Design and implementation of DSP-based magnetic control system for capsule endoscope

PhD ThesisEarly detection methods are key to reducing morbidity rates from digestive tract cancer which is currently one of the fastest growing cancers in the World. Capsule endoscopes (CEs) are a new technology that can be used to improve early detection of the gastrointestinal (GI) tract disorder. The device integrates the technologies such as image processing, optoelectronic engineering, information communication, and biomedical engineering. The capsule is the size and shape of a pill and contains an optoelectronic camera, antenna, transmitter, battery and optoelectronic illuminating light emitting diodes (LEDs). The small size of these devices enables them to offer many advantages over conventional endoscopes such as accessibility to the entire intestine and minimising the risk of perforation, particularly for patients with difficult anatomy (e.g. post-operative scar tissue). Currently used devices are passive and can only follow the natural transit of the intestines, and hence there is considerable interest in methods of controlled actuation for these devices. In this thesis, a novel actuation system based on magnetic levitation is designed, developed and implemented, utilizing a small permanent magnet embedded within the capsule and an arrangement of digitally controlled electromagnets outside the body. The proposed approach is that the magnet can be moved and oriented by DC magnetic force and torque produced by coils placed outside of the human body, with a suitable position feedback sensor enabling closed-loop control. Theoretical analyses of the proposed actuation system are presented which model the magnetic field, force and torque exerted by electromagnetic coil on the embedded magnet. Based on the distribution of the magnetic field, an optimal geometry for the coils is proposed in order to achieve a levitation distance which is realistic for the inspection of the GI tract. Two types of systems are investigated in the thesis, namely single-input single-output (SISO) and multi-input multi-output (MIMO), and the dynamics of these systems are modelled in state space form and hence linear controllers are designed for capsule actuation. The controllers are simulated using Matlab/ Simulink tools to realize the mathematical analysis of the system, and then implemented digitally in real-time using Texas Instruments (TI) TMS320F2812 Digital Signal Processor (DSP) to validate the proposed actuation system. In the SISO system, a linear one degree of freedom (1DOF) proportionalintegral- derivative (PID) controller is designed to move the inserted magnet in the vertical dimension within an area around the operating point and to maintain it at a desired position. A realistic simulation model is designed and implemented to evaluate the proposed controller. Simulation results have shown that the controller is able to successfully hold the embedded magnet in the desired position. For practical validation, the PID controller is implemented in real-time on the DSP system, where pulse width modulation (PWM) is generated to control the coil current, and Hall effect sensors are used for position feedback. Experimental results are obtained under step and square wave input demand. In the proposed system, high frequency noise on the position sensor is initially rejected by hardware implementation of resistor capacitor-low pass filter (RC-LPF) circuit. The accuracy of the position feedback is increased by calibrating the DSP’s on-chip analogue-digital converter (ADC) in order to reduce conversion error due to inherent gain and offset errors. To further reduce the influence of the position feedback noise, an average of ten repeated samples based on mean filter is implemented by the DSP in order to reduce the influctuation of the sensor reading. The tracking performance of the actuation system based on two Hall effect sensors on the opposite coil’s poles is investigated under step trajectory input. In an improved actuation system, position feedback is provided by using an AC magnetic field to obtain the capsule position information, decoupling this from the DC actuation field. The noise of the position feedback in the improved system is reduced by replacing the PWM current drive with a linear power amplifier driven from a digital to analogue converter (DAC), hence reducing AC interference. Positioning sensor noise was found to be further reduced by implementing digital filtering based on a coherent detector using the DSP, without increasing response time. The performance of the actuation system using these position sensors is compared based on settling time, overshoot, steady-state error, and control input parameters in order to validate the proposed improvement in the position feedback. The experimental results have shown that the controller based on both sensing strategies satisfactory control of the magnet’s position. However, the response of the system based on AC position sensing has the shortest settling time, smallest overshoot value and steady-state error. In the MIMO system, several linear controllers such as pole placement (PP), Entire Eigenstructure Assignment (EEA), and linear Quadratic regulator (LQR) techniques are designed and their tracking performances are compared. Simulation results have shown that, based on acceptable control inputs, the LQR controller has the fastest response with minimal overshoot value and steady state error. However, the LQR controller based on 2DOF is unable to maintain stable control of the magnet due to the insufficient position feedback from the two coil sensors. Specifically, it is not possible to achieve a stable 2D system since the orientation angle of the magnet is not resolvable. Therefore, the position feedback is improved by obtaining the device position and orientation information from a pair of 3-axis orthogonal coils. A realistic simulation model for the 3DOF LQR controller is designed and implemented to evaluate the developed system. Simulation results have shown that this controller is can achieve the necessary stability. In conclusion, based on the results from the 1D control system, the thesis shows that the DC magnetic field, which is used for capsule movement, can be also used to provide the controller acceptable position feedback. However, the use of AC magnetic field for positioning purpose provides more accurate position information. In order to implement 2DOF control system successfully, two 3-axis orthogonal coil sensors are considered which are used to provide the actuation algorithm with more accurate feedback of position and orientation information.Ministry of Higher Education, Iraq

