|Volume 21 Issue 01 - Publication Date: 1 January 2002
|An Autonomous Crop Treatment
Robot : Part II. Real Time Implementation
|T. Hague Silsoe Research
Institute, Silsoe, UK , B. Southall Sarnoff Corporation, USA
and N. D. Tillett Silsoe Research Institute, Silsoe, UK
|Implementation of an autonomous
vehicle for precision treatment of crop plants is described. The navigation
system integrates the vision system described in Part I with inertial and
odometric sensing. A modular approach is adopted, where the crop grid observation
model is re-formulated as a non-linear compression filter, which combines
a set of observations of crop plants into a single pseudo-observation of
the position of the crop planting grid relative to the vehicle position.
The compression filter encapsulates all internal detail of the vision system
(camera calibration, crop layout, etc.). The output from this vision module
can be used as an observation in the conventional way by the vehicle's navigation
|Plant features classified into
crop and weed by the vision module are registered into a treatment map.
The need to treat targets from a moving platform requires time delays in
the processing of observations to be considered. A method of compensation
is introduced which allows time delayed vision observations to be used;
the effectiveness of the technique is illustrated by an example with an
artificially extended time delay.
|In field trials of the vehicle
have been performed, and the accuracy of both vehicle navigation and crop
treatment are reported. We conclude that the navigation accuracy falls within
the 20 mm root mean square error region thought appropriate for precise
horticultural operations, and that spray application is sufficiently accurate
for the treatment of individual crop plants.