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Configuration of MPC with Slave Controller
4.3Commissioning
The parameterization of the controller and the commissioning is done „from interior to exterior” as in any cascade control. First the slave controller is tuned (see chap- ter 3) and switched to automatic mode. Afterwards the slave controller is switched to cascade mode and the master controller is parameterized. While tuning the mas- ter controller please consider that the whole inner closed control loop of the slave controller is the controlled process of the master controller. Therefore the adjust- able parameters of the master controller are not independent of the tuning of the slave controller. The step experiments for the identification of the MPC models can only be executed after the linking of the stabilizing slave controller, as the addi- tional
A dead band can be used in the slave controller, if the level is not to be exactly controlled to its set point. The controller has no reason to interfere with the process as long as the controlled variable is inside the dead band. The control deviation seems to be zero for the controller. Therefore, the control signal can be smoothed to avoid valve wear, and variations of the drain flow can be reduced to obtain a smooth feed for the downstream process components. The dead band should be adjusted before the measurement data for the MPC configurator is recorded, as the dead band influences the behaviour of the slave control loop. A dead band of at least the same size must also be specified for the corresponding control channel of the master controller. Of course, the master controller is not able to reach the set point more precisely as it is allowed by the dead band of the slave controller.
18 | MPC Level |
V 1.0, |