Dynamic Response Requirements Research Articles

Feedforward Control Strategy of a DC-DC Converter for an Off-Grid Hydrogen Production System Based on a Linear Extended State Observer and Super-Twisting Sliding Mode Control

With the large-scale integration of renewable energy into off-grid DC systems, the stability issues caused by their fluctuations have become increasingly prominent. The dual active bridge (DAB) converter, as a DC-DC converter suitable for high power and high voltage level off-grid DC systems, plays a crucial role in maintaining and regulating grid stability through its control methods. However, the existing control methods for DAB are inadequate: linear control fails to meet dynamic response requirements, while nonlinear control relies on detailed model structures and parameters, making the control design complex and less accurate. To address this issue, this paper proposes a feedforward control strategy for a DC-DC converter in an off-grid hydrogen production system based on a linear extended state observer (LESO) and super-twisting sliding mode control (STSMC). Firstly, a reduced-order simplified model of the DAB was constructed through the structure of DAB. Then, based on the reduced-order simplified model, a feedforward control based on LESO and STSMC was designed, and its stability was analyzed. Finally, a simulation comparison of PI, LESO + terminal sliding mode control (TSMC), and LESO + STSMC control methods was conducted in a DC off-grid hydrogen production system. The results verified the proposed control method’s enhancement of the DAB’s rapid dynamic response capability and the system’s transient stability.

Network reliability evaluation and management science applications in resource allocation for police organizations

The effective allocation of resources within police patrol departments is crucial for maintaining public safety and operational efficiency. Traditional methods often fail to account for uncertainties and variabilities in police operations, such as fluctuating crime rates and dynamic response requirements. This study introduces a fuzzy multi-state network (FMSN) model to evaluate the reliability of resource allocation in police patrol departments. The model captures the complexities and uncertainties of patrol operations using fuzzy logic, providing a nuanced assessment of system reliability. Virtual data were generated to simulate various patrol scenarios. The model’s performance was analyzed under different configurations and parameter settings. Results show that resource sharing and redundancy significantly enhance system reliability. Sensitivity analysis highlights critical factors affecting reliability, offering valuable insights for optimizing resource management strategies in police organizations. This research provides a robust framework for improving the effectiveness and efficiency of police patrol operations under conditions of uncertainty.

Depth Control of an Underwater Sensor Platform: Comparison between Variable Buoyancy and Propeller Actuated Devices.

Underwater long-endurance platforms are crucial for continuous oceanic observation, allowing for sustained data collection from a multitude of sensors deployed across diverse underwater environments. They extend mission durations, reduce maintenance needs, and significantly improve the efficiency and cost-effectiveness of oceanographic research endeavors. This paper investigates the closed-loop depth control of actuation systems employed in underwater vehicles, focusing on the energy consumption of two different mechanisms: variable buoyancy and propeller actuated devices. Using a prototype previously developed by the authors, this paper presents a detailed model of the vehicle using both actuation solutions. The proposed model, although being a linear-based one, accounts for several nonlinearities that are present such as saturations, sensor quantization, and the actuator brake model. Also, it allows a simple estimation of the energy consumption of both actuation solutions. Based on the developed models, this study then explores the intricate interplay between energy consumption and control accuracy. To this end, several PID-based controllers are developed and tested in simulation. These controllers are used to evaluate the dynamic response and power requirements of variable buoyancy systems and propeller actuated devices under various operational conditions. Our findings contribute to the optimization of closed-loop depth control strategies, offering insights into the trade-offs between energy efficiency and system effectiveness in diverse underwater applications.

