Real-time plasma electron density feedback control system based on FPGA on J-TEXT

The J-TEXT newly deployed three-wave polarimeter–interferometer (POLARIS) system provides a better temporal and spatial resolution of the plasma electronic density than the that of old HCN interferometer system. The new plasma electron density feedback control system is implemented on the already existing POLARIS data acquisition system which is based on FlexRIO field-programmable gate array (FPGA). An analog output card is added to control the piezoelectric crystal valve of the gas puffing. The density feedback control system is able to extract the phase-shift information from the intermediate frequency signal using fast Fourier transform, calculate density of multiple chords, and output control signal to the piezoelectric crystal valve in real time. NI P2P technology is used to transfer data from a FlexRIO FPGAs to another in real time without using the CPU; thus, all FlexRIO FPGAs onboard can calculate the density with only one acquiring the reference chord signal. This system is also able to calculate density profile. With the density profile, it can use compensated central chord integrated or average density as control target. Also, the real-time density profile data are useful for the future plasma control system and disruption detection system.

Real-Time Feedback Control of Carbon Content of Zirconium Dioxide Thin Films Using Optical Emission Spectroscopy

In this paper, a real-time location feedback control system based on multi-sensor network is proposed for the precise control of a moving robot. The target tracking network system is a real test-bed that consists of a group of ultrasonic sensor nodes, a mobile robot and two laptops. In order to pursue excellent tracking performance and modify the robot’s trajectory promptly, Extended Kalman Filtering algorithm as well as a kind of scheduling scheme based on location is applied in the system. The experiment result validates the correctness of the Extended Kalman Filter (EKF) and shows that the target tracking network system is effective for robot feedback control.

This paper compares algorithms for velocity estimation for feedback control using position encoder measurements. Simulations and experiments for position-velocity control of motors using both fixed-time and fixed-displacement algorithms are compared for various operating conditions. While no single approach is optimal for all situations, least-squares fit algorithms are promising in general. Mathematical models are developed to predict the performances of the algorithms. Specifically, upper bounds on absolute and relative errors for each of the algorithms under different constant velocity and constant acceleration conditions are derived. The algorithms are extensively tested in simulation and also on data obtained from an experimental setup consisting of a motor, two encoders with different resolutions, and a real-time feedback control system. The theory and simulations are confirmed by experimental results.

We present the analysis of a local (z = 0.04 - 0.2) sample of 31 galaxy clusters with the aim of measuring the density of the X-ray emitting gas in cluster outskirts. We compare our results with numerical simulations to set constraints on the azimuthal symmetry and gas clumping in the outer regions of galaxy clusters. We exploit the large field-of-view and low instrumental background of ROSAT/PSPC to trace the density of the intracluster gas out to the virial radius. We perform a stacking of the density profiles to detect a signal beyond r200 and measure the typical density and scatter in cluster outskirts. We also compute the azimuthal scatter of the profiles with respect to the mean value to look for deviations from spherical symmetry. Finally, we compare our average density and scatter profiles with the results of numerical simulations. As opposed to some recent Suzaku results, and confirming previous evidence from ROSAT and Chandra, we observe a steepening of the density profiles beyond \sim r500. Comparing our density profiles with simulations, we find that non-radiative runs predict too steep density profiles, whereas runs including additional physics and/or treating gas clumping are in better agreement with the observed gas distribution. We report for the first time the high-confidence detection of a systematic difference between cool-core and non-cool core clusters beyond \sim 0.3r200, which we explain by a different distribution of the gas in the two classes. Beyond \sim r500, galaxy clusters deviate significantly from spherical symmetry, with only little differences between relaxed and disturbed systems. We find good agreement between the observed and predicted scatter profiles, but only when the 1% densest clumps are filtered out in the simulations. [Abridged]

To overcome productivity issues and revolutionize the stagnating construction industry, a large amount of research efforts has been devoted to robot-assisted construction technology. The advancements in robotics including mechanical system design, tool design, digital system design, and numerical control systems design enabled engineers to create complex geometries that are infeasible for conventional construction methods. In addition, innovative robotic systems that utilize mobile platforms, multiple robots, and unmanned aerial vehicles have demonstrated significant promise in fully automating the construction process. This work will provide a perspective on the state-of-the-art applications of robotics in the revolution of construction, where a comprehensive review of the current development of the relevant software and hardware, 3D concrete printing (3DCP), robot-assisted assembly of discrete prefabricated blocks, real-time quality monitoring and feedback control systems, and typical innovative robot-assisted structural designs are conducted. Finally, the limitations of existing robot-assisted construction technology are identified, which leads to several recommendations for future research toward fully automatic construction.

