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宽幅变温差示扫描量热仪温度控制方法研究与应用
Alternative TitleTemperature Control Method of Wide Range Variable Differential Scanning Calorimeter
郁洋1,2
Department数字工厂研究室
Thesis Advisor胡静涛
Keyword高精度差示扫描量热仪温度控制 前馈-反馈复合控制 冷热协同控制 DMC-PID串级控制
Pages111页
Degree Discipline检测技术与自动化装置
Degree Name博士
2019-05-24
Degree Grantor中国科学院沈阳自动化研究所
Place of Conferral沈阳
Abstract差示扫描量热仪温度控制问题是典型的非线性复杂动态系统的控制问题,具有较强的非线性、滞后和非对称性等特性,传统的线性控制方法无法实现宽幅变温下高精度控制要求。本文基于差示扫描量热原理,针对其温度控制特点,研究适用于宽幅变温和高精度要求下的温度控制方法,论文主要贡献包括以下内容:(1)针对差示扫描量热仪温度模式下不同的控温手段,基于瞬态平衡原理分别建立了不含液氮降温的DSC传热模型和带有液氮降温的传热模型,并分析了模型特性对温度控制的影响,对控制方法的研究提供理论指导。(2)针对高温区恒速升温控制问题,提出了双前馈-反馈复合多控制器方法。针对被控对象滞后特性引起的响应时间长和外部环境温度变化对炉内温度的扰动问题,利用前馈控制中精确控制的特点,分别设计环境温度前馈补偿控制器和设定值输入前馈控制器,有效减小调节时间,提高控制系统的控制精度和鲁棒性。针对被控对象非线性特性,将温度区间划分为若干近似线性子区间,在每个线性子区间设计PID控制器,将多个PID控制器组合起来形成多控制器方法。针对多控制器方法中不同温度区间控制器切换引起的控制量突变的问题,引入平滑滤波因子,实现不同温度区间的控制作用的缓慢过度。(3)针对高温区恒速升温过程的静差问题,从温度控制准确度的要求出发,基于预测控制算法超前预测和最优控制的特点,提出一种基于DMC的高温区恒速升温过程无静差控制方法。在主回路采用DMC控制器,通过预测控制器实现测量值与设定值无静差控制,改善控制系统的跟踪特性。副回路采用PID控制器,通过PID控制器的闭环反馈,加快被控对象的动态响应,改善被控对象的线性度和对参数变化的敏感性。预测控制器控制由PID控制器与DSC加热炉组成的广义对象,动态响应的加快减小了预测模型长度,减小了预测控制器的运算量。针对滞后特性引起预测控制器的过度调节问题,引入滞后参考轨迹的方法,对参考轨迹以滞后时间为基准进行移动,优化过程弥补了时滞带来的影响,系统输出平滑,稳定时间短,稳定时系统温度低。(4)针对低温区温度控制问题,提出基于液氮前馈的冷热协同温度控制方法。由于液氮冷却手段的加入,出现了控制液氮降温和加热丝升温的多周期协同控制问题。考虑到液氮的成本较高和液氮电磁阀控制精度低的问题,从能量平衡角度出发,由恒速降温所需的能量与控制量关系设计前馈控制器进行开环控制,同时,引入加热丝闭环控制,通过加热丝的快速调节作用实现精细控制,对扰动及其他因素引起的误差进行反馈补偿,形成以液氮前馈控制为主,加热丝反馈控制为辅的冷热协同复合多控制器系统,从而在保证控制精度的基础上达到减小电能和液氮消耗的目的,进而实现了满足热分析功能的宽幅变温要求。(5)在所研究控制方法的基础上,设计了差示扫描量热仪温度控制的硬件系统和软件架构,并在原理样机上进行了温度控制结果的检测,验证了本文所提方法有效性和实用性。
Other AbstractDifferential scanning calorimeter temperature control is a typical nonlinear complex dynamic system control problem. It has strong non-linearity, hysteresis and asymmetry. Traditional linear control method can not meet the requirements of high precision control in wide range and variable temperature. Based on the principle of differential scanning calorimetry and the characteristics of its temperature control, this paper studies the temperature control method which is suitable for wide range temperature change and high precision requirements. The main contributions of this paper include the following: (1) Based on lumped parameter method, the heat transfer mechanism of differential scanning calorimeter heating furnace is analyzed, and the lumped parameter model of differential scanning calorimeter is established. On the basis of step response test data and least square identification method, the step response model of differential scanning calorimeter is established and its non-linear characteristics are analyzed. (2) To solve the problem of constant temperature rise control in high temperature region, a double feed-forward-feedback composite multi-controller method is proposed. Aiming at the problem of long response time and disturbance caused by external ambient temperature change due to the lag characteristic of controlled object, the feedforward compensation controller of ambient temperature and the input feedforward controller of setting value are designed respectively according to the characteristics of precise control in feedforward control, which can effectively reduce the adjustment time and improve the control accuracy and robustness of the control system. In view of the non-linear characteristics of the controlled object, the temperature interval is divided into several approximate linear sub-intervals, and the PID controller is designed in each linear sub-interval, which combines multiple PID controllers to form a multi-controller method. In order to solve the