Set Of Actuators Research Articles

Adaptive dynamic control allocation for dynamic positioning of marine vessel based on backstepping method and sequential quadratic programming

It is generally assumed in dynamic positioning of over-actuated marine vessels that the control effectiveness matrix (input matrix) is known and constant, or, in case of fault information, it is estimated by the fault detection and diagnosis system. The purpose of the study is to develop the adaptive dynamic positioning control system for an over-actuated marine vessel in the presence of uncertainties and with emphasis on limited information about thruster forces. The proposed approach bases on the MIMO adaptive backstepping method to design the high-level control law and then to give inputs to the control allocation unit. An adaptive solution allows to accommodate the unknown time-varying control effectiveness matrix and to update the thrust distribution due to actuator losses and failures. The effectiveness and correctness of the proposed control schema is demonstrated by simulations involving a redundant set of actuators when some of them have lost partially their efficiency or failed. The evaluation criteria include energy consumption, robustness and accuracy of dynamic positioning during typical vessel operations. Based on simulation tests results, the generated control inputs stabilize the ship position and orientation violated by thruster faults.

Active flow control using dense wireless sensor and actuator networks

This paper describes the design of an active flow control (AFC) system for aeronautics applications based on dense wireless sensor and actuator networks (WSANs). The objective of this AFC system is to track gradients of pressure (or wall shear stress) across the surface of the fuselage of commercial aircraft. This collected information is used to activate a set of actuators that will attempt to reduce the skin drag effect produced by the separation between laminar and turbulent flows. This is expected to be translated into increased lift-off forces, higher vehicle speeds, longer ranges and reduced fuel consumption. The paper describes the architecture of the system in the context of the European research project DEWI (dependable embedded wireless infrastructure) using the concept of the DEWI Bubble and its three-tier architecture especially designed to ensure dependability and interoperability in industrial WSANs. A system-level simulator is also proposed to model each process of the AFC system and the aeronautics DEWI Bubble infrastructure, highlighting the interactions between the network simulation and the results of the computational fluid dynamics (CFD) simulation. The key element in the proposed solution is a polygonal patch of wired sensors and actuators. This patch is provided with a wireless link to a central coordinator or access point conveniently located in the aircraft to maximize coverage to a network of distributed patches. A trade-off between scalability, size of the patches, fluid speed/viscosity, sampling sensor and actuator rates in space and time, and the capacity/delay characteristic of the wireless inter-patch and the wireline intra-patch communication technologies is also here discussed. The hybrid wireless/wired sensor and actuator network achieves great flexibility, scalability, manageability, troubleshooting, and modularity as compared to a solution exclusively based on wireline or wireless components. The final details of the prototype and results in a wind tunnel test-bed are here described, demonstrating the validity of the concept and the use of wireless technologies for aeronautical applications (flexible architecture and innovative services). Future issues regarding security, safety and trustiness of the AFC system are also briefly introduced in the context of the spin-off European project SCOTT (secure connected trusted things).

Experimental study on bi-directional friction linear micro-motor driven by a set of micro-actuator

ABSTRACTThis paper presents a bi-directional friction linear micro-motor (BFLM), which is driven by a set of micro-actuator through friction drive. The BFLM has been fabricated using PolyMUMPs process. The forward and backward movement displacement, velocity and acceleration of the slider are measured. Movement velocities of the slider can be controlled by changing the driving frequency. It is feasible to use one set of actuator to driving the slider bidirectional motion. The BFLM is operated at square-wave frequencies with 38.39 kHz to get the maximum displacement of 100 µm and the average velocities are 10.709 µm/s in forward movement and 10.321 µm/s in backward movement.

Input Matrix Factorizations for Constrained Control Allocation

Control allocation (CA) is part of a hierarchical control architecture and distributes the desired control effort of a controller among a set of redundant actuators as it is used, for example, to meet high reliability requirements. Before applying CA, a factorization of a linear plant's input matrix must be carried out. This paper investigates the influence of this factorization on two common algorithms for constrained CA: direct allocation and redistributed pseudoinverse (RPINV). It is shown why the factorization does not affect the first method, whereas it influences the latter one as soon as the number of actuator saturations exceeds a certain threshold. On this basis a modification of RPINV is proposed, which allows the prioritization of virtual control vector components. If the actuator saturations prevent an exact solution, the errors of those components with high priority are preferentially forced to zero. Finally simulations demonstrate the main results.

