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Motor torque requirements

Josef K.
Hello,
 
I am trying to estimate the torqie required to drive a lead screw. To do this, so far I 've been using a motion instead of the torque and then viewing the required torque to produce said motino throught the ppt. This doesn't seem to be the correct way though as the results I am getting seem completely off.
 
Is there a more standard way to do this?
 
Thanks,
 
Josef K.
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  • 0
    The P-part will result in a constant error. It is basically a "spring" with stiffness P, the force from it is proportional to the error P*error. The error can never be zero in steady-state with only the P-part.
    To eat up the constant error, you need an I-part to your controller. This will integrate the error and add more and more force the longer time goes on if an error remains.
    The D-part is the "damper", it reacts to sudden changes. Be very careful with this. It is easy to make the system unstable.
     
    But you should have seen wild fluctuations with that high P gain.
    I can only draw the conclusion that
    1. You did not deactivate the motion, it is still in there.
    2. You have a sign error in at least one of the terms. This is one reason why I like to build my own PID instead of using the PID block, it makes it easier for me to determine what is going on with each individual part.
     
    The classic way to do an initial tuning of a PID controller is to follow Ziegler-Nichols rule. Note that method is in some cases based on a slightly different formulation of the PID controller.
     
    1. Start with setting I=D=0.
    2. Increase P until the system oscillates with a constant amplitude (limit stable). This P value will be called Ku in articles. The time period of the oscillations is called Tu.
    3. Select P=Kp, I=Ki, D=Kd from the article linked above.
     
     
Reply
  • 0
    The P-part will result in a constant error. It is basically a "spring" with stiffness P, the force from it is proportional to the error P*error. The error can never be zero in steady-state with only the P-part.
    To eat up the constant error, you need an I-part to your controller. This will integrate the error and add more and more force the longer time goes on if an error remains.
    The D-part is the "damper", it reacts to sudden changes. Be very careful with this. It is easy to make the system unstable.
     
    But you should have seen wild fluctuations with that high P gain.
    I can only draw the conclusion that
    1. You did not deactivate the motion, it is still in there.
    2. You have a sign error in at least one of the terms. This is one reason why I like to build my own PID instead of using the PID block, it makes it easier for me to determine what is going on with each individual part.
     
    The classic way to do an initial tuning of a PID controller is to follow Ziegler-Nichols rule. Note that method is in some cases based on a slightly different formulation of the PID controller.
     
    1. Start with setting I=D=0.
    2. Increase P until the system oscillates with a constant amplitude (limit stable). This P value will be called Ku in articles. The time period of the oscillations is called Tu.
    3. Select P=Kp, I=Ki, D=Kd from the article linked above.
     
     
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