Lab 3 - Frequency response

We were also able to evaluate our motor system in terms of its frequency response. To do this, we removed the position control from our model, resulting in a simple forward path transfer function:

V_pwm corresponds to the duty cycle of the PWM signal being sent to H-bridge which acts as the input to the motor system. V_pwm was output from the Arduino board as a sine wave of varying frequencies and amplitudes. The minimum frequency we could take a valid reading at was 10 rad/s with a duty cycle value of 3.5 out of 255. This was the minimum value to overcome friction in the motor and at any lower frequencies the gain was high enough that the motor would reach the edge of its workspace. We took several data points over a frequency range up to 100 rad/s, with a maximum PWM output value of 40. For each frequency and amplitude combination we collect data points from the Hall effect sensor and measured the resulting amplitude in position. The two amplitudes were then divided to find the gain in each case. The resulting comparison is shown below.

The data clearly has similar behavior to the model with the major difference being an offset in the gain. This is most likely due to an incorrect characterization of one or more of our gain values.