Passive Control Strategy Research Articles

Dual multivariable model-free adaptive individual pitch control for load reduction in wind turbines with actuator faults

Thanks to the great advances in the installations of large wind turbines, individual pitch control (IPC) has gained mounting interest among researchers. The actuator faults, however, have become a hindrance with the individual pitch process introducing more actuator actions and the pitch system operating in complex conditions. The traditional fault-tolerant control strategies of the IPC, which are mainly based on the system modeling information, and require the process of fault diagnosis, isolation or parameter estimation. The subsequent model errors and unmodeled dynamics have somehow limited the application of the strategies. Therefore, this paper proposes a passive fault-tolerant individual pitch control scheme independent of the above process, and based on the scheme, a dual multivariable model-free adaptive control strategy with differential characteristic is constructed. The benchmark 5 MW wind turbine model provided by FAST is employed to evaluate the performance. The results show that, compared with the traditional individual pitch control strategy, the proposed scheme can achieve almost identical load control and even better power control under fault-free conditions. Once the fault occurs, the proposed scheme can quickly compensate for the faulty actuator dynamics, and finally achieve almost the same performance in power and load control as under the nominal conditions.

Application of adaptive fuzzy control to suppression vibration response of floating offshore wind turbine

Floating offshore wind turbine is a complex rigid-flexible coupling nonlinear system, and the accurate dynamic model is difficultly established. Therefore, the wind-wave interference cannot be improved by adopting the conventional control strategy. In order to solve this problem, an adaptive fuzzy controller (AFC) is used to suppress the dynamic response of floating wind turbine. Two correction factors are introduced to optimize the fuzzy rule, and the traditional fuzzy controller (FC) is firstly obtained. Since the balance positions change and structural parameter perturbation of the wind turbine, an AFC is designed and validated. Finally, the suppression vibration responses ability of floating offshore wind turbine by using the different control strategies is studied under the random wind-wave disturbance and blade pitch control system coupling effect. The simulation results show that the tracking ability of the AFC to the target value is obviously higher than that of the FC; Comparing with the passive control strategy, the suppression vibration effect on the power spectral density (PSD) of the platform pitch (PFPI) motion peak can increase by 39.06% by adopting the AFC.

Flutter Optimization of a Wing–Engine System with Passive and Active Control Approaches

In the present study, the flutter performance of a composite thin-walled beam wing–engine system is optimized by implementing two different control approaches: 1) passive open-loop and 2) active closed-loop control. Sequential quadratic programming and genetic algorithm methods are applied in the optimization process. In the passive control method, variable stiffness is acquired by constructing laminates of thin-walled beam with curvilinear fibers having prescribed paths. The goal is to exploit the desirable fiber paths with improved flutter performance to determine an optimized wing–engine aeroelastic configuration. In the active control strategy, piezo-composite actuators and the linear quadratic Gaussian algorithm are used to improve the flutter characteristics. A novel optimization strategy based on the total energy of the aeroelastic system is introduced and applied in both passive and active control strategies. The minimum total aeroelastic energy is an indication of ideal optimization variables, which leads to optimum flutter performance. The governing equations are formulated based on Librescu’s thin-walled beam theory and Hamilton’s principle. An unsteady aerodynamic model based on incompressible indicial aerodynamics is applied. The governing equations of motion are solved using a Ritz-based solution methodology. Numerical results demonstrate a 16 and 46% improvement in the flutter speed of the wing–engine system using the proposed passive and active control approaches, respectively. The presented results provide valuable information concerning the design of advanced lightweight and high-aspect-ratio aircraft wings with mounted engines in terms of favorable aeroelastic performance characteristics.

Research on Power Battery Balance System

This article introduces the importance of the balance system in the battery management system, and analyses the reasons for the inconsistency between battery cells. Also, it introduces the differences between passive balance and active balance management control strategies, and analyses the capacitive, inductive, transformer and DC/DC converter balance management control strategies in the lithium battery active balance management control strategy.

Active Damping and Passive Control Strategy for Three-Phase LCL Grid-Connected Inverter

Compared with traditional controllers such as PI based on classic control theory, the article applies passive control (PBC) theory to the design of three-phase LCL grid-connected inverter controllers. The mathematical model of the system based on Euler-Lagrange (EL) is established, and the damping method of the trap is used to suppress the resonance spikes generated by the system, so that the system meets the requirements of grid connection. The simulation results verify the feasibility of the scheme.

