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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 -
Parameter identification of the KUKA LBR iiwa robot including constraints on physical feasibility
(2017)IFAC-PapersOnLine ~ 20th IFAC World Congress. ProceedingsThe newly released KUKA LBR iiwa R820 robot stands for intelligent industrial work assistant (iiwa) and is, like its predecessor LBR IV, equipped with torque sensors in each joint, and can be controlled through a real-time interface. Although the dynamic model of the robot is not published by the manufacturer, its knowledge is indispensible for simulation and control based on the system model. This paper presents the identification of ...Conference Paper -
Modeling, Identification, Estimation and Adaptation for the Control of Power-Generating Kites
(2018)IFAC-PapersOnLine ~ 18th IFAC Symposium on System Identification, SYSID 2018. ProceedingsLarge-scale kites, flying high-force crosswind trajectories, have been proposed for wind power generation. A two phase operational cycle generates net positive power using a ground-based motor/generator. In the traction phase the kite flies a high-force trajectory while reeling out the generator-connected tethers. A low-force retraction phase reels in the tethers and returns the kite to the start of the cycle. Highly variable conditions ...Conference Paper -
Transverse Contraction-based Stability Analysis for Periodic Trajectories of Controlled Power Kites with Model Uncertainty
(2018)2018 IEEE Conference on Decision and Control (CDC)In this paper we propose a procedure for estimating the region in which a controller robustly stabilizes a system which is subject to affine parametric uncertainty by applying transverse contraction-based stability tools. The method consists of an optimization problem in which transverse contraction conditions are verified via sum-of-squares programs. The optimization approach can be used either to maximize the bounds on the allowable ...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 -
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 -
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 -
Globally Optimal AC Power System Upgrade Planning under Operational Policy Constraints
(2018)2018 European Control Conference (ECC)In order to accommodate the increasing amounts of renewable generation in power distribution systems, system operators are facing the problem of how to upgrade transmission capacities. Since line and transformer upgrades are costly, optimization procedures are used to find the minimal number of upgrades required. The resulting design optimization formulations are generally mixed-integer non-convex problems. Traditional approaches to solving ...Conference Paper -
Low-complexity first-order constraint linearization methods for efficient nonlinear MPC
(2017)2017 IEEE 56th Annual Conference on Decision and Control (CDC)In this paper, we analyze first-order methods to find a KKT point of the nonlinear optimization problems arising in Model Predictive Control (MPC). The methods are based on a projected gradient and constraint linearization approach, that is, every iteration is a gradient step, projected onto a linearization of the constraints around the current iterate. We introduce an approach that uses a simple ℓ p merit function, which has the computational ...Conference Paper -
Circuit Generation for Efficient Projection onto Polyhedral Sets in First-Order Methods
(2015)2015 European Control Conference (ECC)First-order numerical optimization methods are a common choice for low-cost embedded MPC implementations. Their applicability is typically restricted to problems with simple constraints due to the difficulty of Euclidean projection onto more complex feasible sets. However, many practical problems have non-trivial polyhedral constraints. For such polyhedral sets, the projection can be explicitly written as an evaluation of a piecewise ...Conference Paper