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对复杂形状的曲面进行超声检测时,传统的半闭环控制无法消除传动环节的误差,因此难以检测到材料中1.2 mm以下的缺陷。为改善系统并提高精度,可以在负载上增加光电编码器形成全闭环控制系统。通过光电编码器将负载运动的实际位置反馈给控制卡,由控制卡实现传动误差的实时补偿,提高运动精度。为验证该方法的有效性,对全闭环系统进行建模并且用Matlab求出了系统的动态响应曲线,分析表明全闭环控制能够减少传动环节的延时和误差。实际应用中,对同一个飞机螺旋桨叶片分别采用半闭环和全闭环系统进行检测,结果表明,全闭环控制可使系统的位置误差由15.43μm减少到9.51μm,检测飞机螺旋桨叶片时的缺陷误判几率由8.3%降为3.2%。
In ultrasonic testing of complex shaped surfaces, the traditional semi-closed-loop control can not eliminate the error of the transmission link, so it is difficult to detect the defects below 1.2 mm in the material. In order to improve the system and improve the precision, a photoelectric encoder can be added to the load to form a fully closed loop control system. The actual position of the load motion is fed back to the control card through the optical encoder, and the real-time compensation of the transmission error is realized by the control card so as to improve the movement accuracy. In order to verify the effectiveness of this method, the closed-loop system is modeled and the dynamic response curve of the system is obtained by Matlab. The analysis shows that full-closed loop control can reduce the delay and error of the transmission. In practical application, the same aircraft propeller blades were tested by semi-closed loop and full closed-loop system respectively. The results show that the full closed loop control can reduce the system position error from 15.43μm to 9.51μm, and the misjudgment of defects in the detection of aircraft propeller blades The odds dropped from 8.3% to 3.2%.