34th Annual Frequency Control Symposium

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.

When we examine the impacts of space weather on society, do we really understand the risks? Can past experiences reliably predict what will happen in the future? As the complexity of technology increases, there is the potential for it to become more fragile, allowing for a single point of failure to bring down the entire system. Take the Global Positioning System (GPS) as an example. GPS positioning, navigation, and timing have become an integral part of daily life, supporting transportation and communications systems vital to the aviation, merchant marine, cargo, cellular phone, surveying, and oil exploration industries. Everyday activities such as banking, mobile phone operations, and even the control of power grids are facilitated by the accurate timing provided by GPS. Understanding the risks of space weather to GPS and the many economic sectors reliant upon it, as well as how to build resilience, was the focus of a policy workshop organized by the American Meteorological Society (AMS) and held on 13–14 October 2010 in Washington, D. C. The workshop brought together a select group of policy makers, space weather scientists, and GPS experts and users. Arif Alikhan, assistant secretary for policy development in the U.S. Department of Homeland Security, kicked off the meeting by stressing that authorities should see GPS and resilience through an all-hazards lens rather than plan for each emergency scenario on a case-by-case basis. Whether a GPS signal error or disruption is caused by a solar storm, an intentional jammer, or some other source, government and industries need to plan to respond to the incident and restore capability as quickly as possible, although, Alikhan remarked, “The number of potential scenarios is infinite, and we have neither the time nor resources to plan against them.” Alikhan suggested that risk managers conceptualize the scope of critical assets in need of protecting through a resilience and risk analysis framework. He recommended that decision makers take an inventory of all functions provided for by their institutions“ use of GPS. Next, through risk-informed prioritization, planners can ascertain whether a backup is really needed for any services provided by GPS. “In this fiscal environment,” Alikhan said, “we will need to shrink the haystack, or size of the problem, in order to be effective.” Because the interdependencies of critical infrastructures are not fully appreciated by the public and private sectors, he stressed that a mix of governmental, commercial, and international stakeholders should develop plans and procedures to make systems more resilient. The remainder of the workshop was organized around discussions in three sessions: (1) identifying the vulnerability of GPS technologies and services to space weather, (2) identifying how this vulnerability affects users who depend on GPS, and (3) developing opportunities and policies for building resilience. In the first session, participants agreed that the vulnerability of GPS needs to be defined for different segments (e.g., satellites, signals, users). While some understanding of user needs exists, the definition of user requirements needs more clarification because space weather events will affect some technologies more than others. Also, a threat assessment would be valuable to best understand how severe the impacts might be and what mitigation options are available. With the recent news that Google™ is building self-driving robotic cars that depend on GPS, trying to capture possible future vulnerabilities is extremely challenging. During a debate on how much to stress the impact of a solar flare as massive as the 1859 Carrington event, many warned that while the public should be made aware of such a potential occurrence, it should not govern planning, since such a doomsday scenario is uncertain and expected to happen only very infrequently. When discussing in the second session how users of GPS are affected, participants discovered that communicating with GPS stakeholders and users is a challenge because many do not understand the impacts of adverse space weather. In particular, many of the service providers and end users of GPS were not in business during the previous solar maximum and therefore are not familiar with space weather hazards. To help remedy this, outreach approaches were discussed, and some participants argued that the space weather community should anticipate the needs of the users. Others instead urged the space weather community to deal only with the service providers—not end users—and ask them rather than tell them what they need. Despite this debate, there was broad agreement that space weather researchers should develop better measurements and predictions of the ionosphere. In addition, participants agreed that scintillation specifications and predictions would be useful to many users of GPS. Improved predictions would be possible by installing more dual-frequency stations and scintillation monitors, they noted. The workshop concluded with a discussion of policy options for building resilience. Participants debated what measures could be taken, such as developing new policies, investing in research and development, changing industry practices, and public and private sector collaboration. Scott Pace, director of George Washington University“s Space Policy Institute, stressed in his presentation that stakeholders and disaster planners should focus on three aspects: prediction, detection, and mitigation. Better space physics/heliophysics science is needed, and it was recommended that this be a top priority for the Solar and Space Physics decadal survey, which sets future nationwide research targets and is currently under review by the U.S. National Research Council. Findings and recommendations from the workshop will be published in a report by AMS. The results will be widely distributed to various stakeholders, including policy makers, GPS service providers, federal agencies, research communities, and international organizations. Genene Fisher is a senior policy fellow in the American Meteorological Society's Policy Program. E-mail: [email protected]

