Abstract
To improve the quality of fertiliser centrifugal spreading, several control devices have already been developed to manage some disruptions occurring on horizontal fields. However, controls which manage disruptions on non-flat fields due to changes in tractor attitude (pitch and roll) have not been developed. In this study, the design of a new control device is developed for a twin-disk spreader by considering two new degrees of freedom for each disk and controlling the longitudinal and lateral tilts of each disk. These tilt corrections are derived from solving a constrained optimization problem. The cost function is the weighted sum of squared differences between the travelled distances of the particles obtained in the considered topography and those that would have been obtained on a horizontal surface. The weighting coefficients are provided by the experimental angular mass flow distribution. In order to reduce the computation time and expect the use of the method for a real-time correction device, a simplified optimization problem is proposed. The method is assessed for three ground surface configurations: longitudinal slope break, side slope break and combined slopes. The simulation demonstrates that using the new control device the application errors are lower than 10% while they reach up to 40% without tilt correction. Moreover the study shows that the problem of optimization uniformity on non-flat fields can be solved computing the travelled distance for only a very few number of particles of mean diameter. This helps in reducing the computational time required to solve the optimization problem and in making possible the development of real-time control devices.
Highlights
In agriculture, centrifugal spreaders are widely used for fertilizer application, with up to 90% of the market share in Europe (Van Liedekerke et al, 2009)
Considering the results presented in Abbou-ou-cherif et al (2017a) and their analysis, it has been assumed that the application errors could be reduced by keeping particle travelled distances equal to those obtained on a flat field, regardless of the tractor orientation
Considering two new degrees of freedom for the disk, the optimal longitudinal and side tilts were derived from a constrained optimization problem
Summary
Centrifugal spreaders are widely used for fertilizer application, with up to 90% of the market share in Europe (Van Liedekerke et al, 2009). Numerous sensors and control mechanisms have been developed and marketed to improve spreading accuracy and environmental compliance (Yule and Grafton, 2013). Modern centrifugal spreaders can adjust the fertilization rate using variable rate technologies (VRT), based on field information provided by geographical information systems (GIS). Using simulations, Virin et al (2006) already demonstrated that such control systems improve the accuracy of the spreading, keeping the applied rate in a range of +/−10% of the local targeted application for flat fields. When spreaders are used on non-horizontal surfaces, the accuracy of the spreading may be called into question
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