| 1. |
- Atta, Khalid Tourkey, et al.
(författare)
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A geometric phasor extremum seeking control approach with measured constraints
- 2019
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Ingår i: 2019 IEEE 58th Conference on Decision and Control (CDC). - : IEEE. ; , s. 1494-1500
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, we propose an extension for the phasor extremum seeking control approach to solve constrained optimization problems. The proposed technique uses phasor estimates of the objective function and the constraints to compute a geometric constraint satisfaction approach that avoids the violation of the constraints. The proposed method is illustrated to solve several nonlinear optimization problems subject to equality and inequality constraints. Finally, the effectiveness of the proposed approach is illustrated for the optimal operation of a parallel isothermal stirred-tank reactor system.
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| 2. |
- Atta, Khalid Tourkey, et al.
(författare)
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Extension, Validation, and Simulation of a Cone Crusher Model
- 2019
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Ingår i: 18th IFAC Symposium on Control, Optimization and Automation in Mining, Mineral and Metal Processing, MMM 2019. - : Elsevier. ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- This work presents an extension and validation for a control oriented model of cone crushers. Compared to earlier work, the aspect of energy consumption was added to the model. Validation was carried out using measurement data from two different crusher models and was based both on laboratory data and field experiment data. Using the results from the field trials, a plant simulator for a secondary crushing circuit has been implemented.
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| 3. |
- Atta, Khalid Tourkey, et al.
(författare)
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Phasor extremum seeking control with adaptive perturbation amplitude
- 2016
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Ingår i: 2016 IEEE 55th Conference on Decision and Control, CDC 2016. - Piscataway, NJ : Institute of Electrical and Electronics Engineers (IEEE). - 9781509018376 ; , s. 7069-7074
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose a perturbation amplitude adaption scheme for phasor extremum seeking control based on the plant's estimated gradient. By using phasor extremum seeking instead of classical extremum seeking, the problem of algebraic loops in the controller formulation is avoided. Furthermore, a stability analysis for the proposed method is provided, which is the first stability analysis for extremum seeking controllers using adaptive amplitudes. The proposed method is illustrated using numerical examples and it is found that changes in optimum can be tracked accurately while the steady-state perturbations can be reduced significantly.
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| 4. |
- Birk, Wolfgang, 1968-, et al.
(författare)
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Improving District Heating System Operation through Control Configuration Selection and Adaptive Control
- 2019
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Ingår i: 2019 18th European Control Conference (ECC). - : IEEE. ; , s. 2944-2949
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Konferensbidrag (refereegranskat)abstract
- This paper discusses the joint use of control configuration selection and adaptive model predictive control for the reconfiguration and improvement of a control system for the heat generation and distribution in a district heating system. The traditional PID-type multi-loop controller configuration is assessed from its feasibility and potential to be improved, on the basis of automatically generated models. The studied test case is the district heating system in Luleå, Sweden.It is found that a multivariable controller for a subsystem of the complete system could largely improve the performance of the system and thereby addressing confirmed oscillations in the system. An adaptive model predictive controller is implemented in the realistic simulator OPTi-Sim for the district heating system in Luleå, Simulation results confirm that the oscillations which are present in the simulation with the current control scheme can be largely reduced through the use of the proposed controlled.
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| 5. |
- Birk, Wolfgang, 1968-, et al.
(författare)
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Reinforcement of knowledge acquisition in course chains using student-held seminars
- 2020
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Ingår i: Bidrag från 7:e utvecklingskonferensen för Sveriges ingenjörsutbildningar. - : Luleå tekniska universitet. ; , s. 164-165
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This work in progress paper presents an approach for knowledge reinforcement of students by introducing student-held course seminars reflecting back on the knowledge from prior courses relevant to current course topics. The paper discusses the motivation of the approach, its practical implementation, and observation made during two consecutive course instances. Further, course evaluations are used to reflect on the efficacy of the proposed approach and its future refinement.
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| 6. |
- Guay, Martin, et al.
