【作者】 李丙林；

【导师】 尤文；

【作者基本信息】 长春工业大学 ， 机械工程， 2019， 博士

【摘要】 超临界流体萃取是以高压、高密度的超临界流体为萃取剂,从液体或固体中提取高沸点或热敏性的有效成分,以达到分离或纯化为目的的一项新型提取技术。超临界流体萃取是一种无污染提取技术,被广泛应用在食品和化学工业。超临界流体萃取技术虽然在许多方面已得到应用,但还远没有发挥其应有的作用。萃取过程中溶剂萃取性能受温度、压力、流量等参数的影响。本文以CO₂超临界萃取过程为研究对象,针对温度和压力两个被控变量的建模、优化与控制问题进行了深入研究,主要研究内容与创新工作如下:第一,采用非等间隔灰色优化模型描述非线性温度-压力模型的线性部分;使用Peng-Robinson状态方程描述非线性温度-压力模型的非线性部分。讨论了非线性温度-压力模型的输入输出解耦条件,提出了此类系统的状态与输出变换方法,使不可输入/输出解耦系统转变为可干扰解耦系统,实现了温度和压力的完全解耦,并对其进行了解耦PID控制。第二,针对超临界流体萃取过程中的参数优化问题,开展了基于径向基神经网络的预测分析技术研究,利用超临界流体萃取实验中所测得的实际数据,以萃取压力、萃取温度和CO₂流量组成三维特征向量,以实际萃取率为标签值训练径向基神经网络,并应用训练好的神经网络搜索优化的SFE生产参数。第三,使用传递函数和状态空间方法分析了线性自抗扰控制中扩张状态观测器标准化改造的解析结果,使用根轨迹工具分析了改造结果随对象参数不同时的特性变化,使用伯德图分析了PD控制器的控制效果,给出了自抗扰控制器的一些分析结论和参数整定原则,为线性自抗扰控制器的应用提供了理论基础。第四,提出了温度与压力的自抗扰控制方法,讨论了控制器设计和参数整定的方法。当存在外部正弦或混沌扰动时,温度PID控制无法实现温度的稳定控制,压力PID控制虽然可以实现压力的稳定控制,但出现较大波动。当存在较宽频率的正弦扰动时,自抗扰控制器也可以实现温度与压力的稳定控制,温度残差始终小于0.1℃,且随着干扰频率增加而降低,具有良好的扰动抑制能力,性能优于PID控制。最后,总结了全文所做的工作,提出了今后需要进一步研究的问题。更多还原

【Abstract】 Supercritical fluid extraction,which is a new extraction technology,can extract the effective components with high boiling point or heat sensitivity from liquid or solid with high pressure and high density supercritical fluid as extraction agent.Supercritical fluid extraction is a pollution-free extraction technology,which is widely used in food and chemical industry.The study on supercritical fluid extraction has been developed rapidly and got some achievements in many fields,however,there are still many problems need to be further researched and discussed.In the separation process,the solvent extraction performance has been affected by temperature,pressure,flow and other parameters.In this paper,a CO₂ supercritical extraction process is taken as the research object to conduct an in-depth study on the modeling,optimization and control of temperature and pressure,which are the two controlled variables in this system.The main research contents and the innovation work in this paper are shown as follows:First,the linear part of the nonlinear temperature-pressure model can be described by non-equidistant grey optimization model.Peng-Robinson equation of state is used to describe the nonlinear part of the temperature-pressure model.Discussing the input/output decoupling condition of the nonlinear temperature-pressure system,a state and output transformation method of this class of system is proposed in this work.It can transform a input-output decoupling system into a disturbance decoupling system to realize the complete decoupling control of temperature and pressure.The decoupling PID controls of the nonlinear temperature-pressure model can be implemented in this work.Second,for the problem on parameters optimization of supercritical fluid extraction,RBF neural network prediction technology has been researched.With the data measured in experiment,a vector,which consists of pressure,temperature,and CO₂ flow rate,is constructed to train RBF neural network for predicting extraction rate with different process parameters.Third,using transfer function and state space method to analyze the analytical results of extended state observer in the standardization transformation in linear active disturbance rejection control,using the root locus to analyze the characteristics of transformation results with different parameters,using the Bode diagram to analyze the control effect of PD controller,some conclusions and parameters setting principles are given to provide the theoretical basis for active disturbance rejection controller.Fourth,discussing the methods of the controller disign and parameter turning,an active disturbance rejection controller is proposed.While there is external sinusoidal or chaotic disturbance,temperature PID control can not achieve temperature stability control.Although pressure PID control can achieve pressure stability control,there is a big fluctuation.While there is a wide frequency sinusoidal disturbance,active disturbance rejection controller can achieve stability control for temperature and pressure with the small residual and good disturbance suppression ability.The temperature residual is always less than 0.1℃and decreases with the increase of interference frequency.The performance of the active disturbance rejection controller is better than PID control.Finally,the main content of this dissertation is summarized,and further works are discussed.更多还原