| 1. |
- Khademhosseinieh, Banafsheh, 1981-
(författare)
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Towards an Approach for Efficiency Evaluation of Enterprise Modeling Methods
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nowadays, there is a belief that organizations should keep improving different aspects of theirenterprise to remain competitive in their business segment. For this purpose, it is required to understand the current state of the enterprise, analyze and evaluate it to be able to figure out suitable change measures. To perform such a process in a systematic and structured way, receiving support from powerful tools is inevitable. Enterprise Modeling is a field that can support improvement processes by developing models to show different aspects of an enterprise. An Enterprise Modeling Method is an important support for the Enterprise Modeling. A method is comprised of different conceptual parts: Perspective, Framework,Method Component (which itself contains Procedure, Notation and Concepts), and Cooperation Principles. In an ideal modeling process, both the process and the results are of high quality. One dimension of quality which is in focus in this thesis is efficiency. The issue of efficiency evaluation in Enterprise Modeling still seems to be a rather unexploited research area.The thesis investigates three aspects of Enterprise Modeling Methods: what is the meaning of efficiency in this context, how can efficiency be evaluated and in what phases of a modeling process could efficiency be evaluated. The contribution of the thesis is an approach for evaluation of efficiency in Enterprise Modeling Methods based also on several case studies. The evaluation approach is constituted by efficiency criteria that should be met by (different parts of) a method. While a subset of these criteria always need to be fulfilled in a congruent way, fulfillment of the rest of the criteria depends on the application case. To help the user in initial evaluation of a method, a structure of driving questions is presented.
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| 2. |
- Hast, Martin, et al.
(författare)
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Design of Optimal Low-Order Feedforward Controllers
- 2012
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Ingår i: 2nd IFAC Conference on Advances in PID Control 2012. - 9781627483247 ; , s. 483-488
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Konferensbidrag (refereegranskat)abstract
- Design rules for optimal feedforward controllers with lead-lag structure in the presence of measurable disturbances are presented. The design rules are based on stable first-order models with time delays, FOTD, and are optimal in the sense of minimizing the integrated-squared error. The rules are derived for an open-loop setting, considering a step disturbance. This paper also discusses a general feedforward structure, which enables decoupling in the design of feedback and feedforward controllers, and justifies the open-loop setting.
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| 3. |
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| 4. |
- Hast, Martin, et al.
(författare)
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Low-order feedforward controllers: Optimal performance and practical considerations
- 2014
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Ingår i: Journal of Process Control. - : Elsevier BV. - 1873-2771 .- 0959-1524. ; 24:9, s. 1462-1471
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Tidskriftsartikel (refereegranskat)abstract
- Feedforward control from measurable disturbances can significantly improve the performance in control loops. However, tuning rules for such controllers are scarce. In this paper design rules for how to choose optimal low-order feedforward controller parameter are presented. The parameters are chosen so that the integrated squared error, when the system is subject to a step disturbance, is minimized. The approach utilizes a controller structure that decouples the feedforward and the feedback controller. The optimal controller can suffer from undesirable high-frequency noise characteristics and tuning methods for how to filter the control signal are also provided. For scenarios where perfect disturbance attenuation in theory is achievable but where noise-filtering is needed, the concept of precompensation is introduced as a way to shift the controller time-delay to compensate for the low-pass filtering.
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| 5. |
- Hast, Martin, et al.
(författare)
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Optimal proportional–integral–derivative set-point weighting and tuning rules for proportional set-point weights
- 2015
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Ingår i: IET Control Theory and Applications. - : Institution of Engineering and Technology (IET). - 1751-8652. ; 9:15, s. 2266-2272
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Tidskriftsartikel (refereegranskat)abstract
- In this study, design of low-order feedforward controllers from both reference signal and measurable disturbance for proportional–integral–derivative (PID) controllers is considered. The feedforward controllers from reference are equivalent to the use of a PID controller with set-point weighting. The design problem is formulated as a convex optimisation problem and then solved for a batch of process models. The optimal proportional set-point weights are then used to derive tuning rules that minimise the integrated absolute error. Examples illustrate the usefulness of the proposed method and tuning rules
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| 6. |
- Johansson, Martin, 1973, et al.
(författare)
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Approximate boundary conditions for a fluid-loaded elastic plate
- 2005
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Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 1520-8524 .- 0001-4966. ; 118:6, s. 3436-3446
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Tidskriftsartikel (refereegranskat)abstract
- Approximate boundary conditions for an infinite elastic layer immersed in a fluid are derived. By using series expansions in the thickness coordinate of the plate fields, the displacements fields are eliminated, adopting the three-dimensional equations of motion. The sums and differences of the boundary pressure fields and their normal derivatives are related through a set of approximate boundary conditions, one symmetric and one antisymmetric. These equations involve powers in the layer thickness together with partial derivatives with respect to time as well as the spatial variables in the plate plane. The approximate boundary conditions can be truncated to an arbitrary order, and explicit relations are presented including terms of order five. Comparisons are made with effective boundary conditions using classical plate theories. The numerical examples involve reflection and transmission of plane waves incident on the plate at different angles, as well as the pressure fields due to a line force. Three fluid-loading cases are studied: modest, heavy, and light loadings. The results using truncated approximate boundary conditions are compared to exact and classical plate solutions. The examples show that the accuracies of the power series approximations of order three and higher are very good in the frequency interval considered.
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| 7. |
- Rodrigo, Vicent, et al.
(författare)
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Causal analysis for alarm flood reduction
- 2016
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Ingår i: 11th IFAC Symposium on Dynamics and Control of Process SystemsIncluding Biosystems. - : Elsevier BV. - 2405-8963. ; 49:7, s. 723-728
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Konferensbidrag (refereegranskat)abstract
- The introduction of distributed control systems and the high level of interconnectivity of modern process plants has caused alarm flooding to become one of the main problems in alarm management of process plants. A reduction of alarm flood periods contributes to a decrease in plant incidents. In this work, a combination of alarm log, process data and connectivity analysis is used to isolate consequence alarms originating from the same process abnormality and to provide a causal alarm suggestion. The effectiveness of the method is illustrated on an industrial case study of an ethylene plant, a typical example of a large-scale industrial system.
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