Predictive control of field sprayer liquid system

Abstract

Marksprøjter anvendes vidt og bredt i landbrugsindustrien til at bekæmpe ukrudt og sygdomme, samt til at gøde marker. Sprøjterne klarer denne opgave ved at pumpe væske fra en tank, gennem et sæt dyser monteret på en bom, og ud på planterne på marken. Moderne sprøjter er i stand til, automatisk, at tænde og slukke for individuelle sæt af dyser afhængigt af sprøjtens placering. Dette reducerer mængden af brugte kemikalier samt forhindrer overlap på marken. Ved at tænde eller slukke for dyserne skabes forstyrrelser i væsketrykket ved bommen. Det blev forsøgt at bruge en model predictive controller til at regulere trykket på bommen og bruge dens forudsigende egenskaber til at forvente påvirkningen fra forstyrrelserne. Både brugen af en ikke-lineær og en lineær regulator blev undersøgt ved at bruge henholdsvis en ikke-lineær tilstands-model og en tidsvarierende lineær tilstands-model. Den ikke-lineære regulator blev kasseret på grund af dens lange afviklingstid. I simuleringer var den lineære regulator i stand til at opfylde kravene i ISO 16119-2 standarden, og blev derfor yderligere testet på en testrig, der har de samme funktionaliteter som en sprøjte. Den lineære regulator var ikke i stand til at opfylde kravene i standarden, når den blev brugt på testriggen.

Field sprayers are widely used in the agricultural industry to combat weeds and diseases, as well as fertilizing fields. The sprayers perform this task by pumping liquid from a tank through a set of nozzles mounted on a boom and onto the plants on the field. Modern sprayers can automatically turn sets of nozzles on and off based on their location, reducing chemical usage and preventing overlap. Turning the nozzles on or off creates disturbances in the fluid pressure at the boom. It was attempted to use a model predictive controller to control the pressure on the boom, and using its predictive properties to anticipate the impact of the disturbances. Both the use of a nonlinear and a linear controller was investigated, using a nonlinear state space model and a timevariant linear state space model respectively. The nonlinear controller was discarded due to its long execution time. The linear controller was able to fulfill requirements set out by the ISO 16119-2 standard in simulations, and thus moved on to be tested on a test rig emulating a field sprayer. The linear controller was not able to fulfill the requirements set out by the standard when used on the test rig, due to assumptions intended to linearize the model.

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Predictive control of field sprayer liquid system