Optimal Placement Of Actuators Research Articles

Advances and opportunities in wind energy harvesting using plasma actuators: a review

Abstract The dielectric barrier discharge plasma actuator has been recognized as a leading technology for controlling fluid flow and has found remarkable applications in wind energy harvesting over the past decade. Wind turbine aerodynamics are critical in this concept and performance is mainly determined by flow controllers, although significant technical progress is still required. This paper examines all the critical studies to investigate the potential application of plasma actuators for airflow control over wind turbines. This approach has been divided into three categories: wind turbine airfoils, horizontal-axis wind turbines and vertical-axis wind turbines aerodynamic performance and generated power. Finally, the potential functions of plasma actuators in current and future wind turbine generators are discussed. These actuators offer promising solutions to increasing power output, minimizing torque fluctuations and enabling self-starting capabilities, particularly in vertical-axis wind turbines. By adjusting blade pitch angles in conjunction with plasma actuators, significant improvements in airflow optimization and power extraction have been demonstrated. Despite the advancements, challenges persist, such as determining optimal actuator placement and overcoming structural limitations, especially concerning 3D effects and high Reynolds numbers. While plasma actuators enhance aerodynamic efficiency, their complexity needs to be balanced against marginal gains in power production, especially in high-megawatt turbines, for which controlling flow at low wind speeds is challenging. Future research must focus on the sustainable integration of plasma actuators, pitch angle adjustments and active control mechanisms to fully exploit the potential of wind energy for a sustainable future.

Stress-Aware Optimal Placement of Actuators for High Precision Quality Management in Composite Aircraft Assembly

Stress-Aware Optimal Placement of Actuators for High Precision Quality Management in Composite Aircraft Assembly

Stepwise Optimization of Actuator Placement for Large-scale Space Structure During on-orbit Assembly

Stepwise Optimization of Actuator Placement for Large-scale Space Structure During on-orbit Assembly

Optimal Actuator Placement for the High-Precision Control of Quasi-Static Elastic Plates

Optimal Actuator Placement for the High-Precision Control of Quasi-Static Elastic Plates

Optimal actuator placement for control of vibrations induced by pedestrian-bridge interactions

In this paper, an optimal actuator placement problem, with a linear wave equation as the constraint, is considered. In particular, this work presents the framework for finding the best location of actuators depending upon the given initial conditions, and where the dependence on the initial conditions is averaged out. The problem is motivated by the need to control vibrations induced by pedestrian-bridge interactions. An approach based on the shape optimization techniques is used to solve the problem. Specifically, the shape sensitivities involving a cost functional are determined using the averaged adjoint approach. A numerical algorithm based on these sensitivities is used as a solution strategy. Numerical tests illustrate the theoretical results.

Optimal placement of sensor and actuator for controlling the piecewise linear Chua circuit via a discretized controller

Controlling the dynamics of chaotic systems is a task which is often addressed in an empirical way, particularly for placing sensors and actuators. Here, we show that selecting the measured variable and placing the actuator can be guided by considering the observability and controllability symbolic coefficients and applying the notion of flatness. This approach is here demonstrated on the piecewise linear Chua circuit, whose specific features are leveraged in constructing a discretized controller with a switch mechanism and optimally placed sensor and actuator. The feedback linearization is compared to a homogeneous and a passivity-based control laws, the flat control laws being more efficient than the others. It is thus shown that the proposed flat control law by feedback linearization is very efficient. The continuous time and discretized Chua circuit, governed by differential and difference equations, respectively, are treated. Most likely, these results could be extendable to a large group of natural and experimental systems.

Co-design of active vibration control and optimal sensor and actuator placement for a flexible wing using reinforcement learning

This paper presents applying reinforcement learning to find the optimal sensor/actuator placement (OSAP) policy and optimal control for the flexible wing. The “co-design” objective is to find the OSAP and its associate controller to render the optimal closed-loop performance. The nonlinear vibration dynamics of the flexible wing are modeled in the linear parameter varying (LPV) approach so that LPV- H ∞ controllers can be designed. The co-design problem is formulated into mixed-integer semi-definite programming (MISDP). As a special form of combinatorial optimization, MIDSP solves integer optimization for sensor/actuator selection and convex optimization for controller design. A modified reinforcement learning algorithm is applied to solve this NP-hard optimization problem and obtain a converged solution. In addition, RL is compared with the greedy algorithm and genetic algorithm to demonstrate its strengths and drawbacks in solving high-dimensional MISDP. The solutions obtained by RL and the greedy algorithm are verified and compared in the high-fidelity simulation with the full-order model.

