Laurence P. Ketteringham

Estimation of Upper-Limb Orientation Based on Accelerometer and Gyroscope Measurements

A solution is proposed to the estimation of upper-limb orientation using miniature accelerometers and gyroscopes. This type of measurement device has many different possible applications, ranging from clinical use with patients presenting a number of conditions such as upper motor neuron syndrome and pathologies that give rise to loss of dexterity, to competitive sports training and virtual reality. Here we focus on a design that minimizes the number of sensors whilst delivering estimates of known accuracy over a defined frequency range. Minimizing the sensor count can make the measurement system less obtrusive, as well as minimising cost and reducing the required bandwidth if using a wireless solution. Accurate measurement of movement amplitude up to 15 Hz is required in our immediate application, namely to quantify tremor in multiple sclerosis patients. The drive for low numbers of sensors and good accuracy at higher frequencies leads to a novel design based on composite filters. The simple estimator structure also gives good insight into the fundamental accuracy limitations based on the sensors chosen. This paper defines the underlying mathematics, and quantifies performance for an estimator for shoulder, upper arm, lower arm and hand orientations. Good estimation accuracy up to 15 Hz is indicated, and this with a reduced total sensor count of 18 compared to 24 that would be required for more conventional estimator architectures.

Surface pasteurisation of shell eggs

Microbial and visual contamination of eggs during production and processing is of concern to the consumer and to the egg industry for both health and economic reasons. While egg washing has the potential to reduce significantly the amount of visual and microbial contamination of eggs, there are substantial concerns as to the effectiveness of current egg washing technology. It is also unclear whether the use of egg washing results in salmonella moving from the exterior of the egg shell through the shell into the contents of the egg where they may grow to high levels. A short investigation was carried out on the applicability of four different heat treatments (hot air, hot water, infra-red radiation, and atmospheric steam) for the surface pasteurisation of shell eggs. The aim of this work was to assess temperatures on the outside and interior of the shell to identify the highest surface temperatures that could be achieved without damaging the contents of the egg. Initial results show that temperatures sufficient to achieve significant reductions in salmonella numbers can be attained on the outside of an egg without raising interior temperatures to those that would cause coagulation of the egg contents.

The use of high thermal conductivity inserts to improve the cooling of cooked foods

The cooling of many cooked foods is limited by the rate at which heat can flow from the centre to the surface of the product. Investigations have studied the benefit of using high heat transfer devices including heat pipes, thermosyphons and solid metal rods to increase the cooling rate of hot foods. Cylinders of heated mashed potato, with or without high conductivity inserts, were cooled from 70°C to 10°C and 3°C in a blast chill room operating at 0°C. The inserts reduced the cooling time between 6% and 29% with heat pipes producing the greatest effect. The results show that heat pipes, thermosyphons and other heat transfer devices are a viable way for improving the cooling rate and uniformity of cooling of foods. The inserts have the potential to produce significant time saving and improvements in food quality and safety.

Immersion chilling of trays of cooked products

Abstract Cooking systems producing complete, or ingredients for, chilled meals are designed to achieve temperatures of 70°C for 2 min in the centre of the food, which should cause a 10 6 -fold destruction of Listeria monocytogenes. However, spore-forming micro-organisms will survive this process and multiply if the food is not rapidly reduced to a temperature below 10°C. Experimental investigations have been carried out to study the cooling of different thicknesses of cooked solid–liquid mixtures under a range of immersion chilling conditions. An iterative computer model of the process has been developed and used to extend these data to cover alternative processing conditions and a range of cooked meals. If surface freezing was to be avoided then it was found that only the shallowest (10 mm) tray could be chilled within the limits of the most severe European Guidelines. However, the model also predicted that the 40 mm trays of food would cool within the limits of the Guidelines if oriented differently.

Inverse dynamics modelling of upper-limb tremor, with cross-correlation analysis

A method to characterise upper-limb tremor using inverse dynamics modelling in combination with cross-correlation analyses is presented. A 15 degree-of-freedom inverse dynamics model is used to estimate the joint torques required to produce the measured limb motion, given a set of estimated inertial properties for the body segments. The magnitudes of the estimated torques are useful when assessing patients or evaluating possible intervention methods. The cross-correlation of the estimated joint torques is proposed to gain insight into how tremor in one limb segment interacts with tremor in another. The method is demonstrated using data from a single patient presenting intention tremor because of multiple sclerosis. It is shown that the inertial properties of the body segments can be estimated with sufficient accuracy using only the patients height and weight as a priori knowledge, which ensures the methods practicality and transferability to clinical use. By providing a more detailed, objective characterisation of patient-specific tremor properties, the method is expected to improve the selection, design and assessment of treatment options on an individual basis.

Validation of Inverse Dynamics Modelling and Correlation Analysis to Characterise Upper-Limb Tremor

Inverse dynamic modelling can be used to estimate the torques that drive tremor movements in individual joints. The cross-correlations between torques in different joints can then be used to identify key patterns of forcing that drive the movement. The inverse dynamic model is dependent on assumed inertial properties of individual limb segments. This work examines the sensitivity of the torque estimates and the subsequent cross-correlation analyses to uncertainties in the assumed inertial properties by introducing reasonable errors to the estimates. It is shown that, although the errors in the torque magnitudes are non-negligible (max. 23%), the general patterns of forcing change negligibly. The method therefore provides a convenient and robust means of achieving detailed characterisation of tremor movements in a clinical setting.

Intention Tremor in Multiple Sclerosis: Measuring and Modelling Arm Dynamics and Elbow Torque

This paper reports on a project to measure and control tremor in individuals with multiple sclerosis (MS). It discusses systems for measuring and modelling upper limb movements and intention tremor, together with initial movement measurement and torque modelling data. The system uses microelectromechanical systems (MEMS) sensors to measure movements of the upper limb representative of everyday tasks. Surface electromyogram (EMG) measurements are taken simultaneously to provide gross muscle activity data. A dynamic model is used to simulate the movements, allowing particular sites to be studied in detail. Initial movement data is presented, comparing analysed EMG data and torque estimated by the dynamic model around the elbow joint. Despite the simple analysis, a good fit was obtained. The dynamic model includes a neuromuscular modelling system which will be used in future work to simulate the interactions between measured movements containing intention tremor and the intention behind them, allowing better understanding of the tremor and creating better descriptions of the tremor. Future work will use measured data and modelling to develop methods of attenuating intention tremor, by providing real-time feedback control of tremor reduction devices, without adversely affecting the underlying intended movement.Copyright