2 research outputs found

    Aerial Vehicles

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    This book contains 35 chapters written by experts in developing techniques for making aerial vehicles more intelligent, more reliable, more flexible in use, and safer in operation.It will also serve as an inspiration for further improvement of the design and application of aeral vehicles. The advanced techniques and research described here may also be applicable to other high-tech areas such as robotics, avionics, vetronics, and space

    Vision based localization and trajectory tracking of nonholonomic mobile robots

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    Localization is one of the most difficult and costly problems in mobile robotics. Vision and odometry/AHRS (Attitude and Heading Reference System, three axial gyroscopes, accelerometers and magnetometers) sensors fusion strategy is prevalent in the recent years for the robot localization, due to its low cost and effectiveness in GPS-denied environments. In this thesis, a new adaptive estimation algorithm is proposed to estimate the robot position by fusing the monocular vision and odometry/AHRS sensors, and utilizing the properties of perspective projection. By the new method, the robot can be localized in real time in the GPS-denied and mapless environments, and the localization results can be theoretically proved convergent to their real values. Compared to other methods, our algorithm is simple to implement and suitable for parallel processing. To achieve the real-time performance, the algorithm is implemented in parallel using GPU (Graphics Processing Unit), and therefore it can be easily integrated into mobile robots’ tasks like navigation and motion control, which need the real-time localization information. Simulations and experiments were conducted to validate the good convergence and longtime robustness performances of the proposed real-time localization algorithm.With the developed vision based localization method as a position estimator, a new controller for trajectory tracking of the non-holonomic wheeled robot is proposed without direct position measurement. The nonholonomic motion constraint of mobile robots is fully taken into account, compared to most of existing visual sevo controllers for mobile robots. It is proved by Lyapunov theory that the proposed adaptive visual servo controller for the wheeled robot gives rise to asymptotic tracking of a desired trajectory and convergence of the position estimation to the actual position. Experiments on a wheeled robot are conducted to validate the effectiveness and robust performance of the proposed controller.Adopting the similar idea, the new vision based localization method is once again embedded into a trajectory tracking controller for the underactuated water surface robot. It is proved once again by Lyapunov theory that the proposed adaptive visual servo controller for the underactuated water surface robot gives rise to asymptotic tracking of a desired trajectory and convergence of the position estimation to the actual position. Experiments are conducted on an underactuated water surface robot to validate the effectiveness and robust performance of the proposed controller.The contribution of this thesis can be summarized as follows: firstly, a novel localization algorithm based on the fusion of the monocular vision and AHRS/odometry sensors is proposed. Secondly, with the former localization method embedded as a position estimator, a new controller for visually servoed trajectory tracking of the nonholonomic wheeled robot is developed. Finally, by adopting the similar strategy, this thesis proposes a new controller for visually servoed trajectory tracking of the underactuated water surface robot without direct position measurement.定位是移動機器人中最困難和花費最高的問題之一。由於其低成本和在無GPS(全球定位系統)環境中的有效性,視覺和里程計/ AHRS(姿態航向參考系統,三軸陀螺儀,加速度計和磁力計)傳感器融合是近年來流行的機器人定位策略。這篇論文提出了一種新的自適應估計算法,融合單目視覺和里程計/ AHRS 傳感器,並利用透視投影的特性來估計機器人位置。利用這種新方法,機器人可以實時地在無GPS 和無地圖的環境中被定位,而且定位結果可從理論上證明收斂到他們的真實值。與其它方法相比,我們的算法很容易實現,並適於並行處理。為了得到實時性能,算法是用GPU(圖形處理單元)來並行實現的,因此它可以很容易地集成到移動機器人需要實時定位信息的任務,如導航和運動控制。仿真和實驗驗證了我們的實時定位算法具有很好的收斂及長時間的魯棒表現。利用上述基於視覺的定位方法作為位置估計器,我們為一階非完整移動機器人的軌跡跟踪提出了一種新的、不直接依賴位置測量的控制器。相比於大多數現有的用於移動機器人的視覺伺服控制器,我們的方法充分考慮了移動機器人的非完整運動約束。我們通過Lyapunov穩定性理論證明了本論文所提出的自適應視覺伺服控制器可以保證一階非完整移動機器人對理想軌跡的跟蹤,並且被估計的機器人位置會漸近收斂到其實際的位置。我們在輪式機器人上進行了相應的實驗,驗證了本論文所提出的控制器的有效性和魯棒性。採用類似的思路,這種基於視覺的定位方法被再次嵌入到二階非完整移動機器人(欠驅動水面機器人)的軌跡跟踪控制器。我們再一次通過Lyapunov穩定性理論證明了本論文所提出的自適應視覺伺服控制器可以保證二階非完整移動機器人對理想軌跡的跟蹤,並且被估計的機器人位置會漸近收斂到其iv實際的位置。我們在欠驅動水面機器人上進行了相應的實驗,驗證了本論文所提出的控制器的有效性和魯棒性。這篇論文的貢獻可以歸納如下:首先,基於單目視覺和AHRS/測距傳感器的融合,我們提出了一種新的定位算法。其次,通過將上述基於視覺的定位方法內嵌為位置估計器,我們為一階非完整移動機器人(輪式機器人)設計了一種新的基於視覺伺服的軌跡跟踪控制器。最後,通過採用類似的避免機器人位置測量的策略,本文為二階非完整移動機器人(欠驅動水面機器人)設計了一種新的基於視覺伺服的軌跡跟踪控制器。Wang, Kai.Thesis (Ph.D.)--Chinese University of Hong Kong, 2014.Includes bibliographical references (leaves 93-100).Abstracts also in Chinese.Title from PDF title page (viewed on 20, December, 2016).Detailed summary in vernacular field only.Detailed summary in vernacular field only.Detailed summary in vernacular field only.Detailed summary in vernacular field only
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