Online activity matching using wireless sensor network

In this thesis we explore the use of Wireless Sensor Networks to perform online activity matching for sport coaching applications. The goal is to find one or more suitable algorithm to match the movement of a trainer and a trainer and to find spatial and temporal differences. Such a system can aid the trainer in group lessons where it is difficult for the trainer to keep track of all the trainees. In this work we consider fitness like movements such as encountered in aerobic lessons. We limit ourselves to only one one sensor node on the trainer and one sensor node on the trainee, but this well extends to more sensors per trainer and trainee. It also scales well to more trainees per trainer. We use Sun SPOT as wireless sensor nodes, and extend the set of sensors to obtain more inertial measurement capabilities. The accelerometer and gyroscope sensor are used to capture the movements. The gravity vector is extracted and improved with a Kalman filter using the accelerometer and gyroscope data. An automatic segmentation technique is used that examines the movement data for rest and activity periods and changes in movement direction. The segmentation and the movement information is communicated with the node of the trainee where the movements are compared. We choose to use Dynamic Time Warping (DTW) to perform the spatial and temporal matching of the movement. Because DTW is computationally intensive, we developed an optimized technique which we call Fast Incremental Dynamic Time Warping (FIDTW). From the result of the FIDTW algorithm, feedback is then generated and provided to the trainee. We test all the design choices extensively using experiments, and perform a total system test using different test methods to validate the taken approach. The single person test methods show that the system can reliably discriminate spatial and temporal differences, and provide usefull feedback. The two person test results show that improvements are possible and that more research is needed to make the system give reliable feedback.