Optimal placement of sensor and actuator for controlling low-dimensional chaotic systems based on global modeling.

Controlling chaos is fundamental in many applications, and for this reason, many techniques have been proposed to address this problem. Here, we propose a strategy based on an optimal placement of the sensor and actuator providing global observability of the state space and global controllability to any desired state. The first of these two conditions enables the derivation of a model of the system by using a global modeling technique. In turn, this permits the use of feedback linearization for designing the control law based on the equations of the obtained model and providing a zero-flat system. The procedure is applied to three case studies, including two piecewise linear circuits, namely, the Carroll circuit and the Chua circuit whose governing equations are approximated by a continuous global model. The sensitivity of the procedure to the time constant of the dynamics is also discussed.

A Hierarchical Optimization Method for the Design of Active Hybrid Structures

In structural engineering, active structures that combine the principles of lightweight construction with bending elastic component behavior are increasingly being investigated. For the realization of a prototype of an active hybrid roof structure at the laboratory of Hybrid Structures at BTU Cottbus-Senftenberg, preliminary investigations on a case study are conducted in the framework of this publication in order to improve the design process of these types of structures. These active hybrids require a higher design effort than classical structures from the field of structural engineering due to a larger number of relevant objectives. Consequently, this study devotes special attention to these essential target criteria and their mathematical formulation. Furthermore, in order to improve the efficiency of this design process, a hierarchical method is derived that is subdivided into two successive partial procedures, which contain specific heuristics that are developed. In this method, after structural optimization, an optimal actuator placement is performed. The subject of a design process involving optimal actuator placement is relatively unexplored for active structures in which components are subjected to large elastic bending deformations and is therefore the focus of this study. In order to verify the functionality of the method and the plausibility of the results of the derived partial methods, a validation of the methodology is performed. Therefore, results of analyses of an active truss structure are compared with those of an active hybrid structure, both derived using the presented method. In addition to validating results, the study intends to investigate whether the performance of an active hybrid structure generated by the proposed method is sufficiently competitive compared to a state-of-the-art active truss structure derived by the same procedure.

A nonlinear optimization method for large shape morphing in 3D printed pneumatic lattice structures

Shape morphing has been increasingly investigated as a solution to increase the functionality and efficiency of structures. The main criteria to assess the quality of a shape morphing structure in this paper are: accuracy of deformation and range and number of achievable target shapes. The lightweight lattice structures used in this work inherently address the first criteria. The focus of this work is to address accuracy and range by developing a nonlinear optimization method that can handle large shape changes and a variety of target shapes for 2D and 3D overdeterminate lattice structures. The accuracy and deformation range of the method are verified numerically using finite element analysis and experimentally through a modular, 3D printed pneumatic lattice toolkit. The method is shown to replicate desired target shapes with a minimum accuracy of 80.4% for case studies in 2D and 69.1% in 3D. The simulation and the experimental results replicate results from the actuator placement optimization with a minimum accuracy of 92.3% and 76.2% respectively in 2D, and 88.2% and 69.6% in 3D. The impact of varying the size and degree of static overdeterminacy of a structure on its deformation range is evaluated. The proposed optimization method provides designers with more design freedom in terms of the structure type, target shape, and deformation range than shown in similar publications.

Validation of a nonlinear force method for large deformations in shape-morphing structures

Reducing energy and material consumption is a priority for the construction, aerospace, and automotive industries. Shape morphing addresses these concerns by broadening the band of functionality of a structure by adapting its shape to an external stimulus, such as pressure, or an internal stimulus, such as embedded actuation. This work outlines the development of an actuator placement optimization method for overdeterminate lattice structures with the objective of achieving predetermined large shape changes accurately. The deformation is modeled with both a linear and a nonlinear force method to determine their validity for large-shape change and their usefulness for the field of shape morphing. The linear and nonlinear methods are compared in four benchmark problems and two case studies relevant to the field of shape morphing. The nonlinear method is shown to achieve a level of accuracy 10^2 to 10^4 higher compared to FEM simulation, while using 23% fewer actuators and up to 77.3% less elongation of actuators, which makes it more favorable for shape-morphing applications. Two case studies for applications in aerospace and construction show that the nonlinear force method is better equipped for large shape change in overdeterminate meshed freeform target shapes and doubly curved surfaces with a high variable density. However, the nonlinear force method is less computationally efficient than the linear force method, as expected. A judicious choice of constraints can help reduce the run time.

