A Smart Sensor Node for the Internet of Elevators Non Invasive Condition and Fault Monitoring
The signal processing scheme of a smart sensor node for the Internet of Elevators is presented. The sensor node is a self contained black box unit only requiring power to be supplied, which enables a cost efficient way to modernize existing elevator systems in terms of condition monitoring capabilities. The sensor node monitors the position of the elevator using an inertial navigation system in conjugation with a simultaneous localization and mapping framework. Features reflecting the elevator system's operation and health condition are calculated by evaluating the ride quality parameters defined by the ISO 18738 1 standards, the vibration versus frequency spectrum, and the vibration versus position spectrum. Abnormal stops are identified by detecting decelerations that deviate from the typical deceleration pattern of the elevator or when the stopping position of the elevator does not match the learned floor levels. Furthermore, the condition of the door system is monitored by tracking the magnetic field variations that the motion of the doors creates; the number of door openings and the time required for the doors to close are estimated. The capability and performance of the blacksignal processing scheme are illustrated through a series of experiments. The experiments show, inter alia, that using low cost sensors similar to those in a smartphone, the position of the elevator car can, with 99.9% probability, be estimated with an error of less than 1 m for travels up to 43 s long. The experiments also indicate that small degradations in the doors' closing time can be detected from the magnetic field measurements.
IEEE Sensors Journal