High-efficiency holograms fixed in lithium niobate after recording using a digital fringe stabilization system

The article is dedicated to optimizing the digital current control loop of a thyristor converter-driven electric drive, essential for ensuring stable, precise, and reliable operation of electric drives in automated and industrial systems. The primary goal of this research is to develop and enhance the digital current regulator (DCR), which enables the drive system to achieve desired performance, including rapid and stable response to current changes without excessive overshoot or oscillations. Optimization of the current loop improves energy efficiency, enhances dynamic properties, and increases resistance to external disturbances, all of which are critical for modern electric drive systems. The introduction discusses key aspects of digital current loop optimization, specifically dynamic characteristics such as time delays, sampling rate, and bandwidth, which significantly impact the efficiency of digital controllers. Special attention is given to the tuning of proportional-integral (PI) controller parameters, allowing quick and stable response to current changes. The developed model allows preliminary simulation of the current loop’s performance, providing an opportunity to test different configurations before actual implementation. To improve the accuracy and stability of the system, filtering methods are proposed to reduce the impact of high-frequency noise, ensuring the system’s precision and robustness against external interference. Optimization criteria are introduced, including minimizing the integral square error (ISE) and reducing energy consumption, which significantly decreases system losses and increases the energy efficiency of electric drives. In developing the optimized control loop, the following assumptions are considered: 1) the thyristor converter (TC) operates in continuous current mode, 2) the current loop dynamics are studied within a narrow range of TC phase angle changes, and 3) a discrete dynamic TC model is used with averaging of electromotive force (EMF) over the conduction interval. Optimizing the digital current loop addresses several critical tasks, including enhancing control accuracy, reducing overshoot and oscillations, and improving the system’s dynamic response, allowing for reduced delays and a faster reaction to load changes. The optimization results of the digital current regulator (DCR) show reduced energy consumption and significant improvements in control accuracy. The high-speed performance of the digital current loop enables fast transient processes within a single sampling interval of the thyristor converter, which is crucial for systems requiring rapid regulation. Additionally, the digital control loop provides flexibility in control, as it allows for system adjustments to different operating conditions through a software-based approach. The study’s final results demonstrate the potential of digital current loops in modern electric drives. With advances in microprocessor technology, digital regulators enable more complex control algorithms, including adaptive and predictive strategies, which further enhance system efficiency. These approaches are especially relevant for industrial electric drives that require high precision and response speed, making digital current loops a promising solution for contemporary automated control systems.

A digital control system is probably the best technical solution to the problem of automatic control of the Virgo interferometric antenna for gravitational wave detection, provided that very critical specifications concerning residual noise introduced by the digital system in the measurement band are met. For this purpose, a model of the digital system has been developed and tested to quantify the main sources and levels of noise. Experimental measurements, obtained using a prototype of the automatic control system, and theoretical analysis of the performances of the digital control loops have demonstrated the feasibility of a digital control system.

The insertion of communication networks in closed-loop of digital control systems makes the system synthesis and analysis complex. In this paper, we consider the combination of classical reliability, risk and safety evaluation with typical control system through digital networked control systems. The main purpose is to study the influence of transmission delays and packet dropouts on the reliability of digital networked control systems by using a modified statistical method-Monte Carlo simulation. The behaviors of two types of fault are modelled by different statistical distribution. The control strategies we apply for digital control systems are Proportion Integration Differentiation control strategies, generated by Genetic Algorithm. In terms of a realistic system model, we evaluate and compare the influences on the reliability of digital networked control systems with different control strategies from quantitative aspect. Numerical examples are presented to illustrate the effectiveness and correctness of the approach.

