Fast System Response Research Articles

Experimental validation of model-free predictive control based on the active vector execution time for grid-connected system

The application of Model-Free Predictive Control (MFPC) in power electronic systems has garnered increasing attention. In this paper, MFPC control based on replacing the classical factory model with an ultra-local model (ULM) is studied. Generally, the Integral Sliding Mode Observer (ISMO) is used to estimate the unknown part in the ULM where the non-physical factor in the ULM is selected with approximate values ​​ranging from the nominal value of the system which is contrary to the concept of MFPC control. In this research, an improved adaptive integral sliding mode observer (AISMO) based MFPC (AISMO-MFPC ) is proposed to estimate this factor with the unknown function in the ULM equation. The new observer design enables the estimation of this factor based on the current error, which allows for independent prposedcontrol of the system parameters.To obtain the lowest current ripple, the concept of active vector execution time (AVET ) has been incorporated into the proposed control where two vectors are selected in the sampling period to minimize the cost function instead of selecting a single vector. ULM is also used to calculate AVET which facilitates the implementation of the imposed control. The combination of the proposed AISMO-MFPC and AVET gives faster system response and reduces the current ripple and lower harmonics, especially in case of mismatch parameters. Finally, the effectiveness of the proposed control is confirmed under various conditions by the presented simulation and experimental results.

Incremental Nonlinear Dynamics Inversion Control with Nonlinear Disturbance Observer Augmentation for Flight Dynamics

A flight controller formulation based on incremental nonlinear dynamics inversion (INDI) control with nonlinear disturbance observer (NDO) is proposed. INDI control is a nonlinear controller based on incremental dynamics. Aimed to attain robustness for nonlinear dynamics inversion (NDI)-based controller, incremental dynamics are derived using the first-order Talyor series expansion to nonlinear systems. The incremental dynamics-based controller requires information on state derivative terms to strengthen the robustness property of the nonlinear controller. The proposed controller utilizes the first-order low-pass filter to obtain the state derivative estimate to implement incremental dynamics into the system. Because the incremental form creates uncertainty term which is an aftermath of the Taylor series expansion, the proposed controller adopts the NDO to eliminate this effect. The controller is applied to the generic transport model which was developed by NASA for simulation purposes. The proposed NDO-based INDI control underwent simulations, together with an INDI controller without disturbance observer, and showed that the developed method results in better performances, providing important advantages where it compensates the uncertainties, removes the steady-state error, and shows less oscillating longitudinal body rate response than the baseline controller, desirable for aerodynamics applications with faster system response.

Extreme learning machine‐based super‐twisting integral terminal sliding mode speed control of permanent magnet synchronous motors

AbstractThis article proposes an extreme learning machine (ELM)‐based super‐twisting integral terminal sliding mode control (STITSMC) for speed regulation of a permanent magnet synchronous motor (PMSM). First, the PMSM is modeled in a non‐cascade control structure for fast system response and uncertainty compensation in the speed and torque loops. Second, the STITSMC is designed with integral actions in both the sliding surface and the reaching law to reduce chattering. Third, the ELM is constructed to compensate for the system lumped disturbance, and relax the disturbance upper bound required by the controller which further reduces the chattering. Fourth, the stability of the whole control system is proved based on the Lyapunov method and the finite time convergence regions are derived for both the reaching and the sliding phases. Finally, the comparative simulations and experiments are conducted to show the superiority of the proposed control.

