Cooperative Multi-robot Localization Based On EKF

With the fast development of mobile robotics, single robot with limited ability is inadequate to meet the demands of complicated task. As a result, multi-robot cooperation has become a focus in this field. Cooperative multi-robot localization is one of the main requirements for mobile robot autonomy. Nowadays, there have been numerous approaches to localization problem fusing exteroceptive and proprioceptive sensors, but a number of theories and approaches are limited on emulation phase, lacking of actual experiment to validate them.A survey of the developments of multi-robot systems is given in the first part of this paper. Furthermore, the fundamental problems, critical technology and the development trend of cooperative multi-robot localization are introduced systemically. The construction of the multi-robot system and the information interchange between different sensors are the precondition and basis of cooperative localization. Not only are the Pioneer 3 mobile robot platform and multi-sensors illuminated, but also are software systems discussed including multi-sensor fusion, multi-robot communication, task control and management based on ARIA, image grabbing and processing, etc.Relative pose detection and mobile robot's state estimation and updating are central aspects for cooperative localization. In order to solve cooperative multi-robot localization in unknown environment effectively, an approach to relative pose estimation and updating which is based on Extended Kalman Filter is proposed, and an analytical expression for position uncertainty propagation in ideal instance is provided. When a robot in team observes other robots, each team member's pose and covariance is updated by using of the relative observable information. The observed information is shared by each other in the team. Compared with single robot localization, this approach enhances the precision in cooperative localization.A cooperative multi-robot localization experiment based on Pioneer 3 is designed and implemented, which includes two experiments, one in constant velocity motion and the other in variable velocity motion. According to the experiment data analysis and discussion, especially the analysis of error propagation in multi-robot localization, it shows that this cooperative localization algorithm is valid and effective.