Full Digital Control Research Articles

A fully digital power supply system for TLS corrector magnets

This study focuses on the development of a fully digital power supply system (FDPSS) for the Taiwan Light Source (TLS) storage ring corrector magnet, which includes the fully digital correction power supply (FDCPS), digital communication card (DCC), and a virtual operation interface. The DCPS adopts a full-bridge circuit architecture, with the TI TMS320F28335 digital signal processor (DSP) as the core, combined with an 18-bit high-resolution A/D converter and discrete PID algorithm to achieve closed-loop current control, ensuring a stable output current value of the system. The DCC can control eight DCPS modules through an RS485 protocol with a virtual instrument control interface. This new system can replace the analog signal-modulated Bira MCOR30A power supply system, which has been in operation for 25 years in the TLS storage ring and can be upgraded to an FDPSS. This article aims to discuss the design concepts, hardware implementation, and testing of FDCPS and DCC to demonstrate the advantages of full digital control and to achieve the goal of independently researching and developing the prototype of FDPSS. Ultimately, after long-term testing and verification, the system's output current stability is less than ± 20ppm, indicating that this new system has high-precision and high-stability output current characteristics. In this study, upgrading the TLS storage ring corrector magnet power supply system to full digital control significantly improves output current stability and accuracy.

Control of parallelized bioreactors I: dynamic scheduling software for efficient bioprocess management in high-throughput systems

The shift towards high-throughput technologies and automation in research and development in industrial biotechnology is highlighting the need for increased automation competence and specialized software solutions. Within bioprocess development, the trends towards miniaturization and parallelization of bioreactor systems rely on full automation and digital process control. Thus, mL-scale, parallel bioreactor systems require integration into liquid handling stations to perform a range of tasks stretching from substrate addition to automated sampling and sample analysis. To orchestrate these tasks, the authors propose a scheduling software to fully leverage the advantages of a state-of-the-art liquid handling station (LHS) and to enable improved process control and resource allocation. Fixed sequential order execution, the norm in LHS software, results in imperfect timing of essential operations like feeding or Ph control and execution intervals thereof, that are unknown a priori. However, the duration and control of, e.g., the feeding task and their frequency are of great importance for bioprocess control and the design of experiments. Hence, a software solution is presented that allows the orchestration of the respective operations through dynamic scheduling by external LHS control. With the proposed scheduling software, it is possible to define a dynamic process control strategy based on data-driven real-time prioritization and transparent, user-defined constraints. Drivers for a commercial 48 parallel bioreactor system and the related sensor equipment were developed using the SiLA 2 standard greatly simplifying the integration effort. Furthermore, this paper describes the experimental hardware and software setup required for the application use case presented in the second part.

Peak and Valley Current Control for Cuk PFC Converter to Reduce Capacitance

Traditional power factor correction (PFC) converters usually employ a large electrolytic capacitor to ensure a stiff output voltage. However, the electrolytic capacitor is not expected in terms of the reliability and the size of the system. This article proposes a peak and valley current control for Cuk PFC converter to remove the bulky electrolytic capacitor. The proposed control is realized by a combination of analog and digital circuits. The analog circuits are used to accomplish the real-time comparison between the actual currents and their reference values. And the digital circuits are employed to deal with simple logical judgement. Different from the existing full digital control technique, which needs a high-quality digital signal processor (DSP) to process complex arithmetic operation, the proposed control concept even can only require a low performance microcontroller unit. Besides, the control delay is avoided. This article first analyzes the operation stages of the Cuk PFC converter. Then, design considerations of main circuit and control circuit are introduced. Finally, the experimental results from 200W Cuk PFC converter are presented to verify the effectiveness of the proposed control.

