The quality of composite preform has great influence on its mechanical properties. Aiming at the problems of difficulty in robot teaching and unstable braiding angle in the process of braiding three-dimensional complex component, a control method of robot is proposed. Firstly, the mandrel is discretized to ensure that the axis of each discrete mandrel is perpendicular to the braiding point plane, and the orientation and direction of the tool center are calculated. Then, the take-up speed of the robot is calculated, so that the self-adjustment of the braiding angle can be realized in the braiding process. The experimental results show that the control method can effectively reduce the braiding angle error of variable cross-section mandrel within 2°, and can improve the quality of composite products in actual production.
Aiming at the problems of complex trajectory, low efficiency and high operational difficulty of the robot in multi-point punching of warp-knitted vamp, a method of optimizing punching trajectory based on improved ant colony optimization algorithm and Radau pseudospectral method is proposed. After obtaining the position coordinates of punching points, an improved ant colony optimization algorithm is used to calculate the punching sequence of the shortest path through all punching points, and then Radau pseudospectral method is used to solve the optimal trajectory of the laser punching robot. Improved ant colony optimization algorithm combines a distributed calculation method and the positive feedback mechanism. Radau pseudospectral method can transform the optimal control problems into nonlinear programming problems, and the combination of the two can quickly and reliably obtain the optimal solution. To verify the method, under the condition of selecting the same number and location of punching points, the experiments of Radau pseudospectral method to solve the trajectory planning of laser punching robot is carried out. The experimental results show that improved ant colony optimization algorithm can calculate the path of the vamp punching point in a shorter time and with high accuracy. Radau pseudospectral method can obtain smooth trajectories satisfying various constraints, which can meet the requirements of accuracy and efficiency in practical production.
Aiming at the current problems of duplicated paths and low work efficiency in machine punching of warp knitted vamp marker points, this paper proposes a punching path planning method of machine vision combined with intelligent algorithms. The method can improve the timeliness of visual recognition of punching location by limiting the search area and similarity function threshold, and improve the ability of global search and adaptive adjustment in punching path planning by combining with the improved ant colony algorithm to calculate a more accurate and optimized path more efficiently. Through the visual recognition test and the simulation test of the improved ant colony algorithm, the results show that the template matching can correctly identify the positioning hole marker points for different styles, rotation directions and lighting conditions, and the recognition accuracy is 0.43 mm and the repeat positioning accuracy is 0.09 mm; meanwhile, the improved ant colony algorithm can effectively avoid the local optimal solution, which can improve the optimal rate of the result by about 38% and the algorithm can reduce the number of iterations of the optimal solution within 60 times, which greatly saves the calculation time of path planning. The method can be used to improve the efficiency of punching in the actual warp knit vamp punching.
The braiding process is an important process for composite fabrication. Aiming at the problem of inner fabric folds and outer fabric sparseness in the bending of the complex geometric mandrel during braiding, a control method for off-center braiding is proposed. The mathematical description of the yarn position in the braiding process under the off-center condition is carried out, solving the differential equation for the convergence length using Euler's method to obtain the convergence length at any moment. The prediction model of the yarn on the mandrel is established to describe the spatial position of the fell point in the coordinate system of the mandrel end face and the coverage rate of the preform is solved by using the coverage rate formula under the off-center condition. The braiding experiments of the two mandrels are carried out to verify the feasibility of the prediction model and the control method. The experimental results show that the prediction model of off-center braiding can ensure that the error between the predicted value and the actual value of the braiding angle is within 5°. At the same time, off-center braiding can reduce the inner coverage rate of the bending mandrel and improve the outer coverage rate, and the error of the coverage rate is controlled within 10%. The errors are mainly caused by neglecting the slip of the yarn on the mandrel and the variation of the fell point due to the yarn interaction.
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