Recognition and path planning strategy for autonomous navigation in the elevator environment

This paper presents a robust and reliable method for a mobile robot to get on/off an elevator in a multistory building. Getting on/off the elevator requires the robot to perform two different tasks: a recognition task and a navigation task. First, we propose a recognition algorithm for the elevator buttons and status so that the robot reacts flexibly to the current elevator status. We first apply an adaptive threshold to the current image in order to get a binary image. Then we extract the candidates of the buttons and the floor number after preliminary filtering. Ambiguous candidates are rejected using an artificial neural network, and a matching method is applied to finally recognize the call buttons, destination floor buttons, moving direction and current location of the elevator. Second, we suggest a path planning algorithm to navigate into and out of the elevator without any collision. By constructing an occupancy grid map and computing a target function, we find the best position for the robot to get on the elevator. Then we plan an optimal path to the best position using a potential field method. Experiments were carried out in several simulated and real environments including empty, crowd and blocked scenarios. The approach presented here has been found to allow the robot to navigate in the elevator without collisions.