Quote:
Originally Posted by Elfonzo
I find it necessary to alert all teams who have already purchased the Andymark Swerve and Steer Module of issues in its performance. Andymark is offering a better, "absolute zero," (as we like to call them,) sensor. This "better" sensor always has a point it can refer to as zero, eliminating the need for pre match centering/zeroing. However, because the gear that the sensor is attached to and reading from is 12 tooth, and the gear used for turning the assembly is 40 tooth, the sensor has effectively 3&1/3 "zero's" This causes HUGE problems when trying to read the position. If you have not completed your electronics board and given the programmer(s) a chance to test it, be prepared to come up with major issues.  |
You will definitely have a problem trying to get the current angle of the module when you first turn on the robot (3-1/3 rotations/module rotation = 10 zero-ing angles), which is why you'll need to make sure the wheels are aligned before grabbing the initial position of the encoders.
You can get the current position by keeping a running sum of the encoder ticks, making sure to add the right change when it wraps around a zero point. Get the position by calculating the modulus of the total encoder ticks in a full module rotation (resolution * 3-1/3) and the current value. If you run over (or under), be sure to wrap around past the other extreme.
Quote:
Originally Posted by JesseK
There's a local team who started swerve on Day 0 for the first time ever. They got it up and running with programming by the end of Week 3. They're using AM's product, but haven't reported a problem zero-ing it out since they're good about pre-aligning the wheels to each other at the start. They're using CAN via the Talon SRX, and it works incredibly well.
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I wonder if they're using the hall effect encoder?
http://www.andymark.com/product-p/am-2816a.htm
Which would make this much more trivial*, given the position is accumulated on the SRX and one simply needs the total encoder ticks per revolution of the module.
*Well, not trivial...