Digital Synchronization Research Articles

Concept and theoretical performance analysis for decentralised digital synchronisation in distributed radar sensor networks

AbstractThis paper presents a decentralised technique for achieving frequency, time, and phase synchronisation of platforms cooperating in a distributed radar sensor network. The proposed method is advantageous for existing digital radar systems as it can be implemented entirely in the software without the use of additional RF hardware required by other techniques. The synchronisation signal model for signals transmitted and received in various clock domains is presented and an estimation model is subsequently derived for estimating and correcting the clock drifts. A modified version of a previously developed phase and clock bias correction procedure is outlined for correcting time and phase after frequency synchronisation. A comprehensive theoretical performance analysis of the technique is performed in which the expected maximum achievable performance is derived in terms of the Cramér–Rao lower bound for frequency, time, and phase measurements. Multiple Monte Carlo simulations show that the proposed technique approaches this performance limit. Finally, a simulated distributed transmit beamforming scenario is provided to show the application of the proposed technique in a practical system architecture. The results of this show that as the signal‐to‐noise ratio approaches moderate levels, the proposed synchronisation technique enables the beamforming network to achieve nearly optimal coherent energy gain at the beamforming destination.

Digital twin-based cross-enterprise production-delivery synchronization in a highly dynamic environment

Efficient collaboration between production and logistics is crucial for timely order fulfillment and stable operations of system, necessitating closer cooperation between manufacturers and third-party logistics providers. However, achieving cross-enterprise synchronization presents three main challenges. First, concerns regarding information privacy and security lead to disjointed and non-shared resources. Second, the decision-making is not coordinated and consistent in dealing with dynamic interference. Third, differentiated strategies emerge as manufacturers and 3PLs employ different batch processing methods for customer orders in pursuit of economies of scale. This multifaceted disconnect leads to significant asynchronization in cross-enterprise production-logistics, resulting in inefficiencies and increased costs throughout the system. To address these challenges, this paper focuses on three key aspects: a digital twin-based cross-enterprise information-sharing framework, a cross-enterprise synchronized mechanism, and a collaborative optimization based distributed decision method. These aspects provide an intelligent production-logistics synchronization solution in the unique environment of Industry 4.0. Finally, through a case study of a paint enterprise, this paper comprehensively evaluates the differences in performance of the Production-Logistics Synchronization System (PLSS) under various synchronization modes. The results indicate that the proposed solution enhances the collaborative efficiency of production-logistics while ensuring the information security of the collaborating parties, effectively reducing production and delivery costs.

Digital twin-based multi-granularity synchronisation for production-warehousing under batch processing mode

Batch production is a cost-effective way that boosts efficiency in manufacturing systems. As customer demands become increasingly customised, there is a growing need to consolidate numerous small-batch orders. However, if batch production exceeds the optimal level, it may lead to the premature completion of customer orders, causing temporary congestion in the finished goods warehouse and prolonged resource occupation. Consequently, an essential focus of this study pertains to coordinating decision-making units like workshops and warehouses within batch production setups to ensure stable system operation amidst dynamic customer demands. The proposed solution encompasses a Digital Twin-based Multi-level Synchronised Control System (DTMCS) framework, featuring the Multi-granularity Synchronised Control Mechanism (MgSCM) and a collaborative optimisation model for batch production and warehouse planning. By examining a practical case study from a paint manufacturing company, the research delves into the effects of four synchronised control patterns on various system performance metrics, such as operating costs, equipment and warehouse utilisation rates, and system stability. Overall, this study provides an adaptable and cost-effective solution for enhancing production-logistics synchronisation.

