Virtual Signal Generator Research Articles

Formation Control for Leader–Follower Wheeled Mobile Robots Based on Embedded Control Technique

The formation control problem for leader–follower wheeled mobile robots (WMRs) is investigated in this article. A formation control strategy is proposed based on the embedded control technique. Different from the conventional design philosophy of designing the formation controller based on the formation tracking errors directly, the proposed strategy decomposes the formation control task into two subtasks. One is the virtual signal generator (i.e., virtual follower) design, and the other is the trajectory tracking controller design. The virtual signal generator is devised to act as a virtual follower such that it “achieves” the desired formation control goal, whose output is taken as the reference trajectory for the follower. To solve the subtask of trajectory tracking controller design, an unconstrained controller and a constrained controller with saturated velocities are designed, respectively. A rigorous stability analysis of the closed-loop system is given under these two kinds of controllers. Comparative simulations and experiments among the unconstrained controller with higher gains/lower gains and the constrained controller are given to illustrate the feasibility and effectiveness of the proposed formation control strategy.

RF 모듈의 PHM 적용을 위한 가상데이터 생성 및 고장 분석 도구 개발

Purpose: This study proposes virtual data generation methods and develops a fault analysis tool for the prognostics and health management (PHM) of a radio frequency (RF) module, which is the main component used in electronic warfare devices.BRMethods: Current signals are assumed to be measured on the RF module and selected for virtual data generation. The three fault modes of the RF module are identified with help of an electronic warfare developer group.BRResults: The following fault modes are identified: 1) Delaying initial booting time, 2) continuously decreasing current, and 3) outlier of current signal. Accordingly, different types of signals are generated virtually, and the fault analysis tool is developed in the MATLAB software environment.BRConclusion: Virtual signal generation for different fault modes and its application in the analysis tool can be implemented for other types of electronic warfare as well. In addition, it can be applied to build prognosis models during the initial product development phase, despite the lack of field data.

Multiple model unfalsified adaptive generalized predictive control based on the quadratic inverse optimal control concept

AbstractUnfalsified adaptive control (UAC) is a class of switching control systems which deals with the control of uncertain systems. The UAC includes a bank of controllers, a supervisor, and a system in which the supervisor selects a stabilizing controller based on the system input and output data. Feasibility is the only assumption required in the UAC strategy, which guarantees that there is at least one stabilizing controller in the controller bank. UAC uses the cost detectability definition to prove closed‐loop stability. The combination of UAC and multiple model supervisory adaptive control (MMASC) results in the proposed unfalsified multi‐model control methodology that enjoys appropriate transient performance and stability proof with required minimum assumptions. In practical controller implementations, the effect of actuator constraints on the control signals is crucial. Despite the significance of constrained systems analysis in real applications, the input constraints in the structures of unfalsified control are not generally considered. Also, the stability analysis of constrained unfalsified control is key to its practical applications. In this article, the input constrained systems are considered using the constrained generalized predictive control (GPC) as the main controllers. Subsequently, to handle virtual signal generation for the GPCs in the UAC context, the inverse optimal control strategy is engaged and formulated to solve the signal generation problem. Simulation results are employed to show the effectiveness of the proposed methodology.

A Novel Fast Open-loop Phase Locking Scheme Based on Synchronous Reference Frame for Three-phase Non-ideal Power Grids

Rapid and accurate phase synchronization is critical for the reliable control of grid-tied inverters. However, the commonly used software phase-locked loop methods do not always satisfy the need for high-speed and accurate phase synchronization under severe grid imbalance conditions. To address this problem, this study develops a novel open-loop phase locking scheme based on a synchronous reference frame. The proposed scheme is characterized by remarkable response speed, high accuracy, and easy implementation. It comprises three functional cascaded blocks: fast orthogonal signal generation block, fast fundamental-frequency positive sequence component construction block, and fast phase calculation block. The developed virtual orthogonal signal generation method in the first block, which is characterized by noise immunity and high accuracy, can effectively avoid approximation errors and noise amplification in a wide range of sampling frequencies. In the second block, which is the foundation for achieving fast phase synchronization within 3 ms, the fundamental-frequency positive sequence components of unsymmetrical grid voltages can be achieved with the developed orthogonal signal construction strategy and the symmetrical component method. The real-time grid phase can be consequently obtained in the third block, which is free from self-tuning closed-loop control and thus improves the dynamic performance of the proposed scheme. The proposed scheme is adaptive to severe unsymmetrical grid voltages with sudden changes in magnitude, phase, and/or frequency. Moreover, this scheme is able to eliminate phase errors induced by harmonics and random noise. The validity and utility of the proposed scheme are verified by the experimental results.

