uncertainties of 0.17 mas and 0.32 mas in Right Ascension and Declination, respectively, approaching the uncertainty level of the best-determined timing-based MSP positions. Additionally, incorporating the new observations into historical ones, we refined the pulsar proper motion and the parallax-based distance to the <10 µas yr-1 level and the subparsec level, respectively. Conclusions. The realization of the PINPT strategy promises a factor-of-five positional precision enhancement (over conventional VLBI astrometry) for all kinds of compact radio sources observed at <2 GHz, including most fast radio bursts.

Eye Mapping: Innovative Technique for Precise Iris Positioning in Prosthetic Eye.

The aim of this technique is to institute "Augmented Reality Tool" in the field of maxillofacial prosthesis for an accurate and precise iris positioning in a prosthetic eye. A congenital defect, irreversible damage, a painful blind eye, sympathetic ophthalmia, or the requirement for histological confirmation of a suspected illness can all result in the absence or loss of an eye. In such circumstances, meticulous preoperative, surgical, and prosthetic planning using a multidisciplinary approach is imperative for successful rehabilitation. Augmented reality filter was used to provide precise mapping of facial landmarks and to aid in iris positioning. Smartphone device (S22) was used and artificial intelligence (AI)-generated Instagram application was unfurled and augmented reality (AR) filter was instituted. The filter available in the application made it possible to see and confirm the iris shell's location in three dimensions from various angles. The dimensions thus provided, aided in the correct positioning of the iris in the prosthetic eye. Iris positioning stands as one of the crucial steps in fabricating a patient-specific ocular prosthesis. In the present case report, iris positioning was done using AI has provided an excellent esthetics results and patient compliance was met with satisfaction. Accurate positioning of iris can be done using AR tool which is popular, easily accessible, less technique sensitive, and can be performed with slightest efforts in small clinical set-ups. Relating to patient, it is comfortable, economic, and trouble-free procedure. How to cite this article: Zilpilwar NR, Nimonkar SV, Chitlange P, et al. Eye Mapping: Innovative Technique for Precise Iris Positioning in Prosthetic Eye. J Contemp Dent Pract 2024;25(7):711-714.

A Comprehensive Review of Evolving Brand Image Strategies: From Universal Appeal to Targeted Resonance in Modern Marketing

In today’s fierce market competition, brand image building has become the object of attention of major corporations, more and more enterprises take brand image building as the key work of marketing, such as Amazon, and Disney. Therefore being fully aware of the model and internal mechanism of brand image sharping in enhancing brand market competitiveness, it can provide an effective reference for enterprises to improve the efficiency of brand image building. This paper is devoted to reviewing the history route of brand image building, and summarizing the typical cases, then summarize the business strategies of several different brands. Finally, we summarize the effective business strategy for brand image building, the first is high-quality products, good quality and cheap products always can attract more customers; the second is precise brand positioning, targeting customers to gain competitive advantages; the third is high-quality corporate culture, good cultural atmosphere can enrich the connotation of enterprises and the external competitiveness, to stand out from the homogenized products; the forth is great ethical image, enterprises though attend public welfare activities and other ways to create a positive brand image, then enhance customer’s loyalty.

Factors Contributing to the Success of iPhone in the Chinese Market and Competitive Strategies

As one of the largest smartphone markets in the world, China’s huge market demand makes it an important player. Since entering the Chinese market, the iPhone has won a wide user base with its high-end brand image and innovative technology. The study focuses on analyzing the factors that have contributed to Apple’s success in the Chinese market, including brand building, product innovation, marketing strategies, and user experience. It also explores how Apple’s competitive strategies have helped it stand out in a fiercely competitive market environment. The study employs a combination of quantitative and qualitative research methods. By analyzing market data, conducting consumer surveys, and conducting market research, the study evaluates Apple’s performance and consumer preferences in the Chinese market, and explores Apple’s competitive strategies and market positioning. We found that Apple’s success in the Chinese market is mainly due to its strong brand effect, continuous technological innovation, precise market positioning, and effective marketing strategies. Apple has won the recognition of Chinese consumers with its high-quality products and excellent user experience. At the same time, it has successfully addressed competition pressure through differentiated competition strategies and the establishment of a unique ecosystem.

