In my last post, I put a couple of motors head-to-head and decided to move forward with the Steadywin GIM6010-8. Over the last month, I've been testing it with various 3rd party controllers. Here are the contenders:

• Stock motor controller (ODrive 3.6 clone)
• Bare motor + Odrive Micro
• Bare motor + Tinymovr R5.3
• Bare motor + MJBots Moteus C1

The main reasons to use the bare motor with a 3rd party controller are:  

1. The bare motor costs less than $50, 
2. You can design the motor directly into your 3D design, and loose the weight of the aluminum shell.
3. You can use the latest and greatest FOC motor technology.

I first heard about this idea when looking at a project by Aaed Musa. However, one thing concerned me. The motor is rated for 11Nm of torque, but Aaed found that it was only producing 3Nm for him.  This seemed suspicious since that's so much lower than what's listed on the product page. I started to suspect that this might be related to his use of the Odrive Micro controllers, which are only rated for 7A, and the motor's maximum current is 25A.

So let's test this theory.

Controller and Torque Testing

To test all the controllers head-to-head, I ordered a couple of motors from Steadywin: one complete motor + controller + shell, and one bare motor. Then, I designed and 3D-printed a custom enclosure for the bare motor, and set up a test base and a digital load cell.

Stock controller

The stock controller is an ODrive clone running a customized version of the 0.5.x ODrive firmware. ODrive closed the source code to their firmware at version 0.6.0. So you won't get the latest features, but the interface will feel familiar if you've used ODrive before.

So how did it do?

At 24A (a little shy of its maximum current), the stall force fluctuated around 55N at the end of a 200mm arm. To convert that to Nm, we multiply that by 0.2M and get 11Nm! 

So with the stock controller, we can get the full force potential promised by the manufacturer.

ODrive Micro

With the ODrive micro, we get all the latest bells and whistles. However, when testing the maximum stall torque, we only got 24N, which converts to 4.8Nm

Tinymovr R5.3

I kinda love this little board. Not only is it small and easy to use, but their documentation is very well written. 

But how does it torque? 

At 15A, it was pushing 47N or 9.4N! Unfortunately, I started hearing cracking from my test base, and I didn't think it was safe or prudent to push it any further. But I feel like I could have gotten the whole 11Nm out of it.

Seriously, this is a great little board.

Nonstarter: MJBots Moteus C1

I really wanted to like the moteus C1 controller. It's open source and sold at a great price. There's so much to love. Unfortunately, I couldn't even get the GIM6010-8 motor spinning on it. I purchased the entire motor development kit to familiarize myself with the controller and got their motor spinning just fine.

I spent a little time trying to troubleshoot the issues, but I gave up without much useful documentation and with clearly easier boards to use. What happens when I run into bigger issues if I can't even get a motor spinning easily?

Conclusion

After trying all the controllers, my favorite was the Tinymovr R5.3 for its ease of use, excellent documentation, and high torque potential. However, paired with the bare motor, the cost is nearly $150 before shipping.  

On the other hand, I can buy the motor with the stock controller and shell for ~$85. For just $10 more, I can get the motor with a built-in absolute encoder on the output shaft. This means that, on a cold start, the robot will know the motor's position, without any homing sequences. Before shipping, this totals to only ~$95 (motor + shell + controller + second encoder). 

I've decided to use the stock controller and built-in second encoder for this project. I've just ordered a couple of them and am starting to prototype the first of the eight legs. Stay tuned!

3D Model

You can download the 3D models I created for the motor shell from printables.