To date, high-precision time synchronisation has been applied in many fields, such as high-precision indoor positioning, multistatic Synthetic Aperture Radar (SAR) and etc. This study focuses on the use of only global positioning system (GPS) L1 civilian signals to achieve regional nanosecond time synchronisation. GPS errors are analysed in this study to determine their effect on GPS timing. This study also examines the specific features of the error in fixed-position timing technology and related error reduction techniques to illustrate the feasibility of nanosecond high-precision time synchronisation with GPS L1 signals in a fixed-position timing mode. Then, the results of a specific GPS timing receiver working in a fixed-position mode and using GPS L1 signals are shown to indicate that the use of GPS L1 signals to achieve nanosecond-accuracy time synchronisation in a local area is feasible. Finally, this study also analyses the impacts of the imprecise position in a fixed-position timing mode.

The usability of tactical radio systems is strongly affected by the characteristic of the VHF mobile radio channel. The design of a channel sounder and preliminary measurements are presented. The channel sounder uses a chirp impulse compression technique based on a surface acoustic wave (SAW) filter with a bandwidth of 6 MHz in the receiver. The transmitted chirp is generated digitally and is designed for a high correlation gain, a small pulse-width and low correlation sidelobes. The chirp is fed to a mixer with a variable local oscillator frequency and transmitted in one of the subbands between 30 and 88 MHz. All local references in the transmitter and the receiver are synchronized by a 10 MHz Global Positioning System (GPS) time reference. Additionally a 1 Hz signal, also GPS synchronized, is used as a trigger signal for the transmitter and the receiver to determine the absolute delay of the different propagation paths. Due to the high stable reference the compressed chirp can be demodulated coherently and the complex position-dependent channel impulse response can be measured. The delay-Doppler power spectrum is calculated which yields the location of scatterers.

Double-terminal traveling wave-based fault location is one of the most reliable and accurate technologies for power transmission line fault location. However, existing methods require a global positioning system (GPS) or accurate communication latency estimation to synchronize data from the two terminals. In this study, we propose an innovative double-terminal traveling wave-based fault location method that is independent of either GPS or communication latency estimation. The basic principle of the proposed method is that the arrival time difference between initial surges could be roughly calculated through the angle of pre-fault phasors by artificially assigning surge arrival points as the time references. Therefore, an approximate fault distance is obtained. The error could be reduced by detecting the fault-point-reflected surge. Extensive simulation experiments were performed using PSCAD/EMTDC software to assess the performance of the proposed algorithm. The results showed that the proposed method is applicable to different fault circumstances and independent of GPS synchronization and communication latency estimation while maintaining accuracy close to those of state-of-the-art algorithms. Finally, hardware experiments were performed to assess the validity and practicability of the proposed method.

A digital control loop scheme for a high speed PLL is suggested to detect amplitude errors at the output of the oscillator. Reliability specifications of the PLL are likely to be violated in case of excessive output swing in the oscillators. In addition, low amplitude swings will have negative influences on the phase noise of LC oscillators. As a result, the performance and reliability of the PLL will be reduced. The design includes a novel amplitude error detector. The amplitude error detector generates a digital word to show the situation of the amplitude error. The structure is implemented in 65nm CMOS technology. The power consumption of one amplitude error detector from 1V power supply is 0.76mW.

