Tham khảo tài liệu 'mobile robots perception & navigation part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Autonomous Navigation of Indoor Mobile Robot Using Global Ultrasonic System 391 c Estimation for heading t angle. Fig. 6. The self-localization of the mobile robot. The autonomous navigation system using the global ultrasonic system is compared to the dead-reckoning navigation system on the straight line connecting the initial posture 650 650 n 4 and the goal posture 900 900 n 4 in the workspace. a Position in x and y axis b Heading angle 392 Mobile Robots Perception Navigation c Trajectory in x - y plane Fig. 7. The dead-reckoning navigation. Fig. 7 shows the results in the case of the dead-reckoning navigation in which the mobile robot cannot reach its goal posture due to the uncertainties in the state equation. In Fig. 7 c the dotted polygons represent the desired postures of the mobile robot with respect to time. The results of the autonomous navigation system based on the self-localization using the global ultrasonic system are presented in Fig. 8 for the same initial and goal postures. As shown in this figure the mobile robot reaches the goal posture overcoming the n uncertainties in the state equation and the heading angle at the final position is around 4 as desired. It should be noted that the posture data in Figs. 7 and 8 are obtained by using the global ultrasonic system also thus these values may be different from the actual postures to some degree. I X 11 X X M X V a Position in X and y axis Autonomous Navigation of Indoor Mobile Robot Using Global Ultrasonic System 393 b Heading angle c Trajectory in x - y plane Fig. 8. Navigation with global ultrasonic system. The size of the ultrasonic region in the work space is dependant on the beam-width of the ultrasonic generator. In the case of a general ultrasonic ranging system in which both the signal generator and the receiver are lumped together an ultrasonic generator with a narrow beam-width is preferable in order to avoid the ambiguity and to enhance the measurement accuracy. On the other .