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Low-cost distributed control system based on serial field bus
348
Abstracts
the controller when the deadbeat observer finishes the tasks. In the first transient period the choice of a cost function with a weighting coefficient related to a positive control input eventually suppresses the plant input to maintain a pure feedforward controller,as well as output error regulation. In the last stable period, assignment of the cost function with a zero-coefficiant input term makes the output error approach zero in the fastest time.
008 Regulating Characteristics of Exact Model Matching K. Ichlkawa, pp 51-55 In an exact model matching (EMM) control system the controller is synthesized so that the resulting closed-loop system transfer function exactly matches the transfer function of a given reference model, where the reference model is selected to meet the given design specifications. Thus, an EMM con¢ol system is essentially a tracking system. The regulating characteristics are evaluated by the disturbance effect. The disturbance effect on the original EMM control system is often intolerably large. By introducing a disturbance prediction technique the regulating characteristics are substantially improved. Thus, a new design method for EMM with both perfect tracking and satisfactory regulating characteristics has been established.
009 Variable Structure Regulators for Industrial Process Control C. Scall, A. Landl, G. Nardi, A. Balestrtno, pp 57-62 VS-PI controllers, with only two parameters variable with the error, are analyzed for low- and high-order systems, and their limitations of performance are clearly pointed out. For high-order systems the VS-PI controller is augmented with a suitable filter with constant parameters; this allows high performance to be maintained, even in the presence of process uncertainty and input saturation. This is shown by a comparison of results with advanced controllers designed according to the IMC procedure.
010 Low-Cost Distributed Control SystemBased on Serial Field Bus F.J. Smtrez, D.F. Garcia, J.R. Arias, J. Garcia, pp 63-68 This paper presents the strategies adopted in the development and implementation of a small-scale lowcost distributed control system, and its more important characteristics. The communications method adopted was the serial field bus, which confers great economy on the system. The sa'ucture used was the star type, where a master unit handles communication with slave units. The system was developed in a personal-computer environment and includes several utilities, in local mode from the process-control stations and in remote mode from the central control room of the plant. The result is a reliable and modular control system, capable of powerful additional possibilities with only small effort. 011 Application Layer for Bitbus-Based Low-Cost Technological Network D. Hruby, K. Fabian, J. Kalina, pp 69-74 This paper presents the fieldbus from the application-layer point of view. The experimental testbed of the system consists of sensors, actuators and PC machines, communicating over Intel's Bitbus. The distributed system is based on the architecture of a standard host PC with a master Bitbus controller and many remote slave Bitbus modules (max 250). Compared to other
commercial fielduNmes, Bithus is at least near enough the IEC standards requirements. New software modules were implemented in order to fulf'fl the distributed real-time constraints. The flexibility of the i8344 microcontrollers used allows implementation of a specialized Logical Link Control sublayer and an Application layer.
012 Low.Cost Signal Sampling Using Local Integrals M,D. van der Laan, W.A. Halang, P. Koblltek, pp 75-79 An alternative method for signal sampling is presented, which is based on practical requirements. Samples are obtained by local integration of the signal. The method can easily be realised in standard low-cost hardware. The local integration is to be carried out by voltage-tofrequency converters. A special V F C design, presented in this paper, minimizes the non-linearity error. The resulting overall system has low complexity. It reduces the work load of the analyzing computer, and relaxes time constraints.
013 Direct Controlling of Scale Models from PCMATLAB J. Houika, B, Slldek, pp 81-86 For direct access to real plants and their scale models from MATL~, the RT-ToOLBOXwas created. It is a hi~,h-level software tool for data acquisition, rapid prototypmg and testing of control algorithms in a MATLAB environmant, using real systems and their scale models. This paper presents basic features of the RT-TooLaox and experience with its use. Tasks supported by RT-ToOLBOX involve both simple access to A/D and D/A converters, and morecomplex tasks like periodical I/O operations, signal filtering, discrete controllersand data recording, which run in background mode with different sampling rates.
014 A Guide to the Design of a Digital Controller R. Caccla, A. De Carli, pp 87-92 It is possible to design a control strategy by means of different procedures with different complexities. Better results are obtained by using dedicated controllers, rather than general-purpose ones such as PID controllers. The design of a dedicated control s~ategy requires, in general, knowledge of the mathematical model of the system to be controlled and a mathematical formulation of its specifications. In this paper a simple design procedure that does not require heavy mathematical support is proposed.
015 Graphical Method for the Robust Analysis of P.I.D. Controllers J. Quevedo, pp 93-98 In this paper a useful method is presented for analyzing the robust stability of processes with structured perturbations in their model parameters. The process controllers considered must have a linear structure and fixed parameters. This method has been implemented with specific software, ANAGRO, which makes it possible to graphically observe whether any risk of instability exists in the controlled process, enables graphical comparison of various PID controllers,and aids in selecting the most robust ones. A N A G R O also provides an index of the robusmess of various controllers for the same process, and allows the analysis of the relative stability (minimum damping value) of the system.
