Optimum Design And Simulations Of A Virtual Fish-like Robot Based On Fish's Muscle Model

Fish-like robot is a new style autonomous underwater robot that mimics fish's swimming motions by electromechanical structures or intelligent materials. Compared with traditional airscrew propulsors, it has features of high efficiency, high maneuverability and low noise etc. Therefore it has been one of the hotspots in the robotics research field in recent years. But the traditional researches mainly adopt a bottom-up research mode, in which there are no good intercrossings or interactions between each subject in fish-like robot research field. Motivated by trying a new top-down research mode, based on the analysis of fish swimming locomotion mechanism and the inspiration of the swimming related structures and functions of fish physiology, a virtual fish-like robot is built in ADAMS by imitating a real fish as realistically as possible structurally and functionally, by using that many virtual experiments such as kinematics and dynamics simulations and optimum design are performed. Furthermore, the virtual fish-like robot could serve as a platform for the intercrossing and interactions between each subject in fish-like robot research field.The general situation and development of fish-like robot research at home and abroad are reviewed and introduced at first. Then the structures and functions of fish's swimming apparatuses are discussed and several basic principles which ensure the high quality of fish swimming are extracted to guide the design of fish-like robot.In order to build a virtual fish-like robot that can mimic swimming motions of real fish, we investigate the locomotion mechanism of fish swimming as well as its kinematic model by using an analytical method based on image sequences presented in this dissertation. First the silhouette of a fish body is extracted, and then an energy function is employed to obtain the skeleton of the fish body automatically. By using a spline based curve fitting technique to fit the data above, we can find out the locomotion mechanism of fish and establish an accurate and practical mathematical model of fish kinematics. The method can obtain more precise data without any human error or additional restricts such as environment or object compared with traditional method. In the experiment we measured and analyzed both steady and transient swimming motions of a Chinese Sturgeon (Acipenser sinensis), including steady swimming, C-starts, S-starts, turning, up-down motions, accelerating and braking. Mathematical models of these motions are established based on the data obtained by our method. Thus a swimming kinematics library that consists of all the fundamental swimming motions is built, which could be used in the learning and training program for the fish-like robot and its controller to generate the swimming motions like a real fish as much as possible.To ensure the virtual fish-like robot be close to a real fish as realistically as possible structurally and functionally, the actuation system of real fish is studied in this paper. The mechanical properties of fish's skeletal muscles are investigated, and the muscle model is established. Furthermore, the principles of actuation in the muscular system of fish are extracted to guide the development of new style actuators and increase the capacity of the fish-like robot. Besides, the dynamics models of the fundamental swimming motions in the swimming kinematics library are established. Therefore the virtual fish-like robot can be used to do virtual experiments such as autonomous navigation, motion control, and route planning etc.Based on the achievements obtained above, we built a virtual fish-like robot in ADAMS by imitating a real fish as realistically as possible structurally and functionally. The virtual fish-like robot actuated by fish's superficial red muscle model has the same physical and kinematic parameters as the specimen of Chinese sturgeon, so it can swim like a real fish. By using the virtual fish-like robot, the kinematics and dynamics simulations of the fundamental motions were conducted in ADAMS, and the experimental results proved not only the accuracy of the mathematical models of the fundamental motions in the kinematics library as well as availability to the motion control of fish-like robot system, but also the veracity, rationality, and validity of the design of the virtual fish-like robot structurally and functionally.In addition, we optimize the design of the virtual fish-like robot and obtain the optimal ratios of each links for several most used types of backbones, which can be used to guide the realization of actual fish-like robot.