Auslesemethoden für magnetoelektrische Sensoren

The detection of weak magnetic fields has the potential to provide additional, non-redundant information in scientific fields such as medical diagnostics, geomagnetic investigations, data storage, amongst others. Many substances feature a low permeability and magnetic fields can penetrate them nearly unhindered which yields the possibility to detect signals that originate from within a volume without contact. Thin-film magnetoelectric sensors are mm-sized magnetometers that transform magnetic fields into a measurable polarisation via a mechanical coupling of a magnetostrictive and a piezoelectric layer. They do not need to be cooled and their high dynamic range allows them to be operated in unshielded environments. The output signal of the cantilever-shaped sensors is enhanced at their resonance frequency which can be exploited to increase the signal-to-noise ratio. This dissertation treats the signal processing for thin-film magnetoelectric sensors from a system point of view. Four main readout methods are investigated, modelled, and evaluated with the aim to lower the limit of detection: The direct detection, magnetic frequency conversion, electric frequency conversion, and a completely novel method utilising the sensor as a microwave resonator. With the focus on the signal-to-noise ratio, the noise sources of the measurement systems are discussed in depth and the dominant noise sources identified. The ultimate noise limit is given by the thermal-mechanical noise of the sensors. Acoustic environmental interference can be reduced with a tuning fork assembly that discriminates magnetic and mechanical excitation of two cantilevers clamped face-to-face. The best limit of detection for thin-film magnetoelectric sensors at 10 Hz is 50 pT/Hz^1/2 achieved with the magnetic frequency conversion leading the way towards measurements of biomagnetic signals.Die Detektion von schwachen magnetischen Feldern hat das Potential in Forschungsfeldern wie der medizinischen Diagnostik, geomagnetischen Untersuchungen, Datenspeicherung, usw. zusätzliche, nicht redundante Informationen verfügbar zu machen. Viele Stoffe haben eine geringe Permeabilität und sind daher für Magnetfelder nahezu uneingeschränkt durchlässig. Dadurch entsteht die Möglichkeit tieferliegende Signale kontaktlos zu detektieren. Dünnfilm magnetoelektrische Sensoren sind millimeter große Magnetometer, welche magnetische Felder über die mechanische Kopplung eines magnetostriktiven und eines piezoelektrischen Materials in eine messbare Polarisation transformieren. Die Sensoren brauchen nicht gekühlt werden und weisen einen hohen Dynamikbereich auf, wodurch sie in ungeschirmten Umgebungen betrieben werden können. In der mechanischen Resonanzfrequenz der balkenförmigen Sensoren wird deren Ausgangssignal erhöht, wodurch das Signal-zu-Rausch Verhältnis verbessert wird. In dieser Dissertation wird die Signalverarbeitung von diesen Sensoren aus Systemsicht behandelt. Mit dem Ziel das Detektionslimit zu senken werden vier Ausleseverfahren untersucht, modelliert und bewertet: Die direkte Detektion, die magnetische Frequenzumsetzung, die elektrische Frequenzumsetzung und ein komplett neues Verfahren, in dem der Biegebalken als Mikrowellen Resonator verwendet wird. Mit dem Fokus auf dem Signal-zu-Rausch Verhältnis werden die einzelnen Rauschquellen der Messsysteme diskutiert und die jeweils dominanten Rauschquellen ermittelt. Das grundlegende Rauschlimit ist das thermisch-mechanische Rauschen des Sensors. Akustische Umweltstörungen können mit einer Stimmgabelanordnung bestehend aus zwei Einzelsensoren unterdrückt werden, welche magnetische und mechanische Einkopplungen bauartbedingt unterscheiden kann. Als bestes Detektionslimit für dünnfilm magnetoelektrische Sensoren bei 10 Hz wird 50 pT/Hz^1/2 gemessen

EUROSENSORS XVII : book of abstracts

Fundação Calouste Gulbenkien (FCG).Fundação para a Ciência e a Tecnologia (FCT)

Advances in Supply Chain Management Decision Support Systems: Potential for Improving Decision Support Catalysed by Semantic Interoperability between Systems