Improved Virtual Vector Control of Single-Phase Inverter Based on Unified Model

A unified model is established for virtual vector control schemes of current-regulated single-phase inverters. Based on this model, it is proved that the cross-coupling interaction between the real and virtual orthogonal axes may induce dc positive feedback and destabilize the system. Therefore, a stability criterion is identified to reveal the special characteristics of the virtual vector control system and provide guidelines for the controller design. It is further explicated that the stability issue imposes an extra limitation on the controller parameters so that they may not be sufficiently optimized. To solve this problem, a family of improved control methods is proposed by inserting a high-pass filter in the virtual signal generation stage so that the corresponding dc gain is changed to zero to eliminate the dc positive feedback. As a result, both the steady-state and transient responses can be significantly enhanced. A comprehensive design procedure is provided for the proposed method and the results are compared with conventional solutions, both theoretically and experimentally, to verify the advantages of the improved strategy.

Design of Virtual Function Signal Generator Based on Sound Card

In this paper, the use of Lab VIEW virtual instrument development platform, designs the virtual function signal generator based on sound card. The instrument can generate sine wave, square wave, saw tooth wave, triangle wave, gauss white noise, superposition of sine wave, custom formula waveform, it can be arbitrarily set parameter as frequency, amplitude, phase, the noise standard deviation, it has simple operation, good interaction, it save the cost and can be widely used in scientific research and experiment teaching.

Measurement of Amplifier Open-Loop Amplitude Frequency Characteristics Based on Virtual Instrument

In the electronic measurement field, how to measure the open-loop amplitude frequency characteristics of the amplifier automatically is a question to be overcame. And now , the system ,which under the integrated development environment that the virtual instrument software LabVIEW provides, to measure the open-loop amplitude frequency characteristics of the amplifier is developed by combining the modern electronic measurement technology and computer data processing technology. The virtual signal generator which is based on the data acquisition card, signal acquisition, correlation analysis, frequency response analysis, etc is included in the system. This design mainly includes the hardware circuit and the software program. The hardware circuit consists of the low noise preamplifier, measured operational amplifier, data acquisition card, power supply, computer, etc. Modular design is adopted in the software part, which includes the design of soft panel, signal generation, collection and analysis module. The advantages of the virtual instrument, such as the digital signal processing, waveform data automatic storage, graphical programming, are fully used in the modern electronic measurement. Simple structure, low cost, high level of test automation are its characteristics.

Design and Application of LAN Interface Communication Module

This paper presents three methods of design and development of an instrument with LAN interface. And the method of designing a communication module of Ethernet interface is adopted. Using this module, it is economical and efficient to change a traditional instrument into a network instrument without changing the hardware of the instrument. The communication module is designed on an ARM9 (S3C2410) platform. By transplanting embedded Linux OS in the platform, developing applications of Ethernet interface and standards RS-232 interface communication in Linux, the transformation of RS-232 port to LAN port is realized successfully in the module. For verifying the feasibility of this method, a signal generator is translated into a network signal generator by connecting with the module through serial port in the interior of the instrument. A virtual signal generator is also developed by LabVIEW on computer, and it can control the signal generator remotely though Ethernet.

함정용 추적레이더 성능 검증을 위한 모의표적신호발생장치 개발

The virtual target signal generator was developed to verify the shipborne tracking radar performance. It was used to DRFM(Digital RF Memory) method to generate the virtual moving targets. The target signal includes Doppler shift and RCS according to the target motion. And the signal generator can make jamming signal and clutter to test shipborne radar performance at real environmental condition. This paper described the functional diagram and the hardware configuration items to meet the test requirements for the tracking radar. And it showed the critical design points for the sub-systems. The signal generator which was developed in this paper shared the operational information of the radar with the radar command and control part. To test the frequency agility of the radar, it had the local oscillator which could do high speed frequency switching according to radar information. By communicating between the signal generator and the radar command and control part, the local oscillator of signal generator could be controlled every pulse. It reduced the instantaneous bandwidth of signal generator and minimized the spurious. So it lowered the probability of generating wrong targets.

