Open-loop Mode Research Articles

Hydrologic outputs generated over the Great Lakes with a calibrated version of the GEM-Hydro model

This dataset contains outputs from a calibrated version of the GEM-Hydro model developed at Environment and Climate Change Canada (ECCC) and is available on the Federated Research Data Repository. The dataset covers the basins of the Laurentian Great Lakes and the Ottawa River and extends over the period 2001–2018. The data consist of all variables (hourly fluxes and state variables) related to the water balance of GEM-Hydro’s land-surface scheme (including precipitation, surface and sub-surface runoff, drainage, evaporation, snow water equivalent, soil moisture…) and mean daily streamflow at 212 gauge locations. These outputs were simulated with a calibrated version of the GEM-Hydro model that was run in open-loop mode (no assimilation) and driven with atmospheric forcings coming from ECCC’s Canadian Surface Reanalysis version 2.1. GEM-Hydro achieves satisfactory simulations of various hydrologic variables when compared to reference datasets. This dataset can be used for example to drive any routing model, compute climatologies or statistics for different hydrologic variables and study their variability as a function of the local geo-morphology, etc.

Design and study of moving-iron torque motor for two-dimensional proportional servo valve

This paper proposes a novel moving-iron torque motor designed for two-dimensional (2D) valves. The torque motor features a strap spring in place of the traditional return spring, effectively reducing the overall number of springs. The unique design allows the torque motor to return to its circumferential neutral position through the return torque generated by the strap spring. In order to analyze the torque-displacement characteristics of the torque motor, an analytical model is established, and a simulation model is constructed based on the equivalent magnetic circuit method, which takes into account the magnetic leakage at the control coil and the working air gap. In order to select a strap spring that matches the stiffness of the magnetic spring of the torque motor, the structural parameters of the spring are optimized using the response surface method with multi-objective optimization, and finally three springs with different stiffnesses are manufactured according to the optimization results. The experimental results show that the maximum step-up time of the torque motor is 20.6 ms, the maximum step-down time is 21.6 ms, the maximum hysteresis loop is 12.5%, and the maximum linearity is 20%. In order to improve the −3dB cut-off frequency of the torque motor, this paper adopts the current closed-loop control method, and increases the maximum cut-off frequency not exceeding 25 Hz in the open-loop mode to 110 Hz.The hysteresis loop and linearity of the torque motor decrease with the increase of the spring stiffness. The amplitude frequency −3dB cutoff frequency increases with increasing spring stiffness.

Fluidic feedback for soft actuators: an electronic-free system for sensing and control

The field of pneumatic soft robotics is on the rise. However, most pneumatic soft robots still heavily rely on rigid valves and conventional electronics for control, which detracts from their natural flexibility and adaptability. Efforts have focused on substituting electronic controllers with pneumatic counterparts to address this limitation. Despite significant progress, contemporary soft control systems still face considerable challenges, as they predominantly depend on pre-programmed commands instead of real-time sensory feedback. To confront these challenges, we propose an electronic-free soft actuator system capable of achieving basic sensorimotor behaviors. The soft actuator employs a fluidic strain sensor to obtain proprioception, detecting changes in air impedance resulting from stretching and compression. Integration of this sensor with a pneumatic valve enables the soft actuator possessing basic sensing and control capabilities. Drawing inspiration from the somatosensory and neuromuscular systems found in biological organisms, we implement both open-loop and closed-loop motion modes using different connection configurations. They facilitate cyclic movement and sensory feedback-regulated motion control using 'material intelligence'. We envisage that this system has the potential to expand to accommodate multiple limbs, thereby pioneering the development of fully fluidic soft robots.

Description and In-Flight Assessment of the POSEIDON-3C Altimeter of the SWOT Mission

The Surface Water and Ocean Topography (SWOT) mission was launched on 16 December 2022 to measure water levels over both open ocean and inland waters. To achieve these objectives, the SWOT Payload contains an innovative Ka-band radar interferometer, called KaRIn, completed with a nadir altimeter called POSEIDON-3C that was switched on a month after launch and a few days before KaRIn. POSEIDON-3C measurements provide a link between large-scale phenomena and high resolution. The POSEIDON-3C design is based on POSEIDON-3B, its predecessor on board JASON-3. It is also a dual-frequency radar altimeter operating in C- and Ku-bands, but with some improvements to enhance its performance. Even though it is a Low Resolution Mode altimeter, its performance over open ocean, inland waters and coastal zones are indeed excellent. This paper first describes the POSEIDON-3C design and its modes with a focus on its new features and the Digital Elevation Model that drives its open-loop tracking mode. Then, we assess the in-flight performances of the altimeter from an instrumental point of view. For that purpose, special and routine calibrations have been realized. They show the good performance and stability of the radar. In-flight assessments thus provide confidence when it comes to ensuring excellent altimeter measurement stability throughout the mission duration.

