CS452 - Real-Time Programming - Spring 2011

Lecture 21 - Calibration

Pubilic Service Announcement

  1. Exam: starts 09.00, Friday, 12 August, 2011; ends 11.30, Saturday, 13 August, 2011.
    Note. Correction from Lecture 20.
  2. First milestone.

First Milestone

Simon and I had a long conversation about previous student experience with the first milestone. We propose to eliminate one requirement.

Why the change?

However, you are still expected to do sensor hit predictions, and that is now explicitly part of milestone 1, not just something we talk about in class.

Stage 2. Calibrating Constant Velocity

An implicitly accepted fact about the world that is essential for calibration.

As long as the future is sufficiently like the past, which it almost always is, calibrations work just fine.

But when it isn't, all bets are off. You need something different disaster recovery. There are two rules of disaster recovery.

  1. Do not further harm.
  2. Start from the beginning.

Back to Calibration

If the future is like the past, then knowing the future is easy: understand the past. Understanding the past is easy in theory, but hard work in practice.

In Theory

  1. Measure
  2. Measure
  3. Measure
  4. ...
  5. Compile data into a useful form

In Practice

You need to figure out what to measure, and how much measurement to do.

  1. Estimate the calibration precision required by your task. E.g., stop within one train length
  2. Estimate the error in typical measurements. E.g.
  3. Make some measurements to test your estimates.
  4. As you make measurements continuously update the calibration.

You need to figure out the best way to structure measurement results so that they can be efficiently applied in doing the task.

  1. The set of tasks that provide calibration must
  2. How much of this should be done on-line? How much off-line?

Where the Steel Hits the Rail

These comments are essentially random.

  1. Measurement is costly.

    Therefore, you should never throw any data away.

  2. You are likely to use floating point.
  3. Each landmark requires a well-defined origin and clearances with respect to that origin. E.g.

Return to: