Soft Synchronization Research Articles

A density-controllable 3D measurement system based on linear profile sensor and universal manipulator

In order to offer a simple and efficient solution for obtaining point clouds, a modular 3D measurement system that incorporates an LPS mounted on a universal manipulator is developed. Unlike the requirement for electronic connections between the LPS and the robot to achieve hard synchronization, we employ a high-low-frequency collaborative strategy for soft synchronization, thereby eliminating the need for complex hardware synchronization modules. Since soft synchronization lacks the high-speed synchronous data acquisition of hard synchronization, we have also proposed an interpolation method on low density data to generate uniform higher-density point clouds, thus enabling a density-controllable point clouds acquisition approach. Experimental results demonstrate the effectiveness and versatility of the system.

Power Consumption Model Construction and Analysis for Soft Synchronization FMCW Radar

Power Consumption Model Construction and Analysis for Soft Synchronization FMCW Radar

GPU implementations of deflate encoding and decoding

SummaryDeflate coding is a very popular lossless data compression method used in zlib, gzip (GNU zip), and zip, which performs the LZSS compression algorithm with Huffman coding. Deflate encoding and decoding involve sequential operations and their parallel acceleration using a GPU is quite hard. The main purpose of this paper is to present GPU implementations for encoding and decoding of Deflate coding. For efficient GPU implementations of Deflate coding, we have used multiple small hash tables for finding matching subsequences in the dictionary by multiple threads in parallel and applied the Single Kernel Soft Synchronization (SKSS) technique to fully utilize GPU computing resources. We have also adopted Huffman coding with gap arrays to accelerate parallel Huffman decoding. We have evaluated the performance of our GPU implementations using an NVIDIA A100 GPU and compared them with parallel/sequential Deflate encoding and decoding on the Intel X86 multicore CPUs using multiple threads/a single thread. Our GPU implementation of Deflate decoding is 1.66x–8.33x faster than the multiple thread implementation and 4.13x–36.56x faster than the single thread implementation.

Energy-Efficiency Strategy for Soft Synchronization FMCW Radar

Soft synchronization frequency-modulated continuous-wave (SS-FMCW) radars not only have the advantage of transmit signal diversity but also greatly reduce the complexity of hardware structure design. Interestingly, the SS-FMCW radar is implemented based on intermittent ramp signals and soft synchronization algorithms. This article proposes a new energy-efficiency strategy, i.e., the soft synchronization constrained energy-efficiency (SSC-EE) strategy. First, based on the principle behind the SS-FMCW radar, we analyze its energy consumption model. Second, an optimization problem is built with transmit signal parameters as the independent variables, soft synchronization performance and radar performances as the constraints, and radar energy consumption as the optimization objective. Furthermore, by formulating the Karush–Kuhn–Tuckers (KKT) conditions, we obtain a closed-form solution. The study on minimizing the theoretical energy consumption sheds light on the design of radar transmit signal parameters in practice. Finally, experimental results show that the SSC-EE strategy can reduce the energy consumption of the SS-FMCW radar without reducing the soft synchronization performance and the radar performances. Specifically, compared to the deterministic strategy, the SSC-EE strategy can reduce the radar energy consumption by 28.3%.

FFBV Algorithm Design for Soft Synchronization FMCW Radar

Whether in military or civilian use, frequency-modulated continuous-wave (FMCW) radars play a very important role, but common FMCW radars need to collect both radar echo signals and hardware synchronization signals during echo signal processing. Therefore, this article proposes a new synchronization algorithm, i.e., the four-threshold frequency band variance (FFBV) synchronization algorithm. Then, we combine theoretical derivation and experimental verification to analyze the performance of the FFBV synchronization algorithm. With assistance of the FFBV synchronization algorithm, the soft synchronization FMCW radar can achieve the same functions without hardware synchronization signals. First, we analyze the principle behind the FMCW radar based on intermittent ramp signals. Second, we analyze the design of the FFBV synchronization algorithm. In addition, we verify the performance of the algorithm when the received signal is corrupted by the additive white Gaussian noise (AWGN). Then, we analyze the performance from two aspects, including the performance of the algorithm under different signal-to-noise ratio (SNR) conditions, as well as the performance comparison with other common synchronization algorithms. Finally, experimental results show that the FFBV synchronization algorithm has achieved good performance in solving the signal synchronization issue of the FMCW radar under the condition of low SNR. Especially, the SNR required by the FFBV synchronization algorithm is 2 and 6.5 dB lower than that required by the three-threshold synchronization algorithm and variance synchronization algorithm, respectively, under the same condition that the accuracy is 90%.

