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View Full Version : [Question(s)] How to Set the Torque limit for Dynamixel MX-28 using MATLAB?



ubs3
03-06-2015, 09:53 AM
Hi,
I am working on an exoskeleton which uses Dynamixel Motors. I wanted to know how to set the torqur limits for the MX motors using MATLAB and not the Dynamixel Wizard.

Help will be much appreiciated

Thank you.

Xevel
03-06-2015, 08:41 PM
Hi,

Not a Matlab user myself (anymore).
How do you plan on talking to the servos aside from the part about setting them up? Chances are you can easily use the same lib to set these values too.

Have a look at http://support.robotis.com/en/product/dynamixel/dxl_communication.htm to get a better understanding of how the communication works.

What you will want to do is send a WRITE_DATA command that targets the relevant registers in the register table (cf support page for the servo you are using, example MX-28 (http://support.robotis.com/en/product/dynamixel/mx_series/mx-28.htm)).

34/35 are the addresses where you want to write if it's only for this time, or if you plan on changing them often.
14/15 are the addresses where you should write the limits if you want them to be remembered after powering them down. (Writing there can take a few ms, and it does not impact the servo directly: it only sets the value that will be written to 34/35 on startup).

These pairs of registers have to be written in one write operation (you can't write them one after the other). Be careful with the endianness (order of the bytes in the number).

Now, be careful that "torque" here is not real torque measured by a torque sensor, it's about what the motor will be given in terms of voltage, with all the differences that entails.
As they say in the support page :

Notes: Current load is inferred from the internal torque value, not from Torque sensor etc.
For that reason, it cannot be used to measure weight or torque; however, it must be used only to detect which direction the force works.