Numerical Investigations of Spanwise-Varied Unsteady Coanda Actuation on High-Lift Configuration

The present study investigates possible lift gains generated by spanwise-varied blowing on a high-lift configuration equipped with a droop nose and a Coanda flap. Two types of numerical simulations are performed and compared: unsteady Reynolds-averaged Navier–Stokes simulations and improved delayed detached-eddy simulations with algebraic sensors. The unsteady Reynolds-averaged Navier–Stokes simulations achieve the best actuation settings at an actuation amplitude of 25% of the jet slit height and an actuation frequency of . No relevant sensitivity is detected with regard to the phase shift of the actuated spanwise segments. In contrast, the algebraic improved delayed detached-eddy simulations results show clear sensitivity to actuation phase shift. The algebraic improved delayed detached-eddy scale-resolving simulations also exhibit different wake dynamics from those of unsteady Reynolds-averaged Navier–Stokes. Based on both the unsteady Reynolds-averaged Navier–Stokes and algebraic improved delayed detached-eddy simulations results, this study demonstrates the benefits that the superposition of a two-dimensional periodic actuation component (no phase shift between actuated segments) has on the lift. The benefits of three-dimensional segmented actuation remain unknown and await further research.

Novel frameworks for the design of fault‐tolerant control using optimal sliding‐mode control

SummaryThis paper describes 2 schemes for a fault‐tolerant control using a novel optimal sliding‐mode control, which can also be employed as actuator redundancy management for overactuated uncertain linear systems. By using the effectiveness level of the actuators in the performance indexes, 2 schemes for redistributing the control effort among the remaining (redundant or nonfaulty) set of actuators are constructed based on an ‐based optimal sliding‐mode control. In contrast to the current sliding‐mode fault‐tolerant control design methods, in these new schemes, the level of control effort required to maintain sliding is penalised. The proposed optimal sliding‐mode fault‐tolerant control design schemes are implemented in 2 stages. In the first stage, a state feedback gain is derived using an LMI‐based scheme that can assign a number of the closed‐loop eigenvalues to a known value whilst satisfying performance specifications. The sliding function matrix related to the particular state feedback derived in the first stage is obtained in the second stage. The difference between the 2 schemes proposed for the sliding‐mode fault‐tolerant control is that the second one includes a separate control allocation module, which makes it easier to apply actuator constraints to the problem. Moreover, it will be shown that, with the second scheme, we can deal with actuator faults or even failures without controller reconfiguration. We further discuss the advantages and disadvantages of the 2 schemes in more details. The effectiveness of the proposed schemes are illustrated with numerical examples.

Design-Oriented Structural Controllability and Observability Analysis of Heat Exchanger Networks

The control-relevant design and analysis of Heat Exchanger Networks (HENs) is an essential issue in terms of the design and intensification of sustainable production systems. The structural controllability and observability of HENs should be studied based on their dynamical model. Recently, a maximum matching based algorithm was developed to determine the locations of the minimum number of actuators and sensors needed to ensure the controllability and observability of linear dynamical systems. In this paper, the ability of concentrated parameter state-space models of the heat exchanger units to serve as building blocks of the network of state variables in HENs, and the use of the resultant network of state variables to study the control of relevant topologies and properties of HENs is highlighted. Based on the results of the systematic analysis, the structural patterns that facilitate the control and observation of HENs with a relatively small number of actuators and sensors were determined. Two methods were proposed to define the sets of additional actuators and sensors which are required to improve the operability of the network by decreasing the order of the controlled system. The first method is based on the interpretation of the placement of the sensors and actuators as a set cover problem, while the second one uses two network science-based measures: closeness centrality and betweenness centrality. The proposed methodologies are demonstrated on a benchmark example that is well covered in the literature.

Adaptive dynamic control allocation for over-actuated dynamic positioning system based on backstepping method in case of thruster faults

The objective of the research considered in this paper is dynamic positioning of a nonlinear over-actuated marine vessel in the presence of limited information about thruster forces. First, the adaptive backstepping method is used to estimate the input matrix which will compensate partial loss of actuator effectiveness in the presence of actuator dynamics. Then, the adaptive commanded virtual forces and moment are allocated into individual thrusters by employing the control allocation algorithm to compensate total faults. The effectiveness of the proposed control scheme is demonstrated by simulations involving a redundant set of actuators, when actuators lose partially their efficiency or failed.