Incorporating Incremental Conductance MPPT Techniques into Solar Power Extraction

Research into alternative, green energy sources such as solar power has been driven by concerns about environmental sustainability, escalating petroleum costs, and surging energy demand. Solar energy can power the entire world sustainably, since it is abundant and easy to access. Solar radiation, cell temperature, and load impedance all play a part in improving the efficiency of solar energy utilization. In order to maximize solar energy utilization, Maximum Power Point Tracking (MPPT) techniques are used. In order to address factors such as solar effectiveness, dynamic response, convergence speed, complexity, cost, and sensor requirements, different MPPT techniques have been developed. Using Incremental Conductance (INC) as an example, this paper provides a comprehensive overview of MPPT techniques. P&O’s drawback of oscillations around the Maximum Power Point (MPP) is overcome by INC, which minimizes them. The MPP voltage is maintained until the incremental conductance equals zero by comparing the instantaneous conductance of the panel with the incremental conductance. In addition to being easy to implement, INC-based methods offer rapid tracking and efficiency gains. Results from simulations demonstrate INC MPPT’s effectiveness in maximizing power extraction from photovoltaic systems, especially when environmental conditions change rapidly.

Actuation delay compensation of robots in semi-physical test.

In general, the traditional spacecraft semi-physical docking tests include the evaluation of docking and separation performance. However, these tests often rely on "specific" equipment, such as specially designed actuators and fast-response hydraulic systems, to meet the stringent dynamic response requirements of semi-physical testing. In this paper, a novel docking test platform is designed based on a general-purpose industrial manipulator using 3-D force and 3-D torque sensors. Different from the traditional solution, this novel platform is well-assembled and cost-effective. Furthermore, an actuation delay compensation method is introduced to improve the performance. Finally, the proposed method is evaluated using simulations. The results show that the novel method is with promising performance in terms of actuation delay compensation.

A Dynamic Decoupling Control Method for PMSM of Brake-by-Wire System Based on Parameters Estimation

Brake-by-wire (BBW) system is a basic and significant component for intelligent vehicles and electric vehicles. During autonomous emergency braking process, the dynamic response requirement of the BBW actuator motor is very high. Hence, a dynamic decoupling control method is proposed for permanent magnet synchronous motor (PMSM) of BBW system to improve the dynamic response performance. First, a PMSM dynamic model and a thermodynamic model of stator winding are built. Then, the inductance and flux linkage parameters are identified based on recursive least squares and the back electromotive force formula, and an accurate relationship between inductance and flux linkage parameters and motor temperature is obtained. Finally, a dynamic decoupling control method based on the intensive binary dichotomy table method is designed. The results both of simulations and experiments show that the proposed method shorten the boost time by 18.30%, thereby reducing the braking time by 9.63%.

Performance up gradation of static VAR compensator with thyristor binary switched capacitor and reactor using model reference adaptive controller

There are various static var compensator configurations are available and listed in the literature. Their performances are evaluated based on their voltage support, dynamic response, losses, cost, and additional filter requirement, if any. In this paper, efforts are made to improve the dynamic performance parameter such as rise time, settling time, and peak overshoots. A new topology with an adaptive controller is presented, in which capacitor and reactor banks are divided in their binary values and connected in the shunt. Capacitor and reactor banks are operated by thyristorised switches. Both these banks are operated in closed-loop form as a cascade control. Amongst these, capacitor bank operates as coarse control, and reactor bank acts as fine control. For the performance enhancement, a model reference adaptive controller is used. The system identification toolbox is used to evaluate the mathematical model of the plant with Matlab. The model's performance was analyzed deeply by the adaptive controller with different reference models such as critical, under, and overdamped. The performance parameters such as rise time, settling time, and peak overshoot in the form of reactive power swings, are evaluated and plotted for different adaptive gains using MIT rules. Abbreviations: : Peak overshoot; : Reactive power of capacitor; : Reactive power of inductor; : Reactive power of TBSC bank; : Reactive power of TBSR bank; : Rise time; : Settling time; e: Error; Gc(s): Transfer function of TBSC plant; Gl(s): Transfer function of Disturbance plant; Gr(s): Transfer function of TBSR plant; SVC: Static VAR Compensator; t:time; TBSC: Thyristor binary switched capacitor; TBSR: Thyristor binary switched reactor; TSC: Thyristor switched capacitor; TSR: Thyristor switched reactor; u(t): System input; v(t): System disturbance; y(t): System output; Ym: Reference model output; Yp: Plant output; γ: Adaptive gain; θ: Theta

