Simulation Research On Interpolation Algorithm For Large Gantry Automatic Fiber Placement Ma Hine Based On Smoothing Of Inflection Point

Carbon fiber composites are widely used in aerospace and other fields due to their excellent specific gravity,high specific strength and large specific modulus.As a key technology for the production of composite parts with complex profiles,automatic fiber placement(AFP)technology has been widely concerned at home and abroad,in order to meet the requirements for the manufacture of large-scale aerospace composite components in China,the Aircraft Digital Assembly Team of Zhejiang University has developed independently a large gantry AFP machine.This paper studies the problem of speed flexibility control and the smoothing of the turning point during the path interpolation process based on the structure of the seven-axis gantry AFP machine.The main research work and achievements of the thesis are as follows:(1)In order to achieve precise control of the end effector of the seven-axis gantry fiber placement machine,according to the structural characteristics of the seven-axis fiber placement machine,the required kinematic model is constructed,and in a Cartesian coordinate system,the motion relations of the X-axis,the Y-axis,and the Z-axis are represented,and then the coordinate systems of the remaining four rotation axes are respectively established,and the transformation relationship between the rotation axes is given by the DH method.Finally,according to the sequence of the seven-axis fiber placement machine kinematic chain,the end effector pose transformation matrix is derived,and the kinematics forward and inverse solutions of the seven-axis gantry fiber placement machine are determined by the minimum displacement method.(2)In the speed planning of the six-axis gantry placement machine,firstly,a variety of machine tool acceleration and deceleration control methods are introduced,and their advantages and disadvantages are compared,and then the cubic polynomial acceleration and deceleration control method is determined for the speed of the seven-axis fiber placement machine.For the problem that the calculation amount of the cubic polynomial Acc/Dec control is relatively large,the equivalent acceleration is used to simplify the calculation,and finally the cubic polynomial Acc/Dec control method based on the equivalent acceleration is introduced in detail.(3)When the fiber placement machine moves on the laying path,due to the path control points are connected to the placement target path by the description of continuous short line segments,the problem of tangential discontinuity occurs at the inflection points of adjacent line segments,which causes the speed of each axis to fluctuate at the inflection point,therefore,based on the Acc/Dec control method,two interpolation methods for local smoothing of the inflection point are proposed.One was to perform polynomial Acc/Dec planning for each axis speed in the transition range of the inflection point after the forward looking Acc/Dec interpolation operation to ensure that the speed of each axis is continuous;the other method used the improved cubic Bemstein-Bezier curve as the inflection point smooth transition curve,which has the properties of tangential continuity continuous curvature,etc.The trajectory includes both the straight line segment,and the hybrid trajectory interpolation operation is performed on the basis of the flexible Acc/Dec control method.(4)In the MATLAB software,the speed planning method and the interpolation calculation method of the seven-axis gantry fiber placement machine are simulated and analyzed,and the interpolation point posture information and the respective axes when moving on the adjacent straight path and the curved path are calculated.And observe the laying speed and flatness of each axis during the movement process,and compare the common points and different points of the local smoothing interpolation methods of these two inflection points,and analyze their advantages and disadvantages.