D.A. Keating

Feedback dew-point sensor utilizing optimally cut plastic optical fibres

A plastic optical fibre reflectance sensor that makes full use of the critical angle of the fibres is implemented to monitor dew formation on a Peltier-cooled reflector surface. The optical configuration permits isolation of optoelectronic components from the sensing head and better light coupling between the reflector and the detecting fibre, giving a better signal of the onset of dew formation on the reflector. Continuous monitoring of the rate of change in reflectance as well as the absolute reflectance signals, the use of a novel polymethyl-methacrylate-coated hydrophobic film reflector on the Peltier element and the application of feedback around the point of dew formation, further reduces the possibility of contamination of the sensor head. Under closed-loop operation, the sensor is capable of cycling around the point of dew formation at a frequency of 2.5 Hz.

An automatic optical fibre feedback potometer for transpiration studies

A new automatic feedback potometer for physiological studies of water uptake by root systems is described. A dual-optical-fibre amplitude-modulating displacement transducer of improved sensitivity is employed to detect the changes in liquid level. The merits of optimal double-cut fibres, which make full use of the critical angle and improve coupling between the emitter and the receiver, have resulted in a sensor that is 64 times more responsive than the simple emitter - detector probe. Positioning the optical fibre transducer in a narrow capillary and using feedback to control the liquid level allows continuous measurement of volumes in the nanolitre range. The optical sensor used does not need re-calibration for the different salt solutions used in such studies.

A practical optical force-feedback microphone:

A novel technique of measuring diaphragm displacement in microphones using a laser-diode Fabry-Perot system is presented. The microphone diaphragm is held within an electrostatic force-feedback loop so as to improve the performance. A second loop operates around the laser, for noise minimisation purposes. Following a brief introduction to the subject of optical detection in microphones, the modified Fabry-Perot interferometer is described, and the complete system with the two feedback loops presented. The characteristics of the laser driver and laser diode are examined. Theoretical responses are shown, for different cases, and noise calculations yield the dynamic ranges without feedback. The effect of feedback is then examined, both around the laser (electronic) and around the microphone capsule (electrostatic), and the dynamic ranges are recalculated to show the advantages of feedback. Intended directions for further research are also discussed.

Coordination of Multiple Mobile Robots via Communication

Research on the coordination of multiple mobile robots has to address three main problems: (i) how to appropriately divide the functionality of the system into multiple roots, (ii) how to manage the dynamic configuration of the system, and (iii) how to realize cooperation behavior. This paper will concentrate on the third aspect. More specifically, the aim of our research is to develop a team of coordinating mobile robots via effective communication for real work applications. We will describe the methodology to achieve cooperative behavior, the experimental mobile robots developed, and potential application areas. The developed system is demonstrated by two examples such as flocking and shared experience learning.

Neural Network Control of a Simple Mobile Robot

In recent years researchers in the Department of Cybernetics have been developing simple mobile robots capable of exploring their environment on the basis of the information obtained from a few simple sensors. These robots are used as the test bed for exploring various behaviours of single and multiple organisms: the work is inspired by considerations of natural systems. That part of the work which involves neural networks and related techniques is discussed. These neural networks are used both to process the sensor information and to develop the strategy used to control the robot. Here the robots, their sensors, and the neural networks used are all described.

Optical sensors for monitoring water uptake in plants

The monitoring of water uptake in plants is becoming increasingly important. Optical sensors offer considerable advantages over conventional methods and several sensors have been developed including an optical potometer that monitors water uptake from individual roots, the detection of xylem cavitation using audio acoustic emissions with an interferometric force feedback microphone, and an optical fiber displacement transducer that detects changes in leaf thickness in relation to leaf-water potential. >

An optical force-feedback microphone measuring audible emissions from plants

calibration curves are independent of tissue bed site and skin pigmentation. The optical fibre pulse oximeter was successfully used in the University of Liverpool Magnetic Resonance Research Centre Scanner, in conditions of electromagnetic interference which caused a conventional pulse oximeter to fail. The pulsatile signal was isolated and routinely used for peripheral gating in the core of the MR scanner. *University of Liverpool, U.K.

A New Reflective Plastic Optical Fibre Displacement Transducer

A novel, dual plastic optical fibre amplitude modulating displacement transducer of improved sensitivity is presented. Results of different fibre optic configurations and the merits of cutting the fibres twice so as to improve coupling and make full use of the critical angle are shown.

Optical sensors for plant/water relations

The potential of optical fibers in monitoring water uptake from plants is considered. Applications include an optical potometers that monitors water uptake from individual roots, the detection of xylem cavitation using audio acoustic emission with an interferometric force feedback microphone, an optical displacement transducer that detects changes in leaf thickness in relation to leaf water potential, and the use of fluorescence to monitor water uptake and translocation.

A new measurement system for high-resolution tactile imaging

Over the last 12 years, consistent effort has been directed toward the development of a usable sense of touch for machines. This research has been somewhat overshadowed by the ongoing development in artificial vision, but has remained important for specialised object identification applications. Over the aforementioned period, a great number of different transduction and measurement principles have been adopted, each claiming to offer certain desirable characteristics. The last five years have shown a reduction in the variation of methods being pursued. One of the main surviving transduction methods is based upon the variable-separation capacitive transducer. The method of capacitance measurement, adopted by two major American research teams developing such sensors, has been a simple charge amplifier. Their measurement methodology has limited the spatial resolution, or inter-tactel separation, and slowed the acceptance of an otherwise near ideal taction device. This paper describes the development, a design model and subsequent construction, of a variable-separation capacitive tactile system which employs an improved measurement system. The system permits the sensor spatial separation to be reduced to the limits of the physical construction method and no longer be confined by the measurement technique. This will, it is hoped, lead to the construction of larger, more densely packed, arrays capable of low-cost, efficient object recognition. The sensor performance, possible applications and intended direction for further research are also discussed.