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Figure 4. Overall workflow of the path planning for the broiler mortality detection and removal robots. The dynamic window approach
(DWA) local navigator is also utilized to avoid live broilers in simulations.

find and eliminate broiler mortality.

3.2. Directed coverage path planning
Thedirectedcoveragepathplanning(DCPP)isutilizedtogenerateanoveralltrajectoryofthebroilermortality
detection robot. It should meet the following requirements:

1. The mobile robot must move through all regions of interest in the barn.
2. Motion trajectories should be simplified as straight lines.
3. The robot should cover the regions with minimal overlapping.
4. The path should be optimized with one of the criteria, such as distance, time, and energy.
5. The start and end points for the robots should be co-located so that farmers do not need to enter the barn
and retrieve the stopped robot from the barn interior.

In this paper, the criterion to generate a directed coverage path is the total shortest path, which could save
runningenergyfortherobots. Inthedecomposedworkingmap, theadjacentgridsshareatleastoneboundary,
while nodes of the adjacent grids are connected to form overall trajectories. There are two commonly used
methods for CPP: zigzag motion planning and spiral motion planning, namely back-and-forth and boundary
sweep methods [17] .

The robot moves along the lengthwise direction of the workspace under the zigzag motion planning, and the
total path length is calculated by Equation (1):
( )
( ) L
L = L − L × + L − L g (1)
L
where L is the total length of zigzag motion planning; is the length of the long side of a workspace; L is
the length of the short side of a workspace; and L is the length of a grid. The robot under the zigzag motion
planning moves along the long side of the workspace L /L times and along the short side L /L − 1 times.
It turns 2(L /L − 1) times.

Under the spiral motion planning, the robot moves along the boundary of the workspace progressively and at
the same time toward the center spirally. The total travel distance (TD) on the short side D is
( )
L × L − L
D = (2)
2 × L

The total travel distance on the long side D is
( )
2 2
2L L − (L ) + L L − 2 L
D = (3)
2L