In this paper, an integration system is proposed to improve the positioning performance of a mobile robot by fusing a Pseudolite Ultrasonic System (PUS), an absolute position measurement system using direct ultrasonic waves, with a Dead Reckoning (DR) odometer. As an integration algorithm of the absolute position measurement system and DR, two methods are proposed. In the loosely coupled method, the PUS and the DR calculate the position independently and a Kalman filter estimates the position using position information from the PUS and the DR. In the tightly coupled method, the PUS provides the distance between the ultrasonic transmitters and receivers without calculating the position directly and the DR provides the translational and rotational displacement of the mobile robot. The Kalman filter then estimates the position using information from the PUS and the DR. In addition, to improve the positioning performance in case the line-of-sight (LOS) between the ultrasonic transmitter and receiver is blocked due to obstacles, a positioning failure detection algorithm and reckoning methods are proposed. The positioning performances of the proposed PUS/DR integrated systems and the validity of the positioning failure detection algorithm are verified and evaluated by experiments.

Abstract. This paper proposes a new method to find an absolute position by using ultrasonic sensors. In order to evaluate the performance of U-SAT (Ultrasonic Satellite system), the autonomous navigation performance of a mobile robot is tested. Experiments were performed in both cases that the mobile robot moves to the target point using relative positioning method in conjunction with U-SAT, which is, absolute positioning methods. The performance of U-SAT is evaluated accordingly with the results of the experiments. As a result, U-SAT could be effectively used as a pseudolites or pseudo-satellites to help a mobile robot navigate intelligently and autonomously in an indoor area.

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This paper presents positioning algorithms for an ultrasonic satellite system (USAT) consisting of multiple ultrasonic transmitters and receivers in buildings. The previously used inverse matrix method of calculating USAT positions suffers from problems related to transmitter layout, and the method is sensitive to sensor noise. To solve these problems, a geometric approach with verification by a comparison of simulations with the inverse matrix method, is suggested. However, when an object is moved quickly, the positioning error is increased. The moving object positioning algorithm with an extended Kalman filter (EKF),which takes account of the dynamics of the moving object, is therefore proposed for estimating USAT positioning during movement. The accuracy of the proposed algorithm is evaluated by simulations and experiments. The experimental results show that the proposed algorithm gives a better performance for dynamic states.

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Abstract. In order for a vehicle to follow a predetermined trajectory accurately, its position must be estimated accurately and reliably. In this paper, we propose new lateral control methods for unmanned vehicles and a positioning system using ultrasonic waves. The positioning problem is considered as an important issue of control problem for unmanned navigation of a vehicle. Dead Reckoning is widely used for positioning of vehicle. However this method has problems because it accumulates estimation errors. We propose a new method to increase the accuracy of position estimation using the Ultrasonic Satellite system. It is shown that we will be able to estimate the position of vehicle precisely, in which errors are not accumulated. We also propose new lateral control methods including a new path planning method and a heading angle modulator. The experimental results show that the proposed methods enable accurate vehicle trajectory tracking under various environmental factors.

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