MEMS fast steering mirror with a large optical aperture and high surface quality for free-space optical communication.

This work presents a MEMS fast steering mirror fabricated by an 8-inch AlScN platform, with a large optical aperture of up to 10 mm and high surface quality (RMS < 20 nm, PV < 120 nm), intended for free-space optical communication. The device comprises a high reflective mirror plate, a pillar and four cantilever beams with AlScN thin films. This device is prepared by a wafer-level eutectic bonding process. A reinforcement structure is proposed to increase the resonant frequency and the resistance to deformation. The mechanical performance, including resonant frequency, step response, linearity, and long-term stability are characterized. The maximum tilting angle is 1.38 mrad at 68 V, the settling time is improved from 400 ms in the open-loop control mode to 0.5 ms with the double step algorithm. The relationship of the resonant frequency, surface figure, and the depth of reinforced ribs is studied through characterizing devices with different depths of reinforced ribs. The bonding quality and the mutual melting states of bonding layers interface are investigated.

Analysis and suppression of cross-axis modulation coupling errors in optically pumped magnetometers

We propose a method based on sensitive-axis high-frequency modulation (SHFM) method combined with PI closed-loop feedback to suppress the cross-axis modulation coupling error (CMCE) of the optically pumped magnetometer (OPM). Cross-axis modulation is a prevalent approach for three-axis measurement of OPM, but this scheme will introduce CMCE. These errors have the potential to pose undetected hazards in applications of multi-axis magnetic field measurement such as magnetoencephalography (MEG). The SHFM method suppressed the CMCE from 18.50% to 2.10% on average compared to the traditional method. Based on the static situation we also introduce PI closed-loop feedback, which suppressed the CMCE from 22.07% in open-loop mode to 2.10% in closed-loop mode. This approach is both straightforward and efficacious, offering seamless integration into an arrayed OPM-based system. Furthermore, SHFM has the potential to mitigate the challenges associated with MEG localization accuracy and other measurement errors introduced by CMCE, and further unleash the potential of applications of OPM–MEG system.

Evaluation of power system instability probability considering output randomness of grid-connected converter

Abstract In recent years, there has been a notable increase in the installed capacity of new energy sources. Nevertheless, the random nature of the output power of G-CCs may potentially result in power system instability. This paper presents a closed-loop interconnection model comprising a G-CC as a feedback subsystem and a VSC-HVDC system as a feedforward subsystem. The instability condition of the closed-loop system is derived from the open-loop mode resonance theory. Subsequently, a mathematical model is developed to represent the random output of the G-CC. This approach allows the probability of open-loop mode resonant instability of the power system to be evaluated, as well as the risk of sub-synchronous resonant instability caused by the output randomness of the G-CC. Finally, validation is performed by building a simulation example system and a time-domain simulation system in MATLAB.

Control of a Micro-Electro-Mechanical System Fast Steering Mirror with an Input Shaping Algorithm

Fast steering mirrors (FSMs) designed by the micro-electro-mechanical system (MEMS) technology are significantly smaller in volume and mass, offering distinct advantages. To improve their performance in the open-loop control mode, this study introduces a control algorithm and evaluates its performance on an electromagnetic-driven MEMS-FSM. The algorithm employs a method to shape the input signal by fitting the system’s transfer function and modifying the step response. This shaped signal is then applied to the system to minimize overshoot, reduce settling time, and improve working bandwidth, thereby enabling faster angular adjustments and improving the stability of the FSM. The experimental results demonstrate an 85.65% reduction in overshoot and a decrease in settling time from 84 ms to 0.4 ms. Consequently, the working bandwidth of the FSM system increases to 2500 Hz, demonstrating the effectiveness of the algorithm in enhancing MEMS-FSM’s performance.

