A method for testing automatic spray boom height control systems

Abstract. An increasing number of horizontal boom sprayers are equipped with systems for sensing boom height and its automatic control independent from crop canopy height or slope of the field. These systems should help maintain an optimum distance from the nozzles to the target area in order to achieve an even spray distribution and control spray drift. In addition, automation of boom control unburdens the operator especially when spraying at high speeds.

The performance of the control system is dependent on the accuracy of the height measurement, the control algorithm and the dynamic behaviour of the spray boom and its suspension.

A test bench was developed to evaluate the performance of boom height control systems on a stationary sprayer. The test bench consists of two target area units placed below each height sensor of the spray boom. Each of those units has an artificial spray target area that can be moved vertically with the help of a motor-driven linear guide unit. A drive signal was synthesized for the target area units in order mimic a canopy surface profile during the tests. This can be applied for both units with uniform or opposite senses of direction for testing the boom height or tilt control separately. Using the test bench the sprayer can be tested in well defined and controlled conditions.

First tests results show the suitability of the test bench and the method for the evaluation of different sprayer types with two sensors. Several statistical parameters were used to describe the performance of the boom control systems.