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A decoupled feedback structure for covertly appropriating networked control systems
(2011)IFAC Proceedings Volumes ~ Proceedings of the 18th World CongressThe use of communication networks for the transmission of control system signals (measurements and actuation) is becoming more widespread. If the communication (or the sensors and actuators themselves) can be modified by a malicious agent then the control of the physical plant can be covertly appropriated. A parameterised decoupling structure is introduced which allows the covert agent a wide range of control actions on the physical plant ...Conference Paper -
Experiment design for impulse response identification with signal matrix models
(2021)IFAC-PapersOnLine ~ 19th IFAC Symposium on System Identification, SYSID 2021This paper formulates an input design approach for truncated infinite impulse response identification in the context of implicit model representations recently used as basis for data-driven simulation and control approaches. Precisely, the considered model consists of a linear combination of the columns of a data (or signal) matrix. An optimal combination for the case of noisy data was recently proposed using a maximum likelihood approach, ...Conference Paper -
Extended Full Block S-Procedure for Distributed Control of Interconnected Systems
(2020)2020 59th IEEE Conference on Decision and Control (CDC)This paper proposes a novel method for distributed controller synthesis of homogeneous interconnected systems consisting of identical subsystems. The objective of the designed controller is to minimize the L2-gain of the performance channel. The proposed method is an extended formulation of the Full Block S-Procedure (FBSP) where we introduce an additional set of variables. This allows to relax the block-diagonal structural assumptions ...Conference Paper -
RF pulse flattening in the SwissFEL facility based on model-free iterative learning control
(2015)Proceedings of the 36th International Free Electron Laser Conference (FEL2014)This paper introduces an iterative approach to producing flat-topped radio frequency (RF) pulses for driving the pulsed linear accelerators in the Swiss free electron laser (SwissFEL). The method is based on model-free iterative learning control which iteratively updates the input pulse shape in order to generate the desired amplitude and phase pulses at the output of the RF system. The method has been successfully applied to the klystron ...Conference Paper -
Model-based klystron linearization in the SwissFEL test facility
(2015)Proceedings of the 36th International Free Electron Laser Conference (FEL2014)An automatic procedure is developed to provide the optimal operating point of a klystron. Since klystrons are non-linear with respect to the input amplitude, a model-based amplitude controller is introduced which uses the klystron characteristic curves to obtain the appropriate high voltage power supply setting and amplitude, such that the operating point is close to the saturation. An advantage of the proposed design is that the overall ...Conference Paper -
Power System Upgrade Planning with On-load Tap-changing Transformers, Switchable Topology and Operating Policies
(2019)2019 18th European Control Conference (ECC)Renewable energy sources are leading to undesired local voltage rise in power distribution systems. One way to reduce such voltage excursions is to upgrade the power system with stronger links or on-load tap-changing transformers (OLTC). While such hardware is readily available, it is costly to deploy and hence optimization-based planning approaches are desired to explore the design space in a systematic way. The approach presented in ...Conference Paper -
Robust-based control design for the beam injector facility
(2016)2016 European Control Conference (ECC)This paper develops a robust control design for the electron beam injector facility in the Swiss Free Electron Laser (SwissFEL) machine. The relationship between radio frequency parameters and the electron beam quantities are commonly modeled as a static response matrix. Typically, the response matrix has a high condition number which makes inverse-based control approaches very sensitive to gain uncertainties. This problem is usually ...Conference Paper -
A variant to Sequential Quadratic Programming for Nonlinear Model Predictive Control
(2016)2016 IEEE 55th Conference on Decision and Control (CDC)Sequential Quadratic Programming (SQP) denotes an established class of methods for solving nonlinear optimization problems via an iterative sequence of Quadratic Programs (QPs). Several approaches in the literature have established local and global convergence of the method. This paper considers a variant to SQP that, instead of solving each QP, at each iteration follows one gradient step along a direction that is proven to be a descent ...Conference Paper -
Two Methods for the Identification of Uncertain Parameters of an Architectural Cable Net Geometry
(2016)2016 IEEE Conference on Control Applications (CCA)Recently, a control algorithm has been presented to control the geometry of a prestressed flexible cable net formwork, which is used for the construction of anticlastic thin concrete shell structures in architecture. The most important uncertainties in the model of the cable net are the parameters of unstressed lengths of its edges. As the control algorithm is model-based, its performance depends on the knowledge of these parameters. We ...Conference Paper -
Nuclear norm minimization methods for frequency domain subspace identification
(2012)2012 American Control Conference (ACC)Frequency domain subspace identification is an effective means of obtaining a low-order model from frequency domain data. In the noisy data case using a singular value decomposition to determine the observable subspace has several problems: an incorrect weighting of the data in the singular values; difficulties in determining the appropriate rank; and a loss of the Hankel structure in the low-order approximation. A nuclear norm (sum of ...Conference Paper