Gabriel Leen

TTCAN: a new time-triggered controller area network

Abstract The controller area network (CAN) communications protocol is used extensively in the automotive and industrial control sectors. Much work has been done to establish the bounded response time of transmissions in an event-triggered CAN. However, a new time-triggered architecture for CAN is being developed and will soon be available on the market. This new control network, referred to as time-triggered controller area network, defines a session layer protocol for CAN, which is based on a static schedule time-triggered paradigm and provides intrinsic deterministic behaviour. This paper describes the new protocol and provides some practical performance equations to calculate utilisation limits for this control network.

A review of recent advances in optical fibre sensors for in vivo dosimetry during radiotherapy.

This article presents an overview of the recent developments and requirements in radiotherapy dosimetry, with particular emphasis on the development of optical fibre dosemeters for radiotherapy applications, focusing particularly on in vivo applications. Optical fibres offer considerable advantages over conventional techniques for radiotherapy dosimetry, owing to their small size, immunity to electromagnetic interferences, and suitability for remote monitoring and multiplexing. The small dimensions of optical fibre-based dosemeters, together with being lightweight and flexible, mean that they are minimally invasive and thus particularly suited to in vivo dosimetry. This means that the sensor can be placed directly inside a patient, for example, for brachytherapy treatments, the optical fibres could be placed in the tumour itself or into nearby critical tissues requiring monitoring, via the same applicators or needles used for the treatment delivery thereby providing real-time dosimetric information. The article outlines the principal sensor design systems along with some of the main strengths and weaknesses associated with the development of these techniques. The successful demonstration of these sensors in a range of different clinical environments is also presented.

Fiber-optic chirped FBG for distributed thermal monitoring of ex-vivo radiofrequency ablation of liver

A linearly chirped fiber Bragg grating (LCFBG) has been used as a temperature sensor for online monitoring of radiofrequency thermal ablation (RFTA). The LCFBG acts as a distributed sensor, with spatial resolution of 75 μm. A white-light setup that records the LCFBG spectrum estimates the temperature profile in real time. Three RFTA experiments have been performed ex-vivo on porcine liver measuring the radial temperature distribution during the heating process. The analysis of thermal maps quantifies the spatial heat distribution along the measurement axis and determines the ablation efficiency.

Optical Fibre Pressure Sensors in Medical Applications

This article is focused on reviewing the current state-of-the-art of optical fibre pressure sensors for medical applications. Optical fibres have inherent advantages due to their small size, immunity to electromagnetic interferences and their suitability for remote monitoring and multiplexing. The small dimensions of optical fibre-based pressure sensors, together with being lightweight and flexible, mean that they are minimally invasive for many medical applications and, thus, particularly suited to in vivo measurement. This means that the sensor can be placed directly inside a patient, e.g., for urodynamic and cardiovascular assessment. This paper presents an overview of the recent developments in optical fibre-based pressure measurements with particular reference to these application areas.

Feedback Stabilized Interrogation Technique for EFPI/FBG Hybrid Fiber-Optic Pressure and Temperature Sensors

This paper discusses a Single Wavelength Interrogation (SWI) technique used to measure fast changing pressure related signals and over a large operational temperature range. The novel technique is based on a fiber-optic pressure and temperature hybrid sensor, and a feedback stabilization technique for a tunable laser source. The fiber-optic hybrid sensor consists of a miniature diaphragm based all-silica Extrinsic Fabry-Perot Interferometric (EFPI) Fiber-Optic Pressure Sensor (FOPS) which additionally incorporates a Fiber Bragg Grating (FBG) temperature sensor. The FBG temperature sensor is used as a feedback element to stabilize the output wavelength of the tunable laser source to operate always in the linear range of the EFPI FOPS.

Conception and preliminary evaluation of an optical fibre sensor for simultaneous measurement of pressure and temperature

This paper presents a novel concept of simultaneously measuring pressure and temperature using a silica optical fibre extrinsic Fabry-Perot interferometric (EFPI) pressure sensor incorporating a fibre Bragg grating (FBG), which is constructed entirely from fused-silica. The novel device is used to simultaneously provide accurate pressure and temperature readings at the point of measurement. Furthermore, the FBG temperature measurement is used to eliminate the temperature cross-sensitivity of the EFPI pressure sensor.