Abstracts
the controller when the deadbeat observer finishes the tasks. In the first transient period the choice of a cost function with a weighting coefficient related to a positive control input eventually suppresses the plant input to maintain a pure feedforward controller,as well as output error regulation. In the last stable period, assignment of the cost function with a zero-coefficiant input term makes the output error approach zero in the fastest time.
008 Regulating Characteristics of Exact Model Matching K. Ichlkawa, pp 51-55 In an exact model matching (EMM) control system the controller is synthesized so that the resulting closed-loop system transfer function exactly matches the transfer function of a given reference model, where the reference model is selected to meet the given design specifications. Thus, an EMM con¢ol system is essentially a tracking system. The regulating characteristics are evaluated by the disturbance effect. The disturbance effect on the original EMM control system is often intolerably large. By introducing a disturbance prediction technique the regulating characteristics are substantially improved. Thus, a new design method for EMM with both perfect tracking and satisfactory regulating characteristics has been established.
009 Variable Structure Regulators for Industrial Process Control C. Scall, A. Landl, G. Nardi, A. Balestrtno, pp 57-62 VS-PI controllers, with only two parameters variable with the error, are analyzed for low- and high-order systems, and their limitations of performance are clearly pointed out. For high-order systems the VS-PI controller is augmented with a suitable filter with constant parameters; this allows high performance to be maintained, even in the presence of process uncertainty and input saturation. This is shown by a comparison of results with advanced controllers designed according to the IMC procedure.
010 Low-Cost Distributed Control SystemBased on Serial Field Bus F.J. Smtrez, D.F. Garcia, J.R. Arias, J. Garcia, pp 63-68 This paper presents the strategies adopted in the development and implementation of a small-scale lowcost distributed control system, and its more important characteristics. The communications method adopted was the serial field bus, which confers great economy on the system. The sa'ucture used was the star type, where a master unit handles communication with slave units. The system was developed in a personal-computer environment and includes several utilities, in local mode from the process-control stations and in remote mode from the central control room of the plant. The result is a reliable and modular control system, capable of powerful additional possibilities with only small effort. 011 Application Layer for Bitbus-Based Low-Cost Technological Network D. Hruby, K. Fabian, J. Kalina, pp 69-74 This paper presents the fieldbus from the application-layer point of view. The experimental testbed of the system consists of sensors, actuators and PC machines, communicating over Intel's Bitbus. The distributed system is based on the architecture of a standard host PC with a master Bitbus controller and many remote slave Bitbus modules (max 250). Compared to other
commercial fielduNmes, Bithus is at least near enough the IEC standards requirements. New software modules were implemented in order to fulf'fl the distributed real-time constraints. The flexibility of the i8344 microcontrollers used allows implementation of a specialized Logical Link Control sublayer and an Application layer.
012 Low.Cost Signal Sampling Using Local Integrals M,D. van der Laan, W.A. Halang, P. Koblltek, pp 75-79 An alternative method for signal sampling is presented, which is based on practical requirements. Samples are obtained by local integration of the signal. The method can easily be realised in standard low-cost hardware. The local integration is to be carried out by voltage-tofrequency converters. A special V F C design, presented in this paper, minimizes the non-linearity error. The resulting overall system has low complexity. It reduces the work load of the analyzing computer, and relaxes time constraints.
013 Direct Controlling of Scale Models from PCMATLAB J. Houika, B, Slldek, pp 81-86 For direct access to real plants and their scale models from MATL~, the RT-ToOLBOXwas created. It is a hi~,h-level software tool for data acquisition, rapid prototypmg and testing of control algorithms in a MATLAB environmant, using real systems and their scale models. This paper presents basic features of the RT-TooLaox and experience with its use. Tasks supported by RT-ToOLBOX involve both simple access to A/D and D/A converters, and morecomplex tasks like periodical I/O operations, signal filtering, discrete controllersand data recording, which run in background mode with different sampling rates.
014 A Guide to the Design of a Digital Controller R. Caccla, A. De Carli, pp 87-92 It is possible to design a control strategy by means of different procedures with different complexities. Better results are obtained by using dedicated controllers, rather than general-purpose ones such as PID controllers. The design of a dedicated control s~ategy requires, in general, knowledge of the mathematical model of the system to be controlled and a mathematical formulation of its specifications. In this paper a simple design procedure that does not require heavy mathematical support is proposed.
015 Graphical Method for the Robust Analysis of P.I.D. Controllers J. Quevedo, pp 93-98 In this paper a useful method is presented for analyzing the robust stability of processes with structured perturbations in their model parameters. The process controllers considered must have a linear structure and fixed parameters. This method has been implemented with specific software, ANAGRO, which makes it possible to graphically observe whether any risk of instability exists in the controlled process, enables graphical comparison of various PID controllers,and aids in selecting the most robust ones. A N A G R O also provides an index of the robusmess of various controllers for the same process, and allows the analysis of the relative stability (minimum damping value) of the system.