Cuffless Wearable Sphygmomanometers Using Dual Digital Optical Frequency Combs in Chalcogenide Chips

AbstractSphygmomanometers typically use a rubber cuff around the upper arm to measure blood pressure, but this method can be uncomfortable. Thus, cuffless sphygmomanometers for continuous blood pressure monitoring in emergencies and healthcare are desirable. While electrical and optical blood pressure sensors offer high sensitivity, they often face issues like limited pressure range, temperature drift, slow response, and wearability problems. To tackle these limitations, the study designs a unique cuffless wearable blood pressure sensor (12 mm × 2 mm × 0.5 mm) featuring two original components: a GeSbS/AsS chalcogenide dual‐microring chip for high sensitivity, and a dual digital optical frequency comb (DDOFC) system for fast response and cost‐effective detection. The sensor is comparable to reported electrical and optical blood pressure sensors in its detection limit (23 Pa) but has a ten‐times faster response rate (2 kHz), a 1000‐times longer stable operation (>4.3 × 107 cycles), and a well‐compensated temperature drift (<0.012 pm/°C) that eliminates the need for temperature control. This innovation shows promise for wearable electronics and mobile healthcare, enabling the capture of critical cardiovascular details for applications like in‐surgery monitoring, orthostatic hypotension studies, and early detection of myocardial ischemia and strokes.

A high-frequency reduced-order model for parameters optimization of AC/DC distribution systems considering random disturbances

Accompanying the rapid development of AC/DC distribution systems, along with the random disturbances introduced by a significant number of distributed generations and loads, the difficulty of system stability analysis has increased. The phenomenon of DC bus voltage instability has become severe, affecting the safe and stable operation of power systems. This paper focuses on the research of multi-terminal AC/DC distribution systems. A reduced-order method for multi-terminal distribution systems is proposed. Through parameter equivalent transformation, the system model is simplified while maintaining its dynamic characteristics. Parameter sensitivity analysis is utilized to identify key parameters influencing the system’s dynamic behavior, achieving an analytical expression of the system’s dynamic characteristics. And stability domain analysis is applied to delineate the variations in system dynamic behavior and responses to random disturbances under different parameter settings. Then a multi-parameter optimization method is designed to enhance system stability while achieving fast system response. Finally, theoretical analysis is validated through software simulation and hardware-in-the-loop experiments.

ENHANCED MODEL-FREE PREDICTIVE CONTROL FOR VOLTAGE SOURCE INVERTERS USING AN ADAPTIVE OBSERVER

In this paper, a free model predictive control based on the active vector execution time (AVET-MFPC) using an adaptive observer is proposed for two-level voltage source inverters. The traditional model-free predictive control (MFPC) uses the sampling period to select one voltage vector for all candidate vectors according to the minimizing cost function principle. With the proposed control, two vectors are selected at one sampling period. The first vector is an active vector that uses the execution time of the active vector to select it, while the second one is a zero vector as it is applied after the active vector. The execution time is calculated using the ultra-local model (ULM) equation. In the traditional MFPC, the factor in the ULM is chosen with approximate values ranging between ±50 % of the nominal value. This paper proposes an adaptive sliding mode observer (ASMO) with an improved design to observe the variation of this factor, especially in case of mismatch parameters and during a step change in the reference signal. Combining the proposed ASMO observer and the AVET-MFPC controller gives faster system response, good tracking results, and less computational burden. Finally, the effectiveness of the proposed control model is approved and confirmed under various conditions, as well as the simulations carried out and the results obtained.

A new hybrid fixed and adaptive gains control algorithm to reduce power losses on LLCL filter-based renewable energy conversion systems with systematic parametrization using Grey Wolf optimizer

Currently, there is a transition in the energy matrix around the world, where traditional sources of energy generation are continually being replaced by energy generation systems based on renewable sources to mitigate the climate crisis. In this bias, this work presents the mathematical modeling of an LLCL filter, used to connect power generation systems based on renewable energy sources to the electrical grid, and presents a novel hybrid fixed-and adaptive gains control strategy for current injection into the grid using this system. The developed hybrid controller is composed of a proportional–integral controller and a direct robust adaptive controller. The first term of the controller guarantees the reference current, while the second term of the controller is used for disturbance rejection. Furthermore, a systematic procedure for the controller’s parametrization based on Grey Wolf Optimizer is also provided. The control of the current injected into the grid is carried out considering the LLCL filter without passive damping resistors in the filter structure to avoid power losses due to the passive filter elements. Additionally, the LLCL filter model considers minimal parasitic resistances to evaluate the controller’s performance and optimize it for the application of interest, aiming to maximize the system performance by ensuring a short transient regime due to the fast closed-loop system response. Simulation results indicate high performance of this optimized control strategy with small tracking error even considering grid impedance variations.