Full Digital Control and Multi-Loop Tuning of a Three-Level T-Type Rectifier for Electric Vehicle Ultra-Fast Battery Chargers

The rapid development of electric vehicle ultra-fast battery chargers is increasingly demanding higher efficiency and power density. In particular, a proper control of the grid-connected active front–end can ensure minimum passive component size (i.e., limiting design oversizing) and reduce the overall converter losses. Moreover, fast control dynamics and strong disturbance rejection capability are often required by the subsequent DC/DC stage, which may act as a fast-varying and/or unbalanced load. Therefore, this paper proposes the design, tuning and implementation of a complete digital multi-loop control strategy for a three-level unidirectional T-type rectifier, intended for EV ultra-fast battery charging. First, an overview of the operational basics of three-level rectifiers is presented and the state-space model of the considered system is derived. A detailed analysis of the mid-point current generation process is also provided, as this aspect is widely overlooked in the literature. In particular, the converter operation under unbalanced split DC-link loads is analyzed and the converter mid-point current limits are analytically identified. Four controllers (i.e., dq-currents, DC-link voltage and DC-link mid-point voltage balancing loops) are designed and their tuning is described step-by-step, taking into account the delays and the discretization introduced by the digital control implementation. Finally, the proposed multi-loop controller design procedure is validated on a 30 kW, 20 kHz T-type rectifier prototype. The control strategy is implemented on a single general purpose microcontroller unit and the performances of all control loops are successfully verified experimentally, simultaneously achieving low input current zero-crossing distortion, high step response and disturbance rejection dynamics, and stable steady-state operation under unbalanced split DC-link loading.

Applying FPGA Control with ADC-Free Sampling to Multi-Output Forward Converter

In this paper, a forward converter with multiple outputs is employed to build up a circuit system with full-digital control without any analog-to-digital (ADC) converter adopted. In this circuit, all the output voltages can be regulated by individual feedback control loops. As transient load variations due to the main output happens, the secondary outputs are affected quite slightly. Furthermore, the output voltage with the largest output current adopts not only the voltage mode control but also the interleaved control and current sharing control. Therefore, if this circuit system adopts full-digital control, the number of ADCs employed is relatively large, and the corresponding cost is expensive. Accordingly, the sampling of multiple output voltages and two-phase currents without any ADCs is used herein. Moreover, a nonlinear control strategy is proposed and applied to the traditional proportional-integral-derivative (PID) controller to accelerate the load transient response. In addition, the field programmable gate array (FPGA) is used as a control kernel.

Research on digital flow control model of urban rail transit under the situation of epidemic prevention and control

Purpose Beijing rail transit can actively control the density of rail transit passenger flow, ensure travel facilities and provide a safe and comfortable riding atmosphere for rail transit passengers during the epidemic. The purpose of this paper is to efficiently monitor the flow of rail passengers, the first method is to regulate the flow of passengers by means of a coordinated connection between the stations of the railway line; the second method is to objectively distribute the inbound traffic quotas between stations to achieve the aim of accurate and reasonable control according to the actual number of people entering the station. Design/methodology/approach This paper analyzes the rules of rail transit passenger flow and updates the passenger flow prediction model in time according to the characteristics of passenger flow during the epidemic to solve the above-mentioned problems. Big data system analysis restores and refines the time and space distribution of the finely expected passenger flow and the train service plan of each route. Get information on the passenger travel chain from arriving, boarding, transferring, getting off and leaving, as well as the full load rate of each train. Findings A series of digital flow control models, based on the time and space composition of passengers on trains with congested sections, has been designed and developed to scientifically calculate the number of passengers entering the station and provide an operational basis for operating companies to accurately control flow. Originality/value This study can analyze the section where the highest full load occurs, the composition of passengers in this section and when and where passengers board the train, based on the measured train full load rate data. Then, this paper combines the full load rate control index to perform reverse deduction to calculate the inbound volume time-sharing indicators of each station and redistribute the time-sharing indicators for each station according to the actual situation of the inbound volume of each line during the epidemic. Finally, form the specified full load rate index digital time-sharing passenger flow control scheme.

