Real time motion in dynamixel motors.

[Raj-Kiran127]

ISSUE TEMPLATE ver. 1.2.0

Please fill this template for more accurate and prompt support.

1. Which DYNAMIXEL SDK version do you use?

• ex) 3.7.31

2. Which programming language/tool do you use?

• ex) MATLAB

3. Which operating system do you use?

• ex)Windows 10

3. Which USB serial converter do you use?

• ex) U2D2

4. Which DYNAMIXEL do you use?

• ex) `MX-28 AT (protocol 1.0)

5. Have you searched the issue from the closed issue threads? Yes

6. Please describe the issue in detail I need to run 3 motors in real time. But as I increase the number of steps motors are taking more time and the motion is not smooth. So I used sync_write, it worked to some extent but am not getting smooth motion and also motors are not completing the motion in given time. How can I trouble shoot the issue please let me know. An add up question - Are there any libraries of sync_write or bulk_read for simulink ?
   Thanks in advance.

7. How can we reproduce the issue? TrialWithSyncWrite.txt

This is the code am trying to run. Please bear with my improper coding style.

[ROBOTIS-David]

Hi Raj,

Your issue has been addressed via Tech Support,

See the quote below, 1) Giving position control(in matlab), when I try to increase the number of steps, motors slow down. How can I achieve a smooth motion for a given position control without slowing down the motors? (code - To_Fro.m)

• Seems that you are updating Goal Position for three DYNAMIXEL at a very detailed time within a loop. The problem in this case, you might see motion jittering or regulated motion speed depending on Baudrate or any control period. I recommend updating position trajectory before the current position reaches the next Goal Position, so that you may see the movement without jittering (See below example). And I highly recommend using a higher baudrate to transmit more command packets at a given time.

i.e)

• Final Position: 2048
• Moving: 1030 -> 1080 (When Present Position is reached before 1050, Goal Position Position should be updated the next)-> 1050 -> 1060 ..... 2048.

2) Using simulink library for dynamixel motors available on matlab file exchange I achieved a smooth motion for 1 motor which finished in the given time but when I try to run all the motors at once, motion is not smooth and the end time is increasing.

• To be honest, I am not used to Matlab (and we do not give simulink tech support for third party libraries), therefore this is difficult for me to give you relevant assistance.
• If you see motion discrepancy, use Sync Write Instruction rather than basic Read/Write.

3) How can I run the motors with real time using position control?

• It's vague for me to understand the point of it. Please give me more clarification on the real-time control in Joint Mode. There are many different concept in real-time (Such as building a loop controller out of DYNAMIXEL)