基于嵌入式Linux平台的球栅尺数显表设计

Design of DRO of Ball Grid Scale Based on Embedded Linux Platform

球栅尺数显表是一种测量球栅尺输出,并计算、显示位移的仪表。文中设计了一款液晶显示的、基于嵌入式Linux平台的多通道高性能球栅尺数显表,该数显表采用基于Cortex A8内核的AM3517为主处理器,FPGA为协处理器的架构方式,设计了基于Qt的图形用户界面。所设计的数显表同时支持4路模拟或数字球栅尺读数头的输入,并且各路读数头的参数可通过图形用户界面独立地进行在线配置。测试结果表明,所设计的多通道数显表可以达到1μm分辨率,测量误差在#10μm范围内,且数值显示稳定,跟踪速度快,支持零点搜索和掉电自动追数等多种实用功能,同时用户交互界面友好,满足高精度数控机床的应用需求。

A digital readout system （DRO） is an instrument which generates the excitation signal for ball grid scale and receives the re- sponse signal. Then the displacement is calculated and displaced by the DRO according to the received signal. In this paper, a multi-chan- nel high-performance DRO based on embedded Linux platform is presented, where LCD is selected as the display device. The DRO a- dopts a framework of ARM plus FPGA, where AM3517 with Cortex A8 core is acted as the main processor and FPGA works as a copro- cessor. Also a graphical user interface based on Qt is implemented. The designed DRO can drive four reading heads, and each reading head can be analog or digital. The parameters of each reading head can be configured independently through a graphical user interface on- line. Test results show that the designed DRO has display resolution of 1 um and the measurement error is limited between -10 um and 10 um. The numerical display of DRO is stable and can track the rapid movement of the scale. The designed DRO supports a variety of useful features, such as zero search and automatic recovery from unexpected power down. Besides the DRO also has a friendly user interface. All these features meet the application requirements of high-precision CNC machine tools.