模糊自适应PID算法在核磁共振谱仪样品旋转控制系统中的应用

Implementation of Fuzzy Self-tuning Proportional Integral Derivative Controller on Sample-tube Spin Control System in Nuclear Magnetic Resonance Spectrometer

在核磁共振(NMR)实验中,样品旋转能够有效消除XY方向磁场的部分不均匀性,从而提高信号分辨率。在商用NMR谱仪中,一般采用PID算法进行待测样品的旋转控制。由于被控对象具有一定的非线性,存在着调节时间较长,稳定后存在误差等缺点。针对该现象,在Varian 500 MHz波谱仪气路系统的基础上,设计一套新的控制电路,在控制方法上引入了模糊PID控制,经过多次实验调试、优化处理,定制了适用于NMR谱仪气控系统的模糊参数隶属函数和模糊规则,设计出一种模糊自适应PID控制算法。结果表明,本系统较原系统稳定时间缩短了约30 s。在相同的实验环境下采样,本系统得到半高宽均值为1.27 Hz,信噪比为2293,优于Varian气控系统采样所得的结果,增强了旋转控制的鲁棒性,加快了响应速度和稳定速度,具有较高的应用价值。

In commercial nuclear magnetic resonance（NMR） spectrometer,a PID controller is generally used to regulate the rotation of samples.There are some faults such as long adjustment time,steady-state error because of the nonlinear character of the object.To improve system performance,a new pneumatic controller system was proposed by using self-tuning fuzzy proportional-integral-derivative（PID） controller to replace the original pneumatic system based on PID.The adjustment time of proposed controller is about 30 s shorter than that of Varian.The result of the experiment under the same environment shows that the half-height width after applying the proposed controller is 1.272 better than 1.396 of Varian and S/N is 2293.114 better than 2245.48 of Varian.The experiment result shows that the proposed controller is robust,quicker response and has great value for application and research.