Optimal component location for PI observer based active control of a galvanizing process.

Optimal sensor and actuator placement is performed for active vibration control. The components are selected to minimize the vibration impact on the strip by H2-norm minimization. Then, active vibration control is based on a PI-observer design allowing, not only to estimate the state, but also the disturbances. Some numerical results illustrate the performance of the proposed active vibration control.

Phase-reduction analysis of periodic thermoacoustic oscillations in a Rijke tube

Phase-reduction analysis captures the linear phase dynamics with respect to a limit cycle subjected to weak external forcing. We apply this technique to study the phase dynamics of the self-sustained oscillations produced by a Rijke tube undergoing thermoacoustic instability. Through the phase-reduction formulation, we are able to reduce these dynamics to a scalar equation for the phase, which allows us to efficiently determine the synchronisation properties of the system. For the thermoacoustic system, we find the conditions for which $m:n$ frequency locking occurs, which sheds light on the mechanisms behind asynchronous and synchronous quenching. We also reveal the optimal placement of pressure actuators that provide the most efficient route to synchronisation.

Research on Optimal Placement of Actuators of High-Rise Buildings Considering the Influence of Seismic Excitation on Structural Modes

Presently, most of the common placement methods of actuators are based on the structural response and system energy to select the optimal locations. In these methods, the contribution of controllability and the energy of seismic excitations to each mode of the structure are not considered, and a large number of cases need to be calculated. To solve this problem, the Clough–Penzien spectral model is combined with the Luenberger observable normal form of the system to calculate the energy of each state. The modal disturbance degree, considering modal energy and controllability, is defined by using the controllability gramian matrix and PBH system controllability index, and the modes are divided into the main disturbance modes (MDMs) and the secondary disturbance modes (SDMs). A novel optimal placement method of actuators based on modal controllability degree is proposed, which uses MDMs as the main control modes. The optimal placement of actuators and the vibration control simulation of a 20-story building model are carried out. The results show that the vibration reduction effect of the proposed placement method is significantly better than that of the method of uniformly distributed actuators (Uniform method) and the classical placement method of actuators based on the system controllability gramian matrix (Classical method).

Actuator placement optimization for guided waves based structural health monitoring using fibre Bragg grating sensors

Structural health monitoring (SHM) systems have a potential to reduce lifecycle costs of structures. They may be used for maintenance planning which reduces the maintenance cost as well as for lifetime extension. As a result, there is a lot of active research in the area for SHM of civil and mechanical structures. The SHM system should be low cost, suitable for continuous monitoring, able to detect small levels of damage. Guided waves (GW) based SHM techniques allow monitoring of large plate-like structures with few sensors and have been identified as the most promising of techniques for SHM. Several different actuators and sensors have been developed and used for the GW based SHM. FBG sensors due to their low weight, and ability to be multiplexed have been long thought to be an ideal sensors for SHM. The recent development of the edge filtering approach has increased their sensitivity to GW sensing and made them ideal sensors. Unfortunately the FBG sensors are passive sensors and show directional sensitivity. These operational constraints make extension of the earlier developed GW based SHM techniques for FBG sensors difficult. Recently the authors developed a technique for damage detection specifically designed for a network with FBG sensors. This paper develops a methodology for a design of an actuator-sensor (AS) network for improving the damage assessment capability using the developed method. The paper develops a two-step methodology for the optimization of actuator placement for an AS network with FBG sensors. In the first step the number of actuators needed for the optimization are determined based on actuator densities. Once the number of actuators is known, a genetic algorithm (GA) is developed for the optimization of the their positions. The cost function is developed based on two new metrics (namely coverage2—coverage with at least 2 AS pairs and coverageR—radial coverage based on edge reflections) which are defined by the application demand. The optimized placement is then used to successfully detect and localize the damage. The study also shows the merit in the use of the specific metrics and the sufficiency of the metrics developed for improving the damage detection capability of the specific method.

