Real-time combinatorial tracking of a target moving unpredictably among obstacles

Many applications require continuous monitoring of a moving target by a controllable vision system. Although the goal of tracking objects is not new, traditional techniques usually ignore the presence of obstacles and focus on imaging and target recognition issues. For a target moving among obstacles, the goal of tracking involves a complex motion problem: a controllable observer must anticipate that the target may become occluded by an obstacle and move to prevent such an event from occurring. The paper describes a strategy for computing the motions of a mobile robot operating in a 2-D workspace without prior knowledge of the target´s intention or the distribution of obstacles in the scene. The proposed algorithm governs the motion of the observer based on current measurements of the target´s position and the location of the local obstacles. The approach is combinatorial in the sense that the algorithm explicitly computes a description of the geometric arrangement between the target and the observer´s visibility region produced by the local obstacles. The algorithm computes a continuous control law based on this description. The new tracking strategy has been implemented in a real-time robotic system.