Đang chuẩn bị nút TẢI XUỐNG, xin hãy chờ
Tải xuống
Tham khảo tài liệu 'sliding mode control part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 234 Sliding Mode Control 0 10 20 30 40 50 60 70 80 89 0 10 20 30 40 50 60 70 80 89 0 10 20 30 40 50 60 70 80 89 Time s 480 420 360 300 240 180 E 120 60 0 u image coordinate pixels 0 80 160 240 320 400 480 a Path on the plane. b Evolution of the robot state. c Motion of the image points. Fig. 9. Robustness under image noise using a hypercatadioptric imaging system. -0.2l 0 10 Time s a Evolution of the epipoles. b Input velocities. Fig. 10. Performance of the reference tracking and the velocities given by the sliding mode control law for the servoing task of Fig. 9. orientation error. This is achieved in spite of the uncertainty in the distance between the current and the target locations d . As mentioned before it is enough to fix this value in the controller thanks to the robustness of the control law. We claim that the second phase regarding to depth correction may be carried out exploiting also the information provided by the epipolar geometry. This could be a way to avoid the switching to a totally different approach for depth correction. 6. Conclusions In this chapter a robust control law to perform image-based visual servoing for differential-drive mobile robots has been presented. The visual control utilizes the usual teach-by-showing strategy in which the desired location is specified by a target image previously acquired. The mobile robot is driven toward the target by comparing a set of visual features in the current view of the onboard camera and those on the target image. The visual features are gathered through the epipolar geometry and exploited in a sliding mode control law which provides good robustness against image noise and uncertainty in camera parameters. The major contribution of this work is the validity of the approach for generic imaging systems. This extends the applicability of the proposed control scheme given that a generic camera allows a major maneuverability of the robot than a conventional camera because its wide field of view. .