Study On Swimming-walking Bionic Mixed Motion Of Underwater Self-reconfigurable Robot

Underwater self-reconfigurable robot is a new kind of underwater robot that combines related techniques of underwater exploration and operation system and land self-reconfigurable robot and focuses on the issue of structure detection in complex environments. Such robot, based on centralized functional structure of normal underwater robot, distributes all or most of its motion, operation and sensing subsystems to many similar or identical intelligent units. These units can jointly achieve overall function by connecting as a network, and make the robot move in different ways by underwater dynamic reconfiguration based on requirements of each task and perception of its own status and environment. In addition, swimming-walking, as the major motion mode of such robot, also plays an indispensable role, since exercise performance directly confines the robot’s range of application and determines its ability to fulfill tasks.This thesis starts from achieving swimming-walking of underwater self-reconfigurable robot, researches on key issues including its dynamics modeling, CPG-based control network, stability of swimming-walking, and self-reconfiguration strategy, etc., proposes new solutions and proves them with many simulation and experiments. Main content and contribution of this thesis are as follows:(1) In view of complex and changeable configuration of underwater self-reconfigurable robot, this thesis proposes a unified modeling method based on path matrices and Kane equations. This thesis introduces unified configuration description based on path matrices and gives how Kane method establishes kinematic and dynamicequations. Then this thesis goes on to derive kinematic and dynamic function of underwater self-configurable robot based on unified configuration description and Kane method. Building of kinematic and dynamic equations for such robot can serve as a foundation for research on issues like CPG-based control network and stability of swimming-walking.(2) This thesis, in light of rhythmic characteristics of swimming-walking of underwater self-reconfigurable robot, proposes to use CPG network to control swimming-walking of different configuration. It introduces in detail amplitude-controller phase oscillators, base on which double strands CPG that is applicable to underwater self-reconfigurable robot is created. This thesis also introduces a method of making CPG network evolving from path matrices, and presents structure and output waveform of CPG network corresponding to typical configuration of underwater self-reconfigurable robot.(3) This thesis, considering the special environment that underwater self-reconfigurable robot works in, analyses respectively the stability of two motions:swimming and walking. As for swimming, stability can be achieved by resisting interference from surrounding environment through moment of couple formed by gravity and buoyancy. Considering changing configuration during swimming and it’s difficult to locate center of gravity and buoyancy, this thesis proposes to calculate respectively moment of couple of each module and add them with reference module as a base. The stability of underwater walking can be analyzed in terms of the balance of force and torque.This thesis proposes two kinds of stability criterion. The first kind focuses on translational displacement and slippery soles due to water blast. The second kind focuses on the issue of turning over happened during underwater walking. The thesis provides calculation method of ZMP with hydrodynamic influence and shows how to judge if ZMP is in the convex polygon.(4) In this thesis, an expert database of underwater self-reconfigurable robot strategy iscreated to provide method of configuration classification, method of describing configuration and factors that influence choice of best configuration. Using double selection mechanism, this thesis proposes to first choose suitable configurations based on the kind of task and location of underwater operation, and then, through fuzzy reasoning and center of area with comprehensive optimization as standard, select the optimal configuration from suitable configurations. The thesis also introduces in detail how to transform from current configuration to optimal configuration.(5) In order to verify the effectiveness of proposed theory, simulation and verification platforms of underwater snake-like configuration and underwater quadruped walking configuration are established. They can achieve adaptive swimming and control of head concussion of underwater snake-like configuration, and analyze the influence of spring-damper coefficient and CPG parameter to the speed of underwater quadruped walking. With tank experiment, the effectiveness of CPG-based control network in two situations are verified: swimming and creep of underwater snake-like configurationIn this thesis, the theoretical research on underwater self-reconfigurable robot can help improve exercise capacity of such robot, expand its field of application, and provide theoretical basis and verification platform for following research in this field.