TODOS: Thermal sensOr Data-driven Occupancy Estimation System for Smart Buildings

Occupancy sensing and estimation in large commercial buildings has become a significant problem to be solved, with applications ranging from occupancy-based HVAC control to space planning, and security, etc. Thermal sensing is a promising technology to solve this problem, being easy to deploy in practice and allowing an actual occupancy count in a particular room without violating the data and privacy concerns. While initial strides have been made to solve this problem with thermal arrays, there are many problems that remain unsolved, including accuracy performance, overlapping of sensing areas that lead to under/over-counting, and data training requirements for different zones. In this paper, we introduce TODOS1, a novel system for estimating occupancy in intelligent buildings. TODOS uses a low-cost, low-power thermal sensor array along with a passive infrared sensor. We introduce a novel data processing pipeline that allows us to automatically extract features from the thermal images using an artificial neural network. Through an extensive experimental evaluation(2), we show that TODOS provides occupancy detection accuracy of 98% to 100% under different scenarios. In addition, it solves the issue of occupancy over/under-counting by overlapping sensing areas when using multiple thermal sensors in large rooms. This is done by treating the entire area as a single input thermal image instead of partitioning the area into multiple thermal images individually processed. Furthermore, TODOS introduces a data augmentation technique that allows the generation of training data for rooms of different sizes and shapes, without requiring specific training data from each room. Using these data, TODOS can train specifically designed neural networks optimized for any room size and shape, and achieve almost the same level of occupancy detection accuracy in rooms where experimental labeled training data is available, making it a viable solution that generalizes to the different rooms in large buildings.