Suppression of solar array vibration by torque compensation using a magnetorheological actuator: A hardware-in-the-loop test study

Sun-tracking-induced vibrations of a large flexible solar array are characterized by a wide frequency range and persistent disruptions, making them an important challenge for a high-precision spacecraft. This paper describes a hardware-in-the-loop test for a novel vibration suppression method that employs magnetorheological torque compensation. To provide the compensating torque, a test bench is built using a magnetorheological actuator (MRA). A comprehensive model is employed to quantitatively analyze suppressions in terms of solar array driving, solar array motion, and spacecraft disturbance. For comparison, the test is run in both open-loop and closed-loop modes. The results demonstrate that with closed-loop control, the maximum fluctuation of driving torque decreases by 50.90%. The sun tracking achieves a more stable speed. Moreover, disturbances produced by the vibration of the solar array are decreased by 59.84%. These findings suggest that using torque compensation with an MRA can successfully reduce the sun-tracking-induced vibration of a large flexible solar array while minimizing the impact on the spacecraft platform.

A simultaneous energy self-sufficient desalination and energy output process based on a novel membrane stack design

Electrodialysis (ED) uses electric energy to conduct the desalination, while bipolar membrane reverse electrodialysis (BMRED) converts the chemical energy containing in acids and alkalis into electric energy. Here, a novel membrane stack (BMRED-ED) based on BMRED and ED was designed to realize the simultaneous energy self-sufficient desalination and energy output process. The stack was studied in two different operation modes systematically. Results of the open-loop operation mode demonstrate that the maximum power density (Pd,max) can obtain a highest value of 4.53 W·m−2, and the maximal average apparent permeability (α) between the open circuit voltage (OCV) and theoretical electromotive force (EMF) is 92.23 %. Results of the closed-loop operation mode indicate that the final desalination ratio (ξdel) can attain as high as 89.57 %, and the corresponding energy utilization ratios of the desalination (ηdes) and the energy output (ηout) are 0.90 % and 14.00 %, respectively. Moreover, the effect of desalinated salt solution concentrations and discharging current densities on the closed-loop operation performance are much more remarkable than that of cation species in the alkali and salt solutions. This work provides a feasible and competitive strategy for simultaneous energy self-sufficient desalination and energy output.

Moving horizon estimation and control of a binary simulated moving bed chromatographic processes with Langmuir isotherms

Simulated moving bed chromatographic (SMB) chromatographic processes are widely used for separations in pharmaceutical and biotechnological industries. In the present work, the control of such processes is proposed based on a semi-centralized control scheme that utilizes a combination of model predictive control (MPC) and classical PID control. The necessary information from the process, i.e. the internal concentration profiles, for the MPC is obtained by a moving horizon estimator (MHE) in real-time from the available limited measurements (the cycle-averaged concentrations of the extract and raffinate product streams and the dimensionless retention times of the concentration waves in the regeneration zones). As a test case study, the separation of a hypothetical system governed by the Langmuir isotherms in the nonlinear concentration range of the isotherms is considered. First, the stand-alone MHE is validated in open loop mode with no plant-model mismatch under deterministic and stochastic conditions. In the latter case, the true measurements are subject to random normally distributed noise. To evaluate the performance of the proposed control strategy, a reference tracking (change of the requirements for both the purities and the retention times) scenario is simulated. The investigated scenarios are: (i) no plant-model mismatch, (ii) MHE with ideal noiseless measurements and finally (iii) MHE under the influence of measurement noise. Results show that the controller is able to follow the change of the references from reduced purity to complete separation and vice versa closely.

In-depth characterization of exhaust particles performed on-board a modern cruise ship applying a scrubber

To comply with environmental regulations, ship operators may adopt exhaust after-treatment devices such as scrubbers or selective catalytic reduction (SCR). Beyond gaseous emission control, these technologies impact the exhaust particles emitted from marine engines to the atmosphere. This study characterizes comprehensively the chemical composition and physical properties of exhaust aerosol particles upstream and downstream a hybrid scrubber operating in open loop mode on-board a modern cruise ship. The study considers two engines, one equipped with SCR and both with scrubber, during engine load conditions of 75 % and 40 %, and the influence of marine gas oil (MGO) use in addition to heavy fuel oil (HFO). At least 4 different particle types were observed in the exhaust based on transmission electron microscopy (TEM) studies both upstream and downstream scrubber, and both scrubber and SCR affected the particle number size distribution (PSD). The geometric mean diameter (GMD) of the particles increased over scrubber both due to removal of nucleation mode particles and particle growth in the scrubber. The scrubber effectively decreased particle number (PN) and, also, non-volatile particles, but the effect depended on particle size and no significant decrease was observed in number of particles above 50 nm, typically comprising black carbon (BC) and in the case of HFO combustion, also asymmetrical metal containing particles. In addition to PN, concentrations of PAH compounds were reduced in the scrubber. The results may be further utilized when including the exhaust aerosol characteristics from ships applying scrubbers to emission inventories, as well as climate and air quality models.

