Encoder with CAN for Drive Train

[bradleybaldwin]

Okay so all the wheels were in the correct orientation and they were spinning in the correct direction. The problem though was that the back two wheels were spinning slower than the front two wheels. According to the build team this is because of a gear ratio problem. If they cannot fix it what are my other alternatives?

[Greg McKaskle]

Can you measure or calculate the ratio of motor input to wheel velocity for the back and front wheels?

If so, you can try to fix it in the SW. After the vector math, the Holonomic VI updates four labeled motors. You can scale the outputs so that the wheel speeds are normalized. I'd make a copy of the VI under a new name. Note that if the ratios are very different, I suspect the nonlinearities in the drive system are going to make this way less satisfying than correcting it with a gear or sprocket change. But since it is a quick SW experiment, I'd give it a try.

Greg McKaskle

[Ether]

Originally Posted by bradleybaldwin

Okay so all the wheels were in the correct orientation and they were spinning in the correct direction. The problem though was that the back two wheels were spinning slower than the front two wheels. According to the build team this is because of a gear ratio problem. If they cannot fix it what are my other alternatives?

You mentioned that you have wheel encoders installed but had trouble getting closed-loop wheel speed control to work.

Find a nearby team that has experience with drivetrain wheel speed control using encoders.

Take the 4 wheel speed outputs from the LabVIEW Cartesian mecanum VI and use each one as a setpoint for a closed-loop wheel speed controller for the associated wheel.

It goes without saying (but I'll say it anyway): Unless you fix the drivetrain gearing issue, this will work only up to a point. Beyond a certain speed, the motors on the slower-geared wheels will not be able to generate torque. And at low speeds, the motors on the faster-geared wheels will not be able to generate as much torque as the other motors. All-in-all, a kludgey solution. Tell the mechanical team they must fix the drivetrain.