| 1. |
- Abdalmoaty, Mohamed, 1986-, et al.
(author)
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On Re-Weighting, Regularization Selection, and Transient in Nuclear Norm Based Identification
- 2015
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In: IFAC-PapersOnLine. - : Elsevier. - 2405-8963. ; 48:28, s. 92-97
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Journal article (peer-reviewed)abstract
- In this contribution, we consider the classical problem of estimating an Output Error model given a set of input-output measurements. First, we develop a regularization method based on the re-weighted nuclear norm heuristic. We show that the re-weighting improves the estimate in terms of better fit. Second, we suggest an implementation method that helps in eliminating the regularization parameters from the problem by introducing a constant based on a validation criterion. Finally, we develop a method for considering the effect of the transient when the initial conditions are unknown. A simple numerical example is used to demonstrate the proposed method in comparison to classical and another recent method based on the nuclear norm heuristic.
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| 2. |
- Chistiakova, Tatiana, et al.
(author)
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Nonlinear system identification of the dissolved oxygen to effluent ammonia dynamics in an activated sludge process
- 2017
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In: IFAC-PapersOnLine. - : Elsevier B.V.. - 2405-8963. ; 50:1, s. 3917-3922
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Journal article (peer-reviewed)abstract
- Aeration of biological reactors in wastewater treatment plants is important to obtain a high removal of soluble organic matter as well as for nitrification but requires a significant use of energy. It is hence of importance to control the aeration rate, for example, by ammonium feedback control. The goal of this paper is to model the dynamics from the set point of an existing dissolved oxygen controller to effluent ammonia using two types of system identification methods for a Hammerstein model, including a newly developed recursive variant. The models are estimated and evaluated using noise corrupted data from a complex mechanistic model (Activated Sludge Model no.1). The performance of the estimated nonlinear models are compared with an estimated linear model and it is shown that the nonlinear models give a significantly better fit to the data. The resulting models may be used for adaptive control (using the recursive Hammerstein variant), gain-scheduling control, L2 stability analysis, and model based fault detection.
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| 3. |
- Fager, Patrik, 1988, et al.
(author)
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Dual Robot Kit Preparation in Batch Preparation of Component Kits for Mixed Model Assembly
- 2020
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In: IFAC Proceedings Volumes (IFAC-PapersOnline). - : Elsevier BV. - 1474-6670. ; 53, s. 10627-10632
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Conference paper (peer-reviewed)abstract
- Kitting is a materials supply principle that plays a vital role for performance in mixed model assembly systems. The kit preparation process, whereby component kits are created, is central when kitting is applied. Kit preparation is a form of materials handling and is associated with several ergonomic and quality related issues. Robotics holds a great potential for decreasing the need for human labour, but literature on the topic is scarce. The purpose of this paper is to identify the time efficiency potential of a dual robot application for kit preparation. To address the purpose, a mathematical model is developed that allows dual robot kit preparation to be analysed and compared with manual kit preparation. Furthermore, the model supports identification of a suitable batch size given a lead time requirement from the assembly system. A numerical example shows dual robot kit preparation to be slightly more efficient than its manual ditto for preparation of 2, 3 and 4 kit batch sizes. The paper’s makes a theoretical contribution in terms of the time efficiency model of dual robot kit preparation. This model is also useful for practitioners when evaluating the potential of dual robot arm kit preparation in their own processes.
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| 4. |
- Fasth Berglund, Åsa, 1978, et al.
(author)
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Variations in cycle-time when using knowledge-based tasks for humans and robots
- 2021
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In: IFAC-PapersOnLine. - : Elsevier. - 2405-8963. ; 54:1, s. 152-157
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Journal article (peer-reviewed)abstract
- Operator4.0 was coined in 2016 to create a research arena to understand how the physical, cognitive, and sensorial capabilities of an operator could be enhanced by automation. To create an interaction between operator and robots, there are important factors that needs to be defined. Two important factors are the task and function allocation. Without well-defined tasks it is hard to allocate the tasks between the robot and the human to create resource flexibility. Furthermore, it the tasks are knowledge-based rather than rule-based, the cycle time between operators can differ a lot. Two assumptions are discussed regarding knowledge-based tasks and automation. These are also tested in an experiment. Results show that it is a large variation of the cycle time for both humans (between 1,58 minutes up to 4,40 minutes) and robots (between 1,94 minutes up to 4,49 minutes) when it comes to knowledge-based and machine learning systems.
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| 5. |
- Ilka, Adrian, 1987, et al.
(author)
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Gain-Scheduled MPC Design for Nonlinear Systems with Input Constraints
- 2015
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In: IFAC Proceedings Volumes (IFAC-PapersOnline), 1st IFAC Conference on Modelling, Identification and Control of Nonlinear Systems, MICNON 2015; Saint Petersburg; Russian Federation; 24 June 2015 through 26 June 2015; Code 117503. - : Elsevier BV. - 1474-6670. ; 48:11, s. 912-917
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Conference paper (peer-reviewed)abstract
- A novel methodology is proposed for discrete model predictive gain-scheduled controller design for nonlinear systems with input(hard)/output(soft) constraints for finite and infinite prediction horizons. The proposed design procedure is based on the linear parameter-varying (LPV) paradigm, affine parameter-dependent quadratic stability and on the notion of the parameter-varying guaranteed cost. The obtained design procedure is in the form of BMI. Numerical examples show the benefit of the proposed approach.
