Structure Control Approach Research Articles

Sliding‐mode variational structure study of Cuk converter based on target holographic feedback

SummaryWith the rapid advancement of new energy sources, distributed power supplies have gained widespread adoption in DC microgrid systems. The stability of the DC‐DC converter, serving as the central component for energy transfer between the distributed power supply and the DC bus, holds significant importance in ensuring the overall system performance. Due to the intricate nature of real‐world operating conditions, the DC bus voltage is frequently subject to uncertainties such as fluctuations in distributed power supplies and random variations in loads. As a consequence, the reliability of DC‐DC converters faces escalating demands, making it challenging for conventional linear controllers to ensure consistent operation of DC‐DC converters across a broad range. This study focuses on addressing this issue by investigating the Cuk converter, which serves as a representative example of a single‐input multiple‐output system. The operating characteristics and control challenges of the Cuk converter are analyzed, and a nonlinear control strategy based on target holographic feedback is proposed to enhance the system's stability. Considering the non‐minimum phase characteristics of the Cuk converter and its inability to be linearized through exact feedback, a sliding mode variable structure control approach is introduced, utilizing target holographic feedback. Through simulation and experimental analysis, the effectiveness of the model and the theoretical analysis are validated.

Slenderness tuning to adjust and regulate constant force mechanisms (STAR-CFM)

Force regulation and adjustment is a challenge in some applications because it requires sensor-controller feedback loops resulting in high system complexity, low range of adjustability, and poor compactness. The objective of this paper is structural control using slenderness tuning to adjust and regulate constant force mechanisms (STAR-CFM) in which the constant force (CF) is regulated passively and adjusted semi-actively. First, a FE parametric study of the baseline CFM with structural imperfections is conducted. Second, a structural control strategy is implemented to adjust the CF value by tuning slenderness using a structural tie. A detailed optimization is conducted to provide the maximum change in the CF under the defined constraints. The proposed methodology provides a CFM with a high energy similarity index, i.e., SCF>0.92. Our experimental validation confirms the effectiveness of the proposed structural control approach, achieving a significant adjustment range of the control force (CF) up to four times the baseline value. The STAR-CFM provides a compact design compared to the literature designs with a non-dimensional operational displacement of s = 0.45. The STAR-CFM advancements may minimize the mechanical and control system complexity in many applications.

Diffusion-controlled bridging of the Au Island and Au core in Au@Rh(OH)3 core-shell structure.

Hybrid nanostructures have garnered considerable interest because of their fascinating properties owing to the hybridization of materials and their structural varieties. In this study, we report the synthesis of [Au@Rh(OH)3]-Au island heterostructures using a seed-mediated sequential growth method. Through the thiol ligand-mediated interfacial energy, Au@Rh(OH)3 core-shell structures with varying shell thicknesses were successfully obtained. On these Au@Rh(OH)3 core-shell seeds, by modulating the diffusion of HAuCl4 in the porous Rh(OH)3 shell, site-specific growth of Au islands on the inner Au core or on the surface of the outer Rh(OH)3 shell was successfully achieved. Consequently, two types of distinct structures, the Au island-on-[Au@Rh(OH)3] dimer and Au island-Au bridge-[Au@Rh(OH)3] dumbbell structures with thin necks were obtained. Further modulations of the growth kinetics led to the formation of Au plate-Au bridge-[Au@Rh(OH)3] heterostructures with larger structural anisotropy. The flexible structural variations were demonstrated to be an effective means of modulating the plasmonic properties; the Au-Au heterostructures exhibited tunable localized surface plasmon resonance in the visible-near-infrared spectral region and can be used as surface-enhanced Raman scattering (SERS) substrates capable of emitting strong SERS signals. This diffusion-controlled growth of Au bridges in the Rh(OH)3 shells (penetrating growth) is an interesting new approach for structural control, which enriches the tool box for colloidal nanosynthesis. This advancement in structural control is expected to create new approaches for colloidal synthesis of sophisticated nanomaterials, and eventually enable their extensive applications in various fields.

