Structural health monitoring of a linear robot by fiber Bragg grating sensors and cyber-physical system

Robots with linear motion provide high accuracy and repeatability for industrial automation but may perform lower precision and stability when working long hours because of mechanical vibrations and thermal deformation caused by internal motors and ball screws. Structural health monitoring (SHM) can identify the discrepancy and avoid unexpected downtime costs, but electromagnetic interference (EMI) from the motor lowers the signal-to-noise ratio (SNR) of conventional wired sensors and may invalidate the feedback controller. This study presents an SHM system based on optical fiber Bragg grating (FBG) sensors, which provide accurate time-deformation relations and frequency spectrum results. The SHM-FBG system contributes to preventative maintenance and compares the dynamic signal of six selected points on a linear robot. The experiments also consider the boundary condition of (a) with spring loading and (b) without spring loading. Short message services (SMS) based on the long-term evolution (LTE) cellular network have converted the linear robot into an internet of things (IoT) device. The SHM-FBG system is designed to provide long-term observation of the electro-mechanical system and will send a short message to the administrator if mechanical vibrations or thermal deformations exceed predefined limits and detect acoustic emission of components before systematic failure.