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| 6. |
- Lennartson, Bengt, 1956
(author)
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Multi criteria Hinf optimal PID controllers from an undergraduate perspective
- 2012
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In: IFAC Proceedings Volumes (IFAC-PapersOnline). - : Elsevier BV. - 1474-6670. - 9783902823182 ; 2:1, s. 697-702
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Conference paper (peer-reviewed)abstract
- A simple design method for robust PID controllers is presented. It is based on a multi criteria H∞ optimal control formulation, which is shown to be easily solved by a few lines of MATLAB code. This optimal solution for PID controllers including low pass filtering, is complemented by a simple paper and pen solution that can be used to obtain nearly optimal solutions. The presented approach is shown to give significantly better results compared to ordinary text book solutions based on frequency domain loop shaping. The paper also includes a discussion on how to best formulate PID controllers for design, and how additional filtering may easily improve high frequency robustness.
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| 7. |
- Pettersson, Pär, 1985, et al.
(author)
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Intrinsic differences between backward and forward vehicle simulation models
- 2020
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In: IFAC-PapersOnLine. - : Elsevier. - 2405-8963. ; 53
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Conference paper (peer-reviewed)abstract
- Two common methods for predicting the energy usage in vehicles through mathematical simulation, the 'backward' and the 'forward' schemes, are discussed and compared in terms of the longitudinal vehicle behaviour they predict. In the backward scheme, the input driving cycle is initially assumed to be followed perfectly and therefore the vehicle speed is not a dynamic state. In the forward scheme, a driver model controls the vehicle in an attempt to follow the input driving cycle, and the vehicle speed is intrinsically a dynamic state. A theoretical study is made with a simple mathematical vehicle model, where it is shown that the two methods neither predict the same expected energy use nor energy variation. Next, the simulation model that is used for the CO2 rating of heavy-duty trucks in Europe, VECTO, is used as an example of the backward method, and an equivalent implementation in a forward scheme is attempted. Two numerical experiments are made with these models: a detailed study of the longitudinal vehicle behaviour on a reference mission; and a study of the predicted CO2 emissions on a family of stochastically generated missions. The conclusion is that the backward method is easier to use but the forward method has a greater potential to predict realistic behaviour.
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| 8. |
- Stotsky, Alexander, 1960
(author)
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Efficient Iterative Solvers in the Least Squares Method
- 2020
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In: Ifac Papersonline. - : Elsevier BV. - 2405-8963. ; 53:2, s. 883-888
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Journal article (peer-reviewed)abstract
- Fast convergent, accurate, computationally efficient, parallelizable, and robust matrix inversion and parameter estimation algorithms are required in many time-critical and accuracy-critical applications such as system identification, signal and image processing, network and big data analysis, machine learning and in many others. This paper introduces new composite power series expansion with optionally chosen rates (which can be calculated simultaneously on parallel units with different computational capacities) for further convergence rate improvement of high order Newton-Schulz iteration. New expansion was integrated into the Richardson iteration and resulted in significant convergence rate improvement. The improvement is quantified via explicit transient models for estimation errors and by simulations. In addition, the recursive and computationally efficient version of the combination of Richardson iteration and Newton-Schulz iteration with composite expansion is developed for simultaneous calculations. Moreover, unified factorization is developed in this paper in the form of tool-kit for power series expansion, which results in a new family of computationally efficient Newton-Schulz algorithms. Copyright (C) 2020 The Authors.
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| 9. |
- Veselý, Vojtech, 1940, et al.
(author)
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Robust Switched Controller Design for Nonlinear Continuous Systems
- 2015
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In: IFAC Proceedings Volumes (IFAC-PapersOnline), 1st IFAC Conference on Modelling, Identification and Control of Nonlinear Systems, MICNON 2015; Saint Petersburg; Russian Federation; 24 June 2015 through 26 June 2015; Code 117503. - : Elsevier BV. - 1474-6670. ; 48:11, s. 1068-1073
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Conference paper (peer-reviewed)abstract
- A novel approach is presented to robust switched controller design for nonlinear continuous-time systems under an arbitrary switching signal using the gain scheduling approach. The proposed design procedure is based on the robust multi parameter dependent quadratic stability condition. The obtained switched controller design procedure for nonlinear continuous-time systems is in at bilinear matrix form (BMI). The properties of the obtained design are illustrated on simulation examples.
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| 10. |
- Hang, Chang C., et al.
(author)
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Practical Aspects of PID Auto-Tuners Based on Relay Feedback
- 1988
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In: 2nd International IFAC Symposium on Adaptive Control of Chemical Processes 1988 (ADCHEM '88), Lyngby, Copenhagen, Denmark, 17-19 August. - 1474-6670. ; 21:7, s. 153-158
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Conference paper (peer-reviewed)
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