Grade change on a paper machine is a transition from one set of operating conditions to another. During the transition, without proper coordination and control, the entire process could have radical fluctuations and p...
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Grade change on a paper machine is a transition from one set of operating conditions to another. During the transition, without proper coordination and control, the entire process could have radical fluctuations and produce significant amounts of off-spec paper or even cause sheet break. The production loss and the efforts to recycle off-spec waste are very costly. To address the issue, this paper formulates the dynamic models of paper-making processes and presents an effective control of grade change transitions. The method has been applied to several hundreds of paper machines. A real application example is included here to demonstrate the actual performance of the described approach.
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.
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.
Flexible manipulators provide significant advantages over commonly used rigid robots, such as high operation speed and high power efficiency. However, the controller design for these manipulators is very complicated b...
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ISBN:
(纸本)078035446X
Flexible manipulators provide significant advantages over commonly used rigid robots, such as high operation speed and high power efficiency. However, the controller design for these manipulators is very complicated because of the nonlinear vibration dynamics. In this paper, a rule-based scheme for implementing a fuzzy logic controller to drive a flexible manipulator is proposed. The phase portrait plane has been adopted to build the rules based on mathematical reasoning rather than the conventional trial and error method, which is dependent on the operator's experience. In order to improve the performance of the fuzzy logic controller, an adjustable weight parameter has been introduced to build the control table. A set of variable width triangular membership functions is used to improve the resolution of the controller. The effectiveness of the control law has been demonstrated with numerical simulation.
The results of analysis using a reduced-order model of combustion instability derived at UTRC and experiments with active control using fuel modulation motivated a study of what performance is achievable using active ...
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The results of analysis using a reduced-order model of combustion instability derived at UTRC and experiments with active control using fuel modulation motivated a study of what performance is achievable using active control. Limitations due to lightly damped or unstable eigenvalues, delay, disturbances, and limited actuator authority and bandwidth are studied. In this part of the paper we focus on linear analysis of a combustion model and study effect of delay in the model and limited actuator bandwidth.
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.
The traditional MDP deals with the cost function which only depends on the state, and the corresponding action. In the real world, however, there are many applications where the cost incurred depends on the particular...
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The traditional MDP deals with the cost function which only depends on the state, and the corresponding action. In the real world, however, there are many applications where the cost incurred depends on the particular transition as well, which makes the traditional MDP solution infeasible for these problems. In this paper, we apply the performance potential theory as an optimization tool for MDP. In particular, the notion of the expanded Markov chain is introduced to map this problem to a general form. Both computation-based and sample-path-based algorithms are developed for potential derivation. We address ourselves to the complexity-reduction techniques. Finally, we apply these techniques to the `Join the Shortest Queue' application, which is a significant component in the analysis of communication system.
This paper describes the robust controldesign of a gas generator engine. A non-linear model of the engine has been developed within Simulink (1) from details previously presented in reference (2). State space H∞ con...
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This paper describes the robust controldesign of a gas generator engine. A non-linear model of the engine has been developed within Simulink (1) from details previously presented in reference (2). State space H∞ controldesigns are performed using a linearized model to represent the key components in the single loop control configuration. The performance criteria are specified in terms of stability margins, bandwidth and desired response of the engine to large step input. The engine is subject to constraints on its manipulated variable (i.e. the throttle valve angle) which cause integral wind up. The H∞ design is simplified to a classical Proportional-Integral (PI) controller. To take a full advantage of the design a technique so-called Utilize Saturation Feedback is used to reduce the effect of the integral windup. The results show that the PI control produces results similar to H∞ at low speeds but that H∞ gives better robustness and performance at higher speeds. Nonlinear simulations with parameter changes support the conclusion that the design is robust.
Residual vibration of flexible structures can be greatly reduced by generating specially-shaped command signals. Input shaping is a type of command generation scheme that is implemented by convolving a sequence of imp...
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Residual vibration of flexible structures can be greatly reduced by generating specially-shaped command signals. Input shaping is a type of command generation scheme that is implemented by convolving a sequence of impulses with any desired system command. The resulting shaped input is used as the reference command. Many types of useful impulse sequences have been proposed. Most of these have contained only positively valued impulses. However, when some of the impulses are allowed to have negative amplitudes, the system rise time can be improved. The improved rise time comes with the potential drawback of actuator saturation. New types of impulse sequences containing negative impulses are proposed. These sequences allow the designer to specify the swing in amplitude between successive impulses. This in turn allows the actuator effort to be controlled.
So far, Two-Degree-of-Freedom controlsystems have been used to realize desirable transient response in the tracking system of a Hard Disk Drive (HDD). It is easy to realize a high speed seek, if the actuator of the H...
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So far, Two-Degree-of-Freedom controlsystems have been used to realize desirable transient response in the tracking system of a Hard Disk Drive (HDD). It is easy to realize a high speed seek, if the actuator of the HDD has a resonance mode at a much higher frequency domain than the desired control domain. However, it is generally difficult to design an actuator that has a resonance mode in a high frequency domain. So, in order to realize a high speed seek, it is important to design a digital controlsystem in consideration of the resonance mode of the actuator. In this case, if the Nyquist frequency of the controlsystem is higher than the resonance mode of the actuator, the controlsystem can be designed by using a method such as a H∞ control theory in consideration of the resonance mode. However, if the Nyquist frequency isn't higher than the resonance mode of the actuator, it is very difficult to realize a high speed seek without mechanical vibration using a conventional method. Then, in this paper the method of applying the N-Delay control theory to the design of the feedforward controller in a Two-Degree-of-Freedom controlsystem, and searching for the optimum time allocation of the N-Delay controller based on an evaluation function are proposed. Using these methods, the frequency component of the feedforward control signal can be diminished at the desired frequency point higher than the Nyquist frequency. The validity of the proposed method is confirmed by the numerical and experimental results with a miniature 2.5-inch hard disk drive.
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