The Experts below are selected from a list of 7155 Experts worldwide ranked by ideXlab platform
Alexandre Trofino Neto - One of the best experts on this subject based on the ideXlab platform.
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assessment of the controlling envelope of a model based Multivariable Controller for vapor compression refrigeration systems
Applied Thermal Engineering, 2010Co-Authors: Leonardo C Schurt, Christian J L Hermes, Alexandre Trofino NetoAbstract:Abstract This paper explores the controlling characteristics of a first-principles model-based Controller specially developed for vapor compression refrigeration systems. Mathematical sub-models were put forward for each of the system components: heat exchangers (condenser and evaporator), variable-speed compressor and variable-orifice electric expansion device. The dynamic simulation model was then used to design a Multivariable Controller based on the linear-quadratic-Gaussian technique using a Kalman filter for the estimator design. A purpose-built testing apparatus comprised of a variable-speed compressor and a pulse-width modulated expansion valve was used to collect data for the system identification, and model and Controller validation exercises. It was found that the model reproduces the experimental trends of the working pressures and power consumption in conditions far from the nominal point of operation (±30%) with a maximum deviation of ±5%. Additional experiments were also performed to verify the ability of the Controller of tracking reference changes and rejecting thermal load disturbances. It was found that the Controller is able to keep the refrigeration system running properly when the thermal load was changed from 340 to 580 W (460 W nominal), and the evaporator superheating degree was varied from 9.5 °C to 22 °C (16.6 °C nominal).
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a model driven Multivariable Controller for vapor compression refrigeration systems
International Journal of Refrigeration-revue Internationale Du Froid, 2009Co-Authors: Leonardo C Schurt, Christian J L Hermes, Alexandre Trofino NetoAbstract:A model-driven Controller for vapor compression refrigeration systems is presented herein. Mathematical sub-models were developed for each of the system components: heat exchangers (condenser and evaporator), variable-speed compressor and variable-orifice electric expansion device. The overall system simulation model was used to design a MIMO Controller based on the linear-quadratic Gaussian method using a state observer of the Kalman filter type. A purpose-built testing apparatus comprised of a variable-speed compressor and a pulse-width modulated expansion valve was used to collect data for the system identification and model validation exercises. It was found that the model reproduces the experimental trends of the working pressures in conditions far from the operation point (±30%) with a maximum deviation of ±5%. Additional experiments were also performed to verify the ability of the Controller of tracking reference changes and rejecting thermal load disturbances as high as 15%.
Qingguo Wang - One of the best experts on this subject based on the ideXlab platform.
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Multivariable process identification and control from decentralized relay feedback
International Journal of Modelling and Simulation, 2000Co-Authors: Qingguo Wang, Changchieh HangAbstract:AbstractThe relay auto-tuning technique for PID Controllers is being extended to tune Multivariable Controllers. In this paper, an auto-tuning method for Multivariable Controllers from decentralized relay feedback is proposed. The frequency response of an m × m Multivariable process is identified from a decentralized relay test using an FFT-based method. For Multivariable Controller tuning, a new set of design equations are derived under the decoupling conditions, where the equivalent diagonal plants are independent of off-diagonal elements of the Controller and used to design its diagonal elements first. The PID parameters of the Controllers are determined individually with linear least squares frequency response defined on the basis of the identified frequency responses. Various typical examples are included for illustration of the effectiveness of this method.
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a frequency response approach to autotuning of Multivariable Controllers
Chemical Engineering Research & Design, 1997Co-Authors: Qingguo Wang, C C HangAbstract:The relay auto-tuning technique for PID Controllers is here extended to tuneMultivariable Controllers. In the case of significant interaction, a fully cross-coupled Multivariable Controller rather than a decentralized Controller should be employed. In this paper, an autotuning method for Multivariable Controllers from sequential relay feedback is proposed. The frequency response a m×m Multivariable process is identified from limit cycles using a FFT-based method, and a Multivariable Controller is computed with linear least squares frequency response fitting. Various typical examples are included for illustration of the effectiveness of the method.
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auto tuning of Multivariable pid Controllers from decentralized relay feedback
Automatica, 1997Co-Authors: Qingguo Wang, Qiang BiAbstract:Abstract A method for auto-tuning fully cross-coupled Multivariable PID Controllers from decentralized relay feedback is proposed for Multivariable processes with significant interactions. Multivariable oscillations under decentralized relay feedback are first investigated, and, in particular, it is shown that for a stable m × m process the oscillation frequency will remain almost unchanged under relatively large relay amplitude variations. Therefore m decentralized relay feedback tests are performed on the process, with their oscillation frequencies close to each other so that the process frequency-response matrix can be estimated at that frequency. A bias is further introduced into the relay to additionally obtain the process steady-state matrix. For Multivariable Controller tuning, a new set of design equations are derived under the decoupling condition where the equivalent diagonal plants are independent of off-diagonal elements of the Controller, and are used to design the Controller diagonal elements first. The PID parameters of the Controllers are determined individually by solving these equations at the oscillation and zero frequencies. The proposed method is applied to various typical processes, where significant performance improvement over the existing tuning methods is demonstrated.
Leonardo C Schurt - One of the best experts on this subject based on the ideXlab platform.
