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POST No. 2407618
Present Position - MX-64 - Limits
2019-10-09 13:28:01 radeshwar

Hi,


I am using multiple MX-64 for one of my application, and I am operating it in Current based Position control Mode.


The actual limit of MX-64 are 0 to 4096 (as per Spec) and my application uses the position which are beyond the limits and I am able to achieve that.


The issue which I am facing is that when I come to 0 Position (Encoder Zero value) ​and switch OFF my system and if I switch ON after few ​hours then my Present Position of my actuator is somewhere between 4094​-4096.


All my logic are based on the Present Position of the actuator, and when I issue Goal Position commands to all my actuator they doesn't move to my desired Goal Position as my Present Position is has changed.


eg:  


Expected Result

Present Position = 0

Goal Position = Present Position + 1000 

i.e Goal Position = 0+1000 = 1000          (Point A - Desired Position)


Actual Scenario

​Present Position = 4095

Goal Position = Present Position + 1000 

i.e Goal Position = 4095+1000 = 5095   (Point B - Different Position)


​I have noticed the same issue at different positions, my goal Position is moving 4096 counts more than what is required and unfortunately this doesn't happen always.


Since I am using multiple MX-64, I am not able to achieve same Position for all, provided I am issuing same Goal Position to all the actuators.


Can I use Multiple turns in Current Based Position Control Mode or can I measure Current in Extended Position Control Mode?


How can I handle this issue, Kindly advice.



Thanks




2019-10-09 13:28:01
radeshwar
2019-10-11 17:46:57 Will Son

Hi,


First of all, when you are using Current-based Position Control mode, the position limit will be extended to -1,048,575 ~ 1,048,575(-256[rev] ~ 256[rev]).

Secondly, if you are cutting the power off near the 0 ~ 4096 position(0 degree or 360 degree position) you could get either 0 or 4096 because of the discontinuity of the value.

The best practice to prevent this effect is to avoid stopping near 0 degree or multiples of 360 degree angle.


When you are using Extended Position Control mode, you can read the Present Current(126) value.

Thank you.

2019-10-11 17:46:57
willson
2019-10-11 22:06:24 Radeshwar SS

Hi Wilson,


I am facing the same issue again.


If I move my actuator beyond (0-4096) and switch OFF and ON the system, it is showing the present encoder value i.e(0 - 4096).


It is not considering the Multi turns it has made in any of the Mode (Current based position Control & Extended Position Control).


Can you explain why is it so?



Thanks.

2019-10-11 22:06:24
radeshwar
2019-10-16 15:41:34 Will Son

Hi,


The turn count is NOT saved in the EEPROM area which means whenever the power switch occurs, the turn information will be reset to "0".

In other words, if you had a present position of "5000", which is 4096 x 1 turn + 904 position, will be reset to 904(4096 x 0 turn + 904) after the power switch.

If your application requires multiturn operation, it is recommended to save the turn count on the controller.

Thank you.

2019-10-16 15:41:34
willson
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