This paper addresses modeling and control issues related to practical high-frequency digital PWM control of constant-frequency boost, buck-boost and flyback converters. Discrete-time models, including the effects of A/D sampling and delays in the digital control loop, are derived for two cases: output voltage A/D sampling during transistor off time in combination with trailing-edge (TE) DPWM, and A/D sampling during transistor on time in combination with leading-edge (LE) DPWM. We show that off-time sampling with TE-DPWM, which is a common approach in digital controller realizations, can result in desirable minimum-phase responses, thus simplifying compensator design in wide bandwidth closed-loop voltage regulators based on boost or flyback converters. The results are verified by simulation and experimental results on a boost converter prototype.

The empirically developed force control in cases of the robotic polishing and the rehabilitation robots serve as a motivation for the study of the peculiar dynamic behaviour of digital force control. The effect of the sampling times of the digital controllers are studied analytically, and the corresponding stability charts are presented for different gain and mechanical parameters describing also the different sampling frequencies at the force sensors and in the digital control loop. The types of bifurcations are also identified at the stability limits. As one of the practical conclusions, the negative role of differential gain is explained in digital force control.Key wordsforce controlled robotsdifferential gaindelayed oscillator

With the development of modern automatic control technology, digital control technology has advanced technology and inherent advantages compared with traditional analog control technology. Therefore, the use of digital instrument and control system has become an inevitable trend of global nuclear power construction. Nuclear power embedded real-time operating system is an important part of digital instrument and control system in nuclear power plant. It is responsible for managing the hardware resources of the whole system and providing operation environment for application software. Its safety directly affects the safety of instrument and control system. This paper studies the application of embedded information technology in the safety of nuclear power plant, and puts forward a safety related scheme of embedded information system. The scheme fully considers the confidentiality, integrity and availability of information in the digital instrument and control system of nuclear power plant. The application results show that the scheme can meet the information security requirements of nuclear power instrument and control system, and has reference and guiding significance for the research and development of nuclear power embedded real-time operating system.

Application of Digital Control Techniques for Satellite Medium Power DC-DC ConvertersThe objective of this paper is to present a work concerning a digital control loop system for satellite medium power DC-DC converters that is done in Space Research Centre. The whole control process of a described power converter is based on a high speed digital signal processing. The paper presents a development of a FPGA digital controller for voltage and current mode stabilization that was implemented using VHDL. The described controllers are based on a classical digital PID controller. The converter used for testing is a 200 kHz, 750W buck converter with 50V/15A output. A high resolution digital PWM approach is presented. Additionally a simple and effective solution of filtering of an analog-to-digital converter output is presented.

Recently, the Plant Input Mapping (PIM) method was proposed as a digital-redesign (or an emulation) approach in digital control system design. This method guarantees stability of a redesigned digital control system for a wide range of sampling periods. In this paper the PIM method is applied to the design of a digital model-matching flight control system. In the model-matching control system design a plant must have no unstable zeros. However, unstable zeros appear for small sampling periods in a step invariance model of a continuous-time (CT) plant with the relative degree greater than two, even if the CT plant has no unstable zeros. Hence, in such a case, the direct-digital approach cannot be applied to the design of a digital model-matching control system. By contrast, the digital-redesign approach such as the Tustin's method or the PIM method is free from the problem. Simulation results for an unstable VTOL aircraft show that the proposed method gives better performance than the conventional design methods.

A high precision temperature control system capable of maintaining the temperature of superconducting quantum interference devices (SQUIDs) constant to within 1.0 μK root-mean square over a narrow frequency band was designed and built for use with the superconducting readout system of the Gravity Probe B experiment. The system utilizes an analog ac temperature bridge with a digital proportional-integral control loop which incorporates a peaking filter. A disturbance attenuation factor of 86 or greater over the required frequency band was demonstrated in system tests with the cryogenic hardware, allowing the SQUID system to achieve the required stability. The control system was robust against variations in the thermal characteristics of the cryogenic hardware.

