A state observer for using a slow camera as a sensor for fast control applications

Gahleitner, Reinhard; Schagerl, Martin

doi:10.1117/12.2006106

Cited by 2 publications

(3 citation statements)

References 4 publications

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“…The standard Luenberger observer uses the model of a given system together with a suitable update term to estimate state variables that cannot be measured. In order to apply it to the multi-rate augmented system dynamics (( 14)-( 15)) certain modifications are required [19]. First of all the system (21)-( 22) should be observable.…”

Section: B a Multi-rate Luenberger Observermentioning

confidence: 99%

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A Multi-Rate State Observer for Visual Tracking of Magnetic Micro-Agents Using 2D Slow Medical Imaging Modalities

Kaya

Denasi

Scheggi

et al. 2018

2018 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)

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Minimally invasive surgery can benefit greatly from utilizing micro-agents. These miniaturized agents need to be clearly visualized and precisely controlled to ensure the success of the surgery. Since medical imaging modalities suffer from low acquisition rate, multi-rate sampling methods can be used to estimate the intersample states of micro-agents. Hence, the sampling rate of the controller can be virtually increased even if the position data is acquired using a slow medical imaging modality. This study presents multi-rate Luenberger and Kalman state estimators for visual tracking of microagents. The micro-agents are tracked using sum of squared differences and normalized cross correlation based visual tracking. Further, the outputs of the two methods are merged to minimize the tracking error and prevent tracking failures. During the experiments, the micro-agents with different geometrical shapes and sizes are imaged using a 2D ultrasound machine and a microscope, and manipulated using electromagnetic coils. The multi-rate state estimation accuracy is measured using a high speed camera. The precision of the tracking and multi-rate state estimation are verified experimentally under challenging conditions. For this purpose, an elliptical shaped magnetic micro-agent with a length of 48 pixels is used. Maximum absolute error in x and y axes are 2.273 and 2.432 pixels for an 8-fold increase of the sample rate (25 frames per second), respectively. During the experiments, it was observed that the micro-agents could be tracked more reliably using normalized cross correlation based visual tracking and intersample states could be estimated more accurately using Kalman state estimator. Experimental results show that the proposed method could be used to track micro-agents in medical imaging modalities and estimate system states at intermediate time instants in real-time.

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Section: B a Multi-rate Luenberger Observermentioning

confidence: 99%

“…In the prediction step, there are no available measurements in between the measurement sampling instants. Therefore, the prediction is based on the augmented system dynamics ( 18)- (19) which is an open-loop system. Denote x ( i| j) as the estimate of x(i) based on the measurement before and on time jT s .…”

Section: A Multi-rate Kalman Filtermentioning

confidence: 99%

A Multi-Rate State Observer for Visual Tracking of Magnetic Micro-Agents Using 2D Slow Medical Imaging Modalities

Kaya

Denasi

Scheggi

et al. 2018

2018 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)

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“…The standard Luenberger observer uses the model of a given system together with a suitable update term to estimate state variables that cannot be measured. In order to apply it to the multi-rate augmented system dynamics ((4.14)-(4.15)) certain modifications are required [180]. First of all the system (4.21)-(4.22) should be observable.…”

Section: A Multi-rate Luenberger Observermentioning

confidence: 99%

Multicolor fluorescence microscopy for tracking magnetic micro-agents

Kaya¹

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The field of microrobotics opens the door to new therapeutic interventions by providing access to hard-to-reach regions of the human body. The envisioned interventions are based on the wireless movement of the micro-agents, part of the microrobotics systems designed to interact with the environments, using external stimuli (e.g., magnetic, sound, light, chemical, temperature). Although a wide variety of micro-agents have been designed, fabricated, and actuated, sensor integration remains a challenge due to size limitations. In order to understand and verify the functionality of the micro-agents, imaging modalities are utilized as external sensors and considered the only feedback source. Since experimental testbeds are fabricated using optically transparent materials, microscopy techniques have been extensively used in preliminary tests and lab-on-a-chip applications.Single-band fluorescence and bright-field microscopy are commonly used to visualize the micro-agents with spatiotemporal resolution. However, single-band fluorescence microscopy renders visualization of only micro-agents and does not provide information about physical surroundings. Clear visualization of surroundings, as well as the microagents, is a requirement to reach the desired location. Bright-field microscopy enables visualization of micro-agents and surroundings, but acquired images do not reveal encoded information about identification and distinction. In this thesis, multicolor fluorescence microscopy is first applied for visualizing magnetically-actuated micro-agents and dynamic surroundings by relatively fast spectrum band change (multiplexing). The main difference of multicolor microscopy is that a sample containing micro-agents is fully resolved in different spectrum bands, and color-coded visualization is acquired. Since color is a visual cue for detection, acquired images enable an increased understanding of the micro-agent functionality and clear distinction of the surrounding media. This thesis aims to fill the gap in the literature on performing real-time multicolor microscopy for micro-agents and surroundings with three parts divided into six chapters.Chapter 1 provides an overview of micro-agents and multicolor microscopy, as well as research questions tackled in this thesis. Subsequently, Part I (Chapters 2-4) describes the imaging, actuation, and tracking tools. A multicolor fluorescence microscope is developed 10 to excite the fluorophores in a round-robin manner and synchronously acquire images from three distinct spectrum bands. Chapter 2 includes the microscope design, fluorophore selection, and spectrum analysis. A tumor environment is created by randomly placing cancer spheroids (formed with cervical HeLa cells) and polystyrene beads as drug carriers in a microfluidic channel. The environment is employed to validate that the microscope generates images with unambiguous color coding by spectral crosstalk analysis. Realtime multicolor microscopy is demonstrated by visualizing the attachment of the beads to a cancer spheroid ...

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A state observer for using a slow camera as a sensor for fast control applications

Cited by 2 publications

References 4 publications

A Multi-Rate State Observer for Visual Tracking of Magnetic Micro-Agents Using 2D Slow Medical Imaging Modalities

A Multi-Rate State Observer for Visual Tracking of Magnetic Micro-Agents Using 2D Slow Medical Imaging Modalities

Multicolor fluorescence microscopy for tracking magnetic micro-agents

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