Technical strategies for effective development and gas recovery enhancement of a large tight gas field: A case study of Sulige gas field, Ordos Basin, NW China

Abstract Based on the analysis of influencing factors of tight gas recovery and reservoir geological characteristics, the types of remaining tight gas reserves in the Sulige gas field are summarized from the perspective of residual gas genesis to estimate residual gas reserves of different types and provide corresponding technical strategies for enhancing gas recovery. The residual gas reserves in the Sulige gas field can be divided into four types: well pattern uncontrollable, horizontal well missing, imperfect perforation, blocking zone in composite sandbodies. Among them, the uncontrolled remaining gas of well pattern and blocking zone in composite sandbodies are the main body for tapping potential and improving recovery factor, and well pattern infilling adjustment is the main means. Taking into account reservoir geological characteristics, production dynamic response and economic benefit requirements, four methods for infilling vertical well pattern, i.e., quantitative geological model method, dynamic controlled range of gas well method, production interference method and economic and technical index evaluation method, as well as a design method of combined vertical well pattern with horizontal well pattern are established. Under certain economic and technological conditions, the reasonable well pattern density of enrichment zone of gas field is proved to be 4 wells per square kilometers, which can increase the recovery rate of the gas field from 32% to about 50%. Meanwhile, five matching techniques for enhancing gas recovery aimed at interlayer undeveloped residual gas have been formed, including tapping potential of old wells, technological technology optimizing of new wells, rational production system optimizing, drainage and gas producing, and reducing waste production, which could increase the recovery rate for 5% based on well pattern infilling. The research results provide effective support for the long-term stable production of 230×108 m3/a of the Sulige gas field and production growth in the Changqing gas area.

Dynamic and static performance optimization of dual active bridge DC-DC converters

High efficiency and fast dynamic response are two main control objectives for dual active bridge (DAB) DC-DC converters. Traditional extended phase shift (EPS) control can significantly enhance the conversion efficiency of DAB DC-DC converters by reducing current stress; however, it cannot fulfill fast dynamic response requirements. In this paper, a novel hybrid control scheme consisting of EPS control and direct power control (DPC), named as EPS-DPC, is proposed. EPS-DPC control has salient features in both efficiency and dynamic performance. In order to verify the outstanding performance of the proposed EPS-DPC scheme, an experimental comparison was carried out on a scale-down DAB DC-DC converter among several control strategies, including single phase shift control with traditional voltage-loop (SPS-TVL), EPS control with traditional voltage-loop (EPS-VTL), and EPS-DPC. Experimental results have been high consistent with theoretical analysis, and verified these advantages of the proposed EPS-DPC scheme.

Design Considerations for Output Capacitance Under Inductance Mismatches in Multiphase Buck Converters

Interleaving is a technique that is commonly used due to its inherent reduction of current ripple and filter capacitance size. However, optimal interleaving is only achieved when the switching cells are identical. Variations of the filter inductance, which are caused by the manufacturing process or magnetic material properties, may lead to the total current ripple of all phases significantly larger than that of the ideal case in steady state, and slow down the energy transfer speed during the transient response. Consequently, in order to meet the voltage ripple and dynamic response requirements of multiphase converters, the calculation of the output capacitor under inductance mismatches has to be reconsidered, which has been rarely mentioned previously. This paper proposes a method to estimate the effect of inductance mismatches on output capacitance selection from two aspects including steady state and transient state. The proposed methodology enables mathematical expressions that allow us to calculate the maximum value of the capacitor considering nonidealities. Monte Carlo simulation is also used during the analysis by varying all of the inductors’ values with respect to tolerance and distribution type to identify the worst case values in real applications, according to this approach, the principle of when the worst condition happens is summarized. Simulated and experimental results of a four-phase buck converter are presented in this study. Good agreement between the estimates and the measured values is demonstrated.

