In this paper,a new system of semi active structural control with active variable stiffness and damping (AVSD) is *** new system amplifies the structural displacement to dissipate more energy,and in turn,effectively r...
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In this paper,a new system of semi active structural control with active variable stiffness and damping (AVSD) is *** new system amplifies the structural displacement to dissipate more energy,and in turn,effectively reduces the structural response in the case of relatively small story drifts,which occur during earthquakes.A predictive instantaneous optimal control algorithm is established for a SDOF structure equipped with an AVSD system Comparative shaking table tests of a 1/4 scale single story structural model with a full scale control device have been *** the experimental and analytical results,it is shown that when compared to structures without control or with the active variable stiffness control alone, the suggested system exhibits higher efficiency in controlling the structural response,requires less energy input,operates with higher reliability,and can be manufactured at a lower cost and used in a wider range of engineering applications.
The aim of this experimental study is the implementation of a practical and efficient closed-loop feedback control of the turbulent flow over a NACA-4412 airfoil equipped with leading-edge zero-net-mass-flux actuators...
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The aim of this experimental study is the implementation of a practical and efficient closed-loop feedback control of the turbulent flow over a NACA-4412 airfoil equipped with leading-edge zero-net-mass-flux actuators. By using prior computation of correlations between particle image velocimetry data and multiple surface pressure measurements, real-time instantaneous low-dimensional estimates of the velocity field over the wing are then computed from the unsteady surface pressure. From such estimates, a direct knowledge of the state of the flow above the airfoil is obtained (i.e., attached, incipient separation, or fully separated flow). We first show the effectiveness of the low-dimensional modeling approach in extracting and estimating the underlying large-scale structures in a turbulent flow, using the proper orthogonal decomposition and the modified linear/quadratic stochastic measurements. We then show how such an approach is used successfully in a simple, but practical, proportional feedback loop to delay the separation of the flow over the wing at high angles of attack. The benefits of closed-loop vs open-loop control are then discussed. These fundamental results validate the use of low-dimensional modeling techniques for further, more sophisticated, closed-loop feedback control algorithms.
This paper investigates robust nonlinear control for close formation flight of multiple fixed-wing aircraft. It aims to achieve precise position control in general flight operation under the aerodynamic impact induced...
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This paper investigates robust nonlinear control for close formation flight of multiple fixed-wing aircraft. It aims to achieve precise position control in general flight operation under the aerodynamic impact induced by the trailing vortices of leader aircraft. One crucial concern is the boundedness of position errors subject to uncertainties and disturbances to be regulated with accuracy. This paper develops a robust nonlinear control algorithm to fulfill precise close formation-tracking control. The proposed control algorithm consists of baseline control laws and disturbance observers. The baseline control laws are employed to stabilize the nonlinear dynamics of close formation flight, whereas the disturbance observers are introduced to compensate system uncertainties and formation-related aerodynamic disturbances. The position control performance can be guaranteed within the desired boundedness to harvest enough drag reduction for a follower aircraft in close formation using the proposed design. The effectiveness of the proposed design is demonstrated via the numerical simulation of the close formation flight of two fixed-wing aircraft.
The purpose of this work is to describe the use of electrospray propulsion devices as miniaturized actuators for precise attitude control of small satellites, including CubeSats. Electrosprays are nonpressurized, pass...
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The purpose of this work is to describe the use of electrospray propulsion devices as miniaturized actuators for precise attitude control of small satellites, including CubeSats. Electrosprays are nonpressurized, passively fed, compact and fuel-efficient electric thrusters capable of producing impulse bits in the 10(-6)N s or lower, depending on the configuration. These characteristics have the potential to allow for long-term pointing in the arcsecond range or better with practically no jitter. Experimental work is performed on a magnetically levitated testbed in vacuum to demonstrate the actuation characteristics under nonoptimal control. It is found that, subject to a noisy attitude sensor and external perturbations, electrospray thrusters are capable of producing pointing accuracies around a given set point of 22 arcseconds 3 sigma error during 10h on a platform similar in size and mass to a 1U CubeSat. The implementation of such capabilities could complement or eliminate the need of reaction wheels and magnetorquers, especially in missions beyond low Earth orbit, while including propulsive capabilities for additional maneuverability in technology development or scientific missions.
For the robot control problems, the input constraint is an issue that must be carefully considered. Considering the control inputs of the robots in the multi-robot system are constrained by different saturations in re...
