Abstract: A control apparatus is disclosed for use in an irrigation system having a plurality of conduit sections pivotally joined at sets of adjacent ends and selectively operable drivers for moving the conduit sections in a forward direction. Each control apparatus maintains the relative alignment of a pair of joined conduit sections. It includes a conduit misalignment indicator having two indicating portions which are directly relatable in position to the relative alignment of the two conduit sections. Further, Hall-effect sensors positioned on one indicating portion opposite from a magnet positioned on the other indicating portion provide for sensing of the relative alignment of the conduit sections. A digital electrical circuit converts the sensor signals into a control signal for initiating operation of the driver when the conduit sections are in lagging misalignment and terminating operation when the conduit sections are in leading misalignment.

Abstract: A corner boom which includes a secondary water conduit is pivotally connected to the end of a center pivot boom which includes a primary water conduit and comprises a series of sections which pivot relative to one another about a center pivot point. The corner boom is supported by a wheeled tower which moves along a predefined path. A first encoder is positioned on the end of the center pivot boom to determine the angular separation between the corner boom and the end section of the center pivot boom. Other encoders are positioned, respectively, on a wheel of the support towers of both the end section and the next adjacent section of the center pivot boom to determine the angle between a reference line and a straight line connecting the center pivot point and the end of the center pivot boom.