Stability of Bipolar Plates in Proton Exchange Membrane Water Electrolysis: Dissolution Studies of Titanium and Stainless Steel

Due to its high current densities and fast system response proton exchange membrane water electrolysis (PEMWE) is an ideal system for green hydrogen production from renewable energies. However, its widespread use is still hindered by the high costs rendering the produced green hydrogen not competitive. Therefore, a cost reduction is highly needed. The bipolar plates (BPPs) are causing a colossal factor in material costs. They are usually produced from titanium and coated with even more expensive materials such as gold or platinum. A possible, cheaper alternative is stainless steel. However, it is suspected to suffer from corrosion leading to the leaching of cations that can poison the catalyst or membrane.[1] Thus, we investigated the stability of BPP materials, the currently used titanium, and its cheaper alternative stainless steel (316L).[2] Therefore, we use a modified scanning flow cell setup coupled to an inductively coupled plasma mass spectrometer for investigating the stability of both materials on-line, as well as with scanning electron microscopy. To mimic the conditions at the BPP under operation, deionized (DI) water and highly diluted (0.5 mM) H2SO4 are chosen as electrolytes combined with a sample temperature of 60 °C.For Ti, we show that the dissolution is negligible, whereas 316L corrodes. For 316L, in DI water mainly Cr dissolves, while in the H2SO4 solution, the dissolution is more pronounced, and all alloy components are detected. Besides the pH value, the applied potentials play a crucial for its stability. However, our findings suggest that the contamination for a typical full cell architecture remains below 1 ppm, even for the highest measured dissolution rate of SS 316L.These capabilities of on-line high-throughput stability tests for BPP materials are, furthermore, used to investigate the influence of contaminations, such as F- or Cl-, and of the temperature-dependence on the stability of 316L. These results give further insights into 316L stability as BPP material and therefore contribute to the development towards cost-effective PEMWE.[1] a) N. Rojas, M. Sánchez-Molina, G. Sevilla, E. Amores, E. Almandoz, J. Esparza, M. R. Cruz Vivas, C. Colominas, Int. J. Hydrogen Energy 2021, 46, 25929-25943; b) H. Becker, J. Murawski, D. V. Shinde, I. E. L. Stephens, G. Hinds, G. Smith, Sustain. Energy Fuels 2023, 7, 1565-1603.[2] L. Fiedler, T. C. Ma, B. Fritsch, J. H. Risse, M. Lechner, D. Dworschak, M. Merklein, K. J. J. Mayrhofer, A. Hutzler, ChemElectroChem 2023, e202300373. Figure 1

Toothpick DNA extraction combined with handheld LAMP microfluidic platform for simple and rapid meat authentication

Adulteration of meat is a global issue, necessitating rapid, inexpensive, and simple on-site testing methods. Therefore, the present study aimed to develop a one-minute toothpick-based DNA extraction method, a handheld microfluidic chip, and a smartphone-controlled portable analyzer for detecting multiple meat adulterations. A toothpick was inserted into the meat to promote DNA release and adsorption. Furthermore, a handheld microfluidic chip was designed for DNA elution on toothpicks and fluid distribution. Finally, a smartphone-actuated portable analyzer was developed to function as a heater, signal detector, and result reader. The portable device comprises a microcontroller, a fluorescence detection module, a step scanning unit, and a heating module. The proposed device is portable, and the app is user-friendly. This simple design, easy operation, and fast-response system could rapidly detect as little as 1% of simulated adulterated samples (following UK standards) within 40 min at a cost of less than USD 1 per test.