Gamified learning experience based on digital media and the application of virtual teaching robots in dance teaching

The research aims to explore the application of gamified learning experience based on digital media and virtual teaching robots in dance teaching. A virtual teaching robot system is designed, which combines technologies such as 3D motion capture, pose calculation, loss function constraint, and similarity matching. Through methods such as bone orientation, digital media audio-visual synchronization, and analysis of robot motion effects, virtual teaching robots have been able to present dance movements. Integrating virtual teaching robots into the teaching process through gamified learning methods. By introducing elements such as tasks, challenges, and rewards into learning, it is possible to stimulate students’ interest and enthusiasm in learning, and improve learning outcomes. The application of digital media based virtual teaching robots in dance teaching has a good effect. The overall structure of the system is reasonable, and the application of virtual reality technology allows students to learn dance firsthand. Through the analysis of skill teaching effectiveness and comprehensive teaching effectiveness, it was found that students have better participation and learning outcomes when learning dance through virtual teaching robots. The implementation of this system can enhance students’ learning enthusiasm and effectiveness, providing a new way for innovation in dance teaching.

Digital synchronization of the MACM chaotic system by using PIC24-microcontrollers and the SPI-protocol

In recent years, chaotic synchronization has received a lot of interest in applications in different fields such as digital applications. The purpose of this work is to achieve the synchronization of the discretized version (DV) of the Méndez–Arellano–Cruz–Martínez (MACM) 3D chaotic system (CS) as master which is coupled to one or more MACM 3D CSs as slaves for three different applications. The Lyapunov Exponents (LEs) analysis is conducted using the numerical-algorithm in MATLAB in order to verify the chaos existence is preserved in the Continuous Version(CV) and DV of the two master–slave MACM CSs once that they are synchronized. Subsequently, the algorithm of the MACM CSs are implemented in two or more isolated embedded systems (ESs) using PIC-24 16-bit microcontrollers which are communicated using the Serial Peripheral Interface (SPI) protocol setting in 16-bits, and the synchronization is validated using the state-variables depicted in digital-to-analog converters (DACs), and the secret-image messages are validated in thin-film-transistor-liquid-crystal displays (TFT-LCDs) depending of the conducted application. In addition, one k-parameter switch is proposed in order to validate the enabled or disabled the synchronization between the master with one or many slave microcontrollers using a 16-bit numerical scaling-arrangement. The first application is the electronic-digital-implementation of the synchronization in real-time of 5 PIC-24 microcontrollers coupled in star-topology, 1 MACM-CS master-node, and 4 MACM-CSs slave-nodes. The second application is the synchronization of the two MACM CSs which are coupled and implemented in two PIC-24 microcontrollers, the master-node is setting to encrypt and transmit a secret-message which involves data to achieve the synchronization and to re-built an image once that the image is received, decrypted and depicted in the TFT-LCD in the slave-node in real-time. The third application is showing the synchronization of the 2 nodes where the message is an decomposed-image stored in a vector-data block in the SRAM (Static Random Access Memory, the stored-data remain in the memory only if the PIC-24 microcontrollers are powered) of the PIC-24 microcontrollers which the process is conducted encrypting and transmitting a secret-message using data to achieve the synchronization and elements of a pixel per finite sample-iterations to receive and decrypt the message in the PIC-24 microcontroller as slave-node, and later the message is re-built in a TFT-LCD. Finally, all the numerical results of the LE studies, comparative security analysis, and the numerical and experimental synchronization of the proposed three applications were validated in the ESs.

Damage volumetric assessment and digital twin synchronization based on LiDAR point clouds

Point clouds are widely used for structure inspection and can provide damage spatial information. However, how to update a digital twin (DT) with local damage based on point clouds has not been sufficiently studied. This research presents an efficient framework for assessing and DT synchronizing local damage on a planar surface using point clouds. The pipeline starts from damage detection via DeepLabV3+ on the pseudo grayscale images from the point depth. It avoids the drawbacks of image and point cloud fusion. The target point cloud is separated according to the detected damage. Then, it can be converted into a 3D binary matrix through voxelization and binarization, which is highly lightweight and can be losslessly compressed for DT synchronization. The framework is validated via two case studies, demonstrating that the proposed voxel-based method can be easily applied to real-world damage with non-convex geometry instead of convex-hull fitting; finite-element (FE) models and BIM models can be updated automatically through the framework.

