Towards a unified system for multimodal activity spotting: challenges and a proposal

In the existing multimodal systems for activity recognition, there is no single method to process different sensor modalities at different on-body positions. Moreover, sensor types are often selected and optimized so as to accord with the goal of application. The complexity makes those systems infeasible to be deployed for new settings. This paper proposes a unified system which works with any available wearable sensors placed on user's body to spot activities. Each data stream is treated uniformly through our proposed template matching WarpingLCSS to spot activities. With the uniformity in extracting activity-specific patterns from raw sensor signals, our proposed system is compatible with respect to modalities and body-worn positions. We evaluate our system on the Opportunity dataset of four subjects consisting of 17 hard-to-classify classes (e.g., open/close drawers at different heights) with 17 sensors belonging to three modalities (accelerometer, gyroscope and magnetic field) attached at different on-body positions. The system achieves good performances (63% to 84% in F1 score). Moreover, the robustness and efficiency to addition and removal of sensors as well as activity classes are also investigated.