James M. Gilbert

Small-vocabulary speech recognition using a silent speech interface based on magnetic sensing

This paper reports on word recognition experiments using a silent speech interface based on magnetic sensing of articulator movements. A magnetic field was generated by permanent magnet pellets fixed to relevant speech articulators. Magnetic field sensors mounted on a wearable frame measured the fluctuations of the magnetic field during speech articulation. These sensor data were used in place of conventional acoustic features for the training of hidden Markov models. Both small vocabulary isolated word recognition and connected digit recognition experiments are presented. Their results demonstrate the ability of the system to capture phonetic detail at a level that is surprising for a device without any direct access to voicing information.

Gyrobot: Control of Multiple Degree of Freedom Underactuated Mechanisms Using a Gyrating Link and Cyclic Braking

A novel control strategy is introduced in which a multiple degree of freedom passive joint mechanism is augmented with a single continuously gyrating link. The gyrating link introduces coupling torques to the remaining joints, and the effect of these torques is controlled by cyclically applying holding brakes mounted on the passive joints. This allows position and trajectory control of the mechanism.

Numerical modelling of scanned beam laser soldering of fine pitch packages

Laser soldering provides a useful tool for the electronics manufacturer and has found a number of successful industrial applications. The laser provides highly controllable localised heating in a manner similar to hand soldering and has distinct advantages over other soldering methods. However, the heating processes that occur in laser soldering are complex making it difficult to predict whether a particular operation will be successful. Numerical modelling provides a valuable tool in answering such questions but the modelling process and the assumptions upon which it is based must be understood if the results are to be reliable.This paper explains the assumptions made in deriving a suitable model and describes the use of a commercial finite element modelling package to aid the understanding of laser soldering processes, with a particular emphasis on single and multi‐pass scanned beam soldering operations.

Analytical and numerical modelling for dual-resonator vibration-based electromagnetic generator

This paper presents a method which offers the possibility of widening the bandwidth of an electromagnetic energy harvester by utilizing a novel dual-resonator method. The proposed device consists of two separate resonator systems (coil & magnet), which each comply with their respective resonance frequencies, but which, together, give an extended bandwidth. Basic analytical models are derived and a numerical model is implemented in MATLAB-Simulink. The predictive results indicate that for a low damping system, there is a maximum of 75% improvement of the induced voltage within the Intermediate Region which lies between the two resonator frequencies. Nonetheless, the improvement of the induced voltage in the region does come with some sacrificing of the outputs at the side frequencies, which is highly susceptible to the value of the damping factor of the respective resonators.

A User-centric Design of Permanent Magnetic Articulography based Assistive Speech Technology

This paper addresses the design considerations and challenges faced in developing a wearable silent speech interface (SSI) based on Permanent Magnetic Articulography (PMA). To improve its usability, a new prototype was developed with the involvement of end users in the design process. Hence, desirable features such as appearance, portability, ease of use and light weight were incorporated into the prototype. The device showed a comparable performance with its predecessor, but has a much improved appearance, portability and hardware in terms of miniaturisation and cost.

Sensing in Garment Assembly

Sensing demands in the automated assembly of garments differ considerably from those encountered in rigid materials handling. Attempts to automate in an ‘open loop’ manner, assuming knowledge and consistency of all relevant fabric properties, are usually doomed to failure because such properties are likely to vary from batch to batch, with time, environmental conditions, and can be dependant on the handling history. Sensory feedback can provide information for the selection of appropriate corrective action. Various sensing strategies have been proposed for the detection of presence, position and orientation of fabric stacks and individual panels, with the aim of preparing parts for joining. These are discussed in some detail with particular emphasis on the practicalities of different means with respect to the relevant properties of the materials and the environment. The applications of sensors during sewing operations, for error recovery and for inspection purposes are also described.

Nonlinear Modeling and Verification of a Heaving Point Absorber for Wave Energy Conversion

Although the heaving point absorber (PA) concept is well known in wave energy conversion research, few studies focus on appropriate modeling of nonlinear fluid viscous and mechanical friction dynamics. Even though these concepts are known to have nonlinear effects on the hydrodynamic system, most research studies consider linearity as a starting point and in doing so have a weak approach toward modeling the true dynamic behavior, particularly close to resonance. The sole use of linear modeling leads to limited ability to develop control strategies capable of true power capture optimization and suitable device operation. Based on a 1/50 scale cylindrical heaving PA, this research focuses on a strategy for hydrodynamic model development and experimental verification. In this study, nonlinear dynamics are considered, including the lumped effect of the fluid viscous and mechanical friction forces. The excellent correspondence between the derived nonlinear model and wave tank tested PA behaviors provides a strong background for wave energy tuning and control system design.

Design and optimisation of a footfall energy harvesting system

The scavenging of electrical energy from normal human activity has a number of attractions, and footfall energy is seen as one of the most attractive sources. However, footfall motion is characterised by relatively large forces and low velocities, and this makes it inherently poorly matched to electromagnetic generators which operate most efficiently at high speeds. In order to achieve an efficient velocity amplification, a novel mechanism has been developed which makes use of a spring and flywheel as energy storage elements and a ‘striker’ mechanism which controls energy storage and release. This energy harvesting mechanism is capable of being used either in footwear or under a floor. In this article, the structure of the proposed mechanism is described; the optimisation of the system parameters, based on a dynamic model, is discussed; and experimental results for an under-floor system are presented.

A vibrating cantilever footfall energy harvesting device

Human footfall is an attractive source of energy for harvesting for low-power applications. However, the nature of footfall is poorly matched to electromagnetic generators. Footfall motion is characterised by high forces and low speeds, while electromagnetic generators are normally most efficient at relatively high speed. This article proposes a novel mechanism for converting the low-speed motion of footfall to a higher speed oscillating motion suitable for electromagnetic power generation. The conversion is achieved using a cantilever beam which is deflected by the footfall motion using a special ‘striker’ mechanism which then allows the cantilever to oscillate freely at a relatively high speed. An arrangement of permanent magnets attached to the cantilever causes an alternating magnetic field, and a stationary coil converts this to a usable voltage. This article describes the mechanism and provides a mathematical model of its behaviour which allows the system parameters to be optimised and its performance predicted. The performance of a prototype device is presented, and it is shown that this is capable of generating up to 60 mJ/step and that the conversion efficiency is up to 55%.

Laser soldering control using optical imaging

Purpose – The use of lasers to selectively solder joints in electronic assemblies has a number of advantages over methods which involve heating of the whole assembly. However, the localised energy delivery means that the heating and melting behaviour of the solder is particularly dependent on external and process influences. This paper aims to propose a new approach to monitoring and feedback control of the melting process through image acquisition and processing.Design/methodology/approach – In order to evaluate the proposed feedback strategy, a series of experiments have been performed using a semiconductor diode laser controlled by a PC, which also performs image acquisition and processing operations. Two main processing techniques, based on edge detection and Fourier analysis, have been evaluated.Findings – It has been shown that the proposed technique is capable of controlling laser pulse duration to correct for variations in joint geometry, material parameters and laser energy delivery and results i...