Lab 6 Real System Identification

To analyze the new system, we modified the code used in the previous exercise with the addition of another array to control motor direction. The array was populated with a random distribution of 1's and 0's, which translated to HIGHs and LOWs for output to the H-bridge direction pin.

A plot of the white noise input (in blue) and the system's response (in green) is given below. (Note: the input and response are not given in the same units, and thus the y-axis scale should be ignored.)


Running the system identification, Matlab returned the following bode plot of the estimated transfer function. Comparing the figure below with the expected bode plot (shown above), it is clear that the results are not as accurate as the results for the RC circuit. The phase plot decreases in degrees, but acts more like a 2nd order system than the expected 1st order system. The magnitude plot does not show the expected 20dB/decade slope. Possible causes are the resolution, or lack of calibration, in our accelerometer or noise in the system. One solution not attempted was filtering the data through an op amp filter. Further system identification work will have to be completed on our actual project system in hopes to obtain better results.