2017 21st International Conference on Process Control (PC), 2017
Advisory system for operators of complex industrial processes has been developed and improved by ... more Advisory system for operators of complex industrial processes has been developed and improved by an international team of scientists and people from industry since 2000. Main purpose of the advisory system is to help operator set up manually adjustable parameters of an industrial process, with the aim to reach required production quality. Industrial process is taken for a stochastic process and input signals of its control system are taken for random variables. Based on Bayesian probability theory, a software toolbox was created for handling mixtures of probability density functions describing behavior of the process. Advisory system was tested and pilot application was installed on rolling mills producing metal strips. During the tests, an idea emerged to exploit verified probabilistic approach for complicated diagnostic tasks too. This diagnostics is intended for recognition of process malfunction which cannot be easily revealed by analysis of particular single signals only but analysis in multidimensional data space must be involved instead. Main principle of the advanced diagnostic method consists in finding a representation of process behavior in a short history by a mixture of probability density functions called historical mixture. Process behavior in the latest time period is represented by actual mixture. Difference between historical and actual mixtures is evaluated by calculation of Kullback-Leibler divergence. Mixtures and divergences are calculated repeatedly in time and a big change in the divergence value can be used as a source of alarm for non-standard process behavior.
Commonly used methods of signal processing are often too complex and many of them induce time del... more Commonly used methods of signal processing are often too complex and many of them induce time delay between the original and processed signal. A problem arises how to supply the controller with quality input signals without substantial delay taking limited computing power of the controller's hardware into account. A possible solution based on a signal pre-processing subsystem (SPS) delivering quality input signals to the controller is described in this paper. Concept of the SPS is based on a hardware unit with a real-time operating system managing a composition of application tasks. Hardware and software structure of the SPS is composed to enable to utilize the following specific signal processing strategy. Different signal processing methods process a particular signal simultaneously and an algorithm of continuous decision making provides the momentary best possible result in the form of a weighted combination of outputs generated by single signal processing methods. Solution i...
The method presented in this paper uses a generic C-language written simulation model of an embed... more The method presented in this paper uses a generic C-language written simulation model of an embedded distributed computer system aimed for a safetycritical control application. The considered system is built using Time Triggered Architecture (TTA) concepts. The aim of the presented simulation method is to evaluate the system capability to tolerate a chosen category of faults. The model, being written in ANSI-C, is portable and machine-independent. Its structure is modular and flexible, so that the system to be studied and the experiment setting can easily be changed. The functionality of this model is demonstrated on a set of fault injection experiments aimed mainly to evaluate the correctness of the Time Triggered Protocol (TTP/C) that implements the abstract concepts of TTA. These experiments were done within the EU/IST project Fault Injection for Time triggered architecture (FIT).
Proceedings of the Eighth IEEE International On-Line Testing Workshop (IOLTW 2002)
A silicon independent C-Based model of the TTP/C protocol was implemented within the EU-founded p... more A silicon independent C-Based model of the TTP/C protocol was implemented within the EU-founded project FIT. The C-based model is integrated in the C-Sim simulation environment. The main objective of this work is to verify whether the simulation model of the TTP/C protocol behaves in the presence of faults in the same way as the existing hardware prototype implementation. Thus, the experimental results of the software implemented fault injection ap plied in the simulation model and in the hardware implementation of the TTP/C network have been compared. Fault injection experiments in both, the hardware and the simulation model are performed using the same configuration setup, and the same fault injection input parameters (fault injection location , fault type and the fault injection time). The end result comparison has shown a complete conformance of 96.30%, while the cause of the different results was due to hardware specific implementation of the Built-In-Self-Test error detection mechanisms.
The paper presents a study of several alternatives of a fault-tolerant process controller design.... more The paper presents a study of several alternatives of a fault-tolerant process controller design. We compare controller architectures based on dierent amount of hardware redundancy with those using time redundancy. The system behaviour is evaluated by means of a processoriented simulation model enabling software injection of faults. As an overall measure of controller design quality (which includes both performance and reliability) we use the numerical error of the output. The results obtained on the model are used to show the dependence of the output error upon the relative speed of computation and upon the rate of faults damaging the data. Thus for every set of parameters, a system con®guration which gives the best results, can be determined.
