IEEE Robotics & Automation Magazine - March 2015 - 31

Goal

Goal

Path A

Path A

Start

Path B

Path B

(a)
Goal

Goal

Path B

Start

(b)

Goal

Path A

(c)

Path B

Start

Path A

Path B

(d)

Start

Path A

Goal

Path B
Path A

Start

(e)

Start

(f)

Figure 13. A visualization of the path plan simulation for the tracked rover under different insolation conditions: (a) a low-latitude
region in the morning, (b) a low-latitude region in the daytime, (c) a low-latitude region in the evening, (d) a high-latitude region in
the morning, (e) a high-latitude region in the daytime, and (f) a high-latitude region in the evening. The blue and red lines represent
path A ^W dist = 0.1, W int = 0.8, W ext = 0.1 h and B ^W dist = 0.1, W int = 0.1, W ext = 0.8 h, respectively.

weighting factors in (1) were set to W dist = 0.1, W int = 0.8,
and W ext = 0.1 for path A and to W dist = 0.1, W int = 0.1,
and W ext = 0.8 for path B. The input speed of the rover and
voltage were set to 1.4 cm/s and 10 V, respectively.
Simulation Results
Figure 13 shows visualizations of the simulation results for the
tracked rover under various insolation conditions: in the lowlatitude region [Figure 13(a)-(c)] and in the high-latitude

Power Generation Amount (W)

80

Path A
Path B

70
60
50
40
30
20
10
0

0

100

200

300

400

500

600

700

800

Traveling Distance (m)
Figure 14. The power generated with traveling distance in the
high-latitude region in the morning. Path A ^W dist = 0.1, W int = 0.8,
W ext = 0.1h and path B ^W dist = 0.1, W int = 0.1, W ext = 0.8 h.

region [Figure 13(d)-(f)]. In the figure, the start and goal
nodes are located in the opposite vertices in the DEM.
Figure 13 shows that the shadow shape changed depending on the time and latitude. In the low-latitude region, the
shadows were short because the solar elevation angle was
high. In the daytime, when the solar elevation angle reached
its maximum, there was
no shadow at all. In the
Considering the rover's
high-latitude region, the
shadows were long and
internal and external
observed even in the daytime because the solar
elements, the cost is
elevation angle was small.
Along path A, the rover
derived for an edge.
traveled over a straight line
connecting the start and
goal nodes regardless of
the time and latitude. On the other hand, path B differed
depending on the time and latitude, i.e., insolation/shadow condition. In the daytime, it was a straight line like path A. However, in the morning/evening, it was a winding path that
avoided the shadow. This trend was clearly seen in the high-latitude region, where the shadows were longer.
Path Evaluation and Discussion
Figure 14 shows the power generated with the traveling distance in the morning. Along path A, the power generated frequently became zero when the rover traveled in the shadows.
Along path B, the rover generated power most of the time.
MARCH 2015

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IEEE ROBOTICS & AUTOMATION MAGAZINE

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Table of Contents for the Digital Edition of IEEE Robotics & Automation Magazine - March 2015