(författare)
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A backstepping controller design technique for a class of cascaded nonlinear systems with unknown dynamics
- 2019
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Ingår i: 2019 American Control Conference (ACC). - : IEEE. ; , s. 3093-3098
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Konferensbidrag (refereegranskat)abstract
- In this study, we consider the stabilization of a class of cascaded nonlinear systems in strict feedback form with unknown dynamics and known relative order. The stabilization of the unknown system is achieved by a cascaded feedback design procedure that uses a backstepping-like approach. The unknown system functions are estimated using a phasor estimation approach using a single sinusoidal perturbation. The stability analysis shows the semi-global practical stability of the closed loop system and the practical convergence of the entire system to the origin.
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| 7. |
- Guay, Martin, et al.
(författare)
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Extremum seeking regulator design with derivative action for uncertain systems
- 2019
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Ingår i: 2019 IEEE 58th Conference on Decision and Control (CDC). - : IEEE. ; , s. 6106-6111
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper proposes an extremum-seeking control approach for the regulation of a class of minimum phase nonlinear systems to the optimum of a measured objective function. The nonlinear systems are subject to the effects of exogenous disturbances driven by unknown dynamics. A Lie bracket averaging technique is used to design the extremum seeking regulation mechanism. The internal model is estimated directly using a derivative action that exploits the convexity of the measured cost function. This mechanism avoids the need for an internal model estimation approach. A stability analysis shows that the system achieves a practical output regulation of the unknown optimum equilibrium. A simulation study demonstrates the effectiveness of the technique.
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| 8. |
- Guay, Martin, et al.
(författare)
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Extremum seeking regulator for a class of SISO time-varying nonlinear systems
- 2019
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Ingår i: 11th IFAC Symposium on Nonlinear Control Systems NOLCOS 2019. - : Elsevier. ; , s. 795-800
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Konferensbidrag (refereegranskat)abstract
- This paper proposes an extremum-seeking regulator design based on a Lie bracket averaging technique for time-varying nonlinear systems in the presence of unknown time-varying disturbance dynamics. The approach adopts a post-processing output regulation method for the regulation of nonlinear systems to the unknown minimum of a measured objective function. The stability analysis demonstrates that one can achieve practical output regulation of the unknown optimum equilibrium. A simulation study demonstrates the ability of the proposed technique to solve very general output regulation problems in the absence of exact knowledge of the process dynamics, the disturbance dynamics or a corresponding internal model.
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| 9. |
- Guay, Martin, et al.
(författare)
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Extremum seeking regulator for a class of unknown SISO nonlinear systems
- 2019
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Ingår i: 2019 American Control Conference (ACC). - : IEEE. ; , s. 3032-3037
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Konferensbidrag (refereegranskat)abstract
- This paper proposes an extremum-seeking regulator design based on a Lie bracket averaging technique for nonlinear systems in the presence of unknown disturbance dynamics. The approach adopts a post-processing output regulation method for the regulation of nonlinear systems to the unknown minimum of a measured objective function. The stability analysis demonstrates that one can achieve practical output regulation of the unknown optimum equilibrium. A simulation study demonstrates the ability of the proposed technique to solve general output regulation problems in the absence of exact knowledge of the process dynamics, disturbance dynamics and a corresponding internal model.
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| 10. |
- Nayl, Thaker, et al.
(författare)
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Multi objectives optimization of wind turbines’ power and fatigue loads using perturbation free extremum seeking control
- 2024
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Ingår i: Results in Control and Optimization. - : Elsevier B.V.. - 2666-7207. ; 16
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Tidskriftsartikel (refereegranskat)abstract
- This manuscript introduces a perturbation-free extremum-seeking control strategy specifically designed to enhance the operational performance of wind turbines under optimal conditions. The strategy employed utilizes a perturbation-free extremum-seeking approach to ensure the wind turbine farm operates at maximum power efficiency while also reducing power output fluctuations. By employing this control system, the wind turbine generators are maintained at their optimal power output level, effectively navigating through disturbances such as tower shadow, wind shear, and the erratic nature of wind speeds without introducing external perturbations. The algorithm is adept at managing the blade pitch angles and the turbines’ rotational speed, ensuring a controlled and efficient operation. Furthermore, this paper outlines a perturbation-free method to optimize energy production and decrease fatigue loads, thereby extending the operational lifespan of a wind turbine. The superior operational efficiency of the wind turbine array generators achieved through this approach underscores its effectiveness. The robustness and effectiveness of this perturbation-free control system are validated through comprehensive simulation tests on an array comprising four wind turbine generators. The outcomes of these simulations solidly back the extremum-seeking control system's proficiency in reaching maximum power output without relying on perturbative methods, highlighting its innovative contribution to wind turbine efficiency optimization.