The Global Positioning System (GPS) is a satellite-based radionavigation system that uses stored map information to send location and time data to a GPS receiver. One of the disadvantages of GPS is that it lacks memory, meaning it does not recall or learn from past understandings. A simple way for altering a GPS navigational system to include a learning model based on speeds. It is assumed to be totally self-contained, that means no user input or involvement is required. All the necessary data is obtained from the GPS time, position, and date. Another way can be adding the labels or tags. These velocity profiles are used to extract characteristics from the surroundings in addition to learning, which may then be utilized to increase the accuracy of optimal route selection. The RoadTagger is a program that employs Neural Network to estimate the nature of obstacles on road.

International audience

Autonomous driving is essential for the automation of agricultural systems, and current research primarily relies on using global positioning system (GPS) signals. However, in environments where GPS signals are unstable or denied, such as canopies and smart farms, GPS-based autonomous driving systems face limitations. Therefore, this study proposes an unmanned aerial vehicle autonomous driving system using three-dimensional light detection and ranging simultaneous localization and mapping (3D LiDAR SLAM). The proposed algorithm follows three steps: (1) A map is generated using 3D LiDAR. Because it targets an environment with height restrictions, lightweight and ground-optimized LiDAR odometry and mapping (LeGO-LOAM), which has the characteristic of extracting the ground, is used as a 3D LiDAR SLAM algorithm. (2) Noise is removed through post-processing. (3) A path is generated using the A* algorithm. To evaluate the performance of the proposed system, field evaluations were conducted in an outdoor canopy orchard using GPS and real time kinematic (RTK) GPS data as references. The experimental results verified the limitations of existing GPS- and RTK GPS-based methods and demonstrated the good performance and effectiveness of autonomous driving using 3D LiDAR SLAM. These findings suggest the feasibility of automated operations in environments where GPS is unstable or denied, and efficient agricultural automation may be achieved in conjunction with future harvesting and pollination operations.

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

This paper presents effect of LC with clamping diodes dv/dt filter on current-controlled PMSM drives in case where 3-phase inverter output currents are measured and used in the digital control loop. In particular, this case can be reported in some cases. Firstly, power devices are equipped with integrated pilot current sensors. Secondly, PCB technology based Rogowski coils are installed in inverter leg with analog circuit to feed a signal to microcontroller. Thirdly, hall type current sensors are packaged in inverter output terminal through a bus bar. In those cases, it is inevitable to measure inverter currents because it is hard to move the location of current sensor. In this manner, the effect of filter resonance should be considered properly to control the motor current accurately because the measured inverter output current includes both motor and filter resonant current. If the resonant current of the filter is not compensated properly, it causes the DC offset of motor current which bring about the torque ripples. In order to compensate the offset, inserting a two stage Discrete Fourier Transform (DFT) is used and the calculated offset is subtracted from the sampled current. Judging by simulation and experimental results, it is confirmed that the compensation method eliminates the offset of the motor current effectively, and thereby reducing the torque ripple as well.

Real Time Analysis of Microprocessor Control System

Stability of discrete linear feedback systems with pulse-width-modulation power dispatch An adaptation of the circle criterion to pulse-width-modulation type nonlinearities in a digital control loop is presented. Formulae are derived for both gain and the mode of oscillations of the system response. Standard examples are taken, including that of a plant with a pole at the origin.

Traditional haptic rendering creates virtual springs using DC motors with current amplifiers and encoder-based position feedback. It is well known that the stiffness of virtual environments is limited by quantization, discretization, and amplifier bandwidth effects. In this paper we propose a novel control architecture that, rather than canceling motor electrical dynamics, uses them to achieve better performances. First we recognize that the inductance L provides a natural sensor-less stiff behavior at high frequencies. Second, electrical resistance R serves as the basis of a wave transform that, performed through an analog circuit, allows to build a more stable interface with virtual environments, achieving robustness to servo delays and discretization. Encoder feedback and digital control loop are required only to provide parametric robustness at low frequencies. A prototype 1-DOF system has been implemented and confirms the promise of this novel paradigm