Indoor Ultrasonic Positioning System of Mobile Robot Based on TDOA Ranging and Improved Trilateral Algorithm

Positioning is the base of automatie movement for an indoor mobile robot. To realize its accurate positioning and real-time visualization, an indoor ultrasonic positioning system is proposed with 1 unknown node and 4 beacon nodes. The transmitting module is fixed on the mobile robot as the unknown node and represents where the mobile robot is. 4 receiving modules are fixed on the ceiling as beacon nodes. Ultrasonic and radio-frequency (RF) signals are used to achieve time difference of arrival (TDOA) ranging. After the distance values from the unknown node to fixed nodes are obtained, improved trilateral algorithm is applied to get the coordinates of the unknown node. The transmitting control module, the receiving control module and personal computer (PC) realize real-time wireless communication via RF signals. The position of the mobile robot is displayed visually on the Processing program and will be updated in every half second. Experimental results show that the corrected accuracy of the positioning system reaches 1 cm and the system is of good stability.