Abstract:

Objective Quasi-rotary composite preforms are increasingly used in high-speed aircrafts. The shape and structure of the quasi-rotary composite preform are complex, and the current 4-axis needling system and 6-joint robot needling system cannot meet its weaving requirements. A 7-axis linkage needling system based on a robot platform was proposed for needling of the quasi-rotary preforms.

Method The mechanical structure design, control system design, and needling trajectory planning method of the 7-axis needling system were carried out, and the feasibility of the system was verified by motion simulation and experiment. The needling end-effector adopted apneumatic actuator, which had simple structure, easy maintenance, and light weight. Considering the high-quality needling requirements of large size preform components, a computer numerical control (CNC) rotary table with large load capacity and high accuracy was selected. The needling trajectory planning software was developed to facilitate the generation of the control program of the quasi-rotary preform needling robot.

Results The quasi-rotary composite preform needling robot was composed of a 6-joint mechanical arm, a needling end-effector, and a CNC rotary table. A Kawasaki RS050N mechanical arm was adopted for 6-joint mechanical arm, with end load of 50 kg. Universal TK13250Q CNC vertical and horizontal rotary table was selected as the rotary table. The reduction ratio was 90, and the maximum allowable inertia was 1.2 kg/m², which meet the system operation requirements. The continuous milling program development function of Powershape and Powermill was adopted to design the needling trajectory and output the position and posture information of continuous points on the trajectory. Based on Python language and QT Designer, the post-processing software of 7-axis linkage needling robot program was developed (Fig. 7). Through the simple user interface, the 7-axis needling program was designed, which reduced the workload and the human error caused by the tedious generation process. The main work of converting 6-axis program to 7-axis program was to transform the position and posture of needle points in the plane. The experiment verification results showed that the system achieved the integral needling formation of the quasi-rotary preform, the needling experimental trajectory of the quasi-rotary body was highly consistent with the theoretical design trajectory, the needling trojectory was uniform, and the surface of the preform was flat, which proved the feasibility of the 7-axis linkage needling system (Fig. 10). It was proved feasible to use Powershape and Powermill software for continuous trajectory design and robot 6-axis program output, and the 7-axis linkage needling robot independently developed based on Python could execute the program post-processing. The algorithm for converting programs into 7-axis programs was reliable.

Conclusion This paper presented a 7-axis robot needling system for manufacturing composite preforms with quasi-rotary structures. The needling robot system realized the needling formation of the quasi-rotary preforms. The needling experimental trajectory of the preform parts of quasi-rotary body was highly consistent with the theoretical design trajectory, the needle trajectory was uniform, and the surface of the preform parts was flat, which proved the feasibility of the 7-axis linkage needling system. It was feasible to use Powershape and Powermill for continuous trajectory design and 6-axis robot program output, which facilitated needling trajectory planning of complex special-shaped surfaces. The self-developed algorithm of transform the 6-axis program into the 7-axis program was reliable, and the self-developed post-processing software of the executable program of the 7-axis linkage needling robot based on Python was feasible. The system could be used for high-quality needling of radome preforms and cabin preforms for high-speed aircrafts.

Key words: quasi-rotary preform, needling robot, system design, three-dimensional needled composite, structure design