Optimal flatness placement of sensors and actuators for controlling chaotic systems

Controlling chaotic systems is very often investigated by using empirical laws, without taking advantage of the structure of the governing equations. There are two concepts, observability and controllability, which are inherited from control theory, for selecting the best placement of sensors and actuators. These two concepts can be combined (extended) into flatness, which provides the conditions to fulfill for designing a feedback linearization or another classical control law for which the system is always fully observable and fully controllable. We here design feedback linearization control laws using flatness for the three popular chaotic systems, namely, the Rössler, the driven van der Pol, and the Hénon–Heiles systems. As developed during the last two decades for observability, symbolic controllability coefficients and symbolic flatness coefficients are introduced here and their meanings are tested with numerical simulations. We show that the control law works for every initial condition when the symbolic flatness coefficient is equal to 1.

Actuator placement optimization in an active lattice structure using generalized pattern search and verification

Shape morphing structures are actively used in the aerospace and automotive industry. By adapting their shape to a stimulus such as heat, light, or pressure, a design can be optimized to achieve a broader band of functionality over its lifetime. The quality of a structure with respect to shape-morphing can be assessed using five criteria: weight, load-carrying capacity, energy consumption, accuracy of the controlled deformation, and the range and number of achievable target shapes. This work focuses on the use of lightweight and stiff active lattice structures, where the layout of actuators within the structure determines the final deformation. It uses a statically and kinematically determinate Kagome lattice pattern that has been shown to deform the most accurately with the least energy. The use of a determinate structure justifies the implementation of a simplified deformation model. The deformation resulting from a given actuator layout can be expressed as a linear combination of the deformation of individual actuators, which are all computed in a pre-processing step and expressed with an influence matrix. The actuator layout is thus optimized for several target shapes. The linear combination model is shown to replicate FEM simulations with an average of 94.8% accuracy for all target shapes. The actuator layouts in one-level lattices are tested using a novel design for a 3D printed modular Kagome pneumatic lattice structure. The experimental results replicate the target shapes with an average accuracy of 79.9%. The resulting actuator layouts are shown to form more target shapes with a similar deformation range as similar publications.

Optimal actuator placement and static load compensation for a class of distributed parameter systems

Abstract Adaptive structures where actuators are incorporated into a building structure have the potential to reduce resource consumption in construction industry drastically. However, the performance of static load compensation depends to a large extend on the actuator placement. This paper presents optimal actuator placement for systems with distributed parameters based on the Gramian compensability matrix. To provide a general framework for different kind of loads, static loads are discretized as Dirac impacts. The resulting optimal actuator placement is robust against unknown load amplitudes, as load profiles are only considered qualitatively in the cost function. Further, the optimal control input for a given load results directly from the optimization problem. The procedure is illustrated for a Kirchhoff-Love plate and integrated fluidic actuators.

Optimal actuator placement in adaptive optics systems

Adaptive optics systems are powerful tools that are implemented to degrade the effects of wavefront aberrations. In this article, the optimal actuator placement problem is addressed for the improvement of disturbance attenuation capability of adaptive optics systems due to the fact that actuator placement is directly related to the enhancement of system performance. For this purpose, the linear-quadratic cost function is chosen, so that optimized actuator layouts can be specialized according to the type of wavefront aberrations. It is then considered as a convex optimization problem, and the cost function is formulated for the disturbance attenuation case. The success of the presented method is demonstrated by simulation results.

Security‐aware optimal actuator placement in vehicle platooning

AbstractVehicle platooning, as a large class of cyber‐physical systems, is prone to be under the risk of cyber attacks. One (or more) external intelligent intruder(s) might attack one (or more) of the vehicles participating in a platoon. This paper proposes a general approach to find an optimal actuator placement strategy according to the Stackelberg game between the attacker and the defender. The game payoff is the energy needed by the attacker to steer the consensus follower–leader dynamics of the system towards his desired direction. The attacker tries to minimize this energy while the defender attempts to maximize it. Thus, based on the defined game and its optimal equilibrium point, the defender(s) selects optimal actuator placement action to face the attacker(s). Both cases of single attacker–single defender and multiple attackers–multiple defenders cases are investigated. Furthermore, we study the effects of different information flow topologies, namely, the unidirectional and bidirectional data transfer structures. Besides, the impacts of increasing the connectivity among the nodes on the security level of the platoon are presented. Simulation results for h–nearest neighbor platoon formations along with experimental results using the scaled cars governed by robotic operating system (ROS) verify the effectiveness of the method.