Single segment actuator using shape memory alloy for three-directional bending endoscopic tip

Shape Memory Alloy (SMA) is a specially fabricated alloy which is capable of altering its shape based on external stimuli. With this mechanism, SMA can be used as actuator with highly controlled maneuverability and flexibility. This study was aimed to design, fabricate, test and analyze an SMA actuator with three-directional bending capabilities. The design consisted of a set of SMA actuators with a pseudo-elastic alloy bias wire. A silicone rubber sheathe was fabricated to act as a heat buffer. The actuator was activated with a DC current between 0-900mA at 70% PWM duty cycle. Bending and heat tests resulted in positive bending of about 30° consistently while the instrument without the silicone rubber sheathe on the instrument. Temperature readings on the thermal camera are 40°C. With the silicone rubber sheathe, the bending angle is halved over the entire instrument, but with a smaller decrease in recorded temperature of the main bodies. This SMA-based actuator is prospectively used to improve the maneuverability and flexibility of an endoscopic tip.

Dynamic Control Allocation for Damping of Inter-Area Oscillations

Use of actuator redundancy to achieve higher reliability is a widely accepted engineering design technique and is used in this study to build resiliency and ensure power system stability in the presence of high levels of renewables. This paper presents a new design method for fault-tolerant wide-area damping controllers (WADCs) using modal-based control allocation (MB-CA), which coordinates a set of actuators to contribute to damping of inter-area oscillations. In our proposed method, when an actuator fails or is unavailable (e.g., due to communication failure), the supervisory MB-CA distributes the control signals to the remaining healthy actuators based on effects on the modal system, desired control actions, and actuator constraints. Our proposed block offers the benefits of modular design where it is independent of the nominal WADC. The proposed method consists of mainly two design steps. The first step is to design a WADC based on a fault-free model using robust control methods. The second step is to design an MB-CA to manage actuator availability and constraints. To validate the feasibility and demonstrate the design principles, a set of comprehensive case studies are conducted on a modified 192-bus Western Electricity Coordinating Council system. Numerical results verify the effectiveness of the proposed approach in ensuring resiliency to different actuator failures and actuator availability.

Actuator allocation for integrated control in tokamaks: architectural design and a mixed-integer programming algorithm

Plasma control systems (PCS) in tokamaks need to fulfill a number of control tasks to achieve the desired physics goals. In present-day devices, actuators are usually assigned to a single control task. However, in future tokamaks, only a limited set of actuators is available for multiple control tasks at the same time. The priority to perform specific control tasks may change in real-time due to unforeseen plasma events and actuator availability may change due to failure. This requires the real-time allocation of available actuators to realize the requests by the control tasks, also known as actuator management.In this paper, we analyze possible architectures to interface the control tasks with the allocation of actuators inside the PCS. Additionally, we present an efficient actuator allocation algorithm for Heating and Current Drive (H&CD) actuators. The actuator allocation problem is formulated as a Mixed-Integer Quadratic Programming optimization problem, allowing to quickly search for the best allocation option without the need to compute all allocation options. The algorithms performance is demonstrated in examples involving the full proposed ITER H&CD system, where the desired allocation behavior is successfully achieved. This work contributes to establishing integrated control routines with shared actuators on existing and future tokamaks.

Actuator network design to mitigate contamination effects in Water Distribution Networks

Water Distribution Networks (WDNs) are vulnerable to accidental or deliberate contamination. Such contamination can be detected and identified by deploying a network of sensors. If the sensor network detects the presence of a contaminant, it is also very important to take corrective response actions to minimize the effects of contamination on the population being served. One possible mitigation option is to prevent the contaminated water from reaching any customer, by shutting down the distribution network using shut-off valves placed in the WDN. The design problem considered in this work is to determine pipes where the shut-off valves can be optimally located such that it is possible to prevent the contaminated water from reaching any demand point, regardless of the source node from where the contamination has originated. We refer to this problem as the actuator network design problem. We map the problem of actuator design into a graph partitioning problem and the minimal set of actuators are identified for ensuring the total shutdown of the network.

