A non-linear dynamic predictive device (60) is disclosed which operates
either in a configuration mode or in one of three runtime modes:
prediction mode, horizon mode, or reverse horizon mode. An external
device controller (50) sets the mode and determines the data source and
the frequency of data. In the forward modes (prediction and horizon), the
data are passed to a series of preprocessing units (20) which convert
each input variable (18) from engineering units to normalized units. Each
preprocessing unit feeds a delay unit (22) that time-aligns the input to
take into account dead time effects. The output of each delay unit is
passed to a dynamic filter unit (24). Each dynamic filter unit internally
utilizes one or more feedback paths that provide representations of the
dynamic information in the process. The outputs (28) of the dynamic
filter units are passed to a non-linear approximator (26) which outputs a
value in normalized units. The output of the approximator is passed to a
post-processing unit (32) that converts the output to engineering units.
This output represents a prediction of the output of the modeled process.
In reverse horizon mode, data is passed through the device in a reverse
flow to produce a set of outputs (64) at the input of the predictive
device. These are returned to the device controller through path (66).
The purpose of the reverse horizon mode is to provide information for
process control and optimization. The predictive device approximates a
large class of non-linear dynamic processes. The structure of the
predictive device allows it to be incorporated into a practical
multivariable non-linear Model Predictive Control scheme, or used to
estimate process properties.