Smoke can cause interruptions and upsets in active electronics. Because nuclear power plants are replacing analog with digital instrumentation and control systems, qualification guidelines for new systems are being reviewed for severe environments such as smoke and electromagnetic interference. Active digital systems, individual components, and active circuits have been exposed to smoke in a program sponsored by the U.S. Nuclear Regulatory Commission. The circuits and systems were all monitored during the smoke exposure, indicating any immediate effects of the smoke. The results of previous smoke exposure studies have been reported in various publications. The major immediate effect of smoke has been to increase leakage currents and to cause momentary upsets and failures in digital systems. This paper presents new results from conformal coatings, memory chips, and hard drive tests.The best conformal coatings were found to be polyurethane, parylene, and acrylic (when applied by dipping). Conformal coatings can reduce smoke-induced leakage currents and protect against metal loss through corrosion. However conformal coatings are typically flammable, so they do increase material flammability. Some of the low-voltage biased memory chips failed during a combination of high smoke and high humidity. Typically, smoke along with heat and humidity is expected during fire, rather than smoke alone. Thus, due to high sensitivity of digital circuits to heat and humidity, it is hypothesized that the impact of smoke may be secondary.Low-voltage (3.3-V) static random-access memory (SRAMs) were found to be the most vulnerable to smoke. Higher bias voltages decrease the likelihood of failure. Erasable programmable read-only memory (EPROMs) and nonvolatile SRAMs were very smoke tolerant. Failures of the SRAMs occurred when two conditions were present: high density of smoke and high humidity. As the high humidity was present for only part of the test, the failures were intermittent. All of the chips that failed during the test recovered after enough venting.Hard disks were tested in severe environments but did not fail during the 2 h of monitoring.While the results of the tests documented in this report confirm that digital circuits can indeed be vulnerable to smoke, there is currently no practical, repeatable testing methodology, so it is not feasible to assess smoke susceptibility as part of environmental qualification. As a result, the most reasonable approach to minimizing smoke susceptibility is to employ design, implementation, and procedural practices that can reduce the possibility of smoke exposure and enhance smoke tolerance. Traditional approaches to mitigate its effects in digital safety instrumentation and control, such as redundancy, separation, defense in depth, as well as adherence to standards (e.g., the Institute of Electrical and Electronics Engineers’ IEEE 384) and the Code of Federal Regulations Appendix R of 10 CFR 50, should continue to be applied.

The article discusses an approach that allows you to move from a discrete model of a digital controller to its analog representation, which provides analysis and synthesis of digital systems in the continuous domain, taking into account the quantization period. In the proposed method for the control system, a transition is made from the discrete z-region to the Laplace region. This approach makes it possible to consider the quantization time as an additional parameter of the digital control system settings, evaluate the influence of the selected quantization period not only on the behavior of the set for discrete at the moments of quantization, but also in between, to evaluate the temporal characteristics of the control system at any time. The analog representation of the digital controller enables the calculation of transients using MatLAB. The article provides examples of the synthesis for a digital control system in the frequency domain based on the frequency response characteristic of an open-loop control system taking into account the quantization period. The method can be used by automation specialists to analyze and setting digital control systems