Efficient Voltage Regulation for Microprocessor Cores Stacked in Vertical Voltage Domains

Due to exponential (Moores law) scaling of advanced CMOS technologies, the challenges associated with delivering power to performance and mobile computing systems are outpacing the capabilities of conventional voltage regulator (VR) topologies. To continue to scale throughput at constant power density, the level of parallelism in microprocessor architectures is expected to increase substantially. In this paper, we present a power conversion topology to provide independent multicore regulation in the 0.8–1.4 V range from a 12-V dc bus. The topology uses a multistage ladder converter to manage power delivery to digital circuits stacked in vertical voltage domains. This approach has several advantages with regard to systems efficiency as it allows a more moderate conversion ratio of the main dc–dc converter. Moreover, the parallel converter only needs to process a fraction of the power of each core as the current can be “recycled” by adjacent cores in the stack. We develop a dynamical model for a multiple-input, multiple-output control scheme that uses a simple integral-control law, augmented with fast voltage- and current-mode feedforward. Measurement results of a discrete prototype verify the control scheme and demonstrate the potential advantages in system efficiency but also emphasize the remaining challenges in meeting stringent VR dynamic response requirements.

Dynamic reliability based design optimization of the tripod sub-structure of offshore wind turbines

This work presents an efficient methodology for the Reliability Based Design Optimization (RBDO) of the tripod sub-structure of offshore wind turbines considering dynamic response requirements. The cost of supporting structure of offshore wind turbines is so high that optimization in the design stage is a basic requirement. Traditional design optimization methodology for offshore structures uses deterministic modeling. However, the existence of uncertainties, such as manufacturing tolerances, material properties, and environmental loads, requires a probabilistic optimization technique. Uncertainties in the offshore wind turbines design process may have a strong effect on its dynamic responses but very little researches have been conducted to incorporate the uncertainty property into design optimization of the supporting structures. In this study, a framework of a dynamic reliability based design optimization for tripod sub-structures was proposed. Firstly, a Finite Element (FE) model of a tripod sub-structure of the NERL 5 MW wind turbine was constructed for dynamic response analysis in time domain and generating several accurate sampling points. Secondly, an efficient approximate model was built utilizing these sampling points to replace the original time consuming dynamic response analysis of FE model. At last, this approximate model was used during the optimum iterative procedure with a global optimization algorithm to gain the final best design point considering uncertainties. In this optimization methodology, some sizes of structural components, applied loads, and some material properties are considered as random variables. The structural stress and natural frequency are considered as constraints and the weight of the structure is considered as the objective function. The reliability of the structure is finally determined through Monte Carlo simulations. The results show that the proposed methodology can obtain a reliable design with better dynamic performance and less weight. Compared with the deterministic optimization, the presented dynamic Reliability Based Design Optimization of tripod sub-structure of offshore wind turbines is more rational and practical and this efficient methodology can be applied in the design of other similar offshore structures.

A High-Performance SPWM Controller for Three-Phase UPS Systems Operating Under Highly Nonlinear Loads

This paper presents the design of a high-performance sinusoidal pulsewidth modulation (SPWM) controller for three-phase uninterruptible power supply (UPS) systems that are operating under highly nonlinear loads. The classical SPWM method is quite effective in controlling the RMS magnitude of the UPS output voltages. However, it is not good enough in compensating the harmonics and the distortion caused specifically by the nonlinear currents drawn by the rectifier loads. The distortion becomes more severe at high power where the switching frequency has to be reduced due to the efficiency concerns. This study proposes a new design strategy that overcomes the limitations of the classical RMS control. It adds inner loops to the closed-loop control system effectively that enables successful reduction of harmonics and compensation of distortion at the outputs. Simulink is used to analyze, develop, and design the controller using the state-space model of the inverter. The controller is implemented in the TMS320F2808 DSP by Texas Instruments, and the performance is evaluated experimentally using a three-phase 10 kVA transformer isolated UPS under all types of load conditions. In conclusion, the experimental results demonstrate that the controller successfully achieves the steady-state RMS voltage regulation specifications as well as the total harmonic distortion and the dynamic response requirements of major UPS standards.