Robust Variable Structure Control Approach of Two Series-Connected Five-Phase PMSMs Under Healthy and Faulty Operation Modes

Robust Variable Structure Control Approach of Two Series-Connected Five-Phase PMSMs Under Healthy and Faulty Operation Modes

Active structural control framework using policy-gradient reinforcement learning

This paper presents a novel data-driven approach for active structural control through the use of deep reinforcement learning, wherein, the control system learns to react in an optimal manner through a training process that utilizes deep neural networks within a reinforcement learning framework. The key advantage of this paradigm is the data-driven approach to active control which helps circumvent the need for high-fidelity modeling that typically requires extensive prior knowledge about the structure of interest. Furthermore, the proposed framework is applicable for designing a variety of active controllers, and different external load types, for example, wind and seismic loads for any desired building. The efficacy of the proposed framework is demonstrated in the context of seismic response control through three numerical case studies. The results confirm that the proposed approach yields significant structural response reductions in the linear and nonlinear regimes. Furthermore, implementation issues such as sensitivity to structural property variations, and time delay are thoroughly investigated.

Sound transmission loss of a sandwich functionally graded cylindrical shell integrated with magneto-electro-elastic patches

Magneto-electro-elastic materials offers the inherent capability of energy transformation from one type to another, hence making them suitable for improving the vibroacoustic behavior of the structures. The current article is an analytical investigation into the sound transmission characteristics of a smart functionally graded cylindrical shell equipped with magneto-electro-elastic patches while a steady fluid flow exists outside of the cylinder. The complete set of equations of motion are derived after accounting for all components of displacement according to the first-order shear deformation theory. The utilized patches are controlled via an electric field, indicating the smart nature of the structure. The Power-law model is adopted to calculate the effective mechanical properties of the functionally graded core layer. After defining proper boundary conditions, the vibroacoustic equations are obtained with the aid of Hamilton's principle. A comprehensive validation study is also conducted to show the reliability of the developed formulation. In addition, by examining the effect of a large number of electric, magnetic, flow Mach number, geometric and acoustic parameters, recommendations are made to effectively optimize similar structures that benefit from such materials. One of the important findings of this study is that applying electric and magnetic fields in the low frequency band improves the sound transmission loss. Therefore, the magneto-electro-elastic patches can be used in active structural acoustic control approaches as actuators.

A thinning algorithm based approach to controlling structural complexity in topology optimization

Shape and topology optimization techniques aim to maximize structural performance through material redistribution. Effectively controlling structural complexity during the form-finding process remains a challenging issue. Structural complexity is usually characterized by the number of connected components (e.g., beams and bars), tunnels, and cavities in the structure. Existing structural complexity control approaches often prescribe the number of existing cavities. However, for three-dimensional problems, it is highly desirable to control the number of tunnels during the optimization process. Inspired by the topology-preserving feature of a thinning algorithm, this paper presents a direct approach to controlling the topology of continuum structures under the framework of the bi-directional evolutionary structural optimization (BESO) method. The new approach can explicitly control the number of tunnels and cavities for both two- and three-dimensional problems. In addition to the structural topology, the minimum length scale of structural components can be easily controlled. Numerical results demonstrate that, for a given set of loading and boundary conditions, the proposed methodology may produce multiple high-performance designs with distinct topologies. The techniques developed from this study will be useful for practical applications in architecture and engineering, where the structural complexity usually needs to be controlled to balance the aesthetic, functional, economical, and other considerations. • A structural complexity control approach is proposed for topology optimization. • Efficient designs with controllable topologies can be easily obtained. • This approach is practically useful for creating diverse and competitive designs.

Adaptive Fault Tolerant Attitude Control of a Nano-Satellite with Three Magnetorquers and One Reaction Wheel

In this paper, a passive fault tolerant attitude control is investigated for a nano-satellite with three magnetorquers and one reaction wheel in the presence of actuator constraints, external disturbances, and partial loss of actuator effectiveness as unknown actuator faults. For this purpose, a variable structure control approach is employed due to its ability to deal with the partial loss of actuator effectiveness and adjusting the maximum amplitude of the control signal by a control gain. A modified sliding variable is designed based on angular velocity and attitude errors with an adaptive parameter coefficient. The dynamics equation of the adaptive parameter is extracted during the stability proof of the closed-loop system. Changing the value of this parameter changes the effect intensity of the quaternion errors on the sliding variable and causes the attitude errors to maintain within a limited range. Applying this parameter to the modified sliding variable makes the controller perform well even if the adaptive parameter is significantly reduced. Furthermore, directly using the adaptive parameter in the structure of control law makes the controller generate a chattering-free torque. Comparing the simulation results with the results of two variable structure control methods designed in previous articles shows that its performance in attitude tracking commands has improved. In addition, Monte Carlo simulations with random actuator faults are performed to show the robustness of the proposed controller in the presence of actuator constraints and external disturbances.

