Adaptive Intensity Control For Multiple Infrared Optical Targets In Vision Measurement

With the development of aviation industy in China, a kind of technology of measurement which isflexible and convenient and suitable for real-time measurement on machining locale is urgently needed,The vision measurement system used in large-field is efficient to meet the demands. In this paper, anadaptive control system for luminance of multiple optical targets of infrared LED is design andimplementation as a subsystem of the vision measurement system, it is used for ensuring that imagingspot of LEDs can meet the requirement of measurement by controlling luminance of LEDs in themeasuring process.Resecch status of driving technology of optical targets is analysed, then combining with technicalrequirements of measurement in the process of aircaraft parts’ manufactuing and assembly, some keyproblems of adaptive control system is analysed, finaly, a LEDs control driver with MCU PIC16F873Aand chip MAX6964as its core components is designed. To meet the requirements of accuracy ofadjustment at close range and intensity of LEDs at large range, a push-pull circuit is used to driverLEDs directly, the circuit’s drive voltage is switched by a relay which controls initial adjustment ofLEDs’ luminous intensity. a PWM signal output circuit is designed in terms of the characteristics ofMAX6964’s output port, the PWM signal is used to further adjust the the luminous intensity of LEDs.On the one hand, the problem of the lack of MAX6964’s drive capability is solved; on the other hand,MAX6964’s multi-channel PWM signal is fully utilized. The LEDs control driver is controlled by a PC,the communication circuit is designed so that the communication between PC and LEDs control driveris set up by the RS-422serial interface or wireless in long-distance, and the means of communication isselected according to on-site environmental.Based on the analytical results of timing characteristics of modules in the vision measurementsystem, the interaction and communication protocols and logic of command response between PC andLEDs control driver are formulated, these are used to ensure the reliability and coordination andefficiency of the vision measurement. The programs of adaptive control system is designed, it includestwo parts, the first is microcontroller program, it contains serial receiver/transmitter module, LEDsdriver module, indication and alarm module, key-press modle etc; the second is PC program, it isembedded in the measuring software, control parameters of LEDs’ luminous intensity are produced byPC program according to the imaging spot of LEDs.Finally, the adaptive control system is verified by experiments，the result shows that the system isstable and reliable, the adjustment capacity of LEDs’ luminous intensity meets the dynamicmeasurement range from1.5meters to10meters.