Effects of nozzle geometry and active blowing on lift enhancement for upper surface blowing configuration

Upper Surface Blowing (USB) has been regarded as a promising lift enhancement technique for short-take-off and landing (STOL) applications. The present study conducted numerical investigations to further explore the potential capability of USB technique by passive and active flow control strategies. Computations were accomplished by a Reynolds-averaged Navier-Stokes solver enclosed by the two-equation k-ω shear stress transport turbulence model. The propulsion effect of the up-mounted engine was represented by the Turbine Powered Simulator (TPS). Results show that aerodynamic lift of using USB system is significantly enhanced due to the attenuation of plume edge roll-up vortex which is beneficial to the Coanda effect. Varying nozzle geometries can augment lift by alleviating the three-dimensional edge effect and thus delaying the rollup of plume with a thinner jet sheet. Compared to the passive flow control method by nozzle geometry modification, active constant blowing flow control technique shows a more promising potential for lift enhancement for USB powered system. Within the test cases, a 50% lift increment can be achieved by using constant blowing on the USB system.

Shaking table test of a 1:10 scale thermal power plant building equipped with passive control systems

The seismic performance of electric power system is of paramount importance to maintain functionality of the served urban communities after earthquakes. Passive control techniques are widely accepted as effective measures to improve the seismic resilience of structural buildings. In this study, an actual thermal power plant building characterized by mass and vertical irregularities was studied. For a comparison purpose, two different design schemes in which one adopted the conventional steel braced frame scheme and the other retrofit one endowed with heavy equipment isolation and metallic dampers were considered. Shaking table tests were conducted to investigate the seismic performance of the two cases. The test models were designed and constructed based on the similitude law with a length scale factor of 1/10. Extensive test scenarios were performed with three ground motion pairs taken as inputs. The seismic responses between the conventional model and the retrofit model are compared in terms of tier drift, floor acceleration, base shear and damage observations. The experimental results indicated the effectiveness of employed passive control strategies in mitigating tier drift and base shear responses. The detrimental effects induced by heavy coal bunkers were addressed by using isolation technique. The results validated the metallic dampers have limited control effect in floor acceleration response and the effect is dependent on the seismic input. Discussions were made at the end regarding the scaling effect on the test results and cost-benefit of using passive control devices for the thermal power plant building.

The Influence of Sizing of Wave Energy Converters on the Techno-Economic Performance

Currently, the techno-economic performance of Wave Energy Converters (WECs) is not competitive with other renewable technologies. Size optimization could make a difference. However, the impact of sizing on the techno-economic performance of WECs still remains unclear, especially when sizing of the buoy and Power Take-Off (PTO) are considered collectively. In this paper, an optimization method for the buoy and PTO sizing is proposed for a generic heaving point absorber to reduce the Levelized Cost Of Energy (LCOE). Frequency domain modeling is used to calculate the power absorption of WECs with different buoy and PTO sizes. Force constraints are used to represent the effects of PTO sizing on the absorbed power, in which the passive and reactive control strategy are considered, respectively. A preliminary economic model is established to calculate the cost of WECs. The proposed method is implemented for three realistic sea sites, and the dependence of the optimal size of WECs on wave resources and control strategies is analyzed. The results show that PTO sizing has a limited effect on the buoy size determination, while it can reduce the LCOE by 24% to 31%. Besides, the higher mean wave power density of wave resources does not necessarily correspond to the larger optimal buoy or PTO sizes, but it contributes to the lower LCOE. In addition, the optimal PTO force limit converges at around 0.4 to 0.5 times the maximum required PTO force for the corresponding sea sites. Compared with other methods, this proposed method shows a better potential in sizing and reducing LCOE.

Active Load Management of Hydrogen Refuelling Stations for Increasing the Grid Integration of Renewable Generation

Hydrogen Fuel Cell Electric Vehicles (FCEV) can help reduce carbon emissions, air pollution and dependency on fossil fuels in the transport sector. Clean hydrogen fuel can be generated by a power-to-gas process at refuelling stations equipped with water electrolysers, especially in renewable rich areas. Coupled with onsite hydrogen tanks, the fast response capability of electrolysis, could potentially turn the station demand into a flexible electricity load since the hydrogen can be stored and used when needed. This paper presents a novel real-time load management scheme that actively operates a hydrogen refuelling station to relieve thermal network constraints, handles the fluctuations from renewables, and releases network headroom for connecting renewable generation. The key components involved in the refuelling station and their operational characteristics are explicitly modelled in the analysis. The economic impact of the different operational strategies is also examined. In the case study, the effectiveness of the proposed control strategy to avoid overloading and save curtailment in the local distribution network is verified by running the real-time network simulation at 1 minute steps over a 1 hour window and 5 day window respectively. Moreover, a whole year simulation of the station operation shows that the proposed active control strategy enables wind farms in the local network to avoid 9.5 times more curtailment than under passive control strategy. The station's net cost of electricity consumption thus can be reduced by 7.5%., by making use of excess electricity that would otherwise be curtailed. A further 5% reduction on the cost would be possible if the incentive rewards for offering network constraint management services are in place.

