Modeling,Analysis And Experiments Of Bio-inspired Soft Climbing Robot

In order to imitate the excellent climbing ability of reptiles in nature,this thesis studies the theoretical and technical problems related to the soft climbing robot by using its excellent physique,structure,driving and control performance.Focusing on the two core problems of the robot,i.e.the body motion and the end-attachment,this thesis makes a detailed study from the local design,fabrication and theoretical analysis to the climbing realization of the whole robot system.The main contents and achievements are as follows1.Firstly,in order to master the performance of the soft actuator,the structure of the soft actuator is normalized,modeled and compared.A general structure pattern(abbr.GSP)is proposed for climbing robot's body.According to the GSP,the general kinematic model is established,the mapping algorithm from arbitrary curve to the robot is derived,and the influence of various structure parameters on the production for curve shape is analyzed Based on the analysis of the four kinds of pneumatic soft actuators:single cavity,external multi-cavities,internal multi-cavities and three-chamber omni-directional actuators,the basic structure,design and fabrication of the four kinds of pneumatic soft actuators are analyzed in detail.Combined with the results of finite element simulation analysis and experimental measurement,the external multi-cavities structure is the structure with the best performance.The structure model and structure comparison of the soft actuator can be used for the design,modeling and analysis of the soft climbing robot2.Secondly,in order to solve the problem of unexpected passive deformation of the body caused by gravity or external force in the process of robot crawling,such as the out-plane bending of the body.In this thesis,a rigid-soft combination design method is used,in which anisotropic constraint materials or structures are added to the common actuator to provide the expected limitations.The robot's body has the characteristics of in-plane bending motion,because a kind of self-developed anisotropic structure,two-dimensional follow-up chain,is incorporated into the limit layer of the actuator.The anisotropic rigid-soft combination structure can make the actuator realize the in-plane efficient bending motion.3.In addition,the thesis aims at realizing the end-effector which can adapt to the shape of the object and attach to the object effectively.It is found that the inchworm can not only grasp to the surface of climbing environment,but also operate the object effectively.In this thesis,an passive adaptive soft gripper(PASG)is proposed,which highly imitates the true leg structure of inchworm.The kinematics of PASG is established,all grasping conditions are enumerated and the corresponding grasping adaptability and form-closure are analyzed The constraint equations of PASG's gripping force equilibrium problem is derived,and the FEE(force equation evaluation)problem is formed to evaluate the grasp quality of PASG.In order to solve the FEE problem,a new criterion based on Monte Carlo method is proposed,which can be used as the quantitative index of grasp quality.At the same time,the index can be used to evaluate the quality of general operation problems.First of the experiment,the performance data needed for solving the force equilibrium were measured.Then,the grasping diversity of PASG was tested by gripping wood cylinder,wood cone,stone,3D print block,coffee cup and rough wall.According to the established kinematic and force equilibrium model,the sphere is taken as the holding object to further analyze the relationship between PASG grasping adaptability and the number of grasp contacts;the cylinder,the most common climbing environment,is taken as the holding object to analyze the ability of PASG to resist external forces in different directions under different diameter,grasping position and surface roughness.The results show that PASG can adapt to different objects,has good grasping stability,and can meet the general climbing needs.The force equilibrium criterion can be used to determine the force closure of general point-contact style operation problems4.After studying the two core problems of body actuation and end-attachment of climbing robot,this thesis finally proposes a soft climbing robot S-Climbot(short for soft climbing robot),which is composed of in-plane " ? " body and inner expanding grasping end-effector.The " ? " body is developed based on the anisotropic rigid-soft coupling design method,which imitates the body shape of inchworm.Based on the analysis and study of the climbing experiment results of different objects,an inner expanding end-effector with shape adaptability and stable grasp attachment is proposed.Based on the basic climbing gait of S-Climbot and its control sequence,the gravity balance judgment under any posture is proposed as the foundation of the subsequent automatic climbing.By measuring the performance of S-Climbot's body shape changing with air pressure,and climbing experiments in different environments such as climbing on round bar,irregular cross-section bar and small round bar,the climbing ability,like the adaptability,the mobility and the stability of the robot are fully verified.In this thesis,through the research on the two core problems of the body actuation and end-attachment of the soft climbing robot,taking the inchworm as the bio-inspired animal,the actuation pattern of the in-plane "?" body and the external multi-cavities structure is developed.Combined with the proposed rigid-soft coupling design method,the in-plane high-efficiency bending motion is realized.The PASG and the inner expanding end-effector are developed to meet the requirements of various climbing scenes,which solves the problem of high-efficiency and stable attachment of various materials.Through a series of climbing experiments,the feasibility and practicability of the theory and technology proposed in this thesis are verified.