I have started working with a Panasonic AC servo drive of capacity 400W (manual). While trying to understand how a ac servo works in position control mode. After experimenting I have come to the following conclusions:

The AC servo maintains position by comparing.

For example if I want to reach a position of 1000(say), and I am giving 1002 pulses(forward) and once it is running, I am giving a reverse of 2 pulses when the motor has reached 999(using Quadrature Encoder Interface). The drive will reach a position of 1000 by (999-2=997 position) and the remaining 3 pulses to go forward or reverse is decided by the closeness of the position as going forward of 3 pulses will be close to my 1002 position it will go from 997 to 1000. So finally it will reach a position of 1000.

Now if I want to make a position control algorithm, the thing I have to do is play with forward and reverse pulses. Is it right?

Can anyone give me some guide on position control algorithms? The load will be like a 1 or 2kg.

  • \$\begingroup\$ For starters, post a link to the datasheet for the exact servo drive you're using. \$\endgroup\$
    – HikeOnPast
    Mar 1, 2013 at 4:54
  • \$\begingroup\$ This is the directlink to the manual minas-a5.panasonic.biz/manual/en/minas-a5_manu_e.pdf \$\endgroup\$
    – badz
    Mar 1, 2013 at 5:03
  • 1
    \$\begingroup\$ That's a huge manual! As far as I can tell, if you put it into position control mode you don't need to worry about algoritms, it's got all that built in. \$\endgroup\$
    – pjc50
    Mar 1, 2013 at 13:51
  • \$\begingroup\$ If you are worried about motor shaft position, the drive will close the position loop for you (in position control mode). If you are worried about controlling position of something that the motor is connected to, you'll need to tell us about your system and the position feedback that you have planned. \$\endgroup\$
    – HikeOnPast
    Mar 1, 2013 at 22:00
  • \$\begingroup\$ Yes I will be connecting a load to the motor shaft, and the load will be moving forward and reverse at rpm of about 1500. Well where I am getting confused is, when there is a load connected there will be a inertia due to this my position will not be maintained even if its in position control mode. Hence I am looking for some control algorithms for maintaining my position. and regarding the algorithm, is my assumption that the drive acts according to the errror right? If I am designing an algorithm, I have to play with fwd and rev pulses? Thanks again! \$\endgroup\$
    – badz
    Mar 2, 2013 at 2:41

1 Answer 1


I can tell you that you can read the actual feedback position before starting to move the load, then you can move the load according to the number of pulses you have triggered. After that you can read agian the feedback position and determine the difference between the desired position and actual position. Hence you can make a correction either Cw or CCW


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.