Interactive robotic arm

Hi guys,

I am not sure how it is for you guys, but for me part of the fun of wondering around on a forum like this, is looking at creations of others (and wondering where people get the time to do such cool stuff…:wink: ). However, there is not yet that much to find in the applications catagory, so therefore I thought it might be nice to share the project I am currently working on.

At the moment I am building a robotic arm that is able to interact with a human: soft robotics so to say. The plan is to make it 3 degrees of freedom + an end effector. I will actuate the robot with 4 emax GB4114 motors each driven by their own SimpleFOC shield and will probably use a STM32 to control it all.

Currently, I almost finished the hardware of the ‘elbow joint’. I will attach an arm to this joint, which has the ‘wrist joint’ and end effector attached to it. This all will be mounted on a rotational platform for the rotation around the z axis. As the ‘elbow joint’ needs to apply the most force to overcome gravity, two motors are used there. Also a 1:4 transmission is implemented using a capstan drive. This results in a highly backdrivable, but powerful system with low backlash. However, tensioning it is a bit of challange.

I am now able to drive both motors in position control and will play around with force/impedance control soon. Then I will also swap the Arduino Mega for an STM32 board. After that I will add the arm and the wrist joint. I don’t really know yet what to do for the end effector. For now I would like to keep it simple so I could go for a servo driven claw or something, although this doesn’t really fit in the soft robotics idea of this robot (unless I solve it mechanically with springs or so). I was also thinking about a electromagnet instead, but then I can only pick up metal parts. So perhaps you guys have any suggestions?

So let me know what you think and if you are interested I can keep you updated with pictures and movies etc.


Hey @Jornel,

I love brushless-based robotics :slight_smile: please keep posting your upgrades and your further development of your arm. The capstan drive is a very creative solution! I take you’re not having problem with syncing the movement of both motors.

In my opinion the end effector depends on the type of application you’re thinking for this robot arm. If you want something that keeps the “soft robotics” idea maybe you could do suction with a small DC air pump?

I am very interested in your project. Specially interested in low cost motors like GB4114.

Have you done simple torque test to see how much weight the motor can lift?

Please keep us posted.


That sounds simply awesome, look forward to seeing some pictures!

Have you considered using lighter, smaller motors as you go up the chain (or bigger, heavier ones further down)? 4114 is a pretty hefty one… but I guess that’s where the transmission comes in…

In terms of end effectors, other things I’ve seen include 3D-print heads, pen or brush holders, suction devices (e.g. for pick n place) or welders…

Or what about a small electrified mesh for hunting mosquitos & flies? I think an automated fly-swatting arm would be pretty awesome… :smiley:
Or maybe a camera-attachment, for mounting your GoPro and filming macro-shots or 2.5D scanning?