A Synchronization Control Technique For Soft Connection of Doubly Fed Induction Generator Based Wind Turbines to the Power Grids

Doubly-fed induction generator (DFIG)-based wind turbine generators need to be connected back to integrated power grid after tripping due to disturbances and emergencies in power grid. Re-connection can cause switching transients which may affect overall grid stability. This situation can be avoided if proper synchronization can be ensured for smooth transition of DFIG from island mode to grid-connected mode. To this effect, in this paper, a direct voltage control based synchronization method is introduced that can ensure low or no transient effect during synchronization of DFIG to the grid. The controller is synthesized based on a multi-channel identification methodology and integrated using a designed grid connection logic for soft synchronization. The architecture is implemented on a modified IEEE 39 bus system with DFIG and tested on a real-time simulation platform with different wind speed conditions. It is observed that the proposed architecture makes the grid more stable (with swings in voltage or frequency reduced as much as 60%) during re-connection of wind generators.

Robust Multi-Agent Asynchronously Compensated Decentralized Frequency Synchronization Control Scheme for Microgrids

This paper proposes a new control scheme for synchronization of microgrids based on a multi-agent asynchronously compensated control algorithm. Each distributed generation (DG) unit is considered as an agent which can communicate with other agents or the main power grid. A new reduced-order observer is also introduced to approximate the frequency of each agent. The approximated parameters are then implemented in the proposed controller to control each DG. It is indicated that each agent in the microgrid can be represented as a dynamic oscillator which are interconnected by coupling and communication links. The proposed decentralized control algorithm is given in asynchronously compensated topology which considers the delay in communication links between agents. The deviation from the desired frequency is modeled in the droop-control structure of each DG. The proposed control scheme is configured in both leader–follower and leaderless structures and results in frequency coordination among DGs. Therefore, a soft synchronization load sharing performance achieved when there are nonlinear loads such as plug-in hybrid electric vehicles (PHEVs) in the microgrids. The simulation results validate the effectiveness of the proposed control strategy.

A New Method for Quick and Easy Synchronization of CHP Resources with an EPS

This article provides new ideas for synchronization between an electrical power system (EPS) and a combine heat and power (CHP) system. If an AC generator is used with another AC system, synchronization turns to an indispensable process. It is a frequent event for combined heat and power cogeneration in small quantities and is one of the most important things in daily operation. Also closing the breaker at zero phase difference is very important in synchronization. In this paper we introduce new ideas which will lead two AC systems to a smooth and soft synchronization. Through these ideas a soft synchronization which can provide a perfect phase angle matching is realized. In order to verify the efficiency of the proposed synchronization, matlab program was used for simulation studies and experimental tests were done through using with a real synchronous generator.

A Clock Soft Synchronization Method Based on CAN Bus and Synchronization Error Analysis

Based on information pipeline technology, a clock soft synchronization method used in distributed measurement and control system is proposed. Using a separate information pipeline, the synchronization information is broadcasted to nodes in the distributed measurement and control system by synchronization node every message transaction cycle time, and all nodes automatically synchronize the local clock after receiving it. We analyze the theoretical synchronization error and verify this clock soft synchronization method in CAN bus. The theory analysis and experimental results indicate that the synchronization error mainly consists of propagation delay error, drift error and CAN loop delay error, and it increases linearly with the increasing of transmission distance.