The digital twin synchronization problem: Framework, formulations, and analysis

As the adoption of digital twins increases steadily, it is necessary to determine how to operate them most effectively and efficiently. In this article, the digital twin synchronization problem is introduced and defined formally. Frequent synchronizations would increase cost and data traffic congestion, whereas infrequent synchronizations would increase the bias of the predictions and yield wrong decisions. This work defines the synchronization problem variants in different contexts. To discuss the problem and its solution, the problem of determining when to synchronize an unreliable production system with its digital twin to minimize the average synchronization and bias costs is formulated and analyzed analytically. The state-independent, state-dependent, and full-information solutions have been determined by using a stochastic model of the system. Solving the synchronization problem using simulation is discussed, and an approximate policy is proposed. Our results show that the performance of the state-dependent policy is close to the optimal solution that can be obtained with full information and significantly better than the performance of the state-independent policy. Furthermore, the approximate periodic state-dependent policy yields near-optimal results. To operate digital twins more effectively, the digital twin synchronization problem must be considered and solved to determine the optimal synchronization policy.

DRL-Based Joint Path Planning and Jamming Power Allocation Optimization for Suppressing Netted Radar System

For jammer formations, due to advanced digital signal processing and precise synchronization, suppressing and penetrating netted radar systems face more challenges than ever. In this letter, a deep reinforcement learning-based joint path planning and jamming power allocation optimization (DRL-JPPAO) method is proposed. DRL-JPPAO models the penetration operation by a Markov Decision Process and utilizes the Proximal Policy Optimization algorithm to learn optimal sequential actions, which consist of waypoints and jamming power allocation matrices, to solve it. The learning process is guided by a reward function that depends on the success or failure of penetration and the distance to the target. Empirical results with a newly developed environment show that DRL-JPPAO can learn optimal paths and jamming power allocation strategies jointly, accomplishing the penetration operation effectively and elegantly.

Scientific, technological and other bases of production processes digitalization

Relevance. “Digital transformation”, “digital twin” and similar terms are media phenomena. However, these and related terms hide meanings, goals, objectives, technologies, prospects and dangers inevitable at the present stage of an industrial society development and transformation into post-industrial and beyond. In literature, digital transformation is usually applied to business management and is not concerned with material production. Research objective is to consider "digitalization" in relation to technical and technological objects of industrial production by the example of a coal mine. Methods of research. In the context of industrial civilization and industrial production, using the methods of system analysis and mathematical modeling, the article considers the development and connection between the processes of automation, digitalization, informatization, and intellectualization. It has been shown that it is possible to preserve and develop industrial production based on its digital transformation, which is based on digital twins that transform the concept of automation. The digital twin, which operates in real time and is synchronized with the simulated production process, is considered as a simulation model of matter and energy transformation processes. The descriptions of a coal mine and its digital twin are considered in a general form. The objectives have been formulated for the optimal production control and its digital twin synchronization. Results. The necessary and critical technologies and possibilities for implementing a digital twin have been identified. The relationship has been shown between the digital transformation of the industry, the objectives of large-scale planning, and the emergence of social problems.

Digital synchronization for continuous-variable quantum key distribution

Continuous variable quantum key distribution (CV-QKD) is a promising emerging technology for the distribution of secure keys for symmetric encryption. It can be readily implemented using commercial off-the-shelf optical telecommunications components. A key requirement of the CV-QKD receiver is the ability to measure the quantum states at the correct time instance and rate using the correct orthogonal observables, referred to as synchronization. We propose a digital synchronization procedure for a modern CV-QKD system with locally generated local oscillator for coherent reception. Our proposed method is modulation format independent allowing it to be used in a variety of CV-QKD systems. We experimentally investigate its performance with a Gaussian modulated CV-QKD system operating over a 10–20 km span of standard single mode fibre. Since the procedure does not require hardware modifications it paves the way for cost-effective QKD solutions that can adapt rapidly to changing environmental conditions.