Fiber-optic combined FPI/FBG sensors for monitoring of radiofrequency thermal ablation of liver tumors: ex vivo experiments.

We present a biocompatible, all-glass, 0.2 mm diameter, fiber-optic probe that combines an extrinsic Fabry-Perot interferometry and a proximal fiber Bragg grating sensor; the probe enables dual pressure and temperature measurement on an active 4 mm length, with 40 Pa and 0.2°C nominal accuracy. The sensing system has been applied to monitor online the radiofrequency thermal ablation of tumors in liver tissue. Preliminary experiments have been performed in a reference chamber with uniform heating; further experiments have been carried out on ex vivo porcine liver, which allowed the measurement of a steep temperature gradient and monitoring of the local pressure increase during the ablation procedure.

Recent Improvement of Medical Optical Fibre Pressure and Temperature Sensors

This investigation describes a detailed analysis of the fabrication and testing of optical fibre pressure and temperature sensors (OFPTS). The optical sensor of this research is based on an extrinsic Fabry–Perot interferometer (EFPI) with integrated fibre Bragg grating (FBG) for simultaneous pressure and temperature measurements. The sensor is fabricated exclusively in glass and with a small diameter of 0.2 mm, making it suitable for volume-restricted bio-medical applications. Diaphragm shrinking techniques based on polishing, hydrofluoric (HF) acid and femtosecond (FS) laser micro-machining are described and analysed. The presented sensors were examined carefully and demonstrated a pressure sensitivity in the range of sp = 2–10 nmkPa and a resolution of better than ΔP = 10 Pa (0.1 cm H2O). A static pressure test in 38 cmH2O shows no drift of the sensor in a six-day period. Additionally, a dynamic pressure analysis demonstrated that the OFPTS never exceeded a drift of more than 130 Pa (1.3 cm H2O) in a 12-h measurement, carried out in a cardiovascular simulator. The temperature sensitivity is given by k=10.7 pmK, which results in a temperature resolution of better than ΔT = 0.1 K. Since the temperature sensing element is placed close to the pressure sensing element, the pressure sensor is insensitive to temperature changes.

Modeling and Verification of a Time-triggered Networking Protocol

Analysis estimates that more than 80% of all current innovations within vehicles are based on distributed electronic systems. Critical to the functionality and application domain of such systems is the underlying communication network. Current advances in control networking technology indicate that time-triggered architectures offer improvements in deterministic behaviour, which are particularly appropriate for safety-critical and real-time applications. Here we present novel work on the formal specification and formal verification of a timetriggered protocol: ISO 11898-4 - Time Triggered communication on the Controller Area Network (TTCAN)®. This work has been carried out using the UPPAAL model checker based tool set which is capable of verifying safety properties as formalised by simple reachability properties. These verifiable properties are a subset of those possible in a full realisation of Timed Computation Tree Logic (TCTL). Three TTCAN network automata and a medium automaton were designed. Nine properties including deadlock were examined. The results provide a high degree of confidence in the correctness of the TTCAN protocol specification. The formal verification research work described here was conducted in parallel with the preparation of the ISO standard protocol specification for TTCAN.

Fibre optic pressure and temperature sensor for geothermal wells

In this paper a fibre optic sensor is developed and tested to measure pressure and temperature under simulated wellbore conditions. The sensor consists of a miniature all-silica fibre optic Extrinsic Fabry-Perot Interferometer (EFPI) sensor which has a novel embedded Fibre Bragg Grating (FBG) reference sensor element to determine both pressure and temperature at the point of measurement. The sensor head is completely fabricated from fused-silica components, i.e. completely made of glass, utilizing a 200µm outer diameter silica glass fibre, a silica glass capillary and a Single-Mode FBG. All silica-glass components were spliced together using a conventional fusion splicer to obtain a robust sensor structure.