Reversibility of seawater intrusion in a coastal aquifer: Insights from long-term field observation and numerical modeling

It is essential to understand basis processes affecting the reversibility of seawater intrusion (SWI) and the related timescale after groundwater pumping stopped for coastal groundwater management. Groundwater salinity variations presented by previous studies showed a fast SWI process and the following seawater retreat (SWR) process indicated by overall salinity decrease in the coast karst aquifer in the Dalian Peninsula, northeast China. Cross-sectional variable-density flow and transport simulations using equivalent porous medium (EPM) model, dual-domain (DDM) model and the EPM with a single discrete feature representative of conduit flow (EPM-DF) are conducted to understand the SWI reversibility related to the characteristics of the flow system, including aquifer parameters and seaside boundary conditions. Large dispersity combined with a low salinity concentration at the sea boundary are necessary in the EPM and DDM models to produce a fast SWI and low salinity concentration as observed. The enhanced dispersion in the DDM model enhances the mixing in the transition zone (TZ) and produces more obvious seasonal variation but longer SWR process compared to the EPM model. The EPM-DF model produces significant salinity seasonal variation during the SWI process and a fast decrease in the SWR process. The overall fast system response but low peak concentration during the SWI might be attributed to the highly heterogeneous characteristics of the karst aquifer system, which produces a wide front edge of TZ as observed. The dispersion-dominated EPM and DDM models produced higher degree of SWI reversibility compared to the EPM-DF model, as indicated by the weaker lag effects between groundwater levels and salinity concentration. Moreover, the SWI reversibility may arise not only from the heterogeneous characteristics of the karstic aquifer system but also from the rate for rise in the inland groundwater level during the seasonal variation cycle. An overall SWR process can be divided into two stages: the first stage with rapid decrease in salinity concentration but small changes in toe associated with TZ widening and the second stage with rapid toe retreat during aquifer flushing. The flushing of the brine leakage from the solar salt field may extend the SWR process. Considering this relatively longer water quality response time than the time span in general groundwater management plans, a reasonable objective and how maintain the hydraulic head during the SWI controlling have been of a great concern to the coastal groundwater management.

Research on linear/nonlinear active disturbance rejection switching control of PMSM speed servo system

An improved linear/nonlinear active disturbance rejection switching control strategy is proposed to enhance the dynamic response and disturbance suppression capabilities of the permanent magnet synchronous motor (PMSM) speed servo system. Firstly, facilitated by a tracking differentiator, rapid setpoint tracking is achieved without speed overshoot, effectively addressing the inherent conflict between fast system response and overshooting. Secondly, weight factors are introduced into the control law, and a novel switching criterion based on the step function is designed, enabling the system to smoothly transition between operating modes in the presence of disturbances with varying amplitudes. This facilitates accurate estimation and swift compensation for disturbances, thereby enhancing control precision and robustness. Additionally, a frequency domain analysis of the extended state observer is conducted, leading to the formulation of a parameter tuning scheme for the controller. Lastly, simulation tests validate the feasibility and effectiveness of this strategy as a PMSM speed controller. The system exhibits superior dynamic tracking and disturbance suppression performance over a wide speed range.

Adaptive fast trajectory tracking control for the airship based on prescribed performance

A fast trajectory tracking controller is designed for the airship, involving dynamic uncertainties of parameters, capable of guaranteeing the prescribed performance of tracking errors, and fast response of the closed-loop system. To achieve the decoupling of velocity control and attitude control of the airship, a new guidance and control integration framework is proposed first. Then, based on the dynamics model established by the spinor method, the lumped disturbance, caused by unknown aerodynamic parameter uncertainties and exogenous disturbances, is estimated online using a high-order finite-time observer. The control performance, namely, overshoot and steady-state performance of tracking errors, is significantly improved by utilizing the prescribed output performance constraints, while the convergence rate is further enhanced by combining the finite-time convergence property of the fast terminal sliding mode control. Simulation results attest to the effectiveness of the strategy in this paper. Compared with the adaptive fast terminal sliding mode control, the strategy effectively utilizes the capability of the actuator within the allowed range and reduces the convergence time by more than half with similar control inputs.

