This dissertation is supported by the National Natural Science Foundation of China “Multi-mode motion control for fish swimming based on Central Pattern Generator with sensory feedback”. This dissertation is focused on embedded visual system of a multi-fin robotic fish and realization of autonomous navigation. The paper presents a new type of autonomous robotic fish with vision-based target tracking and obstacle avoidance. The robotic fish can sample images through its eye and recognize the meaningful color patch via a series of vision algorithms. More specifically, an ARM9 (S3C2440)-centered microcontroller in conjunction with a CMOS camera (300 thousand pixels) for image acquisition is developed to effectively handle local visual information serving as the basis of underwater navigation. Meanwhile, a wireless interactive control console is devised, facilitating two-way information transfer. It can access the environmental information captured by the robotic fish in real time and display the obtained results in a visual format online. Experimental results demonstrate the effectiveness of the proposed scheme. The robotic fish developed in this paper has three characteristics: First, the robotic fish is based on the vision system. It has a closed-loop control system with the introduction of visual feedback. The visual and other sensing information processing do not rely on the outside assistance. Next, the robotic fish is designed as a novel multiple control surfaces configuration, which has a four-joint tail, a pair of pectoral fins and a pelvic fin. This makes the autonomous robotic fish have more swimming gaits and enhanced swimming performance through the cooperation of multiple fins and CPG-based control method. Lastly, the frequency of the core processor of the robotic fish is up to 400 MHz. So it can afford a series of image processing algorithms and also ensures realtimeness in control. The experiments on searching color patch and avoiding obstacles validate the swimming stability and control effectiveness.
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