The Research Of Time Synchronization Based On GPS And High-accuracy Real-Time Clock

Time synchronization plays a significant role in power system, industrial control, measurement and other engineering fields. Several main methods of time synchronization are GPS time synchronization technology, Ethernet technology, network time protocol synchronization technology. Different methods have advantages and disadvantages, and behave well in different environments.Matching of objects with same features is always a big problem in the field of binocular stereo vision, especially under the condition of bad imaging environment or image quality. Images with absolute time messages behave much better in matching, while it is a precondition that objects with same features must be in the same time zone of several milliseconds. Computer time synchronization is extremely needed by binocular vision matching.This paper put forward a method of computer time synchronization based on GPS receiver and high accuracy real-time clock. This method needs no atomic clock, expensive clock devices, nor network with top quality. It can achieve a rather good synchronization accuracy with a low price and simple device.The GPS receiver with enough positioning satellites can output PPS(Pulse per Second) signal with high accuracy time message, whose error is no more than dozens of nanoseconds. The falling edge of the PPS represent the very moment of each integral second's beginning. As the time source of the target computer, high accuracy real-time clock(RTC) can keep the high accuracy of the time, after obtain the accurate time from GPS receiver. It drifts ±7.2ms per hour. The computer acquires the time information from the time source through the serial port, which cost some time. But the time delay can be measured by imitating the method of Precision Time Protocol. After compensation, the computer achieves high accuracy time synchronization. PPS generated by computer serial port when an integral second arrives at the computer timeline, can be compared with the PPS of the GPS receiver. The phase difference represents the accuracy of the synchronization. According to the experiments, the accuracy of the method put forward in this paper can be less than 500 microseconds.In the problems in binocular vision matching, after applying this time synchronization method, computers get real-time accurate synchronized time for the images captured by the cameras. Time sequences, determined by the absolute time are the first precondition of binocular matching of vision problems. Under this condition, the matching results and efficiency are much better than before.