Design And Study On Robotic Gripper With The Skeleton Of Changing Cross-section Leaf Spring

As an agricultural country, every year our contry produces a large number of subsidiary agricultural products, the sorting work of which is very labor-effective, so the peple wish a manipulator which can complete the grasping work of thin-skinned and easy-hurt target objects having all shapes and sizes can be invented to help peple finishe such work. The traditional industrial manipulator has played an important role in the grasping work of high load and single objects, but they are at a loss in grasping and sorting the targets of changing shapes and sizes and easy fragile. In order to solve the problem this paper propose a kind of an robotic gripper with the skeletion of changing cross-section leaf spring which are driven by pencil cylinder and transfer motion and force through rigid hinge, which makes the gripper have enough grasping force and a good adaptability to the target objects.Firstly this paper study the deformation of the flexible joint with the skeleton of constant section leaf spring, corrects the mechanical model, solve the deformation parameters using the method of Runge Kutta and Sequential Quadratic Programming, finally concluded the point load and bending moment on the free end of the leaf spring skeleton. Upload the point load and bending moment on the free end of the leaf spring and simulate its deformation in software ANSYS using the method of finite element. At last obtain the stress of the leaf spring in any position and plot the stress curve line, which verify the correctness of mechacial model and the numerial differential method. According to the U shape stress curve, in order to save energy and enhance the flexibility of the joint, this paper designed two kinds of cross-section shape(symmetrical double trapezoidal and parabola shape) of the leaf spring skeleton, which constitute the flexible joint with the skeleton of changing cross-section leaf spring. Afterwards using the flexible joints form the robotic gripper, initial design the structure dimension and draw the 3D model.Then analyze the deformation of the flexible joint with the skeleton of changing cross-section leaf spring under driving load. The deformation of the leaf spring can be equivalent to the large deflection of cantilever deformation, but as the nonlinear variation of the cross-section and load, which makes the model more complicated.This thesis firstly builds the mechanical model under driving load, then using an numerical differentiation method with the help of MATLAB to sovle the model and make contrast with the flexible joint with the skeleton of the constant cross-setion leaf spring, which concluds that the flexible joint with the skeleton of the changing cross-section leaf spring has the advantages of a bigger interaction space, needing less driving load and more saving energy.After knowing the deformation characteristics of the flexible joint under driving load, we will study on the grasping features of the robotic gripper formed by the flexible joints with the skeleton of both the changing and constant cross-section leaf spring under driving load and grasping load. Firstly build the mechanical model respectively, solve the required pressure of the cylinder under needed steady gripper force which provides the basis of practical use. Then do a detailed research on the adaptability of the robotic gipper to the target objects with different diameters and draw the deformation curve of the leaf spring skeleton. The research results indicate that the robotic gripper proposed in this paper has big grasping space, needs no sensor to exact feedback can realize the grasping of both the shape and size changing a lot target objects.At last measure the deformation displacement of the flexible joint with the skeleton of the changing cross-section leaf spring, verify the validity of the mechanical model and the numerical differentiation method through experiment.