Affordable Real-Time PPP—Combining Low-Cost GNSS Receivers with Galileo HAS Corrections in Static, Pseudo-Kinematic, and UAV Experiments

The Galileo High Accuracy Service (HAS) is a free of charge Global Navigation Satellite System (GNSS) augmentation service provided by the European Union. It is designed to enable real-time Precise Point Positioning (PPP) with a target accuracy (at the 95% confidence level) of 20 cm and 40 cm in the horizontal and vertical components, respectively, to be achieved within 300 s. The performance of the service has been confirmed with geodetic-grade receivers. However, mass market applications require low-cost GNSS receivers connected to low-cost antennae. This paper focuses on the performance of the real-time static and kinematic positioning achieved with Galileo HAS and low-cost GNSS receivers. The study is limited to GPS + Galileo dual-frequency positioning, thus exploiting the full potential of Galileo HAS SL1. We demonstrate that the target accuracy of Galileo HAS SL1 is reached with both geodetic-grade and low-cost receivers in dual-frequency static and kinematic applications in open-sky conditions. Precision of a few centimeters is reached for static positioning, while kinematic positioning results in subdecimeter precision. Vertical accuracy is limited by missing phase center offset models for low-cost antennas. In general, the performance of low-cost hardware using Galileo HAS for real-time PPP is comparable to that of geodetic-grade hardware. Therefore, combining low-cost GNSS receivers with Galileo HAS is feasible and justified.

Real-time localization with probabilistic maps and unscented kalman filtering: a dynamic sensor fusion approach

This paper presents a robust position estimation technique for autonomous vehicles navigating urban and highway environments. It employs a probabilistic framework, integrating Monte Carlo simulation and Bayesian filtering via particle filters to represent position estimates beyond Gaussian distributions. To improve accuracy, Unscented Kalman Filtering (UKF) is used to fuse radar and lidar data, facilitating the detection of static, pole-like objects. These objects are matched with landmarks from a detailed reference map generated through 3D lidar scans. The proposed method addresses both lateral and longitudinal localisation challenges, ensuring precise vehicle positioning. Comprehensive simulation tests validate the system's effectiveness, demonstrating reliable performance across various driving conditions.

A collaborative navigation algorithm for UAV Ad Hoc network based on improved sequence quadratic programming and unscented Kalman filtering in GNSS denied area

In global navigation satellite system (GNSS) denied area, collaborative positioning precision is important for unmanned aerial vehicle (UAV) to perform collaborative tasks in Ad Hoc network. Continuous optimization of algorithm complexity and parameter setting has long been a focal point in the field of collaborative positioning research. An algorithm of UAVs collaborative positioning based on improved sequential quadratic programming (SQP) and unscented kalman filter (UKF) is proposed. By optimizing the parameter constraints of SQP, parameters are controlled within certain conditions. The convergence speed of SQP is improved, and more accurate filtering parameters are obtained. The improved SQP and UKF are combined to optimize the location data of UAVs, which improves the precision of collaborative positioning. The simulation results show that the positioning precision can be greatly enhanced by approximately 25% when using the proposed algorithm, as compared to the traditional algorithm. The influence of the collaborative UAV number also is simulated. The positioning performance improve slowly when more than five UAVs are used for collaborative positioning. Therefore, the positioning performance cannot be improved only by increasing the number of UAVs, but also by improving the performance of collaborative positioning algorithm.

Functionalized Nanodiamonds for Targeted Neuronal Electromagnetic Signal Detection.