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For the robot control problems, the input constraint is an issue that must be carefully considered. Considering the control inputs of the robots in the multi-robot system are constrained by different saturations in reality, we address the cooperative circumnavigation control problem of multiple unicycle-type robots with non-identical and unknown input constraints in this paper. A distributed control law is designed to drive the robots constrained by different and unknown input saturations to achieve the cooperative circumnavigation around a moving target. The algorithm proposed in this paper largely reduces the requirement for the maneuverability of the robots to achieve the cooperative circumnavigation. As long as the robots owns the basic maneuverability of circumnavigating around the target, it is proved rigorously that the proposed control algorithm can achieve the desired cooperation circumnavigation of the multi-robot system. The effectiveness of the proposed method is validated by a numerical simulation.
Large dead time is a significant control problem and source of instability for the control loop. A Smith Predictor scheme provides a conventional large dead time compensation leaving other process dynamics to the sepa...
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Large dead time is a significant control problem and source of instability for the control loop. A Smith Predictor scheme provides a conventional large dead time compensation leaving other process dynamics to the separate controller. The real long dead time processes, such as heat transfer and flow control systems, typically exhibit long time delays intertwined with other process dynamics. One of the authors, Roman Gorecki, proposed and implemented a new algorithm, based on the principle of simplification of the control system transfer function, to deal with this issue. The concept of this new algorithm, called a Simplifying controller, is briefly presented. It is followed by the real system example where a heat transfer process control system with use of the Simplifying controller is described. The Simplifying controller algorithm offers improved control for large dead-time process control applications. (C) 1999 Elsevier Science Ltd. All rights reserved.
An efficient C-0 continuous two-dimensional finite-element model has been presented in this paper for the control of laminated composite and sandwich plates embedded/surface-bonded with piezoelectric layers and subjec...
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An efficient C-0 continuous two-dimensional finite-element model has been presented in this paper for the control of laminated composite and sandwich plates embedded/surface-bonded with piezoelectric layers and subjected to mechanical loading as well as electric potential. The problem of modeling of smart laminates involves the coupling between mechanical and electrical fields. The structural component is modeled by an efficient equivalent single-layer plate theory, which ensures interlaminar shear-stress continuity and zero transverse shear-stress conditions at the top and bottom of the plate surfaces. Moreover, this theory contains unknowns defined at the reference plane (i.e., midplane) only. The electric field is modeled using layerwise theory, which contains the unknowns at each layer interfaces. The proposed combine model, which may be called a refined hybrid plate model, is implemented to analyze the coupled problem of piezoelectricity in laminated composites and sandwich plates.
This paper reports on the initial phase of feasibility testing of a control strategy that uses myoelectric signals (MES) from wrist flexor and extensor muscles to control a hand-grasp neuroprosthesis for C7 tetraplegi...
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This paper reports on the initial phase of feasibility testing of a control strategy that uses myoelectric signals (MES) from wrist flexor and extensor muscles to control a hand-grasp neuroprosthesis for C7 tetraplegia. The control strategy was customized to the MES patterns produced during wrist flexion, extension, and relaxation for five able-bodied subjects and two individuals with C7 spinal cord injury. We evaluated the reliability with which the subjects could deliberately activate target neuroprosthesis states and control the degree of opening and closing of a computer-simulated hand using the myoelectric control strategy. Every subject was able to activate at least 99% of the target states for at least 1 continuous second, enough time to prove the activation was deliberate and to achieve significant hand opening or closing. Additionally, every subject was able to control the opening and closing of the simulated hand with enough proficiency to match greater than 87% of the target hand positions for at least 2 continuous seconds. Most of the inadvertent disturbances in simulated hand position were of a magnitude less than 10% of full range of motion for every subject. Future studies will incorporate the control strategy into an electrical stimulation system that opens and closes the hand of an individual with C7 tetraplegia.
This study aims to define a cost-optimal solution based on demand response (DR) actions for a thermal energy storage system with a ground source heat pump in detached residential houses in a cold climate. This study f...
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This study aims to define a cost-optimal solution based on demand response (DR) actions for a thermal energy storage system with a ground source heat pump in detached residential houses in a cold climate. This study finds out the minimum life cycle cost (LCC) of thermal energy storage over the period of 20 years by observing different temperature set points (55-95 degrees C) and sizes (0.3-1.5 m(3)) of a hot water storage tank with developed DR control algorithms. Three different control algorithms were studied: (A) a momentary DR control algorithm based on real-time hourly electricity price (HEP), (B) a backwards-looking DR control algorithm based on previous HEPs and (C) a predictive DR control algorithm based on future HEPs. This research was carried out with the validated dynamic building simulation tool IDA Indoor Climate and Energy. The results show that by using the predictive DR control algorithm the maximum annual savings in total delivered energy and cost are about 12% and 10%, respectively. The minimum LCC can be achieved by the smallest studied storage tank size of 0.3 m(3) with 60 degrees C as the temperature set point, but the effect of storage tank size on LCC is relatively small. (C) 2016 Elsevier Ltd. All rights reserved.
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