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assessment of the controlling envelope of a model based Multivariable Controller for vapor compression refrigeration systems
Applied Thermal Engineering, 2010Co-Authors: Leonardo C Schurt, Christian J L Hermes, Alexandre Trofino NetoAbstract:Abstract This paper explores the controlling characteristics of a first-principles model-based Controller specially developed for vapor compression refrigeration systems. Mathematical sub-models were put forward for each of the system components: heat exchangers (condenser and evaporator), variable-speed compressor and variable-orifice electric expansion device. The dynamic simulation model was then used to design a Multivariable Controller based on the linear-quadratic-Gaussian technique using a Kalman filter for the estimator design. A purpose-built testing apparatus comprised of a variable-speed compressor and a pulse-width modulated expansion valve was used to collect data for the system identification, and model and Controller validation exercises. It was found that the model reproduces the experimental trends of the working pressures and power consumption in conditions far from the nominal point of operation (±30%) with a maximum deviation of ±5%. Additional experiments were also performed to verify the ability of the Controller of tracking reference changes and rejecting thermal load disturbances. It was found that the Controller is able to keep the refrigeration system running properly when the thermal load was changed from 340 to 580 W (460 W nominal), and the evaporator superheating degree was varied from 9.5 °C to 22 °C (16.6 °C nominal).
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a model driven Multivariable Controller for vapor compression refrigeration systems
International Journal of Refrigeration-revue Internationale Du Froid, 2009Co-Authors: Leonardo C Schurt, Christian J L Hermes, Alexandre Trofino NetoAbstract:A model-driven Controller for vapor compression refrigeration systems is presented herein. Mathematical sub-models were developed for each of the system components: heat exchangers (condenser and evaporator), variable-speed compressor and variable-orifice electric expansion device. The overall system simulation model was used to design a MIMO Controller based on the linear-quadratic Gaussian method using a state observer of the Kalman filter type. A purpose-built testing apparatus comprised of a variable-speed compressor and a pulse-width modulated expansion valve was used to collect data for the system identification and model validation exercises. It was found that the model reproduces the experimental trends of the working pressures in conditions far from the operation point (±30%) with a maximum deviation of ±5%. Additional experiments were also performed to verify the ability of the Controller of tracking reference changes and rejecting thermal load disturbances as high as 15%.
Qiang Bi - One of the best experts on this subject based on the ideXlab platform.
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auto tuning of Multivariable pid Controllers from decentralized relay feedback
Automatica, 1997Co-Authors: Qingguo Wang, Qiang BiAbstract:Abstract A method for auto-tuning fully cross-coupled Multivariable PID Controllers from decentralized relay feedback is proposed for Multivariable processes with significant interactions. Multivariable oscillations under decentralized relay feedback are first investigated, and, in particular, it is shown that for a stable m × m process the oscillation frequency will remain almost unchanged under relatively large relay amplitude variations. Therefore m decentralized relay feedback tests are performed on the process, with their oscillation frequencies close to each other so that the process frequency-response matrix can be estimated at that frequency. A bias is further introduced into the relay to additionally obtain the process steady-state matrix. For Multivariable Controller tuning, a new set of design equations are derived under the decoupling condition where the equivalent diagonal plants are independent of off-diagonal elements of the Controller, and are used to design the Controller diagonal elements first. The PID parameters of the Controllers are determined individually by solving these equations at the oscillation and zero frequencies. The proposed method is applied to various typical processes, where significant performance improvement over the existing tuning methods is demonstrated.
H F Wang - One of the best experts on this subject based on the ideXlab platform.
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interactions and Multivariable design of multiple control functions of a unified power flow Controller
International Journal of Electrical Power & Energy Systems, 2002Co-Authors: H F WangAbstract:One of the most important features of a unified power flow Controller (UPFC) is its multiple control function. These control functions have been suggested to be implemented by multiple Controllers. However, study examples presented in the paper demonstrate the existence of the dynamic interactions among different UPFC Controllers, i.e. power flow Controller, AC voltage Controller and DC voltage Controller. Due to the interactions, it is demonstrated in the paper that there are cases where separately designed and individually implemented stable UPFC Controllers may result in poor control performance and even the closed-loop system instability when they are in joint operation. Hence, it is suggested in this paper that the multiple functional UPFC is treated as a multi-input and multi-output (MIMO) control system such that a single Multivariable Controller can be designed for the UPFC to perform the multiple control functions, which takes full account of the control interactions in the MIMO UPFC system.
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Multivariable design of a multiple functional unified power flow Controller
Power Engineering Society Summer Meeting, 2000Co-Authors: H F WangAbstract:One of the most important features of a unified power flow Controller (UPFC) is its multiple control functions. These control functions have been suggested to be implemented by multiple Controllers. However, examples presented in the paper demonstrate the existence of the dynamic interactions among different UPFC Controllers and it is suggested that the multiple functional UPFC is designed to be a multi-input multi-output (MIMO) Controller. It is demonstrated in the paper that a single Multivariable Controller can be designed successfully for the UPFC to perform the multiple control functions which takes full account of the control interactions in the MIMO UPFC system and guarantees the closed-loop system stability.