A real-time and effective double-loop feedback control system for underwater flexible manipulators is raised in this paper. The research object is a kind of underwater flexible manipulator driven by McKibben water hydraulic artificial muscle (WHAM) that can grasp, swallow, and disgorge target objects in its interior space. To make up for the lack of flexibility, an underwater flexible manipulator collaborative working strategy is proposed. A more flexible and smaller flexible manipulator is placed inside the flexible manipulator to assist it in performing difficult underwater works. The control system feeds back the position of internal objects through a built-in binocular camera and the working state of the manipulator through displacement sensors. The control system setups including underwater flexible manipulator subsystem, hydraulic drive subsystem, PLC control subsystem, displacement sensor subsystem, built-in binocular vision subsystem, and upper computer subsystem is built. PYTHON-based built-in binocular vision software and C++-based underwater flexible manipulator control software are also developed to facilitate observation and recording. The underwater flexible manipulator collaborative experiment is designed to verify the performance of the control system and the control algorithm.

Optimization of jet engine sprays has the potential to improve efficiency and reduce environmental impact. Sprays can be continually optimized in multivariate scenarios using real-time feedback control, but a method of controlling the sprays based on physical properties must first be established. In this study, a spray controller was developed to optimize the spray angle obtained from shadowgraphs, with the assumption that the largest angle is desired. The spray angle was used as an example, as it is a physically important parameter which is easily found through shadowgraph imaging. Varying ratios of swirled air to straight air, determined by the image-based feedback controller were introduced into the air portion of a coaxial airblast nozzle while keeping the total air flow rate constant. A golden section search converged on the swirled air ratio that provided the largest angle and was validated from the distribution of spray angle versus swirled air ratio. The ratio that produced a spray with the greatest angle of 25.8 ± 2 deg was found at a swirled air ratio of 0.66 ± 0.03 for a spray with a momentum ratio of 6. The successful design and implementation of this image-based feedback controller is intended to provide a foundation for developing real-time active feedback controllers for sprays.

The present article is a position paper reviewing the main requirements and existing achievements of co-design approaches for real-time control and computing. This problem arises with the increasing complexity of modern computers which require more integrated methodologies, specifically suited to critical embedded systems. The general problem to be solved is the achievement of multi-objective goals (i.e. mixing stability, performance and dependability requirements) under constraints of limited execution resources (combining hardware and software components in CPUs and networks). It is expected that co-design approaches, handling the constraints arising from the control and real-time computing domains at early design time, can improve the overall effectiveness of distributed real-time controllers.

The development process pertaining to the design, fabrication, and testing of a 40-stage free-running arc synchronous distributed energy railgun is presented. Investigation of this type of system will determine the effectiveness of a distributed energy scheme to suppress the plasma restrike phenomenon and increase plasma armature railgun performance [1]. Determined by a computer simulation, the proposed system will have a 1.0 cm × 1.0 cm square bore cross section and a stage length of 15.24 cm producing a total rail length of 6 meters for 40 stages. A free-arc is utilized to relieve the financial burden of a large stored energy facility. A velocity of 8 km/s is desired to emulate conditions during a high altitude microsatellite launch. To achieve this velocity, pulsed power in conjunction with a low pressure (∼ 10 Torr) air environment is required. The pulsed power supplies 15 kJ of energy to provide an armature current (∼ 50 kA) for 1 millisecond. A real-time feedback control system will accurately release the stage energy upon arc arrival. Experimental data collected from a 7-stage prototype distributed system is discussed which will mimic the design and operation of the first 7 stages associated with the 40-stage railgun. The copper rail length is 1.2 m long with a 1 cm × 1 cm square bore cross section and a 15.24 cm stage length. Each distributed energy stage contains a 750 µF capacitor bank, a thyristor with an anti-parallel diode, and a driver board for triggering. The armature is formed using a plasma injector that is powered by a 40 kV Marx generator. Diagnostics for this examination include rail B-dot probes as well as independent Rogowski coils for each stage. Data collected from the rail B-dot probes will be used to measure the armature position and velocity as a function of time. There is no target velocity for this prototype; repeatable energy module operation, accurate stage triggering, and arc propagation toward the muzzle are the main areas focus. Outcomes of these initial experimental results will aid the development of the 40-stage system.

Microwave reflectometry will serve as the primary diagnostic tool for measuring plasma density in ITER. The real-time inversion of high spatiotemporal resolution density profiles is a critical research focus for plasma fueling and control in both current and future fusion devices. A fast density profile inversion algorithm based on a deep neural network model has been proposed for the microwave reflectometry profile inversion database under various discharge parameters on EAST. Firstly, the model directly takes the high-sampling-rate raw time-domain I / Q data from the multi-bands (Q-, V- and W-bands) microwave reflectometer as input and demonstrates rapid and effective feature extraction capabilities. Secondly, the model outputs a two-dimensional vector containing both the positions of the microwave cut-off layers and the density information. Notably, the model exhibits excellent adaptability across different discharge parameters on EAST, including variations in magnetic field strength ( B t 0 = 1.57–2.30 T), different plasma confinement such as L-mode and H-mode, and during phases such as current ramp-up and steady-state discharge. The next step involves integrating this data-driven real-time density profile algorithm directly into the deployed profile reflectometer data acquisition system on EAST to enable parallel computation of data acquisition and processing. This integration aims to provide real-time density profile distribution, particularly during density feedback control experiments, such as gas or pellet injection experiments.