Full Digital Control of an All-Si On-Board Charger Operating in Discontinuous Conduction Mode

This paper deals with the design, tuning and implementation of a digital controller for an all-Si electric vehicle (EV) on-board battery charger operated in discontinuous conduction mode (DCM). This charger consists of two cascaded conversion stages: a front-end power factor corrector (PFC) with two interleaved legs and an isolated phase-shifted full bridge DC/DC converter. Both stages operate in DCM over the complete battery charging power range, allowing lower inductance values for both the PFC and the DC/DC filtering elements. Moreover, DCM operation ensures a large reduction of the reverse-recovery losses in the power diodes, enabling the adoption of relatively cheap Si devices. The main goal of the work is to address the well-known DCM control challenges, leveraging a novel control strategy for both converter stages. This control scheme counteracts the DCM system non-linearities with a proper feed-forward contribution and an open-loop gain adjustment, ensuring consistent dynamical performance over the complete operating range. The designed controllers are tuned analytically, taking into account the delay components related to the digital implementation. Finally, the proposed control strategy is implemented on a single general purpose microcontroller unit (MCU) and its performance is experimentally validated on a 3.3 kW battery charger prototype.

Holographically controlled random numbers from entangled twisted photons

We present a quantum random number generator (QRNG) based on the random outcomes inherent in projective measurements on a superposition of quantum states of light. Firstly, we use multiplexed holograms encoded on a spatial light modulator to spatially map down-converted photons onto a superposition of optical paths. This gives us full digital control of the mapping process which we can tailor to achieve any desired probability distribution. More importantly, we use this method to account for any bias present within our transmission and detection system, forgoing the need for time-consuming and inefficient unbiasing algorithms. Our QRNG achieved a min-entropy of $\text{H}_{\text{min}}=0.9991\pm0.0003$ bits per photon and passed the NIST statistical test suite. Furthermore, we extend our approach to realise a QRNG based on photons entangled in their orbital angular momentum (OAM) degree of freedom. This combination of digital holograms and projective measurements on arbitrary OAM combinations allowed us to generate random numbers with arbitrary distributions, in effect tailoring the system's entropy while maintaining the inherent quantum irreproducibility. Such techniques allow access to the higher-dimensional OAM Hilbert space, opening up an avenue for generating multiple random bits per photon.

Tízéves a teljes hatáskörű digitális elektronikus hajtómű-szabályozó rendszerek fejlesztése a BME VRHT-n

A gázturbinás hajtóművek napjainkban már szinte kizárólagosan digitális elektronikus szabályozó rendszerrel (Full Authority Digital Electronic Control, FADEC) rendelkeznek, jobb pontosságuk, kisebb méretük, tömegük és karbantartásigényük miatt. A BME VRHT jogelődjén 2009-ben indult meg a TKT-1 gázturbinás sugárhajtómű megalkotását és üzembe állítását követően a szabályozórendszer tervezése. A cikk bemutatja a fejlesztés főbb állomásait a kiinduló, valamint további típusokon (Deutz T216, PD-60R), a különféle alkalmazott szabályozási törvényszerűségeket (fordulatszám, hajtómű nyomás- és teljesítményviszony). Továbbá bemutatjuk azokat az algoritmusokat is (PID, lineáris kvadratikus és csúszómód-szabályozások), amelyeket FADEC-rendszereinkben kidolgoztunk.Munkánk egyik legnagyobb eredménye, hogy a gázturbinás sugárhajtómű próbapadján ezeketaz algoritmusokat valós körülmények között is le tudjuk ellenőrizni.

Fast 3D movement of a laser focusing spot behind scattering media by utilizing optical memory effect and optical conjugate planes

Controlling light propagation intentionally through turbid media such as ground glass or biological tissue has been demonstrated for many useful applications. Due to random scattering effect, one of the important goals is to draw a desired shape behind turbid media with a swift and precise method. Feedback wavefront shaping method which is known as a very effective approach to focus the light, is restricted by slow optimization process for obtaining multiple spots. Here we propose a technique to implement feedback wavefront shaping with optical memory effect and optical 4f system to speedy move focus spot and form shapes in 3D space behind scattering media. Starting with only one optimization process to achieve a focusing spot, the advantages of the optical configuration and full digital control allow us to move the focus spot with high quality at the speed of SLM frame rate. Multiple focusing spots can be achieved simultaneously by combining multiple phase patterns on a single SLM. By inheriting the phase patterns in the initial focusing process, we can enhance the intensity of the focusing spot at the edge of memory effect in with 50% reduction in optimization time. With a new focusing spot, we have two partially overlapped memory effect regions, expanding our 3D scanning range. With fast wavefront shaping devices, our proposed technique could potentially find appealing applications with biological tissues.