2017 21st International Conference on Process Control (PC), 2017
Advisory system for operators of complex industrial processes has been developed and improved by ... more Advisory system for operators of complex industrial processes has been developed and improved by an international team of scientists and people from industry since 2000. Main purpose of the advisory system is to help operator set up manually adjustable parameters of an industrial process, with the aim to reach required production quality. Industrial process is taken for a stochastic process and input signals of its control system are taken for random variables. Based on Bayesian probability theory, a software toolbox was created for handling mixtures of probability density functions describing behavior of the process. Advisory system was tested and pilot application was installed on rolling mills producing metal strips. During the tests, an idea emerged to exploit verified probabilistic approach for complicated diagnostic tasks too. This diagnostics is intended for recognition of process malfunction which cannot be easily revealed by analysis of particular single signals only but analysis in multidimensional data space must be involved instead. Main principle of the advanced diagnostic method consists in finding a representation of process behavior in a short history by a mixture of probability density functions called historical mixture. Process behavior in the latest time period is represented by actual mixture. Difference between historical and actual mixtures is evaluated by calculation of Kullback-Leibler divergence. Mixtures and divergences are calculated repeatedly in time and a big change in the divergence value can be used as a source of alarm for non-standard process behavior.
Commonly used methods of signal processing are often too complex and many of them induce time del... more Commonly used methods of signal processing are often too complex and many of them induce time delay between the original and processed signal. A problem arises how to supply the controller with quality input signals without substantial delay taking limited computing power of the controller's hardware into account. A possible solution based on a signal pre-processing subsystem (SPS) delivering quality input signals to the controller is described in this paper. Concept of the SPS is based on a hardware unit with a real-time operating system managing a composition of application tasks. Hardware and software structure of the SPS is composed to enable to utilize the following specific signal processing strategy. Different signal processing methods process a particular signal simultaneously and an algorithm of continuous decision making provides the momentary best possible result in the form of a weighted combination of outputs generated by single signal processing methods. Solution i...
The method presented in this paper uses a generic C-language written simulation model of an embed... more The method presented in this paper uses a generic C-language written simulation model of an embedded distributed computer system aimed for a safetycritical control application. The considered system is built using Time Triggered Architecture (TTA) concepts. The aim of the presented simulation method is to evaluate the system capability to tolerate a chosen category of faults. The model, being written in ANSI-C, is portable and machine-independent. Its structure is modular and flexible, so that the system to be studied and the experiment setting can easily be changed. The functionality of this model is demonstrated on a set of fault injection experiments aimed mainly to evaluate the correctness of the Time Triggered Protocol (TTP/C) that implements the abstract concepts of TTA. These experiments were done within the EU/IST project Fault Injection for Time triggered architecture (FIT).
Proceedings of the Eighth IEEE International On-Line Testing Workshop (IOLTW 2002)
A silicon independent C-Based model of the TTP/C protocol was implemented within the EU-founded p... more A silicon independent C-Based model of the TTP/C protocol was implemented within the EU-founded project FIT. The C-based model is integrated in the C-Sim simulation environment. The main objective of this work is to verify whether the simulation model of the TTP/C protocol behaves in the presence of faults in the same way as the existing hardware prototype implementation. Thus, the experimental results of the software implemented fault injection ap plied in the simulation model and in the hardware implementation of the TTP/C network have been compared. Fault injection experiments in both, the hardware and the simulation model are performed using the same configuration setup, and the same fault injection input parameters (fault injection location , fault type and the fault injection time). The end result comparison has shown a complete conformance of 96.30%, while the cause of the different results was due to hardware specific implementation of the Built-In-Self-Test error detection mechanisms.
The paper presents a study of several alternatives of a fault-tolerant process controller design.... more The paper presents a study of several alternatives of a fault-tolerant process controller design. We compare controller architectures based on dierent amount of hardware redundancy with those using time redundancy. The system behaviour is evaluated by means of a processoriented simulation model enabling software injection of faults. As an overall measure of controller design quality (which includes both performance and reliability) we use the numerical error of the output. The results obtained on the model are used to show the dependence of the output error upon the relative speed of computation and upon the rate of faults damaging the data. Thus for every set of parameters, a system con®guration which gives the best results, can be determined.
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Papers by Pavel Herout