Tau Guidance for Mobile Soccer Robots

Traditional approaches to mobile robot guidance have utilised an internal model of the environment constructed from sensor data in order to plan a course of action. Although this approach has been challenged by behaviour-based robotics (e.g., Brooks, 1991), the creation of "smart perceptual instruments" that attempt to directly couple perception and action has been seriously addressed by the ecological robotics paradigm founded upon Gibson's ecological optics (Duchon et al., 1995). We explore the possibility of using tau information for guidance of a mobile robot. More specifically, an attempt to implement some of the navigation techniques using tau as outlined by Lee (1998) was undertaken. Problems encountered during implementation and possible solutions are given. Although Lee introduced the concept of using tau (τ) for the guidance of movement (Lee, 1998) and although tau is usually said to represent the time to closure of a gap, this is not entirely true. A negative tau represents the time to closure of the gap, while a positive tau represents the time since the closure of the gap (i.e., the gap is opening). A gap can represent a distance, an angle, a difference in force or any other gap. The information on time to closure provided by a sensor can therefore be used to control the closure of a gap and thus to guide movement. Lee also introduced the idea of guidance through tau coupling in which the ratio of taus of different gaps are kept invariant.