  A current problem in the design of small and lightweight autonomous
agricultural robots is how to create sufficient traction on soil to pull an
agricultural implement or load. One promising solution is offered by the
interlock drive system, which penetrates spikes into the soil to create
traction. The combination of soil penetrating spikes and a push-pull design
offers new possibilities for vehicle control. By controlling the interlocking
of the spikes and pushing and pulling them against the main frame, the vehicle
can perform tight maneuvers. To validate this idea, we designed a robot,
capable of creating high traction and performing headland turns. The navigation
of the new robot system is performed by actively pushing the spikes, mounted on
a slide into the soil, while the main frame is pushed back and pulled forward.
The vehicle of 2-meter length was able to turn on the spot, and could follow a
straight line, just using the spikes and the push-pull mechanism. The
trajectory and the performed measurements suggest, that a vehicle which uses
only spikes for traction and steering is fully capable of performing autonomous
tasks in agriculture fields.