Digital twin-enabled real-time synchronization for planning, scheduling, and execution in precast on-site assembly

Planning, scheduling, and execution (PSE) are essential for coordinating tasks during on-site assembly in prefabricated construction. Real-time synchronization supports collaborative decision making for planning and scheduling, and dynamic adjustment of execution in on-site assembly. However, simple and resilient mechanisms are lacking for on-site task allocation and performance in urban areas with limited buffers, and real-time information hasn't been fully used for automatic generation and adjustment of PSE. This paper proposes a digital twin-enabled real-time synchronization system (DT-SYNC), which aims to facilitate PSE using real-time resource status and construction progress information obtained from high-fidelity digital twins. Inspired by functional tickets in graduation ceremony, a real-time synchronization model with cyber-physical visibility and traceability is designed to organize and coordinate operations and resources with enhanced simplicity and resilience, which guarantees that appropriate resources are spatiotemporally allocated to appropriate activities. A numerical experiment and related robotic testbed demonstration are conducted for proof of concept.

Expected Constant Time Self-Stabilizing Byzantine Pulse Resynchronization

In extending fast digital clock synchronization to the bounded-delay model, the expected constant time Byzantine pulse resynchronization problem is investigated. In this problem, the synchronized state of the system should not only be deterministically maintained but be reached from arbitrary states with expected constant time in the presence of Byzantine faults. An intuitive geometric representation of the problem is introduced, with which the classical approximate agreement, randomized Byzantine agreement, and random walk are integrated with some geometric operations. Efficient realizations are also provided for practical uses. Compared with the state-of-the-art solutions, the assumed common pulses need not be regularly generated, the message complexity can be lowered as approximate agreement, and the expected stabilization time is optimal. With this, the provided solution can efficiently convert irregularly generated common pulses to self-stabilizing Byzantine pulse synchronization.

Offline digital twin synchronization using measurement data and machine learning methods

Digital Twins play an important role in modeling production processes to adapt parameters according to predicted situations. Panel bending machines from Salvagnini use this technology to ensure safe operating conditions and to guarantee accurate results for different settings, even with highly variable material properties. Due to constantly increasing accuracy requirements, digital twins have to increase accuracy on the one hand and adapt to new machine generations on the other hand. This work shows how machine learning tools can be used to synchronize digital twins accurately and efficiently with real-world behavior by learning parameter values with measurement data while maintaining interpretable and robust analytical models.

Integrating PHM into production scheduling through a Digital Twin-based framework

Production scheduling has a long history of research but still presents open challenges, when considering production systems with uncertainty. The digitization, and in particular Digital Twins, may play a role in progressing the research field. The paper proposes a framework to exploit the Digital Twin synchronization with the field to include health assessment models into the simulation-based optimization of the production system scheduling. The health assessment is based on a modelling of failure modes and monitoring signals to connect the physical production resources to health and operating states in order to have a more accurate prediction of the makespan with respect to the actual makespan of the production system. The scheduling framework is validated through a laboratory application in the Industry 4.0 Lab at the School of Management of Politecnico di Milano.

From traditional warehouses to Physical Internet hubs: A digital twin-based inbound synchronization framework for PI-order management

Physical Internet (PI) is a new concept to ensure global mobility of physical objects. Conventionally, logistics networks are closed and independent. Under the concept of PI, they are transformed into an open logistics network, providing an efficient way to relocate physical goods to a given place in a short period of time. A hyperconnected city logistics system is conceptualized as the final segment of a PI-network. It uses regional and city hubs as the final leg of last-mile delivery. Inventory at PI-hubs has to be managed efficiently so as to maximize the benefits of PI. This paper proposes a digital twin-based inbound synchronization framework to streamline the operations of a PI-hub in a hyperconnected city logistics system. Digital twins and Internet of Things technologies are proposed for data acquisition and virtualization of real conditions of physical objects, followed by machine learning-integrated models to optimize a joint order fulfillment and replenishment operation in the PI-hubs. Adopting the proposed framework can formulate a Total Inbound Synchronization at three levels: order synchronization, process synchronization and information synchronization. Simulation results show a significant reduction of traveling distance in PI-hubs if the interdependent order fulfillment and replenishment operations are considered as a joint operation. In addition, this paper provides practical implications for logistics service providers to manage information flows within a PI-network driven by digital twins.

