This paper presents a design technique for the two degree of freedom (2-DOF) controlsystem using PID (Proportional-Integral-Derivative)×(n-2) stage PD as a cascade controller for a class of nth order plant. It i...
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This paper presents a design technique for the two degree of freedom (2-DOF) controlsystem using PID (Proportional-Integral-Derivative)×(n-2) stage PD as a cascade controller for a class of nth order plant. It is intended to satisfy both transient and steady state response specifications based on the root locus approach. This controller can be used instead of the conventional PID controller for the higher order plant to obtain better performance. The transfer function of a class of nth order plant should not include zeros, the poles of the plant should have negative real part. The overall system is approximated as a stable and robust second order system. The performances of the controlled system are satisfied by this design technique. Moreover, this technique can also be applied to the plant with small dead time. The cascade controller gain can be adjusted to meet faster responses with a little or no overshoot. Robustness properties given by this controller proposed in this paper have also been demonstrated by numerical examples.
In this paper we consider a link serving multiple service classes. We evaluate the properties of the link admission control policies that are obtained from an efficient scheme proposed by Krishnan and Hubner. The Kris...
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In this paper we consider a link serving multiple service classes. We evaluate the properties of the link admission control policies that are obtained from an efficient scheme proposed by Krishnan and Hubner. The Krishnan and Hubner approach suggests efficient calculations of state-dependent routing criteria for multi-rate networks through state-space aggregation. Through simple examples we show that it is possible that the approximations made in the approach might lead to degraded performance, instead of the expected improvement. We outline and discuss a possible extension to the Krishnan and Hubner approach in an effort to address this problem.
In this paper, we present recent results of using a Kohonen neural network to detect and classify faults occurring in a dynamic system. The measured outputs from the system are first used in a Kalman filter to generat...
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In this paper, we present recent results of using a Kohonen neural network to detect and classify faults occurring in a dynamic system. The measured outputs from the system are first used in a Kalman filter to generate residual vectors that serve as fault indicators. As the residuals are generated they can be sent one-by-one to the Kohonen network, both the Kalman filter and the Kohonen network operating on-line in real time. The Kohonen network detects and categorizes the fault, since the residual vectors serve as signatures for different types of faults. The Kohonen network starts with a few pre-designated categories, each category representing a fault type. As more and more residual vectors become available, the Kohonen network opens new categories for residuals that do not have a good enough match with any of the existing categories. The concept is illustrated by an application example that uses actual fault data commercially recorded by the utilities in Texas.
Mechanical devices usually come with undesirable nonlinearities such as frictions, backlashes and saturation. Under the assumption of linear systems, the commonly seen identification schemes utilize sinusoidal excitat...
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Mechanical devices usually come with undesirable nonlinearities such as frictions, backlashes and saturation. Under the assumption of linear systems, the commonly seen identification schemes utilize sinusoidal excitation signals for parameter identifications. However, the data for identification are unavoidably distorted by the fore-mentioned nonlinearities and the identification result is not satisfactory. In this paper, a method based on binary excitation signals is proposed. The method does not suffer from the problem of nonlinear distortions in signal shape and is able to determine the bias term for asymmetric frictions such that an accurate model can be derived. A 0.01 μm high precision ballscrew table with asymmetric frictions is utilized as a test plant for this approach. The result proves to be very successful.
Under `Free Flight,' each individual aircraft will have the first responsibility to resolve its own conflicts. Therefore, a centralized air traffic controller (ATC) will issue a resolution command only when a phys...
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Under `Free Flight,' each individual aircraft will have the first responsibility to resolve its own conflicts. Therefore, a centralized air traffic controller (ATC) will issue a resolution command only when a physical conflict would be unavoidable if the ATC did not do so. Regarding the operation of an ATC under `Free Flight,' hence, determining when the ATC should issue a resolution command would be one of the most important problems. This paper presents a systematic and efficient algorithm as a solution to this problem. This algorithm is based on the well-known Semi-Definite Program (SDP) relaxation method.
Switching power converters are nonlinear and time variant systems. The classical controller design for a switching power converter based on the linear model derived by one of conventional modelling methods. However th...
