| With the rapid development of bionic robot technology,material technology,rapid prototyping technology,and artificial intelligence,soft robots have become a research hotspot in the robot field.It is based on natural creatures,mainly composed of soft elastic materials or malleable materials,has a high degree of freedom,and obtains a large amount of energy through the bending and twisting of the large amplitude and high curvature.Soft robots can change their shape and size arbitrarily in a limited space,and can well imitate the biological prototypes to complete multiple movement modes such as crawling,jumping,swimming,and grasping.It has the advantages of high human-computer interaction security,strong adaptability to unstructured environments,good mobility,low maintenance costs,and can meet the operation requirements in various complex and changeable environments.In this paper,the structural characteristics and motion mechanism of the California sea lion’s fore flipper,inchworm,and underwater creatures’ tails are investigated and studied in depth.While properly simplifying the bionic body,the large deformation and hyperelastic characteristics of silicone rubber materials are fully utilized.The structural design,mechanical modeling,underwater propulsion,and control strategy of the pneumatic amphibious soft bionic robot have been studied,and on this basis,the prototype model has been prepared for experimental analysis.The final results show that the performance of the prototype is consistent with the original design and numerical simulation prediction,and it can achieve a certain degree of mobility,flexibility,and environmental adaptability.It can provide a theoretical basis and technical support for the structure design,mechanical modeling,underwater propulsion,control strategy,prototype system construction,and tests of the soft bionic robot.Therefore,this paper is of great value and significance,the specific research contents and achievements are as follows:(1)The driving mechanism of the actuator of the pneumatic soft bionic robot is studied,taking silicone rubber as the main material of the robot structure.The structural characteristics,motion forms,and propulsion mechanism of the sea lion’s fore flipper,inchworm,and underwater creatures’ tails are analyzed through the bionic theory,it can provide a research basis for the structure design of the pneumatic amphibious soft bionic robot.Then,the structure of the soft bionic robot is designed by using the theory of mechanism design,and the main functions and motion forms of each actuator are analyzed.The numerical simulation algorithm is used to analyze the motion characteristics of the soft bionic robot,to verify the rationality and feasibility of the established robot structure and motion forms.(2)Based on Yeoh’s second-order constitutive model of silicone rubber material,combined with the structural characteristics and driving mechanism of the actuator of the soft bionic robot,the nonlinear mechanical characteristics of bending and torsional motion of the actuator are analyzed,and the deformation analysis theoretical models between the actuator bending angle,torsion angle and inflation pressure are constructed respectively.Through the idea of piecewise constant curvature modeling of flexible mechanism,the kinematics modeling of the actuator of the soft bionic robot is derived,and the kinematics simulation analysis of the end track of each actuator of the robot is carried out to verify the accuracy of the kinematics modeling theory.The equivalent motion structure of the actuator of the soft bionic robot is analyzed.According to the Lagrangian method and the kinematics model,the dynamic model of the actuator is established.(3)Analyzing the flexible deformation law of the flipper of the soft bionic robot,establishing the chordwise and spanwise flexible deformation equations respectively,and coupling the chordwise and spanwise flexible deformation,which can provide a theoretical basis for the research on the maneuverability of the flipper.Using the Blade Element Theory and the CFD algorithm of the nonlinear bi-directional fluid-structure coupling,combined with the motion characteristics of the sea lion’s fore flipper,the propulsion performance of the flipper is simulated.Among them,the propulsion performance of the soft flipper is compared with that of the rigid material flipper with the same structure and motion characteristics to verify the effect of the underwater propulsion performance of the soft flipper,providing theoretical and technical support for the application of the flexible bionic wing fin technology in underwater propulsion.(4)The Hopfield neuron nonlinear oscillator model is adopted to analyze its dynamic characteristics,and the Hopfield oscillator motion control model is established and improved.The coupling coefficients and amplitude input parameters are adjusted respectively through the propulsion coupling relationship,the tail angle of attack method,and the mechanical model.Then,a two-layer neural network topology is studied to construct the CPG motion control system of the pneumatic amphibious soft bionic robot,and the feasibility of motion control simulation is verified.The control principle and algorithm of the Adaptive Neuro-Fuzzy Inference System(ANFIS)are analyzed.The ANFIS-PID structure is designed by using the Takagi-Sugeno fuzzy inference system.Conducting offline learning and training of the membership function,the CPG-ANFIS-PID motion control strategy of the robot system is constructed,and the accuracy and anti-interference of the control strategy are verified by simulation.(5)Based on the rapid prototyping technologies and the CPG-ANFIS-PID control strategy,the body structure,and control system of the physical prototype of the pneumatic amphibious soft bionic robot is built.Through the experimental research on the motion and dynamic characteristics of the actuator of the soft bionic robot,the motion frequencies,motion angles,and driving moments of the actuator can be obtained,and the correctness of the mechanical model of the actuator can be verified.Through the experimental research on the motion characteristics and hydrodynamic performance of the flipper of the soft bionic robot,the propulsion performance is obtained and the results are compared with the nonlinear bi-directional fluid-structure coupling CFD simulation results,which can verify the good hydrodynamic performance of the flipper.The feasibility of the robot design scheme and control strategy can be verified by conducting the motion performance evaluation experiments of the pneumatic amphibious soft bionic robot in different environments on amphibious,and the qualitative and quantitative analysis of the maneuverability of the robot. |