Fast corrector power supply design for HEPS

High-energy photon source under construction is a fourth-generation synchrotron radiation light source with energy of 6 Gev and ultra-low emittance (lower than 0.1 nm rad). The ultra-low beam emittance requires high beam stability. In order to meet this requirement of low beam emittance, the fast close orbit correction system is used to keep beam on the right orbit. The fast close orbit correction system need fast corrector power supply to drive the calibration magnet to complete track correction. So, a fast corrector power supply prototype with high bandwidth and low current ripple to improve the performance of the fast close orbit correction system to prove the high beam stability had been developed. The prototype use a novel multilevel switch-mode structure to provide the dynamic requirement. The prototype adopts FPGA for full-digital control and use high-speed ADC with temperature control. By using a precision sampling circuit (ADC+DCCT), the prototype outputs current ripple can meet the requirement. The designed for HEPS meet the design requirement. Through test, the prototype has a small signal bandwidth of 10 kHz and output current ripple lower than 20 ppm.

A Fully Synthesizable Ultra-${N}$ Audio Frequency Multiplier for HDMI Applications

This brief develops a highly programmable and fully synthesizable large-N frequency multiplier. It is based on Time-Average-Frequency Direct Period Synthesis (TAF-DPS) and its purpose is to generate audio frequencies in HDMI (high definition multimedia interface) applications in which frequency multiplication ratio is extremely large. The proposed multiplier is a full digital feed-forward frequency control loop. The output frequency is produced by performing a fractional frequency division of the oscillator clock with TAF-DPS. The source of electrical oscillation in the TAF-DPS is a free-running inverter ring that consists of inverters. The novel structure is implemented in a TSMC 0.18 μm 1P6M CMOS process. The implementation is fully digital HDL coding → simulation → synthesis → place & route without any need for analog simulation. The hardware cost is equivalent to 3150 two-input NAND gates. The proposed structure can achieve fast frequency switching within two input reference clock cycles. The multiplication ratio is evaluated experimentally to be as high as 106 with an input signal of 50 Hz; this is the largest ratio and lowest input frequency to be reported to the best of our knowledge. Besides generating an audio clock for HDMI applications, this frequency multiplier is very suitable for frequency measurements and system-on-a-chip applications.

Performance Analysis of Forced Commutated Controlled Series Capacitor Rectifier for More Electric Aircraft

The forced commutated controlled series capacitor (FCSC) rectifier has been recently proposed to power stand-alone variable-voltage variable-frequency generation systems, such as the full authority digital electronic control (FADEC) system, in more electric aircraft. The employment of this rectifier helps to meet increasing power demand requirements while maintaining low current harmonic levels without the need for bulky filters. The FCSC rectifier is controlled to maintain resonance with line frequency variation by inserting variable capacitive reactance in series with the variable-frequency generator's inductive reactance. Unity power factor operation with nearly pure sinusoidal converter input currents is thus achieved, for better utilization of the generator. The FCSC rectifier operation with a variable dc on-board load is analyzed in this paper, including a description of the principle modes of operation of the circuit. The enhancement in circuit's output voltage and output power achieved by replacing the conventional diode bridge rectifier with the FCSC rectifier is also demonstrated. Both rectifiers are analyzed numerically using Saber/Synopsys over a wide range of operating voltages and frequencies. Results are experimentally verified using 1-kW laboratory test rig.

