  This paper presents a novel multimodal human activity recognition system. It
uses a two-stream decision level fusion of vision and inertial sensors. In the
first stream, raw RGB frames are passed to a part affinity field-based pose
estimation network to detect the keypoints of the user. These keypoints are
then pre-processed and inputted in a sliding window fashion to a specially
designed convolutional neural network for the spatial feature extraction
followed by regularized LSTMs to calculate the temporal features. The outputs
of LSTM networks are then inputted to fully connected layers for
classification. In the second stream, data obtained from inertial sensors are
pre-processed and inputted to regularized LSTMs for the feature extraction
followed by fully connected layers for the classification. At this stage, the
SoftMax scores of two streams are then fused using the decision level fusion
which gives the final prediction. Extensive experiments are conducted to
evaluate the performance. Four multimodal standard benchmark datasets (UP-Fall
detection, UTD-MHAD, Berkeley-MHAD, and C-MHAD) are used for experimentations.
The accuracies obtained by the proposed system are 96.9 %, 97.6 %, 98.7 %, and
95.9 % respectively on the UP-Fall Detection, UTDMHAD, Berkeley-MHAD, and
C-MHAD datasets. These results are far superior than the current
state-of-the-art methods.

Computer Vision and Pattern Recognition