【摘要】 为保证安全性与快速性,大型超导磁体预冷过程中需要通过冷热氦气混合来严格控制温差与压降。大型氦低温系统中这一冷热氦气混合过程具有双变量强耦合、非线性以及迟延等难控特性。为实现其自动控制,通过过程的动态特性、系统关联以及控制逻辑分析,设计了分阶段的解耦控制方案。根据相对增益计算,得出弱耦合阶段的变量匹配控制方案;强耦合阶段采用非线性乘法解耦器、不同频率的采样调节器、带有死区的非线性PID控制算法及增益调度进行解耦控制。该方案在DCS中易于实现,可用于超导磁体的降温与回温控制。实际运行结果表明,解耦后系统有较好的稳定性与鲁棒性,温差控制及时且超调量小,在确保冷却装置安全的同时又保证了降温速率,很好地满足了降温实验需求。更多还原

【Abstract】 In order to ensure its safety and speed,the temperature difference and pressure drop should be stricdy controlled via cold and hot helium gas mixing in precooling process of the large-scaled superconductive magnets.This process in the large helium cryogenic system has some hard-controlled characteristic such as the strong coupling,nonlinear and time delay.To realize its automatic control, a grading decoupling control scheme was designed by means of analyzing process dynamics,system coupling and control logic.According to the calculation of relative gain,the variable matching is adopted in the week coupling phase,and a nonlinear decoupler,sampling controllers with different frequencies,nonlinear PID control arithmetic with dead band and gain scheduling were adopted in the strong coupling phase.The scheme is easy to implement on DCS,and can be applied to the cool-down and warm-up control of the magnets. The real running result shows that the decoupled system has a nice stability and robustness.The temperature difference control is in time and has less overshoot,which ensure the safety of the cooled devices as well as the cool-down rate and well meet the requirement of the cool-down experiment.更多还原