The paper presents controldesign and results of a leading experiment in the distance stabilization of large bodies, emulating optical mirrors, with picometer repeatability. The experiment, called COSI (control Optics...
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The paper presents controldesign and results of a leading experiment in the distance stabilization of large bodies, emulating optical mirrors, with picometer repeatability. The experiment, called COSI (control Optics Structure Interaction), was funded by the European Space Agency (ESA) in view of future space telescopes needing picoradian precision over time scales >1 s. Distance stabilization is achieved by actively controlling the optical length of Fabry-Perot cavities in the vacuum. The first experiments stabilized three 0.5 m distances between two 7 kg plates with a residual control error better than 3 pm (1σ), in presence of severe environment noise and artificial micrometer distance variations, thus fully demonstrating feasibility of COSI concept and technology.
We propose here an adaptive observer for estimation of a road friction coefficient, which is important for vehicle control. The observer needs driving torque and wheel speeds of driven and non-driven wheels as inputs....
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We propose here an adaptive observer for estimation of a road friction coefficient, which is important for vehicle control. The observer needs driving torque and wheel speeds of driven and non-driven wheels as inputs. The road friction coefficient is assumed to be represented by a product of a known function and an unknown parameter to be estimated by an adaptive law. It is shown that non-robust adaptive law can get the true value, if there are no disturbance. However, it diverges when disturbances are added. Periodical σ-modification is proposed here as a robust adaptive law. The estimation robustness against disturbances can be improved with the law. Numerical simulation results are presented to show the effectiveness of the law.
Rotating stall is one type of aerodynamic instability limiting the performance of aeroengines. A set of magnetic bearings supporting the compressor rotor is a potential actuator for active control of rotating stall. B...
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Rotating stall is one type of aerodynamic instability limiting the performance of aeroengines. A set of magnetic bearings supporting the compressor rotor is a potential actuator for active control of rotating stall. Based on a first-principles model we show that using this type of actuation, the first harmonic mode of rotating stall is linearly controllable, but the zeroth and the second harmonic modes are linearly uncontrollable. For systems with a stable zeroth (surge) mode, we give an explicit procedure for designing feedback laws such that the Hopf bifurcation of the second mode stall inception is super-critical. We also investigate the effects of magnitude saturation on the size of the region of attraction. We demonstrate the theoretical results by numerical simulations of a model for a transonic compressor at the NASA Glenn Research Center.
In this study, we focus on the error of estimated frequency of disturbance and present a new adaptive frequency tracking and new modification law after examining relation between the error of frequency and output leve...
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In this study, we focus on the error of estimated frequency of disturbance and present a new adaptive frequency tracking and new modification law after examining relation between the error of frequency and output level in detail. We also develop a multiple frequency estimation algorithm, which is insensitive to observation noise and prove the asymptotic stability for adaptive nonlinear algorithm and adaptive frequency tracking method theoretically. The results of simulation show that when estimated frequency by difference equation method approach to the true value, then the output error converges to zero (or equilibrium point) asymptotically. This corresponds to the asymptotic stability condition. The effectiveness of this method and the theoretical proof are verified by simulation. The experimental results show that the proposed algorithm is effective for achieving unbalance vibration suppression.
In this paper the objective is to optimize the control of a coal fired 250 MW power plant boiler. The conventional controlsystem is supplemented with a multivariable optimizing controller operating in parallel with t...
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In this paper the objective is to optimize the control of a coal fired 250 MW power plant boiler. The conventional controlsystem is supplemented with a multivariable optimizing controller operating in parallel with the conventional controlsystem. Due to the strong dependence of the gains and dynamics upon the load, it is beneficial to consider a gain-scheduling control approach. Optimization using complex-μ synthesis results in unstable LTI controllers in some operating points of the boiler. A recent gain-scheduling approach allowing for unstable fixed LTI controllers is applied. Gain-scheduling which interpolates between unstable controllers is not allowed using traditional schemes. The results show that a considerable optimization of the conventional controlled system is obtainable. Also the gain-scheduled optimizing controller is seen to have a superior performance compared to the fixed LTI optimizing controllers operating alone.