High-Speed Parallel Plasmonic Direct-Writing Nanolithography Using Metasurface-Based Plasmonic Lens

Simple and efficient nanofabrication technology with low cost and high flexibility is indispensable for fundamental nanoscale research and prototyping. Lithography in the near field using the surface plasmon polariton (i.e., plasmonic lithography) provides a promising solution. The system with high stiffness passive nanogap control strategy on a high-speed rotating substrate is one of the most attractive high-throughput methods. However, a smaller and steadier plasmonic nanogap, new scheme of plasmonic lens, and parallel processing should be explored to achieve a new generation high resolution and reliable efficient nanofabrication. Herein, a parallel plasmonic direct-writing nanolithography system is established in which a novel plasmonic flying head is systematically designed to achieve around 15 nm minimum flying-height with high parallelism at the rotating speed of 8–18 m·s−1. A multi-stage metasurface-based polarization insensitive plasmonic lens is proposed to couple more power and realize a more confined spot compared with conventional plasmonic lenses. Parallel lithography of the nanostructures with the smallest (around 26 nm) linewidth is obtained with the prototyping system. The proposed system holds great potential for high-freedom nanofabrication with low cost, such as planar optical elements and nano-electromechanical systems.

Critical region in the spatiotemporal dynamics of a turbulent thermoacoustic system and smart passive control

We develop a passive control strategy for suppressing thermoacoustic instability in a bluff-body stabilized premixed turbulent combustor. When the equivalence ratio is varied, there is a transition from combustion noise to thermoacoustic instability via intermittency in the combustor. We perform simultaneous acoustic pressure, 2D-PIV, and CH * chemiluminescence measurements to capture the pressure fluctuations, the velocity field, and the heat release rate (HRR) field during the transition. We measure the spatial distribution of the amplitude of turbulent velocity at the acoustic frequency, time-averaged vorticity, time-averaged HRR, and Rayleigh index and identify various regions of significance. We implement a passive control strategy by targeting these regions with a steady injection of secondary micro-jet of air to optimize the injection location and determine the critical region. Targeting the critical region with secondary air leads to greater than 20 dB suppression of the dominant thermoacoustic mode. We observe that the coherent structure forming from the shear layer following the dump plane gets suppressed, leading to an incoherent spatial distribution of HRR fluctuations. We find that the turbulent velocity amplitude correctly identifies the critical region for optimized passive control during thermoacoustic instability. In contrast, the Rayleigh index identifies the region of the most significant acoustic driving; however, it does not identify the region most sensitive to control. Finally, we extend our analysis by determining the spatial distribution of the Hurst exponent measured from the turbulent velocity field. We show that the Hurst exponent identifies the critical region during thermoacoustic instability and intermittency, unlike the other physical measures. Thus, we develop a smart passive control method by combining the need for finding critical regions in the combustor with the predictive capabilities of the Hurst exponent.

Load balancing and neural dynamic model to optimize replicator dynamics controllers for vibration reduction of highway bridge structures

Earthquakes cause irreparable damages to the built environment, which has led bridge engineers to develop structural control systems to mitigate damage and improve vibration reduction in real-time. Among control systems, base isolation is one of the most commonly used passive control strategies for seismic protection of civil structures. Yet, it lacks real-time adaptability, has lower energy dissipation, and poor performance during near-fault earthquakes. To overcome these limitations, a hybrid control system comprised of semi-active magneto-rheological (MR) dampers and passive base isolation bearings is installed at the deck and piers for vibration reduction of highway bridge structures. This paper, inspired by evolutionary game theory and artificial intelligence, proposes data-driven replicator dynamic control algorithms to distribute the command voltage to the current driver of the semi-active MR dampers. It incorporates a load balancing strategy to reallocate additional resources. To achieve a high-performance design of the game-theory-inspired controllers, a patented neural dynamic model is used to optimize the control parameters. The evaluation of the proposed methodology uses a benchmark control problem based on the 91/5 highway bridge in Southern California subjected to near-field earthquake accelerograms. The performance of five different proposed controllers is compared with conventional Lyapunov and fuzzy logic control algorithms using 21 performance criteria. Results show the load balancing capability of the proposed control algorithms to mitigate the vibrations experienced by the bridge structure and further increase the durability of semi-active devices. The novelty of the methodology impacts how game-theory controllers make control decisions among multiple devices in engineering problems.

