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Unread 27-11-2014, 01:59
bharrison6 bharrison6 is offline
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Join Date: Jan 2014
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Swerve questions (Languages, CAN)

So I am making this thread to ask a couple of specific questions that has not been fully answered in other post that I have read. I am a new mentor for a veteran team, was fully involved last year and this year I am encouraging the team to "push the envelope." The major task we are attempting this year is a swerve pod system.

We are a very financially limited team which means that we are careful not to make anything just yet physically because we can not afford to remake it with some changes in order to meet the rules about off season development, however we do have all our CAD files ready and we have fabrication methods lined up for the first week in January. (I wish off season rules would be less limiting)

While we wait to make our physical pod system we are turning our attention to the other half of the system, the code. One major concern is finite pod angle control. We are experimenting with CAN right now to see what it can do for us. We are planning on using a PWM absolute encoder from us digital to get information about pod angle. http://www.usdigital.com/products/en...tary/shaft/ma3

My first question is "Can the new can motor controllers be used to hold position from a PWM absolute encoder signal?" I know it can use quadrature input from an incremental encoder but those would require at least one full revolution of the pod to find the index in order to work correctly, which is why we are using an absolute encoder. If the motor controllers do not accept PWM from an absolute encoder then that throws out closed loop control of our pods, in this case is there any advantage to CAN since you can get current readings from the PDB now? (Other than having nice and pretty wires)

My second question is "Is there any advantages to using a specific language to make our swerve pod code in" We currently use lab view but here is our worries. 1. If we can't use a closed loop control for pod rotation then we will have to use the RoboRIO to issue commands for motor control. Is there any language which might run faster on the RoboRIO? 2. If we can use closed loop to control our pods is there any advantage to using Java since it has just had a CAN overhaul. (according to "Behind the Lines" S0E02) 3. In the past certain notable teams have used other languages. Bomb Squad uses C++ and Cheesy Poofs use Java. Is there any particular reason for this or is it just personal preference? I know if we had been using java we could have implemented Cheesy Vision. (Not sure if we could have since we are using lab view)

Sorry for the length but I wanted to voice all my concerns in one go. Thanks in advance for the help.

Bryant Harrison