In this note, we propose a simple and useful decentralized approach for the states and parameters estimation of general non-linear discrete-time Multi-Input/Multi-Output (MIMO) systems. Thanks to a simple and useful p...
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In this note, we propose a simple and useful decentralized approach for the states and parameters estimation of general non-linear discrete-time Multi-Input/Multi-Output (MIMO) systems. Thanks to a simple and useful parametrization technique recently developed in [Bou97], we investigate the stability analysis and it turns out that not only asymptotic convergence is assured under very general conditions but also how to enlarge the basin of attraction with high tracking ability. Performances and accuracy of the results are illustrated, first, through a simulation example under severe conditions. Next, the proposed technique will be successfully applied to a real single-link rigid manipulator using only the position measurement.
The problem of robust stabilization of nonlinear systems with partially known uncertainties is considered. A class of continuous adaptive robust state feedback controllers with simpler structure is proposed. It is sho...
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The problem of robust stabilization of nonlinear systems with partially known uncertainties is considered. A class of continuous adaptive robust state feedback controllers with simpler structure is proposed. It is shown that the resulting closed-loop nonlinear systems with uncertainties are stable in the sense of uniform ultimate boundedhess. In contrast with some results presented in the control literature, the proposed adaptive law for updating the estimate values of the unknown parameters is continuous, and the existence of the solutions to the resulting closed-loop systems in the usual sense can well be guaranteed. Moreover, due to the continuity of state feedback controller and adaptive law, the proposed adaptive robust state feedback controllers is easily implemented in practical robust control problems. Finally, an illustrative example is given to demonstrate the utilization of the results.
The theory of Markov Decision Process (MDP) has been widely applied to the networking management such as routing and admission control. However, the traditional MDP approach is mainly hindered by prohibitive computati...
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The theory of Markov Decision Process (MDP) has been widely applied to the networking management such as routing and admission control. However, the traditional MDP approach is mainly hindered by prohibitive computational complexity. The performance potential theory offers an efficient solution to alleviate such difficulties in infinite-horizon MDP problems. The concept `potential' leads to some important properties that allow it to be measured on a single sample path, thereby adapting to the dynamic characteristics in realistic applications such as high speed networks. In this paper, we investigate the application of single-sample-path-based potential theory to the admission control in the network with multiple classes of traffic. Optimal policies under different traffic characteristics are obtained with a fast convergence. Some simple and efficient algorithms are developed for online implementation.
The Electrostatically Suspended Gyroscope (ESG) is a two-axis inertial orientation sensor manufactured by Boeing and currently in use on U.S. Navy submarines. The additional ability of the ESG to act as an acceleromet...
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The Electrostatically Suspended Gyroscope (ESG) is a two-axis inertial orientation sensor manufactured by Boeing and currently in use on U.S. Navy submarines. The additional ability of the ESG to act as an accelerometer is well known, but extraction of precision acceleration measurements from an ESG has not been achieved. The major obstacles to precision accelerometry are the nonlinear dynamics of the ESG rotor and parametric variation of the ESG electronics. In this paper, we derive a model for the ESG dynamics with an eye toward efficient representation of the uncertainties in the model. We represent the model uncertainties and nonlinearities in a framework amenable to μ-analysis and analyze ESG accelerometer precision using μ-analysis tools. Finally, we discuss the implementation of a digital ESG control architecture for use in ESG system identification and testing of suspension control and accelerometer algorithms.
In this paper, we present a phenomenological nonlinear dynamic model for direct injection stratified charge (DISC) gasoline engines and discuss several key control problems for this advanced technology powertrain. The...
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In this paper, we present a phenomenological nonlinear dynamic model for direct injection stratified charge (DISC) gasoline engines and discuss several key control problems for this advanced technology powertrain. The model is developed and validated using dynamometer engine mapping data obtained from a 4-cylinder DISC engine. It captures the static behavior of the key components of a DISC engine, such as the torque and emissions generation and volumetric efficiency, as well as the essential dynamics for the intake manifold and engine rotational inertia. It is shown that the multi-mode operation of a DISC engine dictates a hybrid model structure and also requires a coordinated multivariable control strategy to achieve expected performance.
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