Nonlinear dynamic analysis of a RC bridge subjected to seismic loading

Collapse of bridges in recent earthquakes demonstrates the need to deepen the understanding of the behaviour of these structures against seismic actions. This paper presents a highly detailed numerical model of an actual bridge subjected to extreme seismic action which results in its collapse. Normally, nonlinear numerical models have high difficulties to achieve convergence when reinforced concrete is intended to be represented. The main objective of this work is to determine the efficiency of different passive control strategies to prevent the structural collapse of an existing bridge. Metallic dampers and seismic isolation by decoupling the mass were evaluated. The response is evaluated not only in terms of reduction of displacements, but also in increasing of shear force and axial force in key elements, which can be a negative characteristic of the systems studied. It can be concluded that the use of a metallic damper significantly reduces the horizontal displacements and ensures the integrity of the structure from extreme seismic actions. Moreover, the isolation of the deck, which in principle seems to be the most effective solution to protect existing bridges, proves inadequate for the case analysed due to its dynamic characteristics and its particular geometry and an unpredictable type of axial pounding in the columns. This unexpected effect on the isolation system would have been impossible to identify with simplified models.

Research on the configuration of cable-driven parallel robots for vibration suppression of spatial flexible structures

Specific satellites with ultra-long wings easily suffer from violent vibrations caused by the external disturbance and self-rotation, which do harm to flexible wings and affect the normal operation of satellites. In severe cases, the satellites would be damaged. Therefore, achieving rapid vibration suppression is particularly critical. Besides, to protect flexible wings from damage and reduce energy consumption, the control force should be small. Considering the above two issues comprehensively, a scheme using cable-driven parallel robots (CDPRs) to suppress vibrations is proposed. Furthermore, the influence of different configurations of CDPRs on the control effect is studied in the paper. First, the dynamic model of the CDPR which is comprised of four cables and a flexible structure is established using the finite element method. Then, the dynamic behavior of the model under the controllable cable force is analyzed by the Newmark-β method. An optimization index including the settling time, the maximum cable force and energy consumption is presented. Based on the index, six kinds of CDPRs with different configurations are tested under the control of the proposed Fuzzy-PID method and an active control method, respectively. As a comparison, a passive control scheme is also tested. Finally, numerical simulations are implemented to evaluate the effect of the vibration suppression, and the results are satisfactory.

Passive control strategies for cooling a non-residential nearly zero energy office: Simulated comfort resilience now and in the future

The average global cooling demand in non-residential buildings is expected to increase by over 275% between now and 2050. Controlled passive cooling is fundamental to successful operational performance of buildings and in mitigating energy that would otherwise be consumed by mechanical systems. The aim of this study was to determine the resilience of different passive cooling control strategies in delivering optimal comfort and energy scenarios in both current and future extreme conditions, for low energy indoor office spaces. Simulations were conducted using a calibrated TRNSYS 17 model of a nearly zero energy building. The performance of ten passive cooling control strategies was simulated for climatic conditions in two representative cities, Dublin and Budapest. Each strategy used different combinations of passive cooling systems such as day-time ventilation, night-time ventilation and dynamic solar shading. The effect of static and adaptive indoor temperature set-points and a limit on external relative humidity was also investigated. The thermal comfort performance of each strategy was assessed by using standardised thermal comfort, overheating and overcooling metrics. Findings from the study show that passive control strategies maintained comfortable internal conditions between 57% and 95% of the occupied hours, without the need for mechanical cooling. The most resilient strategies were those that combined multiple measures. Passive control strategies were found to be resilient in the medium-term in Dublin, however, the same systems were not able to maintain comfortable conditions in Budapest in 2050. The use of an external relative humidity limit resulted in increases overheating incidences and failure of some overheating criteria. Based on the reductions in mechanical cooling requirements, it was concluded that there is regulatory need to consider the use passive control strategies in the design of buildings.