도플러 전방향 표지시설(DVOR) 가상 모니터링 시스템 설계 및 구현에 관한 연구

본 논문에서는 협소한 공간에서 예비용 도플러 전방향표지시설(DVOR)의 모니터링 시스템이 실제 운영 상태와 유사하게 동작할 수 있게 하기 위한 DVOR 가상 신호 발생기를 설계 및 제작하여 "DVOR 가상 모니터링 시스템"에 관하여 연구하였다. 설계, 제작된 DVOR 가상 신호 발생기는 현재 운용중인 장비에서 발생되는 신호의 사양에 적합하도록 하였고, 파라미터의 가변으로 장비의 운영 조건을 맞추는 것이 가능하도록 하였으며, 회로구성은 크게 동기 입력부, 변조부, 고이득 증폭부 및 전원부로 하였다. 본 연구에서 설계·구현된 가상 신호 발생기를 이용한 "DVOR 가상 모니터링 시스템"은 측대파 발생 안테나와 같이 실제 시스템을 사용하지 않고도 좁은 공간에서 실제 상황과 같은 운용 상태를 구성 할 수 있어 저비용의 실전 교육용으로 사용하기에 매우 적합하다고 사료된다. This study designed and manufactured "a DVOR virtual signal generator" to make the monitoring system of preliminary Doppler VHF Omni-directional Radio Range(DVOR) run like its real operation status in a narrow space in order to study "a DVOR virtual monitoring system". The designed and manufactured DVOR virtual signal generator is suitable for the specification of signal that is generated in the currently running equipment. In addition, it is possible to control operation conditions of equipment by using parameter variables, and the circuit construction is largely divided into the input part, the modulation part, the high-gain amplifier, and the power part. "The DVOR virtual monitoring system using the virtual signal designed and implemented in this study is very suitable to be used for low-cost actual education as it can construct the operation status like the real situation in a narrow space without using an actual system like an antenna generating side band.

Subspace-Based and DIRECT Algorithms for Distorted Circular Contour Estimation

Circular features are commonly sought in digital image processing. The subspace-based line detection (SLIDE) method proposed to estimate the center and the radius of a single circle. In this paper, we introduce a novel method for estimating several radii while extending the circle estimation to retrieve circular-like distorted contours. Particularly, we develop and validate a new model for virtual signal generation by simulating a circular antenna. The circle center is estimated by the SLIDE method. A variable speed propagation scheme toward the circular antenna yields a linear phase signal. Therefore, a high-resolution method provides the radius. Either the gradient method or the more robust combination of dividing rectangles and spline interpolation can extend this method extend this method for free form object segmentation. The retrieval of multiple non concentric circles and rotated ellipses is also considered. To evaluate the performance of the proposed methods, we compare them with a least-squares method, Hough transform, and gradient vector flow. We apply the proposed method to hand-made images while considering some real-world images.

Array Processing and Fast Optimization Algorithms for Distorted Circular Contour Retrieval

A specific formalism for virtual signal generation permits to transpose an image processing problem to an array processing problem. The existing method for straight-line characterization relies on the estimation of orientations and offsets of expected lines. This estimation is performed thanks to a subspace-based algorithm called subspace-based line detection (SLIDE). In this paper, we propose to retrieve circular and nearly circular contours in images. We estimate the radius of circles and we extend the estimation of circles to the retrieval of circular-like distorted contours. For this purpose we develop a new model for virtual signal generation; we simulate a circular antenna, so that a high-resolution method can be employed for radius estimation. An optimization method permits to extend circle fitting to the segmentation of objects which have any shape. We evaluate the performances of the proposed methods, on hand-made and real-world images, and we compare them with generalized Hough transform (GHT) and gradient vector flow (GVF).