Synergistic Integration of Advanced Control Strategies for Comprehensive PID Controller Tuning using MATLAB

This study investigates the impact of Proportional-Integral-Derivative (PID) tuning on system performance through comprehensive measurements before and after tuning. The parameters analyzed include rise-time, settling-time, overshoot, undershoot, and peak time. Prior to tuning, the system exhibited significant deficiencies, characterized by prolonged rise and settling times, substantial overshoot and undershoot, and extended peak time. Following PID tuning, notable improvements were observed across all parameters. The rise time and settling time were dramatically reduced, indicating a faster system response and improved stability. Moreover, overshoot and undershoot were effectively minimized, leading to greater accuracy and precision in the system's output. These findings underscore the efficacy of PID tuning in optimizing system performance and achieving desired control objectives.

Augmented Finite Control Set MPC Design Technique for Wide Speed Range Control of Permanent Magnet Synchronous Motor Drives

The effective motion control task is highly influencing the final drive performance in wide-range motor drives applications such as electric vehicles (EVs), washing machines, compressors, elevators and lathe machines. Recently, permanent magnet synchronous motor (PMSM) drive has been widely employed in these applications to achieve desired performances such as high efficiency, high torque requirements with minimum size “occupancy”. The PMSM drive features combining with these modern drive applications are highly nonlinear and the desired operation requirements demand high-performance control schemes with fast system response and robustness features. Linear control schemes are usually implemented to drive the PMSM that entail trade-offs between drive performance and simplicity in control implementation. Therefore, this paper presents the nonlinear control technique based on augmented finite control set (AFCS) model predictive control (MPC) scheme (AFCS-MPC). The proposed AFCS-MPC scheme enhances the standard MPC design by augmenting the nonlinear characteristics of the PMSM drive to achieve wide speed range drive performance under both steady-state and dynamic operating conditions. Comparative performance studies have been conducted and presented to confirm the efficacy of the proposed scheme.

Handheld motorized injection system with fiber-optic distance sensors and adaptive time-delay controller

During the last decade, many ophthalmic therapeutic drugs have been clinically approved, and intraocular injection has been a common surgical intervention. Injecting drugs directly into the subretinal space is crucial to treat retinal complications effectively. Here, we report a handheld microinjector with two fiber-optic distance sensors and time-delay control (TDC) to mitigate nonlinear disturbances during the injection task. The conventional method exhibited a cosine error of approximately 77 μm at an angle of 45°, whereas our proposed needle reduced measurement errors to ∼6 μm. Also, TDC-based position regulation is designed to adaptively apply motor inputs by estimating disturbances during the handheld task and achieving fast system responses with minor control errors. Phantom studies show a maximum reduction of 26.5% in root-mean-square error (RMSE) compared to the existing approach. Moreover, ex-vivo experiments demonstrated superior and robust injection performance, resulting in an injection RMSE of 10.3 μm.

Working Performance Improvement of a Novel Independent Metering Valve System by Using a Neural Network-Fractional Order-Proportional-Integral-Derivative Controller

In recent years, reducing the energy consumption in a hydraulic excavator has received deep attention in many studies. The implementation of the novel independent metering valve system (NIMV) has emerged as a promising solution in this regard. However, external factors such as noise, throttling loss, and leakage have negative influences on the tracking precision and energy saving in the NIMV system. In this paper, a novel control method, simple but effective, called a neural network-fractional order-proportional-integral-derivative controller is developed for the NIMV system. In detail, the fractional order-proportional-integral-derivative (FOPID) controller is used to improve the precision, stability, and fast response of the control system due to the inclusion of non-integer orders in the proportional, integral, and derivative terms. Along with that, the auto-tuning algorithm of the neural network controller is applied for adjusting five parameters in the FOPID controller under noise, throttling loss, and leakage. In addition, the proposed controller alleviates the amount of calculation for the system by using model-free control. To verify the effectiveness of the proposed controller, the simulation and experiment are conducted on the AMESim/MATLAB and a real test bench. As a result, the proposed controller not only operates the NIMV system accurately in the target trajectory but also reduces energy consumption, saving up 23.33% and 29.25% compared to FOPID and PID in the experimental platform, respectively.

