Graph Search-Based Exploration Method Using a Frontier-Graph Structure for Mobile Robots

. 2020 Nov 3;20(21):6270. doi: 10.3390/s20216270

Algorithm 5 Breadth-first search (BFS) exploration to decide the next target node
Require: node DB $N o d e$ , the current node’ ID $i d_{c u r}$ , local map DB $M a p$
Ensure: the next target node $n o d e_{n e x t}$
1: $N o d e_{u n e x p_s i b l i n g} \leftarrow find_unexplored_siblings (N o d e, i d_{c u r})$
2: if $N o d e_{u n e x p_s i b l i n g} \neq \emptyset$ then
3: $n o d e_{n e x t} \leftarrow$ Find-Next-Node-In-TSP-Solution $(N o d e_{u n e x p_s i b l i n g}, i d_{c u r})$
4: else if $(f l a g_{loop_closing} \in n o d e_{p a r e n t}) = F A L S E$ then
5: $n o d e_{n e x t} \leftarrow n o d e_{p a r e n t}$
6: else if $(f l a g_{loop_closing} \in n o d e_{c u r}) = F A L S E$ then
7: $N o d e_{u n e x p_c h i l d} \leftarrow find_unexplored_child (N o d e, i d_{c u r})$
8: $n o d e_{n e x t} \leftarrow$ Find-Next-Node-In-TSP-Solution $(N o d e_{u n e x p_c h i l d}, i d_{c u r})$
9: else
10: $N o d e_{u n L C_s i b l i n g} \leftarrow find_unLoopClosed_siblings (N o d e, i d_{c u r})$
11: if $N o d e_{u n L C_s i b l i n g} \neq \emptyset$ then
12: $n o d e_{n e x t} \leftarrow$ Find-Next-Node-In-TSP-Solution $(N o d e_{u n L C_s i b l i n g}, i d_{c u r})$
13: else
14: $N o d e_{u n L C_c h i l d} \leftarrow find_unLoopClosed_child (N o d e, i d_{c u r})$
15: if $N o d e_{u n L C_c h i l d} \neq \emptyset$ then
16: $n o d e_{n e x t} \leftarrow$ Find-Next-Node-In-TSP-Solution $(N o d e_{u n L C_c h i l d}, i d_{c u r})$
17: else
18: $N o d e_{u n e x p} \leftarrow find_unexplored (N o d e)$
19: if $N o d e_{u n e x p} \neq \emptyset$ then
20: $n o d e_{n e x t} \leftarrow find_nearest (N o d e_{u n e x p}, i d_{c u r})$
21: else
22: $n o d e_{n e x t} \leftarrow 0$	▹ The exploration has been completed.
23: end if
24: end if
25: end if
26: end if