-
为了将测试用的所有FBG的应力响应系数都求解出来,所有采用悬臂梁实验进行标定。应变量化标定采用悬臂梁结构,悬臂梁长30.0 mm,一侧固定于支架,另一侧自由悬空,材料选用合金钢,弹性模量6.84×1010 Pa,泊松比为0.31,膨胀系数为21.2 μm/mK。将FBG粘贴于悬臂梁中间,测试实验分别距自由端15.0 mm和20.0 mm,施力范围[0,100 N],五次测量求一次均值,测试结果如图3所示。
由图3可以看出,无论测试位置是15.0 mm还是20.0 mm,其测试点都以线性变化递增,但拟合后的斜率不尽相同。15.0 mm的斜率明显比20.0 mm的更大。可见当测试FBG的位置距自由端越近,其应变响应能力越强。系统可以根据其应变响应参数完成对装配状态的检测。
-
为了模拟温度对应变的影响,在测试位置采用20 W电热灯加热,在FBG位置采用数字温度计进行测量,然后对比温度补偿前后的应变测试曲线,如图4所示。
由图4可以看出,在温度补偿前,应变测试结果随着温度的升高而产生波长偏移,相比之下,当通过温度偏移补偿后,应变测试值不再随温度变化而改变。可见,采用该系统中的温度补偿方式具有很好的温漂校正效果。
-
分别对15.0 mm和20.0 mm的螺钉进行施力测试,施加与装配轴向垂直的偏移应力,施力值设置为20~100 N,采用激光扫描设备测试相应位置的空间位置偏移量,用于对该系统FBG解算位置的对比,15.0 mm螺钉测试数据如表1所示,20.0 mm螺钉测试数据如表2所示。
Force
/NPosition deviation/mm Error FBGs Lidar 20 0.24 0.21 14.2% 40 0.49 0.44 11.4% 60 0.75 0.68 10.3% 80 0.97 0.89 8.98% 100 1.25 1.16 7.75% Table 1. Comparison of position deviation of 15.0 mm screws
Force
/NPosition deviation/mm Error FBGs Lidar 20 0.43 0.39 10.2% 40 0.78 0.72 8.3% 60 1.37 1.25 9.6% 80 1.85 1.69 9.5% 100 2.19 2.02 8.5% Table 2. Comparison of position deviation of 20.0 mm screws
由表1可知,当外部应力增大的时候,位置偏移量也随之增大,采用FBG的平均解算精度约为0.012 3 mm/N,而采用激光雷达测试得到的结果为0.0113 mm/N,可见,采用光纤传感获得的位置变化程度与激光雷达测试结果相近。
由表2可知,相比15.0 mm螺钉而言,20.0 mm螺钉在相同外部应力作用下产生的位置偏差更明显,采用FBG的平均解算精度约为0.0221 mm/N,而采用激光雷达测试得到的结果为0.0202 mm/N,说明结构体越长,得到的应变响应程度越明显。同时,相对误差精度可有所提高。对比两次测试还可以发现,偏移程度的增加虽然会改变偏移比率,但是整个过程始终保持线性变化,这样就保证了测试系统在整个拟合曲线上测试结果的稳定性。进一步验证了该方法的可行性。
Intelligent assembly system of industrial production line based on optical fiber sensing
doi: 10.3788/IRLA20210695
- Received Date: 2021-12-25
- Rev Recd Date: 2022-02-18
- Available Online: 2022-11-02
- Publish Date: 2022-10-28
-
Key words:
- optical fiber network /
- industrial production line /
- intelligent assembly /
- decoupling algorithm
Abstract: The intelligent assembly technology of the industrial production line was a key means to improve the work efficiency of the production line and ensure the uniformity of the products. Increasingly complex industrial product structures have higher requirements for intelligent assembly control accuracy. Among them, feedback correction technology based on real-time online measurement has become a research hotspot. In order to realize the flexible measurement of the intelligent assembly process of industrial production lines, a feedback assembly control method based on optical fiber sensing was proposed. The system uses multiple FBG sensors to obtain the real-time strain of the assembly structure, and the temperature strain decoupling was completed by different packaged FBG sensors. Finally, the conversion of the degree of position deviation was completed by the way of neural network learning, and real-time correction of the assembly position was realized. Matlab was used to simulate the screw structure assembly process, and the stress distribution of screws with different lengths and force levels was simulated. The results show that the longer the screw length, the greater the strain under the same force. And the main strain of the screw is concentrated on the edge of the screw hole. In the experiment, the cantilever beam strain calibration experiment is used to obtain the fitting curves of different package states, the temperature calibration experiment is used to eliminate the temperature drift effect in the strain test data, and the position shift experiment is used to obtain the correction parameters. The results show that for a screw with a length of 15.0 mm, the average resolution of the system is about 0.012 3 mm/N, and for a screw with a length of 20.0 mm, the average resolution of the system is about 0.022 1 mm/N, and it has good linearity.