Feed Gate Adaptation of a Spinner Spreader for Uniformity Control

Variable rate application of fertilisers with traditional spinner-type spreaders is known to suffer from spread pattern uniformity variability as a function of application rate. To demonstrate this variability, simulations using models from the literature were carried out for two cases: (1) a dual disc spreader with segment-type feed gates; and (2) a single disc spreader with conical feed gates. Simulations for the dual disc spreader showed that for higher application rates the pattern becomes 'M'-shaped, whereas for a single disc spreader the pattern becomes skewed, even though the pattern for low rates was near-Gaussian shaped in both cases. In this research, an attempt to eliminate the uniformity variability was made, by developing a feed gate control method based on an optical feedback sensor. Simulations showed that the feed gate method is capable of producing high-quality patterns for any given application rate, in both cases, the dual disc spreader with segment-type feed gates, as well as the worst-case scenario being the single disc spreader with conical feed gates. The performance of the feed gate control method was assessed using data collected from a single disc Lowery 300 spreader. Although the original, uncontrolled pattern of this spreader was of low quality, the adaptive gate control algorithm was capable of producing acceptable patterns around the flow rate of 0·2 kg/s.