Forced Commutated Controlled Series Capacitor Rectifier for More Electric Aircraft

Rising power demands in more electrical aircraft (MEA) put power converters for commercial airplanes under increasing pressure to fulfill current harmonic distortion regulations as specified, for example, in DO-160G. Today, the implementation of filters is seen as an effective tool for dealing with harmonics; however, their increased weight and volume are not welcomed in the aerospace industry. This paper proposes a circuit, named forced commutation controlled series capacitor (FCSC-rectifier), which is able to maintain low individual harmonic current levels without the need for filter components. The FCSC-rectifier includes a variable capacitive line reactance that interacts in a controlled manner with the inductive line impedance. The result is that the converter input current is nearly purely sinusoidal with a power factor of almost unity. The FCSC-rectifier is to be used for stand-alone variable-voltage, variable-frequency generation systems and can, therefore, power the full authority digital electronic control system (FADEC) in an MEA. This paper shows that the FCSC-rectifier can maintain a high power factor and acceptable current harmonic levels without the use of filters, despite large voltage and frequency variations. A full description of the circuit modes of operation is presented in this paper together with simulation results showing circuit performance characteristics over a range of voltages and frequencies. Results are experimentally verified using a 1-kW test circuit.

Design and Test Evaluation of Full Authority Digital Electronic Control System for an Auxiliary Power Unit

A helicopter auxiliary power unit (APU) is initially equipped with a hydro-mechanical control system (HMC). Because HMC's complex structure is difficult to be modified to realize sophisticated control algorithms and the APU is faced with the need for performance improvement, it is urgently necessary to carry out digital control modification of HMC. Based on the analysis of control laws of the original HMC and differences between HMC and digital control system, key techniques involved in the digital control system are studied, such as overall structure, control laws and fuel system based on electric fuel pump, and finally a full authority digital electronic control system (FADEC) is developed for APU. Functions, performances and key techniques of the FADEC system are evaluated on test rig, and the test results show functions of original control system are enhanced and performances of APU are improved more effectively under the control of the designed FADEC compared with the original HMC.

Transitioning Nuclear Power Plant Main Control Room From Paper Based Procedures to Computer Based Procedures

The United States (U.S.) has 99 operating Nuclear Power Plants (NPPs). The majority of these were designed and commissioned in the 1970s and 1980s. Plants are modernizing their control systems and main control rooms to be able to continue operating past their original 40-year license agreements. U.S. NPP main control rooms are migrating towards hybrid controls with both digital and analog systems. Digital upgrades, while costly, provide improved reliability, reduced maintenance cost, and the potential for fewer unplanned outages and fewer human errors. U.S. utilities have been slow to embrace computerized procedure system (CBP) research, even though CBPs demonstrate clear operational and human factors benefits. Most of the CBP research has been oriented to new reactor designs or full digital control rooms and is not applicable to the piecemeal modernization approach favored by U.S. plants. Research is needed to examine how CBPs impact operations in hybrid control rooms, and how current paper based procedures can be efficiently migrated to computerized platforms. Work is underway to develop tools and perform the obligatory research needed to design and validate CBPs for modernized U.S. nuclear control rooms.

Powerplant Reliability Issues and Wear Monitoring in Aircraft Piston Engines. Part II: Engine Diagnostic

This paper introduces a method to efficiently monitor the status of a piston engine during flight. ECUs (Electronic Control Units) make it possible to fly safely without emergencies or urgencies with random electronic failures of components and connections. The same can be easily done on older engines by adding a reliable digital monitoring system and an automated calibration of the carburetors. In fact, their reliability is several order of magnitude inferior to modern turboshafts. In modern engines with FADEC (Full Authority Digital Electronic Control) as the “on” button is pressed the sensors and actuators are checked. The CPUs will then run start-up during the cranking phase (engine running without ignition). If everything is all right, then the engine starts and the post start checks are also performed. During flight, the ECU checks CPUs, sensors and actuators. Therefore, the electronic system can be monitored with high reliability without much effort. The sensors may crosscheck the engine situation and may output very reliable early diagnosis of incoming failures. Statistical data on spare parts are invaluable for monitoring application, signaling weak or not-lasting components and failure modes. This is another advantage of automotive piston engines conversions to aircraft use.

Exploring Strategies To Bias Sequence in Natural and Synthetic Oligomers and Polymers.

