Project of robotic Arm with dynamixel motors

Help & Support Robot Parts
1

Hello everyone!!

Frst of all, sorry about my english, i´m it improving slowly. :wink:

I’m doing the final project of my university degree, in which I have to be able to control a robot arm. The communication between the computer and the engines of the robot is established through arduino program (library ax12.h) and with an arbotix card.

So far, I have managed to move the robot with my hands, and then the program makes the robot repeat the same sequence, but now what I want is to be able to control the torque, in order to create a colaborative robotic arm.
That is, when the robot arm is repiting the sequence, if I hold it or I push it, i want to stop the sequence few seconds, as a security.

My doubt is that I don´t know how to get the feedback or the data of the moments, and I also don´t know how I can make the subsequent control, so that when I want to stop (for example blocking with my hand), it stops.

The robot arm has 4 motors, two MX-64 and another two MX-106, each one are conected to an alimentation of 12V.

Thank you very much!!

2

Hi,

You can probably use the current sensor output from the MX-64 and MX-106 Dynamixel Servos for torque control.
The “Present Current” register address on the MX-64 is 0x126 and **0x44/0x45 **on the MX-106.
You can find more information on the current registers of the MX-64 and MX-106 servos here :

]Current register of MX-64/:m]
]Current register of MX-106/:m]
Hope this helps,

3

thank you for answering bdaouas!!

Yes, I try to do the control of the torque with the current, but I have not been able to get the current values with the library that I´m using (<ax12.h>).
Do you know the code to obtain those values?

I probe codes like:

dxlGetPresentCurrent
dxlgetPresentcurrent
dxlgetCurrent
regData8 = dxlGetCurrent(SERVO_ID[3]);

…

and nothing…

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4

Do you have a Github link for the library you are using ?

5

Sorry bdaouas, I´m sorry but these days I´ve been involved in other project of a robotic car.

Yes, the link is this:

github.com/vanadiumlabs/arbotix … oid/ax12.h

But i can´t see and i can´t know how to obtain the datas of the load from the motors.

6

The Arduino library you are using is intended to work with the AX-12 Dynamixel Servo. You might need a library that works with the Dynamixel MX series like this one.

7

Thank you very much again!

Yes, I know that this library is for the AX-12 servos, but it is the one that was used last year in the project, so, as i am doing this year the continuation of the project I have to continue using that library (of course I can use more ), I will look at the one you have sent me, even though i have already seen and I think there is nothing related to the load or torque.

I have already obtained some values of current in the MX-64 by using this data:
38 / Current Limit / Maximum Current Limit / RW / 1941

But I still have to obtain the values of the MX-106T to start doing the torque/load control.

Urko.