The Cooperative Propulsion Mechanism And Realization Technology Of Actinomorphic Bionic Soft Robot

Animals possess efficient athletic ability and high adaptability to the environment through millions of years of natural evolution and optimization options. There is a variety of environmental media in the transition zone from the ocean to the continent, such as beach, reef, quagmire, rocks, swamps etc. Soft animals living in this zone are supplied with plentiful bionic structure and moving gaits for the development of soft robots. The bionic robot prototype is built to explore its interactive adaptability with natural environments and propulsion mechanism under multi-media, with a view to playing an important role in several applications, such as resource exploration, risk rescue, environmental monitoring, and military reconnaissance etc. This dissertation focuses on the propulsion mechanism and realization method of the radial symmetry soft robot under multiple environmental medias, including bionic kinematics, flexible body modeling and analysis, the material properties of shape memory alloy (SMA), manufacturing method for soft robot, multi-gait control etc. The main research contents and results are summarized as followings:(1) Bionic research on actinomorphic soft animals and exploration of bilaterally symmetrical robot. We summarized the basic structural features and gait patterns of typical radiation symmetrical animals via comprehensive investigations. The radial symmetry soft robot was constructed according to the bionic parameters of Fromia milleporella. The SMA spring worked as the actuator of the robot owing to its advantage of high power weight ratio, large deformation and easy control. The manufacturing method for soft bionic robot was developed on the basis of3D printing rapid prototyping platform, benefiting from which we not only greatly shorten the development cycle of a new robot but also effectively promote the improvement and optimization of biomimetic structures. Meanwhile, imitating the lizard and turtle, a bilaterally symmetrical robot with continuous limb was built to explore its propulsion mechanism. The robot actuated by cam-rope mechanism was able to pass through different terrain environment with tripod gait and diagonal gait, which prepared strong foundation for researching on the propulsion mechanism of radial symmetry robot.(2) Modeling and analysis of the soft robot and material properties of SMA. We summarized the common deformation description and modeling methods for soft limb, and preliminary modeling of the action space of soft limb tip. By comparing the comprehensive performance of two kinds of soft limbs, the unsealed design of soft limb allowed the robot to acquire larger deformation and faster action response. In addition, the pseudo-rigid-body model of soft limb could be built through simplifying its bending process as equal to bending process of cantilever in plane. The kinematics model of radial symmetry soft robot was built by the amended Brayan D-H method. The exploring study on the quasi-static thermo-mechanical coupling characteristics and constitutive model of SMA resulted in acquiring the temperature and enthalpy in martensite transformation and "temperature memory effect" in the SMA incomplete martensite-reverse-transformation process. Meanwhile, the deformation analysis of SMA spring prepared the basic information for the control of soft robot.(3) Research on multi-gait control of soft robot. The issue of path planning for avoidance of both static and dynamic obstacles was solved by the improved artificial potential field method, which was certified by simulation experiment. On the basis of the summary of basic moving gaits of radial symmetry animals, we discussed the mechanism of soft robot movement and presented the movement strategy and control mode for multi-gait, such as crawling, navigating, bypassing, rolling etc. the biological mechanisms and control model of central pattern generator (CPG) was discussed in this dissertation, including the cellular mechanisms for generating rhythmic. Meanwhile, the Wilson-Cowan CPG model was employed to control the radial symmetry soft robot. The motion estimator and neurons bionic neural network closed-loop control system were designed for the control of soft limb.(4) Study on the propulsion mechanism under multi-media environments. Six kinds of environmental media (e.g. flat ground, sand, rock, riprap, mud and rock) were selected for the experiments of propulsion performance of the radial symmetry soft robot. The robot prototype was able to reach the target positions with multi-gait in proposed environmental media via corresponding bionic gait, control strategy and motion changes. Experimental results showed that the actinomorphic robot possesses the performance of the cooperative propulsion and terrain adaptability. Meanwhile, within the fixed duration, the robot moved ahead on the sand with the most displacement, and its speed on the sand was6.5times of the speed on riprap ground and2.2times of flat ground. In addition, the test of extrusion resistance and impact resistance results also verified the robot’s good robustness. Furthermore, the soft robots with multi-limb (single limb, three limbs, four limbs, five limbs and six limbs) were designed according to the morphological parameters of soft animals for exploring their movement mechanism and propulsion performance. The relationship between the movement performance and the physical parameters (mass, body length) of multi-limb robot were obtained through many groups of experiments. The results showed that the six-limb robot acquired maximum displacement and average step length within the fixed duration, were up to251mm and20.8mm respectively. Five-limb robot and four-limb robot with similar body length showed approximate movement, and the same phenomenon between three-limb robot and one-limb robot.