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Switching power converters are nonlinear and time variant systems. The classical controller design for a switching power converter based on the linear model derived by one of conventional modelling methods. However the parameter and load variations and input unregulated voltage are not taken into consideration simultaneously in a controller design. In this paper, we use `input-output feedback linearization' technique for nonlinear control issue, and `Kharitonov, H∞ and μ-synthesis' techniques for robust control issue to design of nonlinear and linear robust controllers to access both satisfactory stability and satisfactory performance, even in case of uncertainties and disturbances, for typical fifth-order DC-DC Switching power converter. The stability and performance of the converter and the effectiveness of the proposed controllers are demonstrated by some simulated results. Making use of simulation results, varies comparisons between these controllers and a variety of other controllers are then made, exhibiting the high efficiency of these methods compared to conventional methods.
Metalorganic chemical vapor deposition (MOCVD) is a promising technology for the growth of epitaxial semiconductors. It has traditionally lacked real-time growth monitoring and control, which limits the precise reprod...
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Metalorganic chemical vapor deposition (MOCVD) is a promising technology for the growth of epitaxial semiconductors. It has traditionally lacked real-time growth monitoring and control, which limits the precise reproducibility needed for high performance devices. Two complementary control approaches are investigated experimentally. The first is a feedforward disturbance rejection strategy using ultrasonic concentration measurements to reject source gas bubbler disturbances. The second is a feedback system using an ultraviolet (UV) absorption sensor for real-time monitoring of reaction chamber gas concentrations. Post-growth X-ray analysis of InP/GaInAs superlattice test devices is used to evaluate controlsystem performance.
The defining characteristic of a networked controlsystem (NCS) is having a feedback loop that passes through a local area computer network. This paper considers nonlinear systems controlled in this manner, and demons...
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The defining characteristic of a networked controlsystem (NCS) is having a feedback loop that passes through a local area computer network. This paper considers nonlinear systems controlled in this manner, and demonstrates that for sufficiently high transmission rates, the network may be considered transparent. Three methods of scheduling data packets are compared: a static scheduler (token ring), the Try-Once-Discard (maximum-error-first) scheduler with continuous priority levels, and the Try-Once-Discard scheduler with discrete priority levels. The third method is of particular interest when only a small number of bits are available for collision resolution. Asymptotic stability is guaranteed in the first two cases, and ultimate uniform boundedness in the third. In the final section, simulations demonstrate the theoretical results. The contributions of this paper are two-fold: first, it extends the earlier results on NCS to nonlinear systems, and second, it allows for finite word-length message identifiers.
The occurrence of flooding in the absorption column of the Rectisol process at Sasol Synthetic Fuels was predicted as part of the overall Advanced control Project on the Rectisol unit. The flooding predictor was used ...
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The occurrence of flooding in the absorption column of the Rectisol process at Sasol Synthetic Fuels was predicted as part of the overall Advanced control Project on the Rectisol unit. The flooding predictor was used as a controlled variable in a multivariable controller with an objective function that maximizes the gas throughput. Data from the Rectisol process corresponding to several different flooding scenarios was analyzed. Results show that the neural network differential pressure predictor was accurate. However, the linear differential pressure predictor performed quite poorly. This indicates that sufficient nonlinear dynamical effects in the Rectisol process exist to warrant the use of a nonlinear model.
A signal flow graph grammar has been developed that generates signal flow graphs by means of subgraph rewriting. It includes some context-sensitive productions and is very concise. An attribute signal flow graph gramm...
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A signal flow graph grammar has been developed that generates signal flow graphs by means of subgraph rewriting. It includes some context-sensitive productions and is very concise. An attribute signal flow graph grammar has also been formalized as an extended grammar of the signal flow graph grammar, in order to formally define and evaluate a variety of information accompanying signal flow graphs. As a specific example of the attribute signal flow graph grammar, we formalized the attributes and semantic rules to extract the relationships of the signals running in signal flow graphs. A parser-evaluator that we have implemented on the basis of the formalized grammar evaluates the attribute values while it parses a diagram in a bottom-up parallel manner. This attribute signal flow graph grammar is expected to become the theoretical and practical foundation for supporting computerized system analysis and design by using signal flow graphs.
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