Lab 4 - A/D, D/A Conversion
A Labview interface to read a 5V DC input and indicate when it is activated. The interface was tested and verifed by applying a 5V signal on a digital input to the analog card.
A Labview interface to read data values using the A/D card displaying the output to a graph on the user's screen and also saving the output to a text file. The interface was tested with a potentiometer connected to the analog card. The interface was successful generating the graphic output on the screen and producing the data text file.
In addition to the above testing, a signal generator was connected to the analog input. We slowly increased the frequency and examined the effects. As the frequency increased, the sine wave fluctuated and became distorted. We determined that at the higher frequencies, the analog card lost its accuracy. We exceeded the limits of the analog card, and thus the output we saw on the screen did not accurately portray the true signal. This experiment showed the importance of knowing the capabilities and limitations of your data acquistion equipment.
Lab 5 - PID Control
A Labview interface was developed to position a DC motor using a proportional controller. This involved using the equation: m = Ke. Since it was only a proportional controller, the position of the motor was not as accurately determined as one would like. The error involved with a proportional controller is too much to handle for an accurate and precise process. The motor would overshoot its target continuously.
A Labview interface was developed to position a DC motor using a full PID controller. This involved using a more extensive equation incorporating not only Kp, but also Ki, Kd, and looking at previous error values. The interface tested successfully with the exception of the error introduced by the analog card itself.
Looking at the PID equation more closely, we changed the parameters Kp, Ki, and Kd to determine their effects. The proportional parameter Kp is used to make sure the motor is going in the right direction. As we increased its value, we saw that the speed increased when it was first starting out and up until it became close to reaching the desired position. The opposite reaction was seen when the value was lowered. Ki, the integral parameter, is used to control the long term effects, or when the motor is about to reach the desired position. As the value was increased, the motor reached its position smoother than with lower values. As for Kd, the differential parameter, it influences the short term response, or when the motor first attempts to start up. A higher value started the motor quicker than smaller values.