Research On Rheological Properties Of Magnetorheological Grease And Its Flexible Manipulator Grippe

The mechanical gripper is a mechanism that grabs and operates objects.It can transmit the motion of the arm to the objects.In actual production,the mechanical gripper is usually designed into a specific shape according to the particular situation of the production site.Although the mechanical gripper designed for specific objects can meet the specified action requirements,it can only adapt to several specific grasping objects.In some operation scenarios,it is required to grasp and operate of objects for different shapes or easily damaged objects.At this time,a more general flexible manipulator is needed to complete the specified action requirements.In this paper,a new type of magnetorheological grease soft robotic gripper is designed based on the magnetorheological effect.The clamping manipulator gripper and magnetorheological material are combined to realize the universal grasping of various shapes and fragile objects.The main research contents of the thesis are as follows:(1)A composite lithium based magnetorheological grease with good sedimentation stability and low zero field viscosity was prepared,and the effects of base oils with different kinematic viscosity on the sedimentation stability and magnetorheological properties of magnetorheological grease were tested.The results show that the settling stability of magnetorheological grease is related to the kinematic viscosity of base oil,that is,the greater the kinematic viscosity of base oil,the better the settling stability of magnetorheological grease.When the kinematic viscosity of the base oil for preparing magnetorheological grease is too low,the magnetorheological grease will undergo static oil separation,which will affect the dynamic viscoelastic properties of magnetorheological grease.(2)The overall structure of magnetorheological grease soft robotic gripper is designed,including motor driving part,connecting rod transmission part and soft fingertip part.The motor drive part is composed of Brushless DC motor and worm gear reducer;The connecting rod transmission part adopts parallel hinge structure.The soft fingertip part is composed of electromagnet.In addition,a simulation analysis of the magnetic field for the soft fingertip is also carried out.(3)The kinematics and grasping ability of magnetorheological grease soft robotic gripper in the grasping process are analyzed.The kinematics of soft robotic gripper is analyzed by analytical method,and the model is built in Simscape for verification.Taking the grasping sphere as an example,the grasping ability of the flexible manipulator is analyzed from various aspects of the contact form between the flexible fingertip and the object,the pressure model in the bladder,the grasping force model,the limit size and grasping accuracy that can be grasped,the force model of the connecting rod and the influence of inertia.(4)According to the designed magnetorheological grease soft robotic gripper,the experimental test platform was built.Under the coil currents of 0A,0.25 A,0.5A,0.75 A,and1A,the ability of the flexible manipulator to grab wooden balls of different diameters(15mm,40 mm and 60mm)and different depths(6mm,11 mm and 17.5mm)were tested respectively,and the results were analyzed and discussed.