Agriculture Reference
In-Depth Information
Master
Indications
Goal
Path generation
Velocity and steering control
Slave
(a) GOTO algorithm
Indications
Master
γ
Slave
d
Velocity and steering control
(b) FOLLOW algorithm
FIGURE 2.29
(a) GOTO and (b) FOLLOW algorithms for a master-slave robot system.
used. When harvesting corn, a combination of one wagon and one harvester is gener-
ally adopted. Therefore, a master-slave system, which uses two vehicles, can be very
useful in actual field operations. Figure 2.29 depicts the concept of the master-slave
structure. The so-called master vehicle performs the functions of making decisions
and sending commands to the slave vehicle. The slave vehicle follows the master and
broadcasts its own status by sending information about its location, orientation, and
operating conditions. Two types of basic operations have been proposed. One is the
GOTO algorithm, and the other is the FOLLOW algorithm. The GOTO algorithm
can be applied when the master wants the slave to go to a specific place, a certain
distance from the current operational position. This type of cooperative work can
be adopted, for example, during hay harvesting. If the master were a tractor with a
hayfork and the slave were a truck, the GOTO algorithm could be used to make the
slave transfer to an operational position to deliver the hay to a barn. On the other
hand, the FOLLOW algorithm uses a more common, cooperative style of interaction.
The slave follows the master at a given relative distance,
d
, and a given angle,
γ
. This
cooperative work produces large benefits in terms of increased overall productivity,
even when using two identical machines. At times, harvesting requires two vehicles,
for example, a harvester and a wagon. The FOLLOW algorithm is suitable for this
type of field management. To use the FOLLOW algorithm, the master broadcasts
an initial command to inform the slave to follow the master at a certain offset and
a certain relative angle. Table 2.2 shows the information formats for communica-
tion between master and slave. In total, eight kinds of formatted strings are used in
