| With development of robot technology and automation technology,intelligence and automation of interactive devices are becoming more and more important.However,traditional steel structure clamps and grippers have some problems,such as high replacement cost and complicated control algorithm,which restrict their applications in some fields.Therefore,flexible grasping has become a hot research.Flexible grippers based on intelligent materials have been widely studied because of its high grasping adaptability and simple control methods,and have a widespread availability prospect in robots,medical treatment,industrial manufacturing and other fields.Magnetic-sensitive rubber in intelligent materials has become a new research in flexible grasping fields due to its characteristics of rapid response,remote control,magnetron deformation and magnetron surface roughness.However,in the current research,the excitation device and flexible fingers of magnetron flexible grippers are split,which makes other electronic components in the working environment vulnerable to the interference or damage of magnetic fields,and there is also one problem that application and grasping performance can be taken into account together or not.Moreover,in these studies,the influence of the magnetic field on the surface roughness has not been considered.In this thesis,flexible gripper based on magnetic-sensitive rubber is taken as the research object to learn structure of human hands,design and optimize the integrated structure of flexible finger and excitation device,and consider influence of magnetic fields on surface roughness,so that the magnetic-controlled bionic gripper designed in this thesis can give consideration to both safety and grasping performance.A set of performance test,optimization method and test platform for magnetically controlled flexible gripper are designed.The main research work of this thesis is as follows:1.This thesis introduces the research background and important engineering significance of the flexible grippers based on magnetic sensitive rubber,and summarizes the research status of flexible grippers based on intelligent materials,magnetic sensitive rubber and magnetic controlled flexible devices.It clarified the problems which exist in the research of magnetically controlled flexible grippers and presented the main research work of this thesis.2.Starting from safety and grasping performance of magnetron flexible grippers,an integrated magnetron bionic flexible gripper which imitates human hands is designed by combining the excitation device and the flexible finger,which is suitable for the end device of robots or sorting grippers in industrial production.The calculation formula of the magnetic field generated by the excitation device is given,which provides theoretical support for the safety assessment of the magnetically controlled bionic flexible gripper.It is difficult to calculate the closed magnetic circuit because of the uncapped structure at one end of the excitation device.Then,Comsol,multi-physical field finite element simulation software is used to model and simulate the excitation device,and the relationship between the size ratio of various parts in the excitation device and the evaluation index is explored.The results show that the size ratio of the iron core to the coil will greatly affect the evaluation index of the magnetic field effect.This shows that the magnetic field effect is best when the radius difference of the iron core is 1:5 compared with the inner and outer radius of the upper coil,which lays a foundation for the research and optimization of the flexible finger.The magnetic field distribution of the exciter with and without a magnetic enclosure is compared by simulation,and it is found that the exciter with a magnetic enclosure can effectively gather the magnetic field and increase the working range.3.On the basis of the excitation device which has been optimized,the influence of the size parameters of the magnetically sensitive rubber on the bending Angle was studied from the magnetic-controlled bending characteristics of the flexible finger.In the Comsol multi-physical field finite element simulation software,the flexible fingers with only one finger were modeled.The single variable method was used to study the influences of the length,width,thickness and distance from the axis of the rectangular flexible fingers on the bending Angle.The results show that the bending Angle increases with the length of the flexible finger and the distance from the axis.The width and thickness of the flexible finger have the opposite influence on the bending Angle,and the thickness has a greater influence than the width.Through simulation,it is also found that the magnetic field direction will affect the bending direction,which indicates that the magnetron flexible gripper can expand the grasp volume of the flexible gripper by changing the magnetic field direction.Samples of NDFEB flexible fingers with different volume ratios were made,and it was found that the flexible fingers with 20% volume ratio had the best bending performance,which only need 22 m T to bend to 90°.It is also found that the magnetic field can increase the surface roughness of the flexible fingers,which further enhances the grasping ability of the flexible grippers and lays a foundation for the performance research and experimental verification of the flexible grippers.Finally,the phenomenon of flexural finger bending and surface roughness variation is explained theoretically,which provides theoretical support for the magnetic field control of flexible finger.4.A grasping performance test method suitable for magnetically controlled flexible gripper is designed and a testing platform is built.The experimental results show that the shape and size of the object grabbed and the length of the flexible finger all affect the grasping force.For objects of one size,an optimal finger length can be found to maximize grasping force.Magnetic-controlled flexible gripper has the largest grasping force on hollow objects and the smallest grasping force on cuboids.In the experiment of grasping a round ball with a four-finger flexible gripper,the maximum grasping energy efficiency is 0.524g/m T.At last,the experiment of grasping adaptability and security of the flexible gripper is carried out.The experiment proves that the flexible gripper can grasp different objects adaptively only through the switch control,and will not affect other electronic devices in the working environment,which guarantees the security. |
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