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Unread 06-02-2017, 09:20
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EmileH EmileH is offline
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AKA: Emile Hamwey
FRC #1058 (The PVC Pirates) & SLFF (NE Way You Want It)
Team Role: Programmer
 
Join Date: Dec 2014
Rookie Year: 2011
Location: New England
Posts: 551
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Concept Discussion: Vision Closed Loop or Encoder/Gyro PID based Closed Loop?

Hello all,

Recently there has been some debate about whether or not a vision closed loop programming technique (where the position of an object in a frame directly drives a motor output) has benefits over a vision software that takes a single frame and calculates an error based on that frame and then drives some-other-sensor-based PID controller with a setpoint based on the frame's error.

Benefits of Vision Closed Loop:
  • Little to no need for high level arithmetic
  • Can be used to lineup while moving as the robot constantly updates to the target

Downsides of Vision Closed Loop:
  • Needs to be run at low latency to be worth it as it is directly updating the motor controller

Benefits of Vision-fed Encoder/Gyro PID Closed Loop
  • Can be run on a slow <5fps processor
  • Less jitter as the loop can be run once to hit the target

Downsides of Vision-fed Encoder/Gyro PID Closed Loop
  • Requires higher level arithmetic to calculate the error to the image
  • If the target moves as a result of robot movement outside of the loop, the loop would target inaccurately.

This is a pure philosophical question rather than an implementation question, so, for a team with a coprocessor vs one that has to run all their vision on the RoboRIO, which is best? Discuss.
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