Real-time programming has always been one of the most challenging programming disciplines. Real-time programming requires comprehensive command of sequential programming, concurrency, and, of course, time. Real-time programming has many application domains. In this chapter, however, we structure our discussion around digital control systems for the following two reasons. Firstly, digital control systems represent a large portion of real-time software in a diverse set of industries. Examples include automotive power train control systems, aircraft flight control systems, electrical drive systems in paper mills, or process control systems in power plants and refineries. Many of these systems distribute their components over networks with significant communication delays. Therefore, we also discuss networked real-time programming (Section 7). The second reason is pedagogical. Digital control is defined by a set of abstractions that are real-time programmable and mathematically tractable in the context of the dynamics of physio-chemical processes. The abstractions clearly define what application engineers (control engineers) expect of real-time programming. These abstractions therefore constitute a precise definition of the real-time programming problem (Section 2). Control engineers design in difference equations and often use modeling tools such as Simulink to simulate and validate their control models. The part of Simulink most commonly used to specify digital control, i.e., discrete-time with the discrete fixed-step solver and mode:auto, is well-explained by the so-called synchronous semantics [7, 38]. The key abstraction, we call the synchronous abstraction, is that any computation and component interaction happens instantaneously in zero time or with a delay that is exactly the same at each invocation. For example, if a controller computes every 20 msec, either the controller is assumed to read its inputs, compute its control, and write the corresponding outputs instantaneously at the beginning of each period in zero time, or to read its inputs instantaneously at the beginning of the period, compute during the period, and write the corresponding output exactly 20 msec (one period) later. In control parlance, these are the causal and strictly causal cases, respectively. Systems of difference equations can directly be expressed and structured in this model. The inclusion of strictly causal components (components with delays of a period or more) is typically required to break feedback loops and to account for the unavoidable computation or communication delays that will be present in the real control system. Real-time programmers design in interrupt handlers, device drivers, and schedulers, which are concepts on levels of abstraction that are obviously unrelated to difference equations. The result is a conceptual and technical disconnect between control model and real-time code that bedevils many control building projects. The control engineer specifies a Simulink design the real-time programmer finds unimplementable. The realtime programmer then fills in gaps to produce an implementation the control engineer finds uncontrollable. The process of interaction as the two iterate to produce a correct design is prolonged by the different backgrounds of control engineers and real-time programmers. This gap explains many of today’s problems in real-time software design for digital control such as high validation and maintainance overhead as well as limited potential for reusability and scalability.

<p>This research paper presents a synthesis approach of a digital optimal PID/LQR control system for DCM (duty-cycle cycle modulation) Buck converters. The step response of the DCM Buck converter is obtained under Multisim virtual simulation framework. The related data file is saved as *.SCP format, and imported into EditPad Lite7 editor, then exported as Matlab file to be processed. The transfer function of the DCM Buck converter is computed from the imported step response data. Then, using the zoh (zero order holder) discretization method with 100 ms resampling period, the z-transfer function of the DCM Buck converter is computed, and that of the analog optimal PID/LQR(linear quadratic regulator) controller is calculated using Tustin’s discretization technique. Furthermore, the step response of the related closed loop digital PID control system is simulated and compared to that of the original analog PID/LQR control system. The simulation results obtained are presented in order to show the high precision as well as the reliability of Matlab-based synthesis of digital optimal PID/LQR control systems for DCM Buck converters.</p>

The Coordinate Rotation Digital Computer (CORDIC) algorithm has emerged as a pivotal method for executing trigonometric and various mathematical operations within digital systems. Field-Programmable Gate Arrays (FPGAs) have witnessed a remarkable surge in adoption for implementing the CORDIC algorithm owing to their inherent flexibility and exceptional performance capabilities. This paper endeavours to provide a comprehensive overview of FPGA implementations of the CORDIC algorithm, elucidating both the advantages and challenges associated with this methodology. It thoroughly examines various FPGA architectures customized for CORDIC implementation, meticulously analyzing their respective trade-offs regarding resource utilization, performance metrics, and accuracy levels. Moreover, the paper explores numerous applications where the FPGA-based CORDIC algorithm shines, illustrating its adaptability across diverse domains like digital signal processing and control systems. These applications underscore the algorithm's efficacy in addressing real-world challenges and its potential to significantly augment system performance and efficiency.By furnishing profound insights into FPGA-based CORDIC implementations, this paper serves as an invaluable resource for engineers and researchers keen on harnessing the capabilities of FPGAs for high-performance mathematical computations in digital systems.

Considering characteristics of nuclear power plant digital instrumentation and control system, challenges of reliability assessment of digital instrumentation and control system are pointed out. As for its dynamic behavior and multi-states failure mode, limitation of traditional methods, research status and applicability of dynamic flowgraph methodology and other advance dynamic reliability assessment approach were introduced and compered. It's concluded that Dynamic flowgraph methodology maybe the dominant one in future after simplify its model procedure and reduction computational cost of its deductive analysis.