CS 452/652 Winter 2022 - Lecture 19

February 18, 2022 prev next

train control assignments need velocity information
- preparatory measurements can be taken without full kernel
- start early before the tracks fill up!
default turnout setting - use trap loops: small (left/right), medium, large
middle turnouts: do not set to C/C! (can lead to derailment)

word length 32 bits
no floating point!
if necessary, use fixed-point integer instead
if necessary, use 64-bit 'long long' integers to hold temporary results during computation

time
- fastest clock: 508 kHz
- 32 bit can represent > 2 hours ⇒ sufficient
location, distance
- millimetre granularity sufficient
- longest short path (without reverse): ~10.5m
  ⇒ 32-bit integer sufficient
- keep in mind: size of train, location of pickup!
velocity
- distance in mm; velocity in mm/s
- distance/velocity? fraction of second → scale up / rearrange
  - example: travel time in ticks for 10ms ticks
    - distance / (velocity / 100)
    - (distance / velocity) x 100
  - compute: (distance x 100) / velocity

speed: train setting 0-14
velocity: actual travel distance per time
1. non-linear with speed
2. different for different trains
3. different for different parts of track?
4. changes over time (wear and tear)
handle at least 1. and 2. by measuring and storing velocity data
- offline experiments → start now!
- continuous online measurements?
- data import/export?

assume ~70ms continuous sensor polling loop
unknown (hopefully constant) measurement error
- train controller box
- signal latency
- etc.
variable measurement error: sensor trigger relative to polling loop → 0-70ms
processing delays? later... (should be small with dedicated measurement program)