Matthew G. Pepper

Design, development, and characteristics of an in-shoe triaxial pressure measurement transducer utilizing a single element of piezoelectric copolymer film

In gait analysis, there is growing awareness of the need to simultaneously measure shear and vertical forces for the diagnosis and treatment assessment of pathological foot disorders. This is especially the case in the measurement of the forces between the plantar surface of the foot and the shoe. Although clinical awareness of the need to simultaneously measure shear and vertical forces under the foot has increased little has been done to provide the technology. This is mainly due to the difficulty in constructing devices capable of carrying out this task in the in-shoe environment. The aim of this paper is to describe the development and characteristics of a miniature triaxial transducer measuring 10 /spl times/ 10 /spl times/ 2.7 mm and a weight of only 2 g. This transducer is capable of simultaneously measuring three orthogonal forces under any location of the plantar surface of the foot utilizing a single element piezoelectric copolymer P(VDF-TrFE). Transducer sensitivity, linearity, hysteresis, crosstalk and temperature dependence is presented. As well as in-shoe force measurement, this triaxial transducer could have other biomedical and general engineering applications, e.g., prosthetic interface forces, handgrip forces, sport, robotics, etc.

In-shoe biaxial shear force measurement: the Kent shear system

The Kent shear system is introduced and preliminary clinical results are presented. A technique utilising copolymer piezoelectric film has allowed the manufacture of biaxial in-shoe transducers capable of simultaneously measuring two orthogonal shear forces. Bipedal measurements are carried out inside everyday footwear over multiple footsteps.

In-shoe foot pressure measurement system utilising piezoelectric film transducers

THE INITIAL aim of this research was to design and develop an in-shoe pressure measurement system for use in a clinical environment, to measure absolute pressure values at discrete predefined anatomical sites to within 10%. A major part of the work was to design and develop the piezoelectric copolymer transducers used in the system (NEVILL, 1991). This work introduces the transducer design and the development of the electronic and data acquisition systems.

Monitoring respiratory activity in neonates using diaphragmatic electromyograph

The monitoring of the development of respiratory function in low-birth-weight or sick neonates is important in its overall treatment. The most direct approach to obtaining information on respiratory function is to monitor the activity of the diaphragmatic muscular system rather than measure the resultant change in lung volume or ventilator output, which cannot be guaranteed to be directly related to the neonates own respiratory activity. The system was designed to assess the feasibility of monitoring respiratory activity in such neonates by measuring the diaphragmatic electromyograph. It is hoped that this system can be used to monitor the development of lung function and possibly, if reliability proves adequate, the synchronisation and control of ventilator assistance. To monitor the EMG, the dominant effect of the ECG was removed using a digital processor. Initial clinical measurements indicate that neonatal respiratory activity can be monitored by measuring the diaphragmatic EMG. Comparative measurements show the EMG method is faster in detecting the inspiratory phase of a breath. Measurements on ventilated neonates showed the presence of intermittent respiratory activity. It also is proposed that clinically relevant information may be deduced from the analysis of the morphology of the detected EMG waveform.

Quantitative Assessment of Upper Limb Motion in Neurorehabilitation Utilizing Inertial Sensors

Two inertial sensor systems were developed for 3-D tracking of upper limb movement. One utilizes four sensors and a kinematic model to track the positions of all four upper limb segments/joints and the other uses one sensor and a dead reckoning algorithm to track a single upper limb segment/joint. Initial evaluation indicates that the system using the kinematic model is able to track orientation to 1 degree and position to within 0.1 cm over a distance of 10 cm. The dead reckoning system combined with the “zero velocity update” correction can reduce errors introduced through double integration of errors in the estimate in offsets of the acceleration from several meters to 0.8% of the total movement distance. Preliminary evaluation of the systems has been carried out on ten healthy volunteers and the kinematic system has also been evaluated on one patient undergoing neurorehabilitation over a period of ten weeks. The initial evaluation of the two systems also shows that they can monitor dynamic information of joint rotation and position and assess rehabilitation process in an objective way, providing additional clinical insight into the rehabilitation process.

