LPS self-calibration method using a mobile robot

This paper introduces a new procedure for the self-calibration of a set of ultrasonic LPSs (Local Positioning Systems), each one of them with a different coverage area. At the end of the process, all the positions of the beacons belonging to the different LPSs are obtained. The method proposed here uses a MR (mobile robot) to automatically take the measurements of distances from the mobile robot position to the different beacons. The process starts considering the pose of the robot on the floor plane at the beginning as the origin of coordinates (being the x-axis the initial direction of the robot in its movement). The procedure implies the following stages: a) a pre-calibration phase in which the MR position is calculated by the onboard dead reckoning and the LPS is calibrated using an inverse positioning algorithm; b) a calibration phase to refine the beacon positions merging the information obtained by both, the dead reckoning and the LPS; c) a navigation phase in which only the MR position is calculated also using the dead reckoning and the LPS (the last depending on the position of the MR inside or outside the coverage area of the LPS); and d) a new LPS calibration if the MR is driven from the first LPS to the new one, repeating the whole process-phases a) to c), and after returning to the initial LPS in order to reduce the errors introduced by the dead reckoning when no LPS correction was available between LPSs. Simulated and real results are presented also to illustrate the performance of the method.