Hey, I'm over here - How can a robot attract people's attention?

This paper describes how sonar sensors can be used to recognize human movements. The robot distinguishes objects from humans by assuming that only people move by themselves. Two methods using either rules or hidden Markov models are described. The robot classifies different movements to provide a basis for judging if a person is interested in an interaction. A comparison of two experiment results is presented. The use of orienting cues by the robot in response to detected human movement for eliciting interaction is also studied.