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 x 10 x 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, cross-talk 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.

Abstract-Two inertial sensor systems were developed for 3D 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.

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