Abstract:

Chemical process startup is mostly a heating process, to satisfy the requirements of speed and stability,some researchers proposed Bang-Bang control combined with other control method for controlling the heating process, but due to strict requirements of Bang-Bang control on switching time and switching point, its practical application is not satisfactory. So based on Bang-Bang control, a buffer heating stage was added. Then the temperature control process could be divided into four parts: full width, zero brake, buffer heating and PID control. The rate of change of temperature was used as switching variable between buffer heating and PID control. In addition, modified switch control was converted to nonlinear programming problems, and switching points of the first three parts were optimized. Simulation comparison revealed that the control method not only avoided the problem caused by inproper selection of switching times and switching points, but overshoot was small and the process could be stabilized quickly.

Key words: process control, process startup control, modified switch control, nonlinear programming

摘要：

化工过程的开工大多表现为一个升温过程。为满足升温过程的快速性而又不失稳定性的要求,有学者提出将时间最优Bang-Bang控制与其他控制方法结合来控制升温过程,但由于Bang-Bang控制对切换次数和切换点要求严格,致使其在实际应用中不够理想。在Bang-Bang组合控制的基础上引入缓冲升温控制,将整个控制系统分为4部分:全幅升温、全幅降温、缓冲升温、PID控制。将温度变化率作为缓冲升温与PID控制的切换变量,将修正切换控制问题等价为非线性规划问题,优化选取全幅升温、全幅降温、缓冲升温最优切换时间点。实例对比分析表明,该切换开工控制方案不仅避免了因切换次数与切换点选取不当导致的不良问题,且超调小,稳定快。

关键词: 过程控制, 开工控制, 修正切换控制, 非线性规划