About brushless motors


I built a small balancing robot using two of your brushed 25:1 20D motors and encoders for them. Everything works very well.

A few weeks ago I showed this robot to someone and he recommended me to use brushless motors for robot movement instead of the above brushed motors. More specifically, he talked about brushless motors for camera gimbals which have lower RPM and higher torque than regular brushless motors used for example on drones, thus being more suitable for moving a robot. He also told me that he built an electronic skatebord with such motors and Electronic Speed Controllers (ESC). So I said hey, why shouldn’t I try it?

However, while ESCs allow you to control the RPM of the motor, they don’t seem to provide any feedback on the motor’s position in the same manner encoders do, which is of paramount importance in balancing a robot. On the other hand I know that the technology for this exists since those motors are used to stabilize cameras in a super precise way (using back EMF or something, I really don’t know precisely). Indeed I found over the web some controllers for camera gimbals which can do it, but they seem to be designed for stabilizing a camera and not a robot and may require extensive tweaking.

Therefore I want to ask you the following questions:

  • I searched this forum for topics related to brushless motors. In all of them you state that you don’t sell brushless motors or their controllers. Why is that? I would really like to see such products from you.

  • There just doesn’t seem to exist any simple controller board which can also provide position feedback. Am I wrong? Why not making one?




I think the short answer is that it’s difficult to do. As far as I know, the gimbals you mention are based on using a separate IMU for feedback, so they can get by without an encoder. For the more general case, I think you need an encoder, and the whole solution is a lot more complex than with a brushed motor. We also have a chicken and egg problem in that getting brushless motors with sensors is not very interesting if we don’t have a controller for them, and developing a complicated controller without a motor to go with it is also not very practical.

That said, we are currently looking into brushless motors, and that is a direction we want to be going in eventually (but we’re not likely to have anything soon).

- Jan