Shepherding Behaviors with Multiple Shepherds
supported by NSF
Jyh-Ming Lien, Samuel Rodriguez, Nancy M. Amato
Project Alumni: Jean-Phillipe Malric

Shepherding behaviors are one class of flocking behaviors in which one or more external agents (called shepherds) attempt to control the motion of another group of agents (called flock) by exerting repulsive forces from shepherds to the flock.

In this work, we extend the idea of shepherding with a single shepherd to using multiple shepherds for large or difficult to manage flocks. More specifically we study how a group of shepherdscan work cooperatively and without communication to efficiently control the flock. In agriculture, it is common to see mutliple shepherd dogs herding a flock.

Shepherd Formation
Two formations that we tried for shepherds to push a flock were a straight line behind the flock and an arc behind the flock. Though both formations do a good job of evenly distributing the force evenly among the flock, the arc formation concentrates the forces toward the center of the flock.

(a) a straight-line formation	(b) an arc behind the flock

Steering
While steering the flock, the shepherds could take on a straight-line or side-to-side motion, behind the flock depending on how many other shepherds were also assigned to a flock group. The side-to-side motion works well for a single shepherd working on a group but when working with other shepherds, the shepherds use only the striaght-line steering.

(a) Steering using side-to-side motion	(b) Steering using straight-line behind the flock

Matching Shepherds with Steering Points
Once the shepherd has determined the possible (formation of) steering points, it needs to choose which steering point it will use. These steering points must be chosen by each shepherd independently, i.e., without communication between shepherds. We show three possible methods for choosing a steering point Vector Projection, Greedy Distance Minimization and Global Distance Minimization.

(a) vector projection	(b) greedy minimization	(b) optimal

Movies

Video The idea is that many of these simple behaviors can all be combined depending on the state of flock to create interesting and complex behaviors. (divx 26 MB, mpeg 28 MB)

Related Projects

Shepherding Behaviors with a Single Shepherd
Group Behaviors using Rule-Based Roadmaps
Planning Motion Among Moving Obstacles
Composable Group Behaviors

Papers

Shepherding Behaviors with Multiple Shepherds, Jyh-Ming Lien, Samuel Rodriguez, Jean-Philippe Malric, Nancy M. Amato, In Proc. IEEE Int. Conf. Robot. Autom. (ICRA), Apr 2005. Also, Technical Report, TR04-003, Parasol Laboratory, Department of Computer Science, Texas A&M University, Sep 2004.
Proceedings(ps, pdf, abstract) Technical Report(ps, pdf)

Shepherding Behaviors, Jyh-Ming Lien, O. Burchan Bayazit, Ross T. Sowell, Samuel Rodriguez, Nancy M. Amato, In Proc. IEEE Int. Conf. Robot. Autom. (ICRA), pp. 4159-4164, New Orleans, Apr 2004. Also, Technical Report, TR03-006, Parasol Laboratory, Department of Computer Science, Texas A&M University, Nov 2003.
Proceedings(ps, pdf, abstract) Technical Report(ps, pdf)

Better Shepherding Behaviors Using Improved Shepherd Locomotion, Ross T. Sowell, O. Burchan Bayazit, Jyh-Ming Lien, Nancy M. Amato, Technical Report, TR03-009, Parasol Laboratory, Department of Computer Science, Texas A&M University, Aug 2003.
Technical Report(ps, pdf, abstract)

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