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After you choose a proper dynamic system model, you must acquire the input and output data from the direct current (DC) servomotor. You then preprocess and use the data to estimate unknown coefficients of the dynamic system model. You can use an encoder or a DC tachometer to measure the shaft speed of the DC servomotor.
Set up the following experimental circuit to excite the DC servomotor and acquire response signals with an encoder.
Set up the following experimental circuit to excite the DC servomotor and acquire response signals with a DC tachometer.
Both circuits use an NI data acquisition (DAQ) card to generate digital stimulus signals. You also can use a reconfigurable I/O (RIO), CompactRIO, or Single-Board RIO device to generate the stimulus signals and acquire data. In these two circuits, a D/A output channel of the NI-DAQ card converts the stimulus signals to analog voltage signals and sends these signals to an amplifier. An A/D input on the NI-DAQ card acquires the original analog signals, converts the signals to digital signals, and records these digital signals for identification. The amplifier sends the enhanced analog signals to drive the DC servomotor. If you use an encoder to measure the shaft speed of the DC servomotor, the encoder generates pulses when the DC servomotor rotates. The encoder sends the pulses to a digital input channel of the NI-DAQ card. A counter in the NI-DAQ card counts the number of pulses and computes the rotational speed of the DC servomotor. If you use a DC tachometer to measure the shaft speed of the DC servomotor, the DC tachometer generates back-EMF voltage signals when the DC servomotor rotates. The DC tachometer sends the voltage signals to another A/D channel of the NI-DAQ card. The NI-DAQ card calculates the rotational speed by using the voltage signals.
|Note Ensure the NI-DAQ card acquires stimulus voltage signals and rotational speed synchronously. Ensure you acquire and save synchronous stimulus signals and response signals with constant time steps.|
You can use the following types of stimulus signals:
In this example, you can use any of these three types of stimulus signals to excite the DC servomotor.
Refer to the following VIs for examples of generating stimulus signals and acquiring data from a dynamic system. You must have the required hardware, such as an NI-DAQ card, to use these examples.
Alternately, if you do not have the required hardware or a DC servomotor, use the SI Data Samples VI to generate the input and output data. This tutorial uses the SI Data Samples VI to complete the following parts. If you also use this VI to complete the following parts, you can get identical results as the results in this tutorial.
You can save this VI and use this VI to complete the following parts of this tutorial.
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