Intracellular sensing technologies necessitate a delicate balance of spatial resolution, sensitivity, biocompatibility, and stability. While existing methods partially fulfill these criteria, none offer a comprehensive solution. Nanodiamonds (NDs) harboring nitrogen-vacancy (NV) centers have emerged as promising candidates due to their sensing capabilities under biological conditions and their ability to meet all aforementioned requirements. This study focuses on expanding the application of NDs and NV center-based sensing to neuronal contexts by investigating their functionalization and subsequent effects on three distinct cell lines relevant to neurodegenerative disease research. Our study concentrates on positioning fluorescent NDs (FNDs) with NV center point defects onto neuronal cell surfaces. Achieving this through specific antibody attachment enhances the proximity of FND to neurites, facilitating the detection of local action potentials. Targeting voltage-dependent calcium channels (Cav2.2) with biotin-streptavidin-bound antibodies enables the precise positioning of FNDs. The functionalized FNDs (f-FNDs) show increased size and zeta potential, confirming the antibody presence without compromising cell viability. Two-color confocal imaging and co-localization algorithms are employed to further attest to the success of the functionalization. The f-FNDs are applied to cell cultures of three cell lines: SH-SY5Y, differentiated dopaminergic neurons, and hippocampal rat neurons; their biocompatibility and effects on synaptic activity are explored. Moreover, preliminary total internal reflection fluorescence - optically detected magnetic resonance (TIRF-ODMR) experiments across cellular sites demonstrate the magnetic field sensitivity of our sensor network. The successful establishment of this sensor network provides a platform for characterizing neuronal signaling in healthy models and conditions mimicking Parkinson's disease.

A robotic fish processing line enhanced by machine learning

This paper presents the design of a comprehensive automatic fish processing line utilizing machine learning algorithms. The processing line encompasses several essential steps, including fish identification by type, fish sorting by size, fish orientation based on shape, and fish cutting at the optimal chopping points. The primary objective of this design is not just automation but also maximizing economic benefits by preserving the maximum amount of fish meat during the cutting process, achieved through the application of machine learning algorithms. To accomplish these goals, we employ a combination of transfer learning and convolutional neural networks to establish criteria for actions across all stages of automatic fish processing. At the heart of the processing station is a conveyor belt equipped with numerous sensors and lenses. Positioned along this conveyor belt are two robotic arms, responsible for precise positioning and cutting operations, all guided by the machine learning algorithms. To provide a visual representation of these design concepts, we have created a 3D SolidWorks model.

Positioning anti-sway control method for tower crane based on improved MFAC

A model-free adaptive control (MFAC) based on partial format is proposed for the complex modeling and uncertain model parameters of the tower crane (TC) in this paper. Firstly, considering the complexity of the TC nonlinear system, the data model of the TC is obtained through the partial format dynamic linearization method. Then, a model-free adaptive controller is designed for the TC, incorporating the change rate of the tracking error and its derivative into the objective function to address the inefficiency of traditional model-free controllers in controlling TCs. The convergence and stability of the proposed controller are also proved. To further improve the dynamic performance of the system, a tracking differentiator (TD) is introduced after the input signal. Finally, MATLAB simulation and experiments are conducted to verify that the proposed method can achieve precise trolley positioning while suppressing the load swing angle.

LEO satellite clock modeling and its benefits for real-time LEO PPP timing

In the kinematic Precise Orbit Determination (POD) process for low earth orbit (LEO) satellites, a significant correlation exists between the orbital and clock parameters. Here, a LEO satellite clock model is proposed to enhance the Precise Point positioning (PPP) timing and time synchronization during the LEO orbit/clock determination. The GRACE-FO satellite was utilized to achieve PPP timing and time transfer for LEO satellites with the real-time (RT) products provided by three analysis centers, namely Centre National d’Etudes Spatiales (CNES), GMV Aerospace and Defense (GMV), and Wuhan Technical University (WHU). For the frequency stability of the PPP timing for LEO satellites, the short-term stability (1280 s) is about 10−13 level, and the long-term stability (10,240 s) is about 10−14 level. Compared with the traditional PPP method (Scheme1), the LEO satellite clock model (Scheme2) is capable of significantly reducing the noise, regardless of whether it is PPP timing or PPP time synchronization. The frequency stability of Scheme 1 shows an improvement in short-term stability (1280 s) by about 8 %-72 % and the max improvement of the long-term stability (10240 s) by approximately 39 %, the result also shows a better improvement in LEO time synchronization.