Agriculture Reference
In-Depth Information
spraying. The working distance for spraying was 280 m, and results are illustrated
for the first path. As seen in the figure, the maximum error was 8 cm, and the RMS
error was about 2 cm. The 2 cm error is accurate enough for field operations.
2.5.2 C
RAWLER
-T
YPE
R
OBOT
T
RACTOR
Crawler tractors are widely used in agriculture because of the lower ground pres-
sure and the higher traction efficiency compared to wheel-type tractors. A crawler
tractor can be applied to the various field operations such as tillage, cultivation, and
snow dispersal. Figure 2.11 shows the hardware structure of a robot tractor (Takai
et al., 2011). The platform vehicle, a 59-kW crawler-type tractor (CT801; Yanmer
Ltd.), was modified. Actuators and an electrical control unit (ECU) were built in the
vehicle to electrically control the vehicle's hydrostatic transmissions (HSTs) (Zhang,
2009), hitch functions, power take-off, and engine speed set. The RTK-GPS and the
IMU were used as navigation sensors. Figure 2.12 shows the schematic diagram of
the system. The PC controlling the robot communicates with all ECUs through the
CAN bus. It enables the robot to control travel direction and speed by changing the
positions of two HSTs, which have functions of shift and steering. Because the HST
had a strong nonlinear property against a control input (Rovira-Más et al., 2010),
RTK-GNSS receiver
Legacy-E+
TOPCON Ltd.
IMU
JCS-701A
Japan Aviation
Electronics Ind. Ltd.
Drift error: 2.0°/min
Accuracy
Horizontal: ±(10 mm + 1.0 ppm × D)m.s.e.
Vertical: ±(15 mm + 1.0 ppm × D)m.s.e.
Vehicle ECU
Control items:
HST for Steering
HST for Shift
Engine speed
Hitch height
PTO
Laser scanner
LMS291
SICK Ltd.
Range: 8-80 m, 180°
Resolution: 0.25°
Accuracy: ±35 mm
Proximity switch
ED-130
KEYENCE Ltd.
Detectable distance: 11 mm ± 15%
Tape switch
TS-16
Tape switch Japan Ltd.
Detectable pressure: 230 g/cm
2
FIGURE 2.11
Crawler-type robot tractor.