Variable Flux Direct Torque Control System of Switched Reluctance Motor

Direct Torque Control (DTC) strategy is very suitable for controlling Switched Reluctance Motors (SRM) due to its advantages of the simple control structure and fast system response, etc. This paper first analyzes the principle of DTC and establishes the DTC model of three-phase 6/4 SRM by Matlab/Simulink. In this paper, a three-closed-loop variable flux DTC system with velocity as the given quantity is constructed to solve the problem that the stator current of constant flux DTC is too large when the motor is in a steady state. The simulation results show that the variable flux DTC system has a better inhibition effect on the stator current and torque ripple of SRM than the conventional DTC system.

Robocentric Model-Based Visual Servoing for Quadrotor Flights

This article proposes a robocentric formulation for quadrotor visual servoing. This formulation presents the task-specific state dynamics of the quadrotor in its body reference frame. Compared with other visual servoing methods, our method allows tightly and integrated state estimation and control on the same robocentric model, and allows a faster system response in aggressive quadrotor flights. On the theory level, we prove the controllability and observability of the proposed robocentric model. Then, we design an on-manifold Kalman filter for the estimation and an on-manifold iterative model predictive control for motion planning and control. We verify our proposed formulation and controller in two crucial quadrotor flight tasks: 1) hovering; and 2) dynamic obstacle avoidance. Experiment results show that the quadrotor is able to resist large external disturbances and recover its position and orientation from two reference visual features. Moreover, the quadrotor is able to avoid dynamic obstacles reliably at a relative speed up to 7.4 m/s, demonstrating the effectiveness of our visual servoing methods in agile quadrotor flights.

Practical deadbeat MPC design via controller matching with applications in power electronics

Several applications, including power electronics and electrical machines, require a fast system response, which is typically achieved via deadbeat control. Hence, there has been an interest in developing model predictive control (MPC) algorithms with deadbeat control properties, i.e., finite-time convergence to a set-point, for power electronics applications. In this paper, we design a practical deadbeat MPC via controller matching. We make use of an existing result for tuning the weight matrices of the MPC cost function such that the corresponding unconstrained MPC solution matches a desired deadbeat controller. This approach allows for a positive definite input weight matrix and provides stability and recursive feasibility guarantees for the resulting MPC controller. We additionally propose a vertex relaxation of the matching problem, which reduces conservatism, and a method for enlarging the terminal set of the deadbeat MPC controller. Three benchmark examples from the power electronics field are used to show the effectiveness of the proposed MPC design.

A Versatile Semiactive Electrically Interconnected Suspension With Heave-Roll Vibration Decoupling Control

This paper develops a versatile electrically interconnected suspension (EIS) system with variable inertance and variable damping (VIVD) in the heave direction and variable stiffness (VS) in the roll direction for vehicles to improve ride comfort. The conventional hydraulicly interconnected suspensions have been utilized to improve ride comfort and prevent rollover, while such a hydraulic system results in more design complexity, maintenance, and cost. The EIS can achieve the suspension interconnection electrically and offer more design flexibility, energy efficiency, and faster system response. The proposed EIS comprises two electromagnetic dampers (EMDs), which are interconnected by an electrical network (EN) with controllable resistors, capacitors, and inductors, enabling the suspension to generate VIVD and VS characteristics in heave and roll, respectively. The system only requires energy for controlling electronic switches, which is low and efficient. Then, a decoupling semi-active control strategy based on <inline-formula><tex-math notation="LaTeX">${\mathbf{H}}_\infty $</tex-math></inline-formula> controller is proposed to mitigate the heave and roll vibration. Moreover, a half-car test rig is developed to evaluate the vibration control performance of the proposed EIS system by conducting a series of comprehensive tests. As a result, the EIS has a significant improvement in performance than a passive suspension. The versatile EIS has reduced the resonance by 13.0&#x0025; compared to non-versatile EIS. The proposed versatile EIS system has great potential in practical application.