Navigation with constraints for an autonomous mobile robot

This paper describes a navigation planning algorithm for a mobile robot capable of autonomous navigation in a quasi-structured, partially known and dynamic environment. This algorithm uses a description of the environment containing both operational and geometric information. An interactive program permits an operator to create the description of the environment composed of structural elements such as walls and furniture. This description is completed by the addition of operational information in the form of a network of places, routes, landmarks and recharge stations. Places and routes include constraints on the actions of the robot as well as other information needed for planning and plan execution. A separate interactive program permits an operator to compose a surveillance mission as parallel sequences of navigation tasks and surveillance tasks, subject to constraints on energy, time, risk and position uncertainty. The planning algorithm described in this paper computes an optimal path for each navigation task according to the optimisation criterion and constraints. The authors introduce the notion of efficient path applied to a new best first search algorithm solving a multiple constraints problem, The paths determination relies on a state representation adapted to deal with environment constraints. The authors demonstrate that the complexity characteristics of their algorithm are similar to those of the A* algorithm. The planning system described in this paper has been implemented on a laboratory workstation and tested using radio-modem communication with a mobile platform equipped with ultrasonic range sensors and an active stereo vision system. This system has been developed for the MITHRA family of autonomous surveillance robots as part of project EUREKA EU 110