A Three Axis Motion Control System For Micro-nano-coornidate Measuring Machine Based On DSP

The rapid development of today's ultra-precision machining technology has led to the birth of micro-nano CMM,one of the key technologies in which is high-precision positioning.A motion control system is designed with DSP processor as the control core.The system is composed of ethernet communication,displacement measurement,motion control and other modules.The Ethernet communication module as a communication bridge between the PC and the DSP is developed.The Displacement measurement module can realize the displacement measurement by counting and subdividing the orthogonal sinewave signal which produced by the displacement sensor.The Motion control module can reach nano scale positioning at last.The paper mainly done the following several works:(1)In order to exchange data between upper and lower computer,this study used RTL8019 AS which is a dedicated network control chip,to expand the Ethernet communication function of DSP control system,and also designed Ethernet communication software,and finally realized data communication between PC and DSP in high speed.(2)The displacement measurement module in this DSP system adopted a combination of hardware counting and software subdivision.The hardware counting part used a special counting chip to count large numbers of signals larger than one quarter of a cycle to obtain large number of shifts.For less than a quarter cycle of the signal,phase subdivision was executed to get the decimal shift by software,and finally adding the both could get the total displacement.(3)The design of hardware circuit of motion control module is completed.The high-precision positioning control software was compiled using the PID control algorithm with adaptive characteristics based on BP neural network,and AC,GATE,DC modes which are provided by the drive motor.(4)The various hardware module were integrated and a four-layer board was used to complete the drawing of this DSP motion control system circuit board.Using this DSP control system to do the positioning control test on the X and Y axes of the micro-Nano coordinate measuring machine which developed by the laboratory.The experimental results showed that the positioning error is better than 36 nm and the standard deviation is less than 20 nm under X-axis.The positioning error is better than 45 nm and the standard deviation is less than 31 nm under Y-axis.Experiments show that the designed DSP control system can achieve the positioning accuracy not less than the PC achieved.