New Ideas for a Soft Synchronizer Applied to CHP Cogeneration

This paper provides new ideas for the synchronization between an electric power system and a synchronous generator. If an individual ac generator is to be operated with another ac power system, the synchronization is an essential process for the parallel operation. For small combined heat and power cogeneration, the synchronization is a very frequent event and one of the most important jobs in daily operation. There are several types of traditional devices that support or control the breaker closure within the synchronizing criteria. However, the actual break closing is not controlled exactly on a zero point phase-angle difference. In this paper, we introduce new ideas that will lead two ac systems to a smooth and soft synchronization. With these ideas, a soft synchronizer that provides the perfect phase-angle matching is realized. To verify the effectiveness of this newly proposed soft synchronizer, we had conducted simulation studies using MATLAB as well as experimental tests with an actual synchronous diesel generator.

Soft Synchronization: Synchronization for Network-Connected Machine Vision Systems

Many computer vision applications require synchronization between image acquisition and external trigger events. Hardware and software triggering are widely used but have several limitations. Soft synchronization is investigated, which operates by time tagging both trigger events and images in a video stream and selecting the image corresponding to each trigger event. A stochastic model is developed for soft synchronization; and, based on the model, the uncertainty interval and confidence for correct image selection are determined, and an efficient calibration method is derived. Soft synchronization is experimentally demonstrated on a Linux image processing computer with a camera connected by the IEEE-1394 serial bus. To minimize timing variability, time tags are associated with images and events in the corresponding interrupt service routines within the operating system of the image processing computer. The model-based analysis applied to the experimental hardware shows that image/event synchronization within inter-frame interval can be achieved with 99% confidence. Experiments confirm this result.

Synchronization resources in heterogeneous environments: Time-sharing, real-time and Java

The asynchronous event distribution system (AEDS) was built to provide synchronization resources within the TJ-II local area network. It is a software system developed to add “soft synchronization” capabilities to the TJ-II data acquisition, control and analysis environments. “Soft synchronization” signifies that AEDS is not a real-time system. In fact, AEDS is based on TCP/IP over ETHERNET networks. However, its response time is adequate for practical purposes when synchronization requirements can support some delay between event dispatch and message reception. Event broadcasters (or synchronization servers in AEDS terminology) are Windows computers. Destination computers (or synchronization clients) were also Windows machines in the first version of AEDS. However, this fact imposed a very important limitation on synchronization capabilities. To overcome this situation, synchronization clients for different environments have been added to AEDS: for time-sharing operating systems (Unix and Linux), real-time operating systems (OS-9 and VxWorks) and Java applications. These environments have different synchronization primitives, requiring different approaches to provide the required uniform functionality. This has been achieved with POSIX thread library synchronization primitives (mutex and condition variables) on Unix/Linux systems, IPC mechanisms for concurrent processes on OS-9 and VxWorks real-time operating systems, and ‘synchronized–wait/notify’ primitives on Java virtual machines.

A distributed synchronization system for the TJ-II local area network

Abstract Synchronization mechanisms for the TJ-II local area network environment have been enhanced by the development of new capabilities. The mechanisms provide “soft synchronization,” that is notification of asynchronous events for situations in which some delay between the real event and message reception is not a critical point, e.g., start of pre-pulse phase, end of discharge, availability of the discharge file after a shot, trigger simulation for data acquisition tests and so on. The synchronization system is based on a distributed architecture where event servers are arranged in a tree structure. Event servers receive messages and then send them to other servers and client computers. The system is built on a two-layered configuration. The first one, devoted to network communication, is based on a de facto standard, Berkeley sockets, thus allowing for easy integration of multi-computer environments. The transport protocol is TCP in order to ensure the reliability needed. The second layer must provide support for local inter-process communication (LIPC) mechanisms. In this way, different processes can be synchronized within a single computer. Of course, this layer is system dependent.

Soft decoding and synchronization of arithmetic codes: application to image transmission over noisy channels

This paper addresses the issue of robust and joint source-channel decoding of arithmetic codes. We first analyze dependencies between the variables involved in arithmetic coding by means of the Bayesian formalism. This provides a suitable framework for designing a soft decoding algorithm that provides high error-resilience. It also provides a natural setting for "soft synchronization", i.e., to introduce anchors favoring the likelihood of "synchronized" paths. In order to maintain the complexity of the estimation within a realistic range, a simple, yet efficient, pruning method is described. The algorithm can be placed in an iterative source-channel decoding structure, in the spirit of serial turbo codes. Models and algorithms are then applied to context-based arithmetic coding widely used in practical systems (e.g., JPEG-2000). Experimentation results with both theoretical sources and with real images coded with JPEG-2000 reveal very good error resilience performances.