Application of low cost inertial sensors to human motion analysis

In this paper the feasibility of utilizing low cost inertial sensors for human motion analysis is presented. The Xsens MTx sensor is used as the standard for comparison with the Sony Move and the Nintendo Wii (Wii Remote with Wii MotionPlus). Initial tests have been carried out by measuring upper limb range of motion and position tracking. Initial measurements utilizing kinematic modeling indicates that the MTx, whose static angle accuracy is 0.3°, can measure a movement of 10 cm with an error less than 0.05 cm. The low cost inertial sensors are capable of measuring the range of elbow flexion motion whose typical range is 150° with an error no greater than 1° and the Sony Move can track movement of 10 cm with an error less than 0.2 cm. In order to track position the system must include tri-axial accelerometers, rate gyros and magnetometers. This requirement is met by the Sony Move. The outcome is that Wii can be used for measuring upper limb range of motion and the Move for range of motion and position tracking based on the kinematic model.

Weightless Neural System Employing Simple Sensor Data for Efficient Real-Time Round-Corner, Junction and Doorway Detection for Autonomous System Path Planning in Smart Robotic Assisted Healthcare Wheelchairs

Human assistive devices need to be effective with real-time assistance in real world situations: powered wheelchair users require reassuring robust support, especially in the area of collision avoidance. However, it is important that the intelligent system does not take away control from the user. The patient must be allowed to provide the intelligence in the system and the assistive technology must be engineered to be sufficiently smart to recognize and accommodate this. Robotic assistance employed in the healthcare arena must therefore emphasize positive support rather than adopting an intrusive role. Weightless Neural Networks are an excellent pattern recognition tool for real-time applications. This paper introduces a technique for look-ahead identification of open doorways and junctions. Simple sensor data in real-time is used to detect open doors with inherent data uncertainties using a technique applied to a Weightless Neural Network Architecture.

Noninvasive detection of ventricular wall motion by electromagnetic coupling: Part 2: Experimental: cardiokymography

The cardiokymograph or displacement cardiograph (DCG) is a non-contacting device which senses movement of the heart throughout the cardiac cycle by the interaction of a radiofrequency (10–20 MHz) electromagnetic field, generated by a sensing coil, with the thorax. In the paper three different techniques of detecting this movement will be discussed: monitoring the changes in sensing resonant frequency (FM modulation), monitoring the changes in impedance of the coil at resonant frequency (AM modulation) and a new technique which monitors the changes in coil impedance at fixed frequency. The sensitivities of these three techniques will be compared. A simplified theory of the mode of coupling between the coil and the thorax will be studied in terms of a transformer model. Preliminary clinical measurements of anterior left and right ventricular motion will be given. The presence of higher-frequency features related to atrial motion and the opening and closing of the aortic and pulmonary values will also be described.

Noninvasive detection of ventricular wall motion by electromagnetic coupling

Radiofrequency coils are used as sensors in various applications such as nuclear magnetic resonance (NMR) imaging and displacement cardiograms (DCGs). In most cases the impedance and the resonant frequency of the coil are monitored to provide the required information. The paper describes the changes in reflected impedance and in resonant frequency of a coil when it is placed near a medium with properties ranging from a lossy dielectric to a pure conductor. The theory of interaction between the coil and the medium is investigated and a model based on the use of vector potentials is developed. One prediction of the theory is that placing the coil over body equivalent saline (lossy dielectric) at 15 MHz results in an increase in the inductance of the coil and a resultant decrease in resonant frequency. This prediction was supported experimentally.

An electric tooth pulp vitality tester

A simple battery-powered constant-current pulse generator able to supply up to 200 μA at a maximum of 250 V is described. The tester incorporates a battery status indicator and an overload, incorrect operation and fault condition audible alarm. A simple test routine helps to ensure that the instrument is operating correctly before each application. For enhanced patient co-operation and comfort the tester is activated by the patient.