High-precision ‘autofarming’ makes possible
farming techniques previously impractical using
metre-level Differential GPS-based control systems: techniques
such as tape irrigation, the
elimination of guess rows, and precise contour farming. A Carrier-Phase
Differential gps
positioning and attitude system with centimetre-level and
0·1° accuracy was installed in a large
farm tractor. Four types of trajectories (lines, arcs, spirals, and
curves) were identified as basic
building blocks necessary to generate a ‘global’ trajectory
for a realistic autofarming path.
Information about each trajectory type was translated into reference state
specifications that
a linear controller used to control the tractor over velocities
between 0·7 and 2·8 m/s to
within approximately 6 cm (1 σ) without implement and
10 cm (1 σ) with implement on
sloped terrain using a previously developed tractor model. These results
are a significant step
towards a realistic autofarming system because they not only demonstrate
accurate control
over various realistic operating speeds but over different types of
trajectories necessary for a commercial system.