Current-Decomposition-Based Digital Phase Synchronization Method for BWPT System

Phase synchronization between the primary and secondary power converters is indispensable to achieve bidirectional wireless power transfer (BWPT). For sharing the phase information without any physical contact, traditionally, some wireless communication devices or auxiliary windings are proposed, yet with the disadvantages of low reliability and high cost caused by the electromagnetic interference and extra devices. This letter proposes a digital phase synchronization method for the BWPT system. Based on the active and reactive components of the ac current flowing into/out of the secondary high-frequency converter (HFC), the voltage phase of secondary HFC can be controlled to synchronize with that of primary HFC by adjusting the reactive current to be zero. The advantages of the proposed method are the fast response and high reliability for phase synchronization. A 1-kW prototype controlled by a field-programmable gate array is built to verify the proposed method. The experimental results prove that the system can quickly switch the power transmission direction in 2 ms with a maximum efficiency of 96.48% and can operate stably when the parameters perturbation occur. This letter is accompanied by an experimental video to prove the feasibility of the proposed method.

Design and implementation of HF signal receiving and processing module based on FPGA

This article designs and implements a receiving processing module based on the Xilinx ZCU102 evaluation board for the signal waveform defined in Appendix C of MIL-STD-188-110C. The focus is on the digital down-conversion, synchronization capture, and adaptive equalization algorithm for this signal processing module. Compare and design two adaptive algorithms, LMS (Least Mean Square) and DLMS (Delayed Least Mean Square). LMS algorithm has better convergence effect than DLMS algorithm, and the calculation efficiency is lower than the DLMS algorithm based on the structure of the systolic array. The signal waveform is tested under CCIR (International Radio Consultative Committee) HF (High Frequency) channel. The experimental results show that the receiving processing module has good feasibility for signals under medium HF channels.

Space-Ground Coherent Optical Links: Ground Receiver Performance With Adaptive Optics and Digital Phase-Locked Loop

In the framework of optical high data rate satellite-to-ground links, we investigate the performance of a coherent receiver which combines an adaptive optics system and a digital carrier synchronization technique. We propose a digital carrier synchronization system based on a phase-locked loop and use end-to-end simulations to characterize the impact of the atmospheric turbulence in the case of a representative low Earth orbit satellite-to-ground transmission link. The results show that classical digital phase-locked loop techniques can be a reliable solution to accurately compensate for the Doppler frequency shift between the incoming signal and the local oscillator at the ground station, in the presence of a preliminary coarse frequency estimation. Adaptive optics compensation enables the loop to lock after a few milliseconds and to accurately track the phase fluctuations. The bit-error-rate performance is not degraded by the digital loop but suffers from the residual signal amplitude fluctuations.

Integrated front-end electronics for single photon time-stamping in cryogenic dark matter detectors

ALCOR is a first prototype of a 32-pixel low-power mixed-signal ASIC developed to readout silicon photomultipliers at low temperature. The chip, designed in 110 nm CMOS technology, performs single photon time-stamping with a maximum event rate of 5 MHz per pixel. The time measurement is performed using low-power TDCs based on analogue time interpolation. The time binning achievable at maximum clock frequency is 50 ps and the target power consumption is less than 5 mW per pixel. Generated data are serialised and transmitted through LVDS drivers. To assert the CMOS electronic behaviour at 77 K, a Test Chip has been produced and tested. Results of a digital synchronisation circuit are reported and discussed.

A Digital Interconnected Bus Providing Voltage Synchronization for the Modular Series-Connected Inverters

The input port or the output port series-connected system is very suitable for medium- or high-voltage applications. For the output series-connected modular inverter system, the important issue is to guarantee that the phase angle of the different modules are exactly the same, otherwise, the total output voltage cannot meet the requirement. This letter proposes a digital synchronization strategy, which adopts a digital interconnected bus to provide the common reference signal for the composed modules. The operation principle, circuit schematic, and control design of the proposed strategy are explained in detail in this letter, and finally, the performance of the strategy is verified on a three-module series-connected inverter system.