View Single Post
  #6   Spotlight this post!  
Unread 22-12-2013, 18:00
DavisDad's Avatar
DavisDad DavisDad is offline
MechE
AKA: Craig Rochester
FTC #8470 (Team Technado)
Team Role: Mentor
 
Join Date: Jan 2012
Rookie Year: 2012
Location: Boston
Posts: 317
DavisDad will become famous soon enoughDavisDad will become famous soon enough
Re: [FTC]: Motor encoders Love'em? or leave'em?

Quote:
Originally Posted by DocMartin View Post
My fellow Mentor and I are at odds on using encoders or not.

I want to hear from you.

Does your team use them or not? and why?

Go!
We're working on a design using VEX 4" Mecanums. We built a prototype to test performance of wheels, motor controller, and gearmotor/encoder combination. We used the Matrix system for cost and availability reasons; the Matrix gearmotor has the encoder integral to the motor.

Our competition design is currently:



For the testing prototype we built:





Things we like about the prototype:
  • Motor controller built in PID speed control worked well (RobotC code)
  • Teleop control is very nice for omni-directional control
  • Speed vs. power is good (quantitative data to follow if we can wrestle the bot away from the drivers )
  • Fabrication was fairly straight forward (see cons)
  • Square shaft for wheel eliminates hub

Cons:
  • Haven't been able to get encoder position control to work with the built in Matrix RobotC code
  • Square shaft VEX to 4mm motor shaft coupling was tricky. We had to learn how to broach a square hole and weld 2 pieces of the coupler together.



I think using the motor controller encoder speed control is excellent; you're telling the motor how fast to go rather than sending a power level that is blind to load and variations in the wheels'/gearbox response to voltage. We pushed chairs around the kitchen at the same speed with no load. Teleop control of the prototype is smoother, more responsive and predictable than any other drive we've tested in 3 seasons; 6 wheel tank, 4-wheel mecanum without encoder feedback.
Reply With Quote