A passivity-based control strategy for nonlinear bilateral teleoperation employing estimated external forces

Teleoperation systems have been presented to handle objects in environments in which the presence of operators are impracticable, unsafe or less effective. In this paper, a passive control strategy employing the new outputs to state synchronization of the master and slave robots is developed to attain position coordination during contact tasks. The proposed control scheme includes position signals plus force signals. However, force measurement in such applications is a major limitation. Therefore, a modified force estimation algorithm is proposed to predict external forces applied on the master and slave robots. The closed-loop bilateral teleoperation system is investigated by employing Lyapunov stability criteria. Finally, the experimental results demonstrate the efficiency of the proposed control scheme. It is observed that, in the presence of the estimated external forces in the control scheme, the slave robot follows the master position in both free and contact motion, and force reflecting occurs properly as well. Moreover, it is verified that the external forces are estimated appropriately through the proposed force estimation algorithm.

Robotic mirror therapy system for lower limb rehabilitation

PurposeThis paper aims to develop a robotic mirror therapy system for lower limb rehabilitation, which is applicable for different patients with individual movement disability levels.Design/methodology/approachThis paper puts forward a novel system that includes a four-degree-of-freedom sitting/lying lower limb rehabilitation robot and a wireless motion data acquisition system based on mirror therapy principle. The magnetorheological (MR) actuators are designed and manufactured, whose characteristics are detected theoretically and experimentally. The passive training control strategy is proposed, and the trajectory tracking experiments verify its feasibility. Also, the active training controller that is adapt to the human motor ability is designed and evaluated by the comparison experiments.FindingsThe MR actuators produce continuously variable and compliant torque for robotic joints by adjusting excitation current. The reference limb joint position data collected by the wireless motion data acquisition system can be used as the motion trajectory of the robot to drive the affected limb. The passive training strategy based on proportional-integral control proves to have great trajectory tracking performance through experiments. In the active training mode, by comparing the real-time parameters adjustment in two phases, it is certified that the proposed fuzzy-based regulated impedance controller can adjust assistance torque according to the motor ability of the affected limb.Originality/valueThe system developed in this paper fulfills the needs of robot-assisted mirror therapy for hemiplegic patients.

Noise reduction performance of a low energy façade-integrated mechanical ventilator

Acoustic comfort and indoor air quality are essential for the health and wellbeing of the occupants of the building. Thus, the façade must guarantee enough sound insulation and ventilation conditions. However, these aspects conflict because opening windows or using ventilation openings reduces the sound insulation of the envelope and allows the exterior noise entrance. To limit noise transmission into the building, ventilators use passive, active or hybrid noise control techniques. This work addresses the noise reduction performance of a mechanical ventilator for façades, evaluating the effect of different options of passive noise control strategies in the sound insulation of the proposed ventilator. In addition, the air change rate and energy consumption of the ventilator were also investigated. Three prototypes were fabricated and tested at an acoustic chamber, along with ventilation tests carried out in a room equipped with a blower door. CFD simulations were used to enhance the aeraulic geometry of the prototypes, prior to its fabrication. The acoustic experiments showed Dn,e,w values up to 55 dB and noise emission levels lower than 25 dB(A). The use of resistive sound absorbers proved to be more effective in mitigating noise than reactive absorbers, over the entire frequency range. The ventilation tests revealed air change rates of 3.7 h−1 at 50 Pa, while the ventilator’s annual energy consumption was 17.52 kWh. The results highlight the proposed device as a viable alternative for decentralised mechanical ventilation, capable of ensuring noise protection and satisfactory ventilation rates, under a sustainable perspective of minimum energy demand.

Passive prosthesis control strategy for downhill ambulation

Microprocessor controlled prosthesis improves the functional outcome of people with above knee amputation but some limitations remain during slope and stairs ambulation. The control strategies desc...

Tunable vibration control in a microelectromechanical resonator array by means of parametric coupling between mechanical and electrical modes

Vibration control in flexible structures at both the micro and macro scale has been a subject of considerable research interest over the last few decades. Various active, semi-active and passive vibration control schemes have been proposed for applications ranging from attenuating unwanted vibrations in structural components to controlling the ring down time in high-Q mechanical oscillators. Here, we present a simple, yet highly effective method to passively attenuate large amplitude resonant vibrations in an array of membrane-based microelectromechanical (MEM) resonators. By capacitively coupling the MEM array to a resonant electrical circuit tuned to half the mechanical resonance frequency, the vibrational energy in the array can be converted to electrical energy via parametric mode coupling between the mechanical and electrical resonator. Simulation and experimental studies indicate that both the rate of vibration attenuation and the degree of suppression can be effectively controlled by tuning electrical parameters such as the resistance and the initial voltage in the circuit. The extension of the control scheme to multi-mode vibrations by making use of multiple shunted electrical resonators will also be briefly discussed.