MPC Designer: Simulation Scenario Dialog Box

Configure simulation settings, specify output signal setpoints, and define disturbance signals on the MPC Designer Simulation Scenario dialog box.

Simulation Settings

Configure the following simulation settings:

Plant used in simulation — In the drop-down-list, select the plant to use in the simulation. You can simulate controllers against:
- Their own internal model, which is the default option. In this case, each controller is simulated with no plant/model mismatch.
- A plant from the Plants section of the Data Browser. In this case, all controllers are simulated against the same plant with potential plant/model mismatches.
Simulation duration — Specify the simulation duration using the indicated time units. The default duration is 10 time units.
Run open loop simulation — To simulate the open-loop response of the plant model to input signal changes, check this option.
Use unconstrained MPC — To ignore all controller constraints during the simulation, check this option.
If your application allows you to anticipate trends in reference signals or measured disturbances, you can use signal previewing to improve reference tracking or measured disturbance rejection.
- Preview references — To enable signal previewing for all output setpoints, check this option.
- Preview measured disturbances — To enable signal previewing for all measured disturbances, check this option.
For more information, see Signal Previewing

Input and Output Signal Tables

For each input and output signal, select a signal type from the Signal drop-down list, and specify the signal properties.

Note

You can modify the Nominal signal values in the Input and Output Channel Specifications dialog box. To open this dialog box, in MPC Designer, on the MPC Designer tab, in the Structure section, click I/O Attributes.

Signals and Disturbances for Closed-Loop Simulations

When you run a closed-loop simulation, you can specify the following signals:

Reference Signals — Specify setpoints for each output signal. If you specify a zero weight for an output in the controller settings, the reference signal for that output is ignored.
Measured Disturbances — Specify the properties of each measured disturbance input. If your defined MPC structure does not include measured disturbances, this table is not displayed in the dialog box.
Unmeasured Disturbances — Specify the properties of each unmeasured disturbance input. If your defined MPC structure does not include unmeasured disturbances, this table is not displayed in the dialog box.
Output Disturbances — Specify output disturbance signals. These disturbances are added to each measured output during the simulation.
Load Disturbances — Specify manipulated variable load disturbances. These disturbances are added to each manipulated variable during the simulation.

Signals and Disturbances for Open-Loop Simulations

When you select the Run open loop simulation option, you can specify the following signals:

Manipulated Variables — Specify manipulated variable input signals.
Measured Disturbances — Specify the properties of each measured disturbance input. If your defined MPC structure does not include measured disturbances, this table is not displayed in the dialog box.
Unmeasured Disturbances — Specify the properties of each unmeasured disturbance input. If your defined MPC structure does not include unmeasured disturbances, this table is not displayed in the dialog box.

Signal Types and Settings

Depending on the signal type, specify the following signal properties:

Size — S
Time — T
Period — P

The meaning of each of these properties depends on the signal type.

For each signal type, the initial value at the start of the simulation, y₀, is the value specified in the Nominal column.

Constant

The signal remains at its initial value for the entire simulation.

$y = y_{0}$ for $t \geq 0$

Step

Before time T, the signal is equal to its initial value. At time T, the signal changes step-wise by S units. The signal remains at this new value during the simulation.

$y = y_{0}$ for $0 \leq t < T$
$y = y_{0} + S$ for $t \geq T$

Ramp

Before time T, the signal is equal to its initial value. At time T, the signal begins to vary linearly with slope S.

$y = y_{0}$ for $0 \leq t < T$
$y = y_{0} + S (t - T)$ for $t \geq T$

Sine

Before time T, the signal is equal to its initial value. At time T, the signal begins to vary sinusoidally with amplitude S and period P.

$y = y_{0}$ for $0 \leq t < T$
$y = y_{0} + S \sin [\frac{2 π}{P} (t - T)]$ for $t \geq T$

Pulse

Before time T, the signal is equal to its initial value. At time T, a square pulse of duration P and magnitude S occurs.

$y = y_{0}$ for $0 \leq t < T$
$y = y_{0} + S$ for $T \leq t < T + P$
$y = y_{0}$ for $t \geq T + P$

Gaussian

Before time T, the signal is equal to its initial value. At time T, the signal begins to vary randomly about y₀ with standard deviation S.

$y = y_{0}$ for $0 \leq t < T$
$y = y_{0} + S w (t)$ for $t \geq T$

where, w(t) is a random Gaussian white noise signal with zero mean and unit variance.

Apply Scenario Settings

Click OK to update the scenario settings and close the dialog box. The app runs the simulation and the input/output response plots update to reflect the new scenario settings. To update the scenario settings and run the simulation without closing the dialog box, click Apply.