Using the NARMA-L2 Controller Block :: Control Systems (Neural Network Toolbox)

Neural Network Toolbox

Using the NARMA-L2 Controller Block

This section demonstrates how the NARMA-L2 controller is trained.The first step is to copy the NARMA-L2 Controller block from the Neural Network Toolbox blockset to your model window. See your Simulink documentation if you are not sure how to do this. This step is skipped in the following demonstration.

A demo model is provided with the Neural Network Toolbox to demonstrate the NARMA-L2 controller. In this demo, the objective is to control the position of a magnet suspended above an electromagnet, where the magnet is constrained so that it can only move in the vertical direction, as in the following figure.

The equation of motion for this system is

where is the distance of the magnet above the electromagnet, is the current flowing in the electromagnet, is the mass of the magnet, and is the gravitational constant. The parameter is a viscous friction coefficient that is determined by the material in which the magnet moves, and is a field strength constant that is determined by the number of turns of wire on the electromagnet and the strength of the magnet.

To run this demo, follow these steps.

Start MATLAB.
Run the demo model by typing narmamaglev in the MATLAB command window. This command starts Simulink and creates the following model window. The NARMA-L2 Control block has already been placed in the model.

Double-click the NARMA-L2 Controller block. This brings up the following window. Notice that this window enables you to train the NARMA-L2 model. There is no separate window for the controller, since the controller is determined directly from the model, unlike the model predictive controller.
Since this window works the same as the other Plant Identification windows, we won't go through the training process again now. Instead, let's simulate the NARMA-L2 controller.
Return to the Simulink model and start the simulation by choosing the Start command from the Simulation menu. As the simulation runs, the plant output and the reference signal are displayed, as in the following figure.

NARMA-L2 Controller Model Reference Control