科氏质量流量计全数字闭环系统的设计与实现

Design and realization of all digital closed-loop system of Coriolis mass flowmeter

科氏质量流量计(CMF,Coriolis Mass Flowmeter)全数字闭环系统,采用现场可编程门阵列(FPGA,Field Programmable Gate Array)和现代数字信号处理方法对CMF传感器进行稳定精确的闭环控制,实时性和精度较高.以高速并行器件FPGA为运算和控制核心,在相位控制中引入FIFO(First In First Out)组件,通过控制FIFO的读、写请求信号来改变时间差,实现对拾振和激励信号的相位差准确、稳定的控制;采用不连续和连续幅值控制相结合的非线性幅值控制方法,快速、准确地设定幅值,适应性强,实现对拾振信号幅值的良好控制,并控制拾振信号以稳定的幅值输出,提高CMF的测量精度和稳定性.实流标定对比实验结果表明:CMF数字闭环在零点稳定性、动态响应特性和重复性方面都优于模拟闭环,并在一定程度上提高了CMF的测量精度.

The digital closed-loop system of Coriolis mass flowmeter（CMF）,in which the field-programmable gate array（FPGA） and digital signal processing methods were used to realize stable and accurate closed-loop control,has good real time and high precision.The speed parallel component FPGA was adopted as core of calculation and control.The first in first out（FIFO） module was brought in the phase control,which change time difference by controlling the read and write request signals of FIFO,to realize the stable and accurate control of phase difference between vibrating and exciting signal.The amplitude was set rapidly and precisely by using nonlinear amplitude control manner with well adaption,which combined discontinuous and continuous amplitude control.It gets the good amplitude control to the vibrating signals,which was output stable by controlling.The measurement accuracy and stability were improved.The experimental results show that the dynamic response and stability of the system is improved.From the real-flow calibration tests,that CMF digital closed-loop is better than traditional analogue closed-loop in stability,dynamic response and repeatability.Furthermore,the measuring precision of CMF is enhanced.