航空底片测试仪的恒张力数字控制系统研制

Tensioning digital control system for aerial negative film tester

在航空底片测试仪的运动过程中,底片张力的变化对底片的位移和定位精度影响很大,从而导致测试结果的稳定性。在对测试仪传动机构的运动学和动力学分析的基础上,建立了全数字闭环控制模型。为了实现张力的实时采样和控制,采用数字信号处理技术(DSP)控制底片在运动过程中的张力,使张力趋于设定的最佳值。使得测试仪获取稳定的、真实的图像数据,为正确测评航空感光胶片成像质量提供了基础。实验结果表明底片平均移动速度最高可达到23m/min;张力设定范围是Fmin=0N,Fmax=30N;张力变化控制量为ΔF=±0.05N;重复定位精度为±10μm;满足了设计要求。

The accuracy of displacement and location of the negative is greatly affected by the change of its tension in the aerial negative film tester. Based on the kinematics and dynamics of the transmission mechanism, a control model was built by means of DSP (digital signal processing) to carry out the real time control of the tension when the negative is in motion. The fixed tension guarantees the stability of the system and the requirement to the accuracy standard, which makes possible for the tester to get the real image data. It lays a good foundation for the accurate testing of aerial negative film. The highest moving speed of the negative is 23 m/min, the range of tension is from F_(min)=0 N to F_(max)=30 N, the variety of controlled tension is ΔF=±0.05 N and the repeating orientation precision of the tester is ±10 μm,which meet the design requirements.