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Evolution-based Dynamic Path Planning for Autonomous Vehicles  133
                                4                    step = 0   4                     step = 15
                                                     time = 0                         time = 0
                               3.5                             3.5
                                3                               3                    1
                             Latitude (deg)  2.5 2  1         Latitude (deg)  2.5 2  1  1


                                                               1.5
                               1.5
                                1                               1                1
                               0.5                             0.5
                                0                               0
                                10  10.5 11 11.5 12 12.5 13 13.5 14 14.5 15  10 10.5 11 11.5 12 12.5 13 13.5 14 14.5 15
                                         Longitude (deg)                 Longitude (deg)
                                             (a)                             (b)


                                4                    step = 30  4                      step = 40
                                                     time = 0                          time = 0
                               3.5                             3.5
                                3                    1          3                    1
                             Latitude (deg)  2.5 2  1  1      Latitude (deg)  2.5 2  1  1


                                                               1.5
                               1.5
                                1                1              1                1
                               0.5                             0.5
                                0                               0
                                10 10.5 11 11.5 12 12.5 13 13.5 14 14.5 15  10  10.5 11 11.5 12 12.5 13 13.5 14 14.5 15
                                         Longitude (deg)                 Longitude (deg)
                                             (c)                             (d)
                                  Fig. 12. Snapshots of off-line path planning with multiple targets


                              Inthisexampleproblem,therearethreetargetsandthreeobstacles.Figure 12
                           shows snapshots of the planning results for different generations in the evolution
                           process. The vehicle is represented by a triangle with vehicle number on it. The
                           dashed circle around the vehicle represents the range of the payload on-board the
                           vehicle. This payload can be a sensor or offensive payload. The square markers
                           represent actual locations of sites. Each of these square markers will have a
                           vehicle number on it if the site is a target and assigned to that vehicle. A solid
                           circle located near each square marker represents an area which covers all of
                           the possible locations of the site represented by the square marker. Each filled
                           square marker with a dashed circle around it represents a site with defensive
                           capabilities which can destroy or change the health states of vehicles if they
                           are within the area marked by the dashed circle. The goal location where the
                           vehicle is required to be at the end of the mission is represented by a hexagram
                           in the plots. This representation of the scenario in the plots is also used in all
                           other planning examples. The results show the ability of the planner to generate
                           an effective path to visit all the assigned targets and avoiding collision with the
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