New spectra of responses and control force for design of equivalent-input-disturbance-based active structural control of base-isolated buildings

This paper presents new spectra of responses and control force for an active base-isolated building that uses the equivalent-input-disturbance (EID) approach for active structural control. The EID approach estimates the effect of disturbances and uses it to suppress building vibrations. This system plugs an EID estimator into a conventional state-feedback control system. Note that these kinds of disturbance-rejection systems contain both feedforward and feedback terms from disturbances to a control output. This paper describes spectra that can handle systems with such structure. The spectra can be used to simplify the design of an active structural control system. This paper illustrates the use of the spectra for control-system design and presents a design algorithm for the EID-based control system. A shear building model and 44 kinds of earthquake waves are used to demonstrate the availability of the spectra.

Drawbacks of Structural Fracture Control Approaches: A Case Study of Nigerian System

Fracture mechanics describes the susceptibility of structures and components to failure due to fracture, fatigue, creep, wear, or corrosion, as well as the prevention and control of crack propagation. Nigeria lacks sound fracture mechanics approaches. The frequent failure of structure is evident, particularly in the building sector, where there have been reported cases of building collapse resulting in the loss of lives and property. However, it is generally attributed to a design deficiency, the use of substandard materials or wrongful selection of materials, inferior quality control methods, inadequate maintenance programs, and the absence of standard regulatory bodies. There’s a growing need for structures that poses structural integrity to be able to withstand and support a given structural load without deforming or fracturing. This can be achieved through the meticulous selection of base materials, development, and implementation of a fracture control plan, the unique design process in the construction and manufacturing industry.

A multi-body control approach for flapping wing micro aerial vehicles

Flapping wing micro aerial vehicle (FWMAV) has a multi-body and periodic dynamics, which is influenced by unsteady aerodynamics. These features make it more difficult to control. Ignoring the wing inertia, dynamics averaging, and using a simple aerodynamic model are the simplifying assumptions for conventional model-based control, although they may result in inaccurate control. To overcome these difficulties, a multi-body control is proposed based on a model-free adaptive variable structure control (MFAVSC) approach. MFAVSC takes advantage of input/output data, while not including any explicit model information. At first, the nonlinear FWMAV dynamics is transformed into an equivalent dynamic linearization description with a concept called pseudo-partial derivative (PPD). After estimating the PPD matrix, model-free adaptive control law is designed based on the optimal criteria. Then, it is augmented by a variable structure control term to guarantee the stability, as well as speeding up its convergence. Finally, simulation results demonstrate the effectiveness of the proposed scheme to trajectory control of the FWMAV.

Decoupled Longitudinal and Lateral Vehicle Control Based Autonomous Lane Change System Adaptable to Driving Surroundings

The purpose of this study is to develop an autonomous lane change control system that adapts to variable surrounding conditions, to ensure vehicle safety and traffic flow stability. In this paper, we propose decision-making and control procedures for realizing autonomous lane changing; to this end, we consider not only behaviors for changing lanes but also those involved in approaching the lane changing state, with a focus on the controller design. A decoupled control structure and longitudinal trajectory-free control approach are suggested. We design a novel inter-vehicle spacing policy and a 3DOF lateral error vehicle dynamics model. To verify the effectiveness of our system, simulation experiments are performed for 12 scenarios, and system assessments are conducted based on four evaluation perspectives. The results confirm that our system can safely control the vehicle amidst various surrounding vehicle conditions and can also ensure vehicle motion stability. Furthermore, we solve the existing dynamic instability problem of lateral control, which arises through longitudinal acceleration variability. Another significant advantage of this model is that the controlled vehicle does not interfere with the target-lane traffic flow and smoothly synchronizes with the flow during lane changing.

