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Angular speed and angular velocity

  1. Mar 29, 2012 #1
    hi i have two different systems (i have tried to upload them but they both exceed the size of the upload limit). One is a dc motor block diagram (it has a PID at its controller) the other is a bldc motor model with a PID controller input. The block diagram of the DC motor consists of an armature block a load block this is where the angular velocity is produced at the output of the load block and if the angular velocity is integrated it provides me with the angular position, there is also a back emf from the velocity. The BLDC model has a contolle then has the BLDC T.F. this is where the angular velocity is produced and therefore when integrated gives the angular position. My question is how comes for the BLDC system why does it no need a load block which provides the inertia, which then generates the velocity by divding the torque generated from the motor?

    thanks mayur
  2. jcsd
  3. Mar 29, 2012 #2


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    Staff: Mentor

    Can you just scan the diagrams and upload them as PDFs? Or take a cell phone picture of them and upload them as JPGs?
  4. Mar 30, 2012 #3
    hi here you are, the DC motor is put into a subsytem i have just shown you the whole block diagram to make it easier to interpret.
    Thanks Mayur

    Attached Files:

    Last edited by a moderator: Mar 30, 2012
  5. Mar 30, 2012 #4
    Hi mp252, the first block diagram is a control system, using a P controller, not a PID controller. This is because the controller is labeled "K" without a pole or zero for PID. This control system includes the model of the BLDC motor called HDD dynamics, which is the block transfer function in that diagram. This single block represents the same information as the entire second block diagram of the DC motor gives.

    The second block diagram is not a control system, it is ONLY the model of the motor. The feedback loop in the second block diagram is characteristic of all DC motors, because it is the natural back EMF feedback. When you apply the G/(1-GH) rule to a feedback, you get a closed loop transfer function, and that is what's used in the first block diagram. to represent HDD dynamics This combines the electrical and mechanical poles into one transfer function, and that's why you don't see a load block in the first diagram.
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