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W05. Control 03

Maintaining distance from an object is both simple and hard. The basic problem is that you want to reduce error, i.e., get to the distance that you want to be at. But, because of the physics of real world, you don't always get exactly there.

That's where Proportional-Integral-Derivative (PID) control comes in. It's a mathy-sounding name, but a pretty simple idea: if you're far away from the goal, drive faster. If you're close, drive slower. If you're there, stop.

Today we'll see how PID control can be used to maintain a distance from a wall. For the tournament, your robot will have to navigate a maze with walls, so this will set you up for the simplest effective solution for solving the maze.

Pre-readings and Videos​

PID control is a fancy name for a simple concept. These videos will help you to understand the process from both an engineering and practical point of video. We also compare this to proprioception, where you set a point for your body to move to, then move until that point is acheived. You can watch this by trying to lock your arm in place: it waivers around the lock (set) point, always increasing and decreasing muscle activation to try to achieve the imperfect set point.

What does a PID controller do?​

Besides being an absolute gem of a Canadian woodworker, entrepreneur and engineer, Mattias Wandel provides solid educational content on engineering concepts such as PID.

Demo of tuning a PID controller​

This video shows the process of tuning a PID controller using knobs.

PID in action​

This video demonstrates a PID controller in action.

PID Simulator​

This PID Simulator gives you a useful real-time graph of what it's like for a PID system to work.

Proprioception​

This is a review paper on proprioception, which is comparable to PID in some regards.

Summary of the Day​

Learning Goals​

  1. Be able to use the concept of a P-controller (from PID control) in the design of a robot wall-following algorithm.
  2. Apply the P-controller to a variety of engineering control contexts where a system is moving towards a set point.
  3. Compare PID control to proprioception and muscle control in the human body.