Millions of years of biological evolution have driven the development of highly sophisticated molecular machinery found within living systems. These systems produce polymers such as proteins and nucleic acids with incredible fidelity and function. In nature, the precise molecular sequence is the factor that determines the function of these macromolecules. Given that the ability to precisely define sequence emerges naturally, the fact that biology achieves unprecedented control over the unit sequence of the monomers through evolved enzymatic catalysis is incredible. Indeed, the ability to engineer systems that allow polymer synthesis with precise sequence control is a feat that technology is yet to replicate in artificial synthetic systems. This is the case because, without access to evolutionary control for finely tuned biological catalysts, the inability to correct errors or harness multiple competing processes means that the prospects for digital control of polymerization have been firmly bootstrapped to biological systems or limited to stepwise synthetic protocols. In this Account, we give an overview of strategies that have been used over the last 5 years in efforts to program polymer synthesis with sequence control in the laboratory. We also briefly explore how the use of robotics, algorithms, and stochastic chemical processes might lead to new understanding, mechanisms, and strategies to achieve full digital control. The aim is to see whether it is possible to go beyond bootstrapping to biological polymers or stepwise chemical synthesis. We start by describing nonenzymatic techniques used to obtain sequence-controlled natural polymers, a field that lends itself to direct application of insights gleaned from biology. We discuss major advances, such as the use of rotaxane-based molecular machines and templated approaches, including the utilization of biological polymers as templates for purely synthetic chains. We then discuss synthetic polymer chemistry, whose array of techniques allows the production of polymers with enormous structural and functional diversity, but so far with only limited control over the unit sequence itself. Synthetic polymers can be subdivided into multiple classes depending on the nature of processes used to synthesize them, such as by addition or condensation. Consequently, varied approaches for sequence control have been demonstrated in the area, including but not limited to click reactions, iterative solid-phase chemistry, and exploiting the chemical affinity of the monomers themselves. In addition to those, we highlight the importance of environmental bias in possible control of polymerization at the single-unit level, such as using catalyst switching or external stimuli. Even the most successful experimental sequence control approach needs appropriate tools to verify its scope and validity; therefore, we devote part of the present Account to possible analytical approaches to sequence readout, starting with well-established tandem mass spectrometry techniques and touching on those more applicable to specific classes of processes, such as diffusion-ordered NMR spectroscopy. Finally, we discuss progress in modeling and automation of sequence-controlled polymers. We postulate that developments in analytical chemistry, bioinformatics, and computer modeling will lead to new ways of exploring the development of new strategies for the realization of sequence control by means of sequence bias. This is the case because treating the assembly of polymers as a network of chemical reactions will enable the development of control strategies that can bias the outcome of the polymer assembly. The grand aim would be the synthesis of complex polymers in one step with a precisely defined digital sequence.

On the Real-Time Estimation of Disk Temperature Spatial Distributions in Aeroengines

This paper presents a novel approach to real-time modeling of disk temperature distribution using proper orthogonal decomposition (POD). The method combines singular value decomposition (SVD) techniques with a series of low-order transfer functions to predict the disk's thermal response over a typical flight. The model uses only typically available full authority digital electronic control (FADEC) measurements to predict temperature with accuracy of ±30 K over the whole flight cycle. A Kalman filter has also been developed based on a single temperature measurement, and the location of the measurement has been assessed in order to select the most appropriate target for instrumentation. Points all around the front and back of the disk have been assessed, and the best practice result is found to be near the center of the disk neck. This represents a compromise between matching the fast dynamic response of the rim, with the slower dynamics of the cob. The new model has been validated against an independent flight simulation.

Out Through the Intake

This article elaborates various challenges presented by stall and surge to the gas turbine research community and jet engine designers. The article also presents several examples of stall and surge faced by the pilots. Stall and surge emerge from basic physics: the behavior of the boundary layer on the compressor blades and stators; however, current technology has no means to completely eliminate it. Engine control systems, such as the Full Authority Digital Electric Control (FADEC), are programmed to keep the operating point of the compressor well away from the surge line. Researchers have been studying stall and surge for decades, looking for ways to predict and combat the phenomena. Meanwhile, there has been some success in using FADEC to either prevent a stall and surge or to limit the number of repetitions. FADEC can also step in during flights in heavy rain or hailstorms. In those conditions, extra fuel is needed to process and evaporate the water being swallowed by the engine. The electronic control system can sense the mismatch between the power setting and the fuel flow and take action to prevent possible engine instability.