Concept Discussion: Vision Closed Loop or Encoder/Gyro PID based Closed Loop?

[EmileH]

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.