High-precision Time Measurement And Control System Based On TDC-GPX

Time-interval measurement technology has played an important role in basic scientific research and practical engineering applications,so research for high-precision time interval measurement technology is significant. This paper comes from laboratory project, intended to design a time measurement and control system in laser ranging field, the system has advantages of high accuracy, wide measuring range, small size, high cost and flexibility.Firstly,this paper introduces the overall architecture of the system, according to the functions and requirements the whole system is divided into four sub-modules, then this paper introduces the software and hardware design process of four sub-modules respectively. Timing generation module is designed to control delay pulse generation time and pulse width in real time, the pulse is used to turn on the laser receiver, this module achieves nanosecond precision delay using FPGA internal clock. Time interval measurement module is designed to measure the laser time of flight based on TDC-GPX chip of German ACAM Company. According to the desired measurement accuracy and range, peripheral hardware circuit and software program is designed based on G-mode. The resolution of this module is 40 ps, the measuring range is 50 us. In 10 us range, the jitter of test data is less than 100 ps. In the range of 10 us to 50 us, the jitter of test data is less than 400 ps. GPS timing module is designed to add a time stamp based on Compass BD-126 module, and to achieve accuracy requirements the module uses FPGA internal clock and second pulse signal to implement timer. In the range of less than 50 ms, the module timing error is less than 8us. Motor and encoder control module takes sample of grating encoder output pulse using STM32 timer encoder mode and captures trigger signal, the sampling resolution is 0.0146 degrees. Motor is controlled to turn alternately positive and negative 30 degrees using the position control modeFinally, actual functional testing and performance analysis are made for each sub-module of the system. Test results show that the system is proper functioning and all the performances meet the expectations.