Auto-tuning of cascade controlled open-loop unstable reactors

Continuous stirred tank reactors (CSTRs) can present operational problems due to complex open-loop behavior such as input and output multiplicities, parametric sensitivity, nonlinear oscillations, etc. There are a number of cases In which It is appropriate to operate a chemical reactor at an unstable steady-state. Traditionally, auto-tuning procedures for cascade control strategies are applied using a sequential, one-loop-at-a-time method. Such a method, however, cannot be used on open-loop unstable systems because the secondary loop cannot stabilize the system when primary loop is open. As a result, we develop a simultaneous auto-tuning procedure. This new method can also be used to auto-time cascade controlled open-loop stable systems, thereby covering the entire range of operation for a CSTR.