Output integral sliding mode fault tolerant control scheme for LPV plants by incorporating control allocation

An integrated integral sliding mode fault tolerant control scheme is proposed for the linear parameter varying (LPV) plants in the output feedback framework. To estimate the unavailable plant states, an unknown input LPV observer is employed. The feedback and observer gains are designed using linear matrix inequalities approach to ensure closed-loop stability nominally and in the situation of actuator faults/failures. An integral sliding modes approach in the LPV framework together with control allocation maintains the nominal performance in the presence of permissible set of actuator faults/failures. A rigorous closed-loop stability analysis is carried out and to show the feasibility of the proposed approach it is tested in simulations on the non-linear plant of a passenger aircraft.

Computationally Informed Design of a Multi-Axial Actuated Microfluidic Chip Device

This paper describes the computationally informed design and experimental validation of a microfluidic chip device with multi-axial stretching capabilities. The device, based on PDMS soft-lithography, consisted of a thin porous membrane, mounted between two fluidic compartments, and tensioned via a set of vacuum-driven actuators. A finite element analysis solver implementing a set of different nonlinear elastic and hyperelastic material models was used to drive the design and optimization of chip geometry and to investigate the resulting deformation patterns under multi-axial loading. Computational results were cross-validated by experimental testing of prototypal devices featuring the in silico optimized geometry. The proposed methodology represents a suite of computationally handy simulation tools that might find application in the design and in silico mechanical characterization of a wide range of stretchable microfluidic devices.

Logarithmic Power Feedback for Extremum Seeking Control of Wind Turbines

When a wind turbine operates between the cut-in and rated wind speeds, the machine is controlled to maximize wind energy capture. The extremum seeking control (ESC) algorithm has been proposed to locate and track the optimal operating condition for power maximization. This is accomplished by applying the ESC to the power signal to determine optimal values for parameters of the control law or actuator settings. Since the power signal is proportional to the cube of the mean wind speed, changes in wind conditions may lead to significant variations in the performance of the ESC algorithm. This paper demonstrates that replacing the power signal with its logarithm yields an algorithm with robust and predictable performance despite variations in the mean wind speed. The theoretical analysis of the ESC with log-of-power feedback is done using a simple differential equation model. Numerical simulations support the theory.

Movement augmentation to evaluate human control of locomotor stability.

Controlling center of mass (COM) position and velocity within a dynamic base of support is essential for gait stability. This skill is often compromised following neurologic injury, creating a need to develop effective interventions to enhance gait stability. A movement augmentation paradigm applied to walking could potentially be used to improve control of COM dynamics. We have developed a cable robot system, the Agility Trainer, to apply continuous frontal-plane forces to the pelvis during treadmill walking. This cable robot system uses a set of series elastic actuators powered by linear motors to create bilateral forces. Here we use the Agility Trainer to create a negative viscosity force field proportional to the subject's lateral velocity. Two healthy young subjects performed two 10-minute walking trials, Baseline and Negative Viscosity. During the first minute of walking in the Negative Viscosity field, participants' lateral COM motion became less controlled when compared to the rhythmic sinusoidal motion observed during Baseline walking. By the 10th minute of walking in the Negative Viscosity field the participants had adapted their gait patterns, decreasing their variation in peak lateral COM speed each stride. These results demonstrate that it is feasible to use the Agility Trainer to apply a movement augmentation paradigm to human walking.

A phenomenological mixture homogenization model for spark-ignition direct-injection engines

In modern turbocharged direct-injection, spark-ignition engines, proper calibration of the engine control unit is essential to handle the increasing variability of actuators. The physically based simulation of engine processes such as mixture homogenization enables a model-based calibration of the engine control unit to identify an ideal set of actuator settings, for example, for efficient combustion with reduced exhaust emissions. In this work, a zero-dimensional phenomenological model for direct-injection, spark-ignition engines is presented that allows the equivalence ratio distribution function in the combustion chamber to be calculated and its development is tracked over time. The model considers the engine geometry, mixing time, charge motion and spray–charge interaction. Accompanying three-dimensional computational fluid dynamics, simulations are performed to obtain information on homogeneity at different operating conditions and to calibrate the model. The calibrated model matches the three-dimensional computational fluid dynamics reference both for the temporal homogeneity development and for the equivalence ratio distribution at the ignition time, respectively. When the model is validated outside the calibrated operating conditions, this shows satisfying results in terms of mixture homogeneity at the time of ignition. Additionally, only a slight modification of the calibration is shown to be required when transferring the model to a comparable engine. While the model is primarily aimed at target applications such as a direct-injection, spark-ignition soot emission model, its application to other issues, such as gaseous exhaust emissions, engine knock or cyclic fluctuations, is conceivable due to its general structure. The fast calculation enables mixture inhomogeneities to be estimated during driving cycle simulations.