Globalization has catapulted ‘cycle time’ as a key indicator of operational efficiency [1] in processes such as supply chain management (SCM). Systems automation holds the promise to augment the ability of supply chain operations or supply networks to rapidly adapt to changes, with minimal human intervention, under ideal conditions. Business communities are emerging as loose federations or organization of networks that may evolve to act as infomediaries in global SCM. These changes, although sluggish, are likely to impact process knowledge and in turn may be stimulated or inhibited by the availability or lack of process interoperability, respectively. The latter will determine operational efficiencies of supply chains. Currently “community of systems” or organization of networks (aligned by industry or business focus) contribute minimally in SCM decisions because true collaboration remains elusive. Convergence and maturity of multiple advances offers the potential for a paradigm shift in interoperability. It may evolve hand-in-hand with [a] the gradual adoption of the semantic web [2] with concomitant development of ontological frameworks, [b] increase in use of multi-agent systems and [c] advent of ubiquitous computing enabling near real-time access to identification of objects and analytics [4]. This paper examines some of these complex trends and related technologies. Irrespective of the characteristics of information systems, the development of various industry-contributed ontologies for knowledge and decision layers, may spur self-organizing networks of business communities and systems to increase their ability to sense and respond, more profitably, through better enterprise and extraprise exchange. In order to transform this vision into reality, systems automation must be weaned from the syntactic web and integrated with the organic growth of the semantic web. Understanding of process semantics and incorporation of intelligent agents with access to ubiquitous near real-time data “bus” are pillars for “intelligent” evolution of decision support systems. Software as infrastructure may integrate plethora of agent colonies through improved architectures (such as, service oriented architecture or SOA) and business communities aligned by industry or service focus may emerge as hubs of such agent empires. However, the feasibility of the path from exciting “pilots” in specific areas toward an informed convergence of systemic real-world implementation remains unclear and fraught with hurdles related to gaps in knowledge transfer from experts in academia to real-world practitioners. The value of interoperability between systems that may catalyse real-time intelligent decision support is further compromised by the lack of clarity of approach and tools. The latter offers significant opportunities for development of tools that may segue to innovative solutions approach. A critical mass of such solutions may spawn the necessary systems architecture for intelligent interoperability, essential for sustainable profitability and productivity in an intensely competitive global economy. This paper addresses some of these issues, tools and solutions that may have broad applicability in several operations including the management of adaptive supply-demand networks [7]

The improvement of meter performance of EM sensing flowmeters using software modelling

This thesis is focused on the improvement of the meter performance and power consumption of non-mechanical flowmeters such as the conventional electromagnetic flowmeter and the fluidic oscillator. Each flowmeter is studied using Finite Element Modelling for the magnetic field, the virtual current and the fluid dynamics in order to simulate flow signal. The meter design of the conventional electromagnetic flowmeter is modified to provide a better signal level by optimising the geometry of the flow channel and the magnetic field. The signal level increase can be used to reduce power consumption. This improvement provides a 1.96 times greater signal or 51% less power consumption for the conventional electromagnetic flowmeter. An alternative coil-less electromagnetic flowmeter is proposed to reduce the energy consumption. A laminated magnetostrictive material/PZT piezoelectric material is used to control the magnetic field from a permanent magnet. Modelling is carried out to optimise the meter and the magnetic field control device. The device can provide a further reduction of 54.7% of energy usage over the improved conventional electromagnetic flowmeter. The modelling of the fluidic oscillator is undertaken not only with the fluidic dynamics but also the flow signal by using the electromagnetic sensing technique. Using these approaches, recommendations for a better signal level are proposed.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Numerical Simulation

Nowadays mathematical modeling and numerical simulations play an important role in life and natural science. Numerous researchers are working in developing different methods and techniques to help understand the behavior of very complex systems, from the brain activity with real importance in medicine to the turbulent flows with important applications in physics and engineering. This book presents an overview of some models, methods, and numerical computations that are useful for the applied research scientists and mathematicians, fluid tech engineers, and postgraduate students

Proceedings of the Third International Mobile Satellite Conference (IMSC 1993)

Satellite-based mobile communications systems provide voice and data communications to users over a vast geographic area. The users may communicate via mobile or hand-held terminals, which may also provide access to terrestrial cellular communications services. While the first and second International Mobile Satellite Conferences (IMSC) mostly concentrated on technical advances, this Third IMSC also focuses on the increasing worldwide commercial activities in Mobile Satellite Services. Because of the large service areas provided by such systems, it is important to consider political and regulatory issues in addition to technical and user requirements issues. Topics covered include: the direct broadcast of audio programming from satellites; spacecraft technology; regulatory and policy considerations; advanced system concepts and analysis; propagation; and user requirements and applications