A method of fast data processing has been developed to rapidly obtain evolution of the electron density profile for a multichannel polarimeter-interferometer system (POLARIS) on J-TEXT. Compared with the Abel inversion method, evolution of the density profile analyzed by this method can quickly offer important information. This method has the advantage of fast calculation speed with the order of ten milliseconds per normal shot and it is capable of processing up to 1 MHz sampled data, which is helpful for studying density sawtooth instability and the disruption between shots. In the duration of a flat-top plasma current of usual ohmic discharges on J-TEXT, shape factor u is ranged from 4 to 5. When the disruption of discharge happens, the density profile becomes peaked and the shape factor u typically decreases to 1.

The density profiles in a fluid interacting with the two identical solid walls of a closed long slit were calculated for wide ranges of the number of fluid molecules in the slit and temperature by employing density functional theory in the local density approximation. Two potentials, the van der Waals and the Lennard-Jones, were considered for the fluid-fluid and the fluid-walls interactions. It was shown that the density profile corresponding to the stable state of the fluid considerably changes its shape with increasing average density (rhoav) of the fluid inside the slit, the details of changes being dependent on the selected potential. For the van der Waals potential, a single temperature-dependent critical value rhosb of rhoav was identified, such that for rhoav < rhosb the stable state of the system is described by a symmetric density profile, whereas for rhoav >/= rhosb it is described by an asymmetric one. This transition constitutes a spontaneous symmetry breaking of the fluid density distribution in a closed slit with identical walls. For rhoav >/= rhosb, a metastable state, described by a symmetric density profile, was present in addition to the stable asymmetric one. The shape of the symmetric profile changed suddenly at a value rhoc-h > rhosb of the average density, the density rhoc-h being almost independent of temperature. Because of the shapes of the profiles before and after the transformation, this transition was named cup-hill transformation. At the transition point, the density of the fluid near the walls decreased suddenly from a liquid-like value becoming comparable with the density of a gaseous phase, and the density in the middle of the slit increased suddenly from a gaseous-like value becoming on the order of the density of a liquid phase. For the Lennard-Jones potential, there are two temperature-dependent critical densities, rhosb1 and rhosb2, such that the stable density profile is asymmetric (symmetry breaking occurs) for rhosb1 </= rhoav </= rhosb2 and symmetric for rhoav outside of the latter interval. These critical densities occur only for temperatures lower than a certain temperature, Tsb,0. The cup-hill transition is similar to that for the van der Waals potential at low temperatures but becomes smoother with increasing temperature.

As integrated circuit feature size continues to shrink, yield loss due to parametric variation will become more and more significant. Real-time feedback control provides a means of reducing parametric variation and therefore limiting this type of yield loss. A challenge in applying feedback control to semiconductor manufacturing processes is selecting the variables to feed back. In many manufacturing processes, the important product variables cannot be measured in real-time and therefore cannot be directly controlled using real-time feedback control. An alternative, which has proven effective, is to feed back process variables closely related to the product variables. Typically, selection of process variables to feed back is based upon qualitative knowledge about the process, which in many cases is limited. In this paper, an empirical methodology for selecting the best process variables for feedback in order to minimize variation in the product variables is presented. Two versions of this methodology are described, a full version and a "lite" version. The latter is an abridged version of the former. Prior to introducing this methodology, a condition under which real-time feedback control will reduce product variable variation is derived. This condition is used to highlight the sources of variance in the product variables, information which is used to explain how the methodology works. The methodology is evaluated using simulated experiments. Both the full and lite versions prove to be effective under the assumptions stated for this study although the full version is clearly superior in terms of performance. Application of the methodology to a reactive ion etch process is described in a companion work.

Microwave interferometry is a reliable, well established, and non-perturbing method to measure the line-integrated electron density of a non-uniform plasma through the phase shift of a wave that propagates the plasma medium. In this paper we combine the phase shift and the attenuation of the wave to experimentally extract both, the line-integrated density and the electron-neutral collision frequency of an atmospheric plasma torch. In addition, a novel method to obtain the 2D spatial plasma density profile of the torch is demonstrated by measuring the microwave power, without any information of the phase. The receiving antenna of the interferometer is moved perpendicularly to the axis of the torch and measures the spatial distribution of the microwave power. The wave is scattered by the plasma and the scattering profile depends on the plasma density profile. Direct comparison of this scattering profile with 3D full-wave simulations provides information on the electron number density profile of the plasma torch.