Robot Sheepdog Project achieves automatic ock control

This paper describes a mobile robot that can enter a circular arena, gather a ock of ducks and manouvre them safely to a speci ed goal position. A minimal simulation model of the ducks' ocking behaviour was developed and used as a tool to guide the design of a general ock-control algorithm. The algorithm was rst tested in simulation then tranferred unchanged to a physical robot which succeeds in gathering a real ock of ducks. This is the rst example of a robot system that exploits and controls an animal's behaviour to achieve a useful task. Robots successfully manipulate many objects in factories and laboratories. Research continues on manipulating objects with complex or variable shapes and dynamics eg. food products (Juste et al., 1997). Recent work in mobile robotics has focused on `adaptive behaviour' in animals, in order to extend the abilities of robots (Maes, 1990) (Hallam and Hayes, 1994), and to better understand the processes occurring in real creatures (Webb, 1994) (McFarland and Bosser, 1993). The Robot Sheepdog Project examines the robotic manipulation of animals by exploiting their adaptive behaviour. In contrast, previous work combining robots and animals (Trevelyan's robot sheep-shearer (Trevelyan, 1992), Silsoe Research Institute's milking robot (Frost et al., 1993)) has deliberately minimised animal behaviour by physical restraint. We have demonstrated a mobile robot that can enter a circular arena, gather a ock of ducks and manouvre them safely to a speci ed goal position. This is the rst example of a robot system that exploits and controls an animal's behaviour to achieve a useful task. The sheepdog's gather-and-fetch task was chosen because of its familiarity and the strong interaction between the dog, shepherd and ock animals. Using ducks instead of sheep allows us to experiment on a conveniently small scale, in a controlled indoor environment. Duck ocking behaviour is recognised by shepherds as similar to sheep; ducks are often used to train sheepdogs because of their relatively slow movement. Figure 1 Sheepdog with duck ock in Lancashire, 1996. Flocking is considered an adaptive behaviour, as it a ords various advantages in hazard-avoidance, mating and foraging. Models of ocking behaviour exist in the literature and are generally derived from Hamilton's observation that ocking may be produced by the mass action of individual animals, each seeking the proximity of its nearest neighbours (Hamilton, 1971). It was later suggested that this behaviour can be well modelled by an attractive `force' acting between the animals, with the magnitude of the attraction varying with the inverse square of the animals' mutual distance (Partridge, 1982) (Warburton and Lazarus, 1991). It is argued that this relationship represents a linear response to sensory information which itself varies with the inverse square of distance. Similar models have produced realistic computer animations of bird ocks (Reynolds, 1987). These ideas are familiar in robotics, where such po-