An Improved Voltage Control Method for EAST Fast Control Power Supply

The Experimental Advanced Superconducting Tokamak (EAST) fast control power supply (FCPS) is an important device for controlling the vertical displacement of plasma during the nuclear fusion power generation process, adopting a multiple H-bridge invertor branch parallel operation structure to output total current. At the beginning of each shot of plasma discharge, FCPS works in open-loop voltage control mode (VCM) or closed-loop current control mode (CCM) determined by the plasma control system to output current for exciting the load coil, to achieve plasma vertical displacement control. VCM has the characteristics of fast dynamic response speed but poor consistency of branch current and insufficient branch current control accuracy and stability because of open-loop control. CCM has the characteristics of high branch current control accuracy but poor dynamic response and robustness because of control delay and control parameters determined based on engineering experience. To achieve fast and robust control, an improved voltage control method (IVCM) is proposed by combining the advantages of VCM and CCM. In the beginning of establishing the output current, FCPS operates in VCM, and rapid establishment of the output current is ensured. After the output current rapidly increases to the critical value, closed-loop current control is added to VCM to ensure the accuracy of output current control. In closed-loop current control, linear super-twisting sliding mode control is designed to achieve fast and robust control, ensuring good consistency and fast dynamic response performance of each branch current. Simulations and experiments verify that the designed IVCM has better compatibility characteristics in output current stability, control accuracy, and consistency of each branch current compared to VCM.

Analisis dan Simulasi Efisiensi Kinerja Sepic Konverter Berbasis Kontroler Konvensional

The technology of components and electronic hardware has evolved to be able to produce a DC/DC current system for power, which is achieved by converting the DC power to higher or lower voltage. This DC voltage variable is commonly called the DC-DC Converter. This final task aims to find out the performance of the DC-DC Sepic Converter series design. The simulated testing of the system using SIMULINK/MATLAB software is subsequently obtained from the data analysis of the theoretical output voltage data and the monitoring of measurements that can be analyzed to determine the error level as well as the level of efficiency of the design of the sepic converter. The test was conducted by setting a constant input voltage of 12 V, a frequency of 50 kHz, with a duty cycle variation of 5% to 65% and a given load of 20 Ω. The result of the design of the Sepic Converter at the time of open loop mode with the value of duty Cycle of 5% produces a minimum voltage that is 0,38 V. Subsequently, when given the duty cicle value of 65%, the maximum voltage is 21,22 V error with the highest error rate of 1 V obtained at the 13th data trial. The average error value is 0,642 V and the standard deviation value is 0,453 V, the greatest efficiency point is 78,50% at the moment of the cycle duty value of 65. While the results of the testing of the Set of Sepic Konverters at the close loop mode, the input tension is given constantly 12 V. The configuration for the parameter value of PI is also constant, namely at the set point of 22,22 V, it is 21,97 V with an error difference 0,25 V.

MODELING OF A STANDALONE SOLAR PHOTOVOLATIC (PV) GENERATION SYSTEM

This brief discusses the Modelling of a Standalone solar Photovolatic (PV) generation system. In this work the simulation of the PV system in open loop mode is carried out in MATLAB/Simulink environment and the real time hardware implementation has also been done. The PV panel output is fed to an inverter which supplies power to domestic load such as fans, lights. A battery and charge controller are also used in the system. The two results have been compared. The simulation and hardware results have been found matching with each other. Key Words: PV system, OFF-grid, Batteries, Inverter and Load.

Feasibility Study of Three-Phase Modular Converter for Dual-Purpose Application in DC and AC Microgrids

The modern concept of a universal converter is intended as a power converter suitable for application in both dc or ac grids using the same external connectors. This novel family was recently proposed to allow an easier integration of renewable energy sources and energy storage systems, interfacing with dc/ac grids and/or loads with a minimum redundancy of power switches and passive elements. This kind of solution and applications are expected to be a reality in the nearest decade, as ac and dc low voltage distribution networks will coexist. Nevertheless, the initial solutions proposed as universal converter were focused on ac single-phase power conversion systems. In this sense, this article proposes and describes a new member of the universal converter family suitable for dc to dc and dc to ac power conversion (both in three-phase three-wire and in three-phase four-wire). The proposed power topology is derived as a modular extension from the single buck-boost bidirectional cell. Its main operation modes (buck and boost) are discussed, and a pulse-width-modulation technique is developed to generate the corresponding switching patterns. The proposed solution is successfully validated in open-loop mode both in simulation and experimentally with a laboratory prototype. The measured efficiency of the power converter was above 97% in the dc to ac mode and around 99% in the dc to dc mode.

