Method and apparatus for pumping a fluid additive into an irrigation system for field application

An irrigation system for distributing a primary fluid or water supply over a ground surface of a field, the system including:

• an irrigation apparatus movable over the ground surface to distribute the primary fluid over the ground surface within a sector of the field, the irrigation apparatus comprising:
• a center structure configured to support a first-end of a first span and to center rotation of distal ends of a plurality of interconnected spans extending outward from the center structure, wherein the first span is separate from the plurality of interconnected spans;
• at least two spans, each comprising a first-end closest to the center structure and a distal-end extending along a longitudinal axis of the system;
• at least one support tower for each span of the plurality of interconnected spans configured to support corresponding spans at a location above the ground surface;
• a fluid application assembly with a fluid supply conduit configured to apply the primary fluid to the ground surface of the sector of the field;
• a fluid additive pumping apparatus configured to pump a fluid additive into the primary fluid distributed by the fluid application assembly of the irrigation apparatus as the irrigation apparatus moves over the sector of the field, the fluid additive pumping apparatus comprising:
• a fluid additive pump assembly in fluid communication with a fluid additive reservoir and a fluid additive injector element via a fluid additive path, said fluid additive path originating at said fluid additive reservoir and terminating at said fluid additive injector element, said fluid additive pump assembly is configured to pump a predetermined volume of fluid additive into the fluid application assembly in a predetermined period of time for distribution of fluid additive to the sector of the field, wherein said predetermined period of time to pump the predetermined volume of fluid additive is used to determine a rate of pumping, said rate of pumping for said predetermined period of time also corresponding to a period of time for the spans to transition over the sector of the field at an intended speed of movement over the ground surface, following a corresponding wheel track for the distal-end of the outermost span, wherein the outermost span is one of the plurality of interconnected spans, from a start position to a stop position of the sector of the field,
• a pump apparatus controller with a memory and a processor, wherein said pump apparatus controller has stored in memory the start position, the stop position, a predetermined start time and a predetermined stop time for application of fluid additive to the sector of the field, a position sensor assembly in communication with the pump apparatus controller, said position sensor assembly configured to periodically sense at a current time a current position within the corresponding wheel track of the distal-end of the outermost span of the irrigation apparatus within the sector of the field, and
• a fluid additive flow sensor in communication with the pump apparatus controller, said fluid additive flow sensor configured to monitor a rate of flow of the fluid additive being pumped through the fluid additive path by the fluid additive pump assembly;
• and
• wherein said pump apparatus controller is configured to be in communication with said position sensor assembly, said fluid additive pump assembly and said fluid additive flow sensor and is configured to receive a current position signal and the current time from said position sensor assembly and is configured to store said current position and the current time in said memory, the pump apparatus controller, using the memory and the processor, is configured to calculate an actual speed of movement of the distal-end of the outermost span as the outermost span transitions through the sector of the field following a corresponding wheel track, based on the calculated actual speed of movement, as compared to the intended speed of movement, the processor further calculates an adjusted fluid additive pumping rate, said adjusted fluid additive pumping rate is configured to be proportionally decreased when the actual speed of movement of the distal-end of the outermost span is slower than the intended speed of movement, wherein said adjusted fluid additive pumping rate is configured to be proportionally increased when the actual speed of movement of the distal-end of the outermost span is faster than the intended speed of movement, wherein adjustments to the rate of pumping by the fluid additive pump assembly are configured to be performed periodically;
• and further wherein said pump apparatus controller calculates the adjusted fluid additive pumping rate based on the actual speed of movement of the distal-end of the outermost span calculated from the current position, the current time and a user-defined stop position and calculates a remaining time period for the outermost span to reach said stop position and wherein said pump apparatus controller monitors an output signal of the fluid additive flow sensor and controls the fluid additive pump assembly to pump fluid additive at an adjusted rate so as to distribute the remaining supply of fluid additive to the sector of the field, as the irrigation apparatus continues moving to reach the user-defined stop position in the remaining time period, based on said calculated actual speed of movement for said distal-end of the outermost span.