Vibration control by active integrated control system under bidirectional ground motions

To improve the safety and security of the structures with irregular plan configuration, the new torsionally effective passive control system (ICS) was first proposed by the author, which utilizes a new design configuration to dissipate the unwanted energy from the structures in the lateral and torsional directions. In this research, a new active structural control approach, which is the active form of the ICS (or active integrated control system, AICS), is introduced as an alternative active control system, especially for the buildings with torsional sensitivity. In the design of active system configurations, two actuators driven by the linear quadratic regulator (LQR) are implemented and used to apply the optimum control forces to the ATMDs and AICS. For examining the performance of the proposed system configuration, the final design is applied to the 9-story Benchmark steel structure subjected to bidirectional three historical earthquakes. The obtained results show the overall performance of structural performance by using the AICS is substantially improved as compared to conventional ones (ATMDs) under selected ground accelerations with a 3% to 6% improvement in the lateral directions and by nearly 20% in the torsional direction in terms of the peak and root mean square response reduction.

Alleviating the right‐half‐plane zero effect on Z‐source converter output voltage regulation using the cascaded sliding mode controller

This study presents the cascaded variable structure control approach with respect to the non-minimum phase nature of the DC–DC Z-source converter (ZSC). The method is based on the sliding mode control technique for output voltage regulation. The control-to-output transfer function of the ZSC contains a right-half-plane (RHP) zero in continuous conduction mode. The RHP zero, obtained by a linearised small-signal model, results in frequency response limitation. In this case, the converter output voltage control should be studied regarding to the RHP zero effect. To alleviate this effect and enhance the dynamic performance, the cascaded sliding mode control method is proposed. The cascaded sliding mode controller guarantees asymptotically minimum phase stability as well as robustness against input voltage variation and load resistance uncertainty. The capability and effectiveness of the proposed control method are supported by experimental results.

Apparent-weakening by adaptive passive stiffness shaping along the height of multistory building using negative stiffness devices and dampers for seismic protection

Apparent weakening by adaptive stiffness shaping of structures using a negative stiffness device (NSD) is a new passive structural control approach to mitigate the response of structures during severe ground motions. Experimental studies confirm significant reductions in acceleration, inter-story drift and base shear experienced by a structure when a NSD is deployed in conjunction with a viscous damper. So far, the focus and application of NSDs has been restricted to response reduction in the story where a NSD is installed and its effect on stories above that. In this paper, we demonstrate the efficacy of deploying NSDs accompanied by dampers at multiple locations along the height of an example nine story structure. Typically, the NSDs in the lower floors undergo large deformations since the energy from a ground motion is transmitted from the bottom to top. To prevent this, we propose a generalized scheme to incorporate NSDs at all floors with different apparent-yield displacements. We incorporate the variations with a view towards minimizing localized inter-story deformations (ISD) and distribute the effects of strong ground motions evenly along the height of the structure. In addition to the variation of apparent-yield of NSDs, we study the effects of supplementing the NSD with linear and non-linear dampers. We compare the response of the nine story structure without passive control devices (BS) to cases where linear dampers (LD) are attached, nonlinear dampers are attached (ND), NSDs in conjuction with linear dampers are attached (NSD + LD) and NSDs in conjunction with nonlinear dampers are attached (NSD + ND). Our results show that if the distribution of apparent yield is properly designed for a structure, NSDs with nonlinear dampers results in a superior performance compared to the other cases considered in this paper.

Modeling and Dynamics Analysis of Marine Planktonic Ecosystem Based on Adaptive Fuzzy Variable Structure Control Approach

Yao, H., 2020. Modeling and dynamics analysis of marine planktonic ecosystem based on adaptive fuzzy variable structure control approach. In: Yang, Y.; Mi, C.; Zhao, L., and Lam, S. (eds.), Global Topics and New Trends in Coastal Research: Port, Coastal and Ocean Engineering. Journal of Coastal Research, Special Issue No. 103, pp. 436–441. Coconut Creek (Florida), ISSN 0749-0208.Based on the logistic model, a new nonlinear dynamic model of marine plankton ecosystem is established considering the fishing behavior and the weakening effect of pollution on plankton and the self purification ability of plankton ecosystem. The dynamic characteristics of the model are analyzed by using the adaptive fuzzy variable structure control method, and the stability conditions of the marine planktonic ecosystem are obtained. On this basis, the adaptive fuzzy variable structure control of the system is designed. Finally, the feasibility and validity of this method for the study of marine planktonic ecological model are verified by numerical simulation.