Micro/Macro or Link-Integrated Micro-actuator Manipulation—A Kinematics and Dynamics Perspective

Smart (active) materials based actuators, hereinafter called micro-actuators, have been shown to be well suited for the elimination of high harmonics in joint and/or end-effector motions of robot manipulators and in the reduction of actuator dynamic response requirements. Low harmonic joint and end-effector motions, as well as low actuator dynamic response requirements, are essential for a robot manipulator to achieve high operating speed and precision with minimal vibration and control problems. Micro-actuators may be positioned at the end-effector to obtain a micro- and macro-robot manipulation configuration. Alternatively, micro-actuators may be integrated into the structure of the links to vary their kinematics parameters, such as their lengths during the motion. In this paper, the kinematics and dynamics consequences of each of the aforementioned alternative are studied for manipulators with serial and closed-loop chains. It is shown that for robot manipulators constructed with closed-loop chains, the high harmonic components of all joint motions can be eliminated only when micro-actuators are integrated into the structure of the closed-loop chain links. The latter configuration is also shown to have dynamics advantage over micro- and macro-manipulator configuration by reducing the potential vibration and control problems at high operating speeds. The conclusions reached in this study also apply to closed-loop chains of parallel and cooperating robot manipulators.

Structural-Acoustic Optimization of Sandwich Panels

Sandwich panels comprising face sheets enclosing a core are increasingly common structural elements in a variety of applications, including aircraft fuselages, flight surfaces, vehicle panels, lightweight enclosures, and bulkheads. This paper presents the optimization of various innovative sandwich configurations for minimization of their structural-acoustic response. Laminated face sheets and core geometries comprising honeycomb and trusslike structures are considered. The design flexibility associated with the class of considered composite structures and with truss-core configurations provides the opportunity of tailoring the structure to the load and dynamic response requirements of a particular application. The results demonstrate how the proper selection of selected key parameters can achieve effective reduction of the radiated sound power and how the identified optimal configurations can achieve noise reduction over different frequency ranges and for various source configurations.

Performance evaluation of doubly-fed twin stator induction machine drive with voltage and current space vector control schemes

The doubly-fed twin stator induction machine (DFTSIM) is of interest as an adjustable speed drive (ASD) and a variable speed generator (VSG), as it combines the advantages of a brushless drive with the potential for high-voltage, high-power, and limited speed range applications. Previous work on the DFTSIM (or its equivalent brushless doubly-fed machine) has considered steady state performance with open loop control or dynamic performance with closed loop control, but has not considered an overall peformance evaluation with an appropriate closed loop speed control. The comparative dynamic and steady state performance of a laboratory DFTSIM drive using ‘voltage space vector control’ and ‘current space vector control’ schemes is discussed. While the magnitude of the control winding voltage (or current) space vector is dynamically controlled to obtain the desired torque in a speed control loop, its position is regulated to operate the machine in synchronous mode. Results show that the maximum efficiency for the voltage space vector control is slightly higher than that for the current space vector control scheme, but the current space vector control offers better dynamic response and minimum converter voltampere requirement. Although the reduction in the converter VA rating with the DFTSIM drive is similar to that achievable with a slip power recovery drive, the brushless DFTSIM drive has a greater potential for applications requiring high reliability and low maintenance. Further, the DFTSIM is a viable alternative in the context of non-conventional power generation such as wind and small hydro.

Primate pleuroesophageal tissue barrier frequency response and esophageal pressure waveform bandwidth in health and acute lung injury.

