Hardware implementation of a sub-pixel algorithm for real-time saw blade deflection monitoring

Deflections of saw blades during timber sawing process due to tension loss lead to downgrading and value loss of timber. In this paper a CCD-type laser triangulation sensor is used to monitor the saw blade deflections. Deflections monitoring has to be done in real-time which compels the necessity to use efficient algorithm with low computational cost. High speed algorithm that makes use of an approximated centre of gravity (COG) and an overall peak-to-peak amplitude methods has been designed and implemented in a Field Programmable Gate Array (FPGA). The approximated COG method tracks the position of the saw blade in real-time. It generates results at 7000 frames/s at the sensor's maximum clock rate of 2 MHz. It also provides a sub-pixel resolution of 1/8 pixel. The overall peak-to-peak amplitude method determines the deflection level of the saw blade based on its recorded positions. Both methods are simple to implement and require low resource usage, while providing reliable real-time results.