problem of sudden change of control variables caused by controller switching in different temperature ranges, a smoothing filter factor is introduced to realize the slow and excessive control effect in different temperature ranges. (3) Aiming at the static error problem of constant-speed heating process in high temperature zone, a DMC-PID cascade control method is proposed based on the characteristics of predictive control algorithm, advanced prediction and optimal control, according to the requirement of temperature control accuracy. The predictive controller is used in the main loop of the control system. The predictive controller is used to control the measured and set values without static error and improve the tracking characteristics of the control system. Secondary loop adopts PID controller, through closed-loop feedback of PID controller, the dynamic response of the controlled object is accelerated, and the linearity of the controlled object and its sensitivity to parameter changes are improved. The predictive controller controls the generalized object composed of the PID controller and the DSC heating furnace. The acceleration of dynamic response reduces the length of the predictive model and the amount of calculation of the predictive controller. Aiming at the problem of over-regulation of predictive controller caused by lag characteristics, the method of lag reference trajectory is introduced to move the reference trajectory on the basis of lag time. The optimization process compensates for the effect of lag. The output of the system is smooth, the stabilization time is short, and the system temperature is low when the system is stable. (4) To solve the problem of temperature control in low temperature zone, a temperature control method based on liquid nitrogen feedforward is proposed. Due to the addition of liquid nitrogen cooling means, the control system is a two-in-one-out non-square multi-variable control system to control liquid nitrogen cooling and heating wire heating. The existence of control input multi-solutions leads to the optimization of control system equilibrium point distribution, resulting in the waste of power and liquid nitrogen. Considering the high cost of liquid nitrogen and the low control precision of liquid nitrogen solenoid valve, from the point of view of energy balance, a feedforward controller is designed based on the relationship between energy and control quantity required for constant speed cooling. At the same time, a closed-loop control of heating wire is introduced to realize fine control through the fast adjustment of heating wire, and feedback compensation for errors caused by disturbances and other factors is made. A multi-controller system with liquid nitrogen feed-forward control and heating wire feedback control is formed, which can reduce power consumption and liquid nitrogen consumption on the basis of ensuring control accuracy, and then meet the requirements of wide range temperature variation of thermal analysis function. (5) On the basis of the control method studied, the hardware and software architecture of temperature control for DSC are designed, and the temperature control effect is tested on the prototype, which verifies the effectiveness and practicability of the method proposed in this paper.
Language中文
Contribution Rank1
Document Type学位论文
Identifierhttp://ir.sia.cn/handle/173321/25161
Collection数字工厂研究室
Affiliation1.中国科学院沈阳自动化研究所
2.中国科学院大学
Recommended Citation
GB/T 7714
郁洋. 宽幅变温差示扫描量热仪温度控制方法研究与应用[D]. 沈阳. 中国科学院沈阳自动化研究所,2019.
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