Agriculture Reference
In-Depth Information
North
φ
d
Navigation point
Y
φ
Vehicle direction
Desired direction
η
Δφ
ω
j
+1
d
ω
c
2
ω
c
1
ω
j
ζ
closest
L
Desired point: ξ
d
X
FIGURE 2.5
Definition of navigation signals based on map.
at a headland of field operations. A navigation map was used to calculate navigation
signals from the RTK-GPS and the IMU.
As shown in Figure 2.5, the offset,
ε
, is calculated from the desired path deter-
ω
c
∗
and
ω
c
∗
, relative to the current vehicle posi-
mined from the two closest points,
tion, and
η
retrieves from the map data. The heading error,
∆φ
, is defined as shown
in Figure 2.5. The heading error
Δφ
is computed from the relative angle between the
desired angle vector,
. The desired angle vector is
defined by the vector whose tail is the point of orthogonal projection along the map
trail and whose head is the point with a look-ahead distance,
L
, forward along the
trail. The desired steering angle,
φ
d
, and actual heading vector,
φ
,
is computed assuming a proportional controller
for both a heading error and an offset as follows,
∆ψ
∆ψ
(
k
) =
k
ϕ
∆ϕ
(
k
) +
k
p
ε
(
k
)
(2.1)
where control gains
k
ϕ
and
k
p
are determined by preliminary experiment.
d
b
B
C
r
A
D
w
x
y
FIGURE 2.6
Algorithm of switchback turning including dynamic path creation based on a
spline function.
