AN OVERHEAD OPTICAL YIELD MONITOR FOR A SUGARCANE HARVESTER BASED ON TWO OPTICAL DISTANCE SENSORS MOUNTED ABOVE THE LOADING ELEVATOR

A yield monitor was constructed for a billet-type sugarcane harvester that uses two laser distance sensors mounted above the loading elevator to measure the height and length of the billet piles per slat. By using this method, a volume-to-mass relationship can be established for the weight flow of sugarcane through the combine for the measurement of yield. Testing of the system indicated that the cumulative billet pile length had the best relationship to harvested weight with a linear line relationship and coefficients of determinations ranging from 0.93 and 0.97. Estimated yields matched actual yields very well with a 0.99 slope and a coefficient of determination of 0.87 and yields were predicted to be within 7.3 metric tons/ha of actual values. Material height did not perform as well as material length and exhibited a power-type curve relationship to harvested weight with coefficients of determination ranging from 0.66 to 0.93, and estimated yields only matched actual yields with a coefficient of determination of 0.46. A third parameter, the product of material height to material length, also returned a power-type curve relationship to harvested weight with coefficients of determination ranging from 0.74 to 0.96 and yield comparisons for this parameter achieved a coefficient of determination of 0.74 which was better than the material height alone, but not as good as material length by itself. Statistical testing indicated that variances in material length were strongly correlated to material flow, but not to sugarcane variety, direction of cut, nor day of testing. Sample analysis indicated that the monitor can predict yields to within 2.2 metric tons/ha of actual values on 0.4 ha (or larger) precision farming blocks. Installation times were fast, easy, and can be performed in the field with little changes to the combine as the sensor bar merely clamps to the upper rails of the elevator. This yield monitoring system may provide yield monitoring in sugarcane on a per field basis that is easy-to-mount, non-contact, and robust from dirt and debris.