| As a kind of soft robot,the bionic fully flexible gripper has good flexibility,stability and adaptability.It can work in a narrow space,and has completed many tasks that industrial robots are not competent for.It has a wide range of application scenarios in the industrial,medical and agricultural fields.Based on the pneumatic multi-cavity type soft gripper,this research proposes a new type of bionic fully flexible gripper,and carries out research work on it.In this thesis,a three port stepped bionic fully flexible gripper driven by gas is designed.The gripper uses elliptical air cavity section shape,stepped cavity and split port control,which makes the interior of the gripper cavity soft and stress free,and enhances the overall sensitivity of the gripper to changes in air pressure,grasping ability and wrapping performance;Multi-ports are used to control and refine the control angle,which enriches the application scenario of flexible gripper;The bottom is pasted with a strain limiting layer,which makes the fingers of the flexible gripper bend to the direction of the strain limiting layer after being forced to bend,completing the directional bending,and solving the packing tightness problem of the traditional single air chamber soft fingers and the single control angle.Ecoflex 00-30 and polydimethylsiloxane are selected as the materials of flexible fingers.Based on the uniaxial tension theory,material specimens are created to conduct uniaxial tension simulation tests on the hyperelastic material Ecoflex 00-30 for finite element simulation.Mooney Rivlin model and Yeoh model are selected for comparative analysis according to the scope of application of the commonly used hyperelastic constitutive models,and Yeoh hyperelastic constitutive model is finally selected for description and calculation,The material parameters were obtained by fitting the data.Based on the piece-wise constant curvature method and virtual work principle,the analytical modeling of the bionic fully flexible finger is carried out to obtain a single airbag model describing its bending deformation performance,and the influence rules of the structural parameters such as the airbag gap,the thickness of the strain limiting layer,and the distance from the strain limiting layer to the bottom of the airbag that affect the bending performance are obtained;The mathematical model of the flexible finger cavity group is established according to the geometric relationship of the arc,and the bending prediction model of the whole finger is finally obtained.Based on the Abaqus finite element analysis platform,this thesis conducts finite element simulation on the flexible finger models with different structural parameters selected according to the control variable method established in Solid Works,and obtains the simulation deformation results of the flexible gripper.The optimal size of the gripper is obtained by comparing and analyzing the bending deformation angles calculated from the simulation results.The single airbag deformation mathematical model of the bionic fully flexible finger is determined according to the selected structure size,and the theoretical bending angle value is obtained by substituting the input air pressure.By comparing the simulated bending angle value and the theoretical bending angle value under the same air pressure,the rule is summarized,the cause of error is analyzed,and the accuracy of the mathematical model description of the relationship between the input air pressure and the bending angle is verified,According to the theoretical data,the function relationship between the bending angle and the input air pressure is obtained by fitting,which can quickly calculate the bending angle of a single airbag of each cavity group under a certain input air pressure,so as to calculate the bending angle of the whole finger.This research is of great significance to the stable grasping of soft,fragile and irregular objects by flexible grippers and the occasions requiring specific bending angles. |
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