Adaptive Wireless Biomedical Capsule Tracking Based on Magnetic Sensing

This paper studies wireless biomedical capsule (WBC) tracking, for magnetic sensing and actuation settings, where an embedded permanent magnet is used inside a passive WBC together with magnetic sensors outside the human body, producing a magnetic field around the WBC. First, a 2D WBC localization scheme is developed based on only magnetic sensing and adaptive recursive least squares (RLS) on-line parameter estimation with forgetting factor. Next, we propose a hybrid localization technique for simultaneous position and orientation estimation with high accuracy. The proposed hybrid localization technique is based on data fusion of magnetic measurements and electromagnetic signals emitted by the WBC for image transmission and other medical information using a similar adaptive RLS parameter estimation scheme. Later, the proposed localization techniques are integrated with an adaptive tracking law to construct an adaptive capsule tracking controller. The simulations demonstrate promising results for the efficiency and accuracy level of the proposed adaptive localization and tracking control schemes.

Vibro-acoustic model of an active aircraft cabin window

This paper presents modeling and design of an active structural acoustic control (ASAC) system for controlling the low frequency sound field transmitted through an aircraft cabin window. The system uses stacked piezoelectric elements arranged in a manner to generate out-of-plane actuation point forces acting on the window panel boundaries. A theoretical vibro-acoustic model for an active quadruple-panel system is developed to characterize the dynamic behavior of the system and achieve a good understanding of the active control performance and the physical phenomena of the sound transmission loss (STL) characteristics. The quadruple-panel system represents the passenger window design used in some classes of modern aircraft with an exterior double pane of Plexiglas, an interior dust cover pane and a glazed dimmable pane, all separated by thin air cavities. The STL characteristics of identical pane window configurations with different piezoelectric actuator sets are analyzed. A parametric study describes the influence of important active parameters, such as the input voltage, number and location of the actuator elements, on the STL is investigated. In addition, a mathematical model for obtaining the optimal input voltage is developed to improve the acoustic attenuation capability of the control system. In general, the achieved results indicate that the proposed ASAC design offers a considerable improvement in the passive sound loss performance of cabin window design without significant effects, such as weight increase, on the original design. Also, the results show that the acoustic control of the active model with piezoelectric actuators bonded to the dust cover pane generates high structural vibrations in the radiating panel (dust cover) and an increase in sound power radiation. High active acoustic attenuation can be achieved by designing the ASAC system to apply active control forces on the inner Plexiglas panel or dimmable panel by installing the actuators on the boundaries of one of the two panels. In some cases, increasing the actuator numbers in the structure advances the active control performance by controlling more structural modes; however, this decreases the STL of the passive control system because of the increase in structure-borne sound transmission paths of the stiffer piezoelectric actuators.

Prediction of Flame Burning Velocity at Early Flame Development Time With High Exhaust Gas Recirculation and Spark Advance

Diluting spark-ignited (SI) stoichiometric combustion engines with excess residual gas improves thermal efficiency and allows the spark to be advanced toward maximum brake torque (MBT) timing. However, flame propagation rates decrease and misfires can occur at high exhaust gas recirculation (EGR) conditions and advanced spark, limiting the maximum level of charge dilution and its benefits. The misfire limits are often determined for a specific engine from extensive experiments covering a large range of speed, torque, and actuator settings. To extend the benefits of dilute combustion while at the misfire limit, it is essential to define a parameterizable, physics-based model capable of predicting the misfire limits, with cycle to cycle varied flame burning velocity as operating conditions change based on the driver demand. A cycle-averaged model is the first step in this process. The current work describes a model of cycle-averaged laminar flame burning velocity within the early flame development period of 0–3% mass fraction burned. A flame curvature correction method is used to account for both the effect of flame stretch and ignition characteristics, in a variable volume engine system. Comparison of the predicted and the measured flame velocity was performed using a spark plug with fiber optical access. The comparison at a small set of spark and EGR settings at fixed load and speed, shows an agreement within 30% of uncertainty, while 20% uncertainty equals ± one standard deviation over 2000 cycles.