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| 11. |
- Simonsson, Johan, et al.
(författare)
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A Graph Theoretical Approach to Modeling of District Energy Networks
- 2024
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Ingår i: IEEE Transactions on Control Systems Technology. - : IEEE. - 1063-6536 .- 1558-0865.
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Tidskriftsartikel (refereegranskat)abstract
- Simulation of thermal dynamics in city-scale district energy grids often becomes computationally prohibitive for long simulation runs. Most current model order reduction methods offer limited interpretability with regards to the nonreduced system and are not in general applicable for varying flow rates, multiple producers, or changing flow directions. This article presents a graph perspective on modeling of district energy networks. Based on spectral graph theory, a novel method for model order reduction of district energy systems is proposed. The method approximates the solution of an optimization problem, minimizing the coefficients of the local truncation error for the advection equation. Furthermore, a method for calculating the intracluster temperature distribution is presented. It is shown that the method can be used to reduce the thermal dynamic model of a city-scale energy grid, resulting in a coarser temporal and spatial resolution, with a significant decrease in simulation time. The relative root-mean-square error (rRMSE) was 2.5% for the temperature in the evaluation scenario, comparing the reduced-order system with the nonreduced system at the instances of the coarser time step.
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| 12. |
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| 13. |
- Simonsson, Johan, et al.
(författare)
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Reduced-Order Modeling of Thermal Dynamics in District Energy Networks using Spectral Clustering
- 2022
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Ingår i: 2022 IEEE Conference on Control Technology and Applications (CCTA). - : IEEE. - 9781665473385 ; , s. 144-150
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Konferensbidrag (refereegranskat)abstract
- Simulation of thermal dynamics in city-scale district energy grids often becomes computationally prohibitive for long simulation runs. Current model order reduction methods offer limited interpretability with regards to the nonreduced system, and are not in general applicable for e.g., varying flow rates, multiple producers, or changing flow directions. This article presents a novel method based on graph theory that approximates the solution of an optimization problem that minimizes the local truncation error for heat transport in the grid. It is shown that the method can be used to reduce the thermal dynamic model of a city-scale energy grid, resulting in a coarser temporal and spatial resolution. The relative root mean square error was 2.3 % for the temperature in the evaluation scenario, comparing the reduced-order system with the nonreduced system at the instances of the coarser time-step.
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| 14. |
- Simonsson, Johan, et al.
(författare)
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Semi-decentralized temperature control in district heating systems
- 2024
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Ingår i: Journal of Process Control. - : Elsevier Ltd. - 0959-1524 .- 1873-2771. ; 140
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Tidskriftsartikel (refereegranskat)abstract
- The supply temperature in district heating systems has traditionally been controlled using feedforward – a robust and well-validated approach for district heating networks with few producers and relatively high supply temperatures. The transition towards lower temperature district heating networks allows for efficient reuse of excess heat from, e.g., industrial processes and data centers. Excess heat is often intermittent, cannot always be assumed to be possible to control with a centralized controller, and can cause temperature disturbances in the grid. Closing the loop using PID control is challenging due to the process’s time-varying nature and long time delays. Model Predictive Control (MPC) suffers from a higher complexity, long computational times, and the need for a well-validated and maintained centralized model. The paper suggests a semi-decentralized approach using the Smith predictor with an event-driven assignment of active controllers and sensors. A reduced order model based on a more comprehensive state space model is derived and used for gain scheduling and input–output pairing using the normalized relative gain array. The focus is on temperature disturbance rejection, and appropriate tuning rules and controller structures are suggested. Simulation results show that the proposed control structure can handle various types of temperature disturbances, even in the presence of model estimation errors.
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