Implementation of a real-time saw blade deflection monitoring system using laser triangulation sensor and FPGA

This report describes the development of a prototype system that is capable of monitoring the deflection of a bandsaw blade during wood sawing process. The deflection is caused by tension loss of the saw blade and leads to downgrading and value loss of timbers. A CCD-type laser triangulation sensor has been proposed to monitor the saw blade deflection. Deflection monitoring has to be done in real-time which compels the necessity to use efficient algorithms with low computational cost to process the data from the sensor. The algorithms are to be deployed on a single FPGA. Fast and simple algorithms have been developed through analysing data collected from actual situations. The algorithms have been successfully implemented into an FPGA using VHDL. The implementation comprises three modules. The modules control the input and output of the sensor, and then use the data from the sensor to track the position of the saw blade in real-time using the approximated centre of gravity method. The overall peak-to-peak amplitude method is then used to determine the deflection level of the saw blade based on its recorded position. The functionality and accuracy of the implementation have been verified through simulations. Deflection level can be updated in real-time at 7000 frames/s at the sensor’s maximum clock rate of 2 MHz. A sub-pixel resolution of 1/8 pixel, which corresponds to 0.1 mm, is also achieved. Moreover, the implementation requires less than 20% of the FPGA resources. Table of