Variable structure control for mismatched uncertain systems using output variables with finite-time convergence

ABSTRACT In this paper, a novel variable structure control (VSC) approach is investigated for a class of mismatched uncertain systems. The VSC approach, which includes output variables only, shows finite-time convergence of the sliding mode, complete invariance to the matched uncertainties, the asymptotic stability property, and is free of the chattering phenomenon. A suitable reduced-order observer (ROO) is constructed to estimate the unmeasured variables. Additionally, a novel finite-time sliding-mode controller (FTSMC), based on the constructed ROO and the output variables, is proposed to stabilize a class of mismatched uncertain systems. To ensure finite-time stability and chattering removal, a discontinuous FTSMC is replaced by a continuous FTSMC utilizing a tanh function. Moreover, a new linear matrix inequality (LMI) condition is derived so that the system in the sliding mode is not only completely invariant to matched uncertainties but also asymptotically stable. Finally, a numerical example is presented, which demonstrates the effectiveness and advantages of this method.

In the shadow of a negative past: repairing and developing trust in construction projects

Trust is foundational to establishing and maintaining relationships. Construction project management research has long touted the importance of trust for project organisation and performance. Yet there has been less research interest in repairing and developing inter-organisational trust once trust has been violated and reduced. This study presents a process-based case study of restoring and enhancing trust in a main-contractor-and-subcontractor relationship after project experiences that deteriorated trust. Drawing on conceptual frameworks of trust repair and development, the research analysed the practices of both main-contractor and subcontractor companies. The analysis reveals that, although involving different project teams, the violation of trust in past experiences impacted relationships and interactions in the focal project. To repair and develop trust requires a process of discovering causes and accepting responsibility, forming interventions to repair dimensions of trustworthiness that have been damaged and evaluating the effectiveness of intervention. The research identifies three types of mechanisms that facilitated trust repair and development in construction: sense-making, structural control and relational approaches. This study contributes to knowledge in that it recognises the temporal embeddedness of inter-organisational relationships in construction projects and empirically demonstrates the process and practices of repairing and developing inter-organisational trust.

NCα-gem-dimethylated peptoid side chains: A novel approach for structural control and peptide sequence mimetics.

The design of linear peptoid oligomers adopting well-defined secondary structures while mimicking defined peptide primary sequences is a major challenge in the context of drug discovery. To this end, chemists have developed cis-inducing peptoid side chains to build robust polyproline type I helices. However, the number of efficient examples remains scarce and chemical diversity accessible through the use of these side chains is limited. Herein, we introduce an array of NCα-gem-dimethylated peptoid residues mimicking proteinogenic amino acids. Submonomer synthesis and block-coupling approaches were explored to access heterooligomers incorporating these novel types of side chains. NMR studies of monomer and trimer models showed that the NCα-gem-dimethylated groups exert complete cis control on the backbone amide conformation. Lastly, a preliminary molecular modeling study gave an insight into the preferred orientation of the substituents of the NCα-gem-dimethyl side chains relative to the peptoid backbone.

Hierarchical Fuzzy Logic-Based Variable Structure Control for Vehicles Platooning

This paper proposes a variable structure control approach for vehicles platooning based on a hierarchical fuzzy logic. The leader-follower vehicle dynamics with model uncertainties is discussed from the viewpoint of a consensus problem. A practical two-layer fuzzy control for the platooning is designed by employing two common spacing policies to ensure system robustness in different scenarios. The two policies, i.e., constant distance and constant time headway, utilize the predecessor-successor information flow from the immediate predecessor and follower other than controlled vehicles. The first layer of the fuzzy system combines spacing control with velocity-acceleration control to achieve a rapid tracking for the desired control commands, and the second layer combines the sliding mode control to adaptively compensate for reducing the state errors caused by parameter uncertainties and disturbances. Shift between different controller parameters is based on performance boundaries to guarantee the stability of individual vehicle and platooning for arbitrary initial spacing and velocity errors. These performance boundaries can be determined by using a Lyapunov method with exponential stability. Simulation of a ten-vehicle large platooning with two spacing policies shows that the control performance of the newly proposed method is effective and promising.