KEYWORDS: Fuzzy logic, Temperature control, Composites, Temperature metrology, Control systems, Laser applications, Fiber lasers, Carbon fibers, Control systems design, Picosecond phenomena
Continuous carbon fiber reinforced thermoplastic composites have problems such as long temperature self setting time, high overshoot, and low control accuracy during laser in situ molding, resulting in poor component forming quality. This article designs a temperature closed-loop control system based on an intelligent fuzzy proportional-integral-differential (PID) controller. By introducing a fuzzy self-tuning PID algorithm, the goal of quickly adjusting to the working temperature when turned on is achieved. The temperature overshoot is significantly reduced, and the temperature control accuracy is improved. According to the requirements of laser in situ forming of carbon fiber reinforced polyether ether ketone composite materials, a laser in situ forming experimental device was built. Through simulation testing and comparison of forming temperature, the results showed that compared with traditional PID controllers, when using an intelligent fuzzy PID controller to control temperature, the temperature control accuracy was maintained at ± 10 ℃, the overshoot percentage was about 2.29%, and the adjustment time was about 9.7 seconds. All indicators met the actual engineering requirements, The temperature setting effect is good and the fitting degree is high. Therefore, the overall performance of the intelligent fuzzy PID controller is far superior to traditional PID controllers, meeting the temperature control requirements in the laser in situ molding process of thermoplastic composite materials.
Since laser beam pointing stability affects the quality and accuracy of work in areas such as laser guidance and laser processing, the paper proposes a method for measuring the laser beam pointing stability based on the linearly angle-displacement transformation characteristics of F-theta lens in order to measure the pointing stability accurately and comprehensively and evaluate the performance of the laser. The method linearly converts an angular offset into a displacement offset that can be accurately measured and evaluate the pointing stability by means of finding the minimum envelope circle. Based on this method, a laser beam pointing stability measurement system with CCD camera as image acquisition unit is built for He-Ne laser source. The experimental results show that the pointing stability of the He-Ne laser is 1.500mrad. The result is only 0.186% affected by the error, which verifies the feasibility of the measurement method and the high-precision measurement of laser beam pointing stability by the system.
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