XL430-W250-T Idler and PWM mode
2018-01-12 17:13:48 best_user


we recently purchased a package of Model X motors, including XL and XH motors. We also have the Idlers from the bracket sets which fit perfectly to the XH motors. However the XL430-W250-T did not include an idler and i could not find one on your website. In this Video https://youtu.be/wkMdi_lFg24?t=25s I found how it should look like but I have no idea where to get it from.

Another question which concerns mostly the XH430 motor. I want to use your PWM control mode which works good. A characteristic I would expect is that it should not resist when being pushed and PWM is 0. However when I click "torque enable" the motor is stiff and resists external forces. To control it I have to enable torque. Is there a possibility for this characteristic? I hope you understand what I am trying to do.

Thank you for your support!

2018-01-12 17:13:48
2018-01-15 11:18:33 Andreas Gerken


i found the Idler with some help in your shop. The Set is HN11-I101 (http://www.robotis.us/hn11-i101-set/) and is sold seperately.

Please add this information to the product description, It should be findable by searching for XL430 and it should appear on the overview page of the X-Series.

My second question about the PWM control is still open.

Thank you!

2018-01-15 11:18:33
Andreas Gerken
2018-01-24 11:23:08 Andreas Gerken

Hi, I will repeat my unanswered question:

1) My question concerns the XH430 actuator. I want to use the PWM control mode. A characteristic I would expect is that it should not resist external forces when the goal PWM is 0. However when I enable the torque the motor stiffens and resists. This seems strange to me and I wonder if there is a way around this characteristic. 

An additional question came up:
2) I modified the Dynamixel SDK "read write" script of protocol 2 to use torque control. I uploaded the code here. It works perfectly with the XH430 motor and it sweeps back and forth. When Using the XL430 motor the CCW motion (positive goal PWM) works as intended but as soon the goal PWM is negative (CW motion) an Error is coming up:
"[RxPacketError] The data value is out of range!"
Since my code is working correctly on the XH430, this might be a bug in the XL430 firmware. Please check my code and your firmware. 

In the Dynamixel R+ Manager, both directions work.

Thank you! Andreas Gerken
2018-01-24 11:23:08
Andreas Gerken
2018-01-29 19:10:32 Will Son


I apologize for the fact that I totally missed your question thread.

Somehow it didn't appear on my screen and I missed it.

I'll look into your cases(XH430 PWM control, negative PWM with XL430)  and see if I can reproduce the same PWM control as you did.

I really appreciate for your patience and I'll get back to you as soon as I figure out the solution.

2018-01-29 19:10:32
Will Son
2018-02-05 11:56:59 Andreas Gerken


thanks for looking into it. Could you reproduce the problem?

Did you also read my first question about the stiffness of the motor when using PWM control?

Thank you, Andreas Gerken

2018-02-05 11:56:59
Andreas Gerken
2018-02-12 16:57:13 Will Son
When using PWM control mode, Goal PWM is used to directly control the motor that is connected to the inverter.
Even if setting PWM to 0, both motor poles will stay at the identical voltage level and this will create an "engine brake" effect.
Therefore, setting Goal PWM to 0 does not mean output torque to be zero.
2018-02-12 16:57:13
Will Son
2018-02-13 14:13:51 Andreas Gerken

Thank you for your support!

With the help of will, I found an error in my script. I used the read_write example as base for my script and modified the write goal position command to a write goal PWM command. I missed to change the number of bytes for the command which are 4 for the goal position and only 2 for the goal PWM.

A working example script can be found in this Pastebin link

2018-02-13 14:13:51
Andreas Gerken
2018-02-14 16:45:39 Will Son

Sounds Great!

Glad you found the solution, and thank you for sharing the code with community :)

2018-02-14 16:45:39
Will Son
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