Fast Nonlinear Predictive Control Using Classical and Parallel Wiener Models: A Comparison for a Neutralization Reactor Process

The Wiener model, composed of a linear dynamical block and a nonlinear static one connected in series, is frequently used for prediction in Model Predictive Control (MPC) algorithms. The parallel structure is an extension of the classical Wiener model; it is expected to offer better modeling accuracy and increase the MPC control quality. This work discusses the benefits of using the parallel Wiener model in MPC. It has three objectives. Firstly, it describes a fast MPC algorithm in which parallel Wiener models are used for online prediction. In the presented approach, sophisticated trajectory linearization is performed online, which leads to computationally fast quadratic optimization. The second objective of this work is to study the influence of the model structure on modeling accuracy. The well-known neutralization benchmark process is considered. It is shown that the parallel Wiener models in the open-loop mode generate significantly fewer errors than the classical structure. This work’s third objective is to validate the efficiency of parallel Wiener models in closed-loop MPC. For the neutralization process, it is demonstrated that parallel models demonstrate better control quality using various indicators, but the difference between the classical and parallel models is not significant.

Simultaneous control of rigidity and hand tremor by adaptive fuzzy Q-learning

Deep brain stimulation (DBS) is a successful treatment for the symptoms of various neurodegenerative diseases, including Parkinson's disease (PD). While DBS has been shown to improve motor symptoms in individuals with PD, it operates mostly in an open-loop mode, meaning that the stimulation settings remain constant regardless of changes in the disease state. To address this issue, the current paper describes the use of a fuzzy Q-learning algorithm combined with a model-free non-linear controller, called FQL-based MFNC, to control both hand tremor and rigidity at the same time. In contrast to previous tuning methods that focus on obtaining the mathematical model of a controlled system, the current technique explores the use of a fuzzy Q-learning agent to achieve the best design for DBS. Initially, a fuzzy reinforcement learning approach is employed to adjust the proposed controller in a simulation setting. Specifically, the FQL algorithm determines the best approach based on a reward function to modify the designed control coefficients, ensuring that the DBS requirements are satisfied despite changes in tremors. Multiple examinations, including Normal, Noise, and Stability tests, along with different indices, have been conducted to validate the efficacy and feasibility of the proposed FQL-based MFNC approach on a dynamic model pertaining to rigidity and tremors.

RPM: An open-source Rotation Platform for open- and closed-loop vestibular stimulation in head-fixed Mice

Head fixation allows the recording and presentation of controlled stimuli and is used to study neural processes underlying spatial navigation. However, it disrupts the head direction system because of the lack of vestibular stimulation. To overcome this limitation, we developed a novel rotation platform which can be driven by the experimenter (open-loop) or by animal movement (closed-loop). The platform is modular, affordable, easy to build and open source. Additional modules presented here include cameras for monitoring eye movements, visual virtual reality, and a micro-manipulator for positioning various probes for recording or optical interference. We demonstrate the utility of the platform by recording eye movements and showing the robust activation of head-direction cells. This novel experimental apparatus combines the advantages of head fixation and intact vestibular activity in the horizontal plane. The open-loop mode can be used to study e.g., vestibular sensory representation and processing, while the closed-loop mode allows animals to navigate in rotational space, providing a better substrate for 2-D navigation in virtual environments. The full build documentation is maintained at https://ranczlab.github.io/RPM/.

Closed-Loop Cavity Shear Layer Control Using Plasma Dielectric Barrier Discharge Actuators

The complex unsteady flow in cavities leads to the formation of large-scale disturbances in the shear layer. Natural closed-loop mechanisms provoke a dramatic increase in pressure pulsations and aerodynamic noise. This paper presents the experimental study of pressure fluctuations in closed-loop control in rectangular cavities using plasma dielectric barrier discharge. The flow velocity was 37 m/s, and the Reynolds number based on a cavity depth was approximately 120,000. The discharge ignition near the leading edge of the cavity provoked the shear layer restructuring. It was found that pressure fluctuations with an amplitude of 120 dB occur at frequencies 480 and 820 Hz. Frequency modulation of the discharge at resonant peaks was carried out by changing the phase shift of the power supply. The peak amplitude was reduced or increased by phase shifts from natural disturbances to forced ones. The optimum energy input was 50 W/m. This was three times less than the power consumption of the open-loop mode. The PIV visualization was organized in the phase-locked mode. The pressure spectrum corresponds to the magnitude of coherent structures in the shear layer of the cavity.