Research On The Control Strategy Of Circular Braiding Process For Special-shaped Structural Mandrel

In the last few years,composite materials have been extensively used in complex structural parts instead of metal materials.The preforms braided by circular braiding machines have excellent performance and have gradually been extensively used in aerospace,shipbuilding,medical and other domains.As an important parameter of the preform,the braid angle has an important influence on the performance of the preform.The main purpose of this study is to keep the braiding angle of special-shaped structural parts stable,and the control strategy in the braiding process of special-shaped structural parts is studied.During the braiding process of the circular braiding machine,when the braiding parameters change,the braiding angle does not change immediately,but has a changing process,which is specifically manifested as a change in the convergence length.This makes the braiding point unstable stage in the braiding process.This study analyzes the relationship between take-up speed,convergence length,braiding length and time in the braiding point unstable stage and gives a specific model.At the same time,it gives the braiding process of special-shaped structural parts two equivalent processing methods in.Aiming at the problem of unstable braiding angle caused by the mandrel when radius of the mandrel changes in the braiding process of special-shaped preforms.A joint control policy for the robot take-up speed and the robot’s secondary advance distance is proposed.Firstly,the special-shaped structure mandrel is discretized to obtain the radius of each segment,and then optimize the take-up speed of the robot,so that the adjustment of the braiding angle can be realized and the relationship between the advancing distance and the actual braiding length can be got.Finally,the braiding length is compensated by the second advance of the robot,and the control parameters of the next segment of the mandrel are calculated based on the changing law of the dynamic convergence length.The results of the experiment indicate that the control policy can effectually reduce the braiding angle error of the special-shaped structure mandrel and keep it within ±3°,which is of great significance for the strict control of the braiding angle in actual production.In the braiding process of mandrel with special-shaped structure,in view of the different cross-sections of mandrels,an inverse solution strategy of take-up speed for mandrels with arbitrary cross-sections is proposed.According to the projection of the centerline of the mandrel on the surface of the mandrel,combined with the grid on the mandrel surface and the expected braiding angle,an expected yarn trajectory is obtained,and the take-up speed of a single yarn is inversely solved through the geometric relationship,and then set the weights of different faces to calculate the average take-up speed in the case of multiple yarns.The results of the experiment show that the higher the dispersion of the mandrel centerline,the more grids on the mandrel surface,the more accurate the calculated take-up speed,and the better the overall effect of the braided preform,this control method is of great significance to the braiding of mandrels with special-shaped mandrels.After solving the parameters required for braiding,set them in combination with the operation panel of the numerical control system.Based on the numerical control system,the control policy proposed in this study is proved,and the results of the experiment show its feasibility,and the braided preform can meet the requirements of daily production.