MPC for discrete-event systems with soft and hard synchronization constraints

Discrete-event systems with only synchronization and no concurrency, also known as timed event graphs or (max, +)-linear systems, have been studied by several authors. The synchronization constraints that arise in these discrete-event systems are hard, i.e. they cannot be broken under any circumstances. In this paper we consider a more extended class of discrete-event systems with both hard and soft synchronization constraints, i.e. if necessary, some synchronization conditions may be broken, but then a penalty is incurred. We show how the model predictive control (MPC) framework, which is a very popular controller design method in the process industry, can be extended to this class of discrete-event systems. In general, the MPC control design problem for discrete-event systems with soft and hard synchronization constraints leads to a non-linear non-convex optimization problem. We show that the optimal MPC strategy can also be computed using an extended linear complementary problem.

Model Predictive Control Approach for Recovery from Delays in Railway Systems

The model predictive control (MPC) framework, a very popular controller design method in the process industry, is extended to transfer coordination in railway systems. In fact, the proposed approach can also be used for other systems with both hard and soft synchronization constraints, such as logistic operations. The main aim of the control is to optimally recover from delays by breaking connections (at a cost). In general, the MPC control design problem for railway systems leads to a nonlinear, nonconvex optimization problem. Computing an optimal MPC strategy using an extended linear complementarity problem is demonstrated. Also presented is an extension with an extra degree of freedom to recover from delays by letting some trains run faster than usual (again at a cost). The resulting extended MPC railway problem can also be solved using an extended linear complementarity problem.

Model Predictive Control for Discrete-Event Systems with Soft and Hard Synchonization Constraints

Max-plus-linear models can be used to model discrete-event systems with only synchronization and no con currency. The synchronization constraints in max-plus-linear discrete-event systems are hard, i.e., they cannot be broken under any circumstance. We consider a class of discrete-event systems with both hard and soft synchronization constraints, i.e., if necessary, some synchronization conditions may be broken, but then a penalty is incurred. We show that — after introducing control variables — this leads to a max-plus-bilinear model. Furthermore, we also show how the model predictive control (MPC) framework can be extended to this class of discrete-event systems.

Evaluation of a soft synchronization technique for DS/SS signals

Soft synchronization of direct-sequence spread-spectrum (DS/SS) signals introduces the capability of despreading with a continuously improving estimate of the spreading code. The soft synchronization technique presented and demonstrated in this paper exploits the eigenstructure of a frequency-channelized DS/SS signal to estimate the code. The estimate improves steadily as more data is collected, resulting in an improved estimate of the message signal. This allows commencement of despreading at an early stage when the code-estimate is still imperfect. Under infinite-time average assumptions a perfect code estimate can be obtained when the signal is received in arbitrary levels of white background noise. This paper demonstrates the synchronization performance of the technique through simulations under finite time-average conditions for environments with fading, multipath, and multi-user interference. The soft synchronization capability is demonstrated. Results show that the technique can remove frequency offsets on the received signal that are integer multiples of the code repeat rate, and that its performance is not degraded by multipath.

Soft synchronization of direct sequence spread-spectrum signals

A new technique for soft synchronization of direct-sequence spread-spectrum (DSSS) signals is presented. The technique, referred to as the dominant mode despreading (DMDS) algorithm, exploits the eigenstructure of a frequency-channelized DSSS signal to estimate the spreading code and underlying message sequence of the signal. Unlike other despreading techniques, the estimate of the code and data improves steadily with the number of code repeats. The technique is applicable to arbitrary spreading codes and message sequences and can operate in environments containing arbitrary levels of white background noise, and for signals with arbitrary unknown timing phase or carrier frequency offset. The technique requires the DSSS signal to have a constant-modulus spreading code and unrelated message and code-repeat rates. This paper introduces the basic technique, theoretically analyzes the algorithm to prove convergence under infinite time-average conditions, and demonstrates the algorithm via computer simulation for a single DSSS signal received in the presence of white Gaussian noise.