Software mixing

Currently, my PS3 controller code uses the channel mixing built into the Sabertooth speed controller. This means that I send it speed and turn commands, and the speed controller mixes these to drive R2 in a tank style, where you vary the speed in the feet to go forward/back or turn.

The problem with this is that not many speed controllers do this, so I am very much tied into using the Sabertooth with my code and the Sabertooth doesn’t support brushless motors. Droid 2 is going to use an ODrive, which has no mixing built in.

Well, until now!

I’ve abstracted out the speed controller portion of the code and added a function that takes the two axis from the drive stick and then outputs the required motor speeds. In this video you can see when I push the stick forward, the top number changes to show the position of the axis, and motor 1 is set a signal of 1, or full speed forward and motor 2 gets -1, or full reverse. (Remember, the motors are flipped)

I got the bulk of the code from here:

https://electronics.stackexchange.com/questions/19669/algorithm-for-mixing-2-axis-analog-input-to-control-a-differential-motor-drive

which uses cartesian to polar (and back) transformations.

I still need to hook up the motors, I’m waiting for some connectors to turn up, to check that it actually works and to do the code changes to send the correct signals, but this is a good step forward.

The other benefit to this change is that now I’m not limited to dual motor controllers, and can look at buying cheaper single controllers with a lot less smart technology built in.

Preston Comic Con tomorrow, so R2 and I are out all day, but if the connectors turn up that I’ve ordered, sunday will be a day of connecting and testing the motors.

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