Dynamic intraesophageal pressure (Pes) is used to estimate intrapleural pressure (Ppl) to calculate lung compliance and resistance. This study investigated the nonhuman primate Ppl-Pes tissue barrier frequency response and the dynamic response requirements of Pes manometers. In healthy monkeys and monkeys with acute lung injury undergoing ventilation, simultaneous Ppl and Pes were measured directly to determine the Ppl-Pes tissue barrier amplitude frequency response, using the swept-sine wave technique. The bandwidths of physiologic Pes waveforms acquired during conventional mechanical ventilation were calculated using digital low-pass signal filtering. The Ppl-Pes tissue barrier is amplitude-uniform within the bandwidth of conventional Pes waveforms in healthy and acute lung injury lungs, and does not significantly attenuate Ppl-Pes signal transmission between 1 and 40 Hz. At Pes frequencies higher than conventional clinical regions of interest the Ppl-Pes barrier resonates significantly, is pressure amplitude dependent at low-pressure offsets, and is significantly altered by acute lung injury. Allowing for 5% or less Pes waveform error, the maximum Pes bandwidths during conventional ventilation were 1.9 Hz and 3.4 Hz for physiologic and extreme-case waveforms in healthy lungs and 4.6 Hz and 8.5 Hz during acute lung injury. In monkeys, the Ppl-Pes tissue barrier has a frequency response suitable for Ppl estimation during low-frequency mechanical ventilation, and Pes manometers should have a minimum uniform frequency response up to 8.5 Hz. However, the Ppl-Pes tissue barrier adversely affects the accurate estimation of dynamic Ppl at high frequencies, with varied airway pressure amplitudes and offsets, such as the Ppl encountered during high-frequency oscillatory ventilation.

Intra-arterial pressure measurement in neonates: dynamic response requirements

A computer simulation of a catheter manometer system was used to quantify measurement errors in neonatal blood pressure parameters. Accurate intra-arterial pressure recordings of 21 critically ill newborns were fed into this simulated system. The dynamic characteristics, natural frequency and damping coefficient, were varied from 2.5 to 60 Hz and from 0.1 to 1.4, respectively. As a result, errors in systolic, diastolic and pulse arterial pressure were obtained as a function of natural frequency and damping coefficient. Iso-error curves for 2%, 5% and 10% were constructed. Using these curves, the maximum inaccuracy of any neonatal catheter manometer system can be determined and used in the clinical setting.

Flight investigation of helicopter low-speed response requirements

A flight experiment has been conducted using the Canadian National Aeronautical Establishment's variable-stability airborne simulator to define the dynamic response requirements for operations at hover and low speeds. Fourteen Attitude Command/Attitude Hold, Rate, and Rate Command/Attitude Hold configurations were evaluated by six pilots using both conventional controls and a four-axis integrated sidestick over a low-speed course consisting of precision hover, landing, sidestep, and dash/quickstop tasks. The results indicate that with conventional controls all three response-types were acceptable as long as their response bandwidth was sufficiently high, and higher bandwidths were required in roll than in pitch. With the four-axis sidestick, there was a preference for the Rate systems. The range of acceptable bandwidths was lower, and the spread in pilot ratings smaller, than were found in a similar ground-based simulation.

Digital Computer Application in the F-15 Engine Air Inlet Control System

The F-15 is a high-performance air superiority fighter capable of speeds in excess of Mach 2.5. Trade studies showed that an inlet with three variable compression ramps and a variable capture area feature would enhance overall weapon system performance. The control mechanism that was chosen for positioning the inlet variable surfaces is presented. A study showed that a serial digital computer mechanization for the air inlet controller Air Inlet Controller (AIC) was preferred over an analog or parallel digital computer mechanization. The details of the production digital AIC are described. The accuracy and dynamic response requirements of the AIC were determined by simulation and other studies. Extensive ground tests and a wind-tunnel test verified the excellent operation of the digital AIC. Several AIC reprogrammings were required during the ground, wind-tunnel, and flight testing in order to optimize the aircraft performance. These were easily accomplished due to the digital mechanization. Flight test results show that the inlet control system and the AIC have adequate steady-state accuracy and dynamic response characteristics for control of the inlet system to provide excellent performance and low inlet distortion during extreme aircraft maneuvers.