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FA-93771 / Solar tracker geometry / Open access

Hazard stow angle selection: wind stow threshold · case 01

Wind exactly at the stow limit leaves rows at their tracking or manual angle.

Verified by executionVariant 1 · 7 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The wind comparison is strict.

THE FAILURE

The wind comparison is strict.

Unsuccessful approach: Raising the limit ignores the configured stow speed.

Case contract

Priority: wind >= 20 m/s gives [0.0, 'wind']; then a manual angle (clamped to +-max_angle) gives 'manual'; then hail from azimuth hail_from gives +max_angle when (hail_from - axis_az) mod 360 is strictly between 0 and 180, else -max_angle ('hail'); then snow alternates rows: even rows +max_angle, odd rows -max_angle ('snow'); otherwise [None, 'normal'].

Why this case matters

Single-axis and dual-axis solar trackers turn a sun direction into actuator commands; a sign, frame or limit mistake points a whole plant away from the sun or into a mechanical stop.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(hazards, row, axis_az, max_angle, manual):
    wind = hazards.get('wind', 0)
    if wind > 20:
        return [0.0, 'wind']
    if manual is not None:
        return [float(max(-max_angle, min(max_angle, manual))), 'manual']
    hail = hazards.get('hail_from')
    if hail is not None:
        rel = (hail - axis_az) % 360
        return [float(max_angle if 0 < rel < 180 else -max_angle), 'hail']
    if hazards.get('snow'):
        return [float(max_angle if row % 2 == 0 else -max_angle), 'snow']
    return [None, 'normal']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['boundary: wind exactly at stow limit', [{'wind': 20}, 0, 180, 60, 30], [0.0, 'wind']],
  ['boundary: hail along the axis', [{'hail_from': 180}, 1, 180, 60, None], [-60.0, 'hail']],
  ['normal: snow on odd row', [{'snow': True}, 3, 180, 60, None], [-60.0, 'snow']],
  ['regression: wind stow threshold', [{'wind': 20, 'hail_from': 270}, 2, 180, 50, -70],
   [0.0, 'wind']],
  ['regression: wind stow threshold (partial repair)', [{'wind': 20, 'hail_from': 90}, 4, 0, 50, 0],
   [0.0, 'wind']],
  ['control 1', [{'wind': 15, 'hail_from': 180}, 5, 180, 50, 0], [0.0, 'manual']],
  ['control 2', [{'wind': 20, 'hail_from': 90, 'snow': False}, 2, 180, 50, -70], [0.0, 'wind']]],
 [['boundary: wind exactly at stow limit', [{'wind': 20}, 0, 180, 60, 30], [0.0, 'wind']],
  ['boundary: hail along the axis', [{'hail_from': 180}, 1, 180, 60, None], [-60.0, 'hail']],
  ['normal: snow on odd row', [{'snow': True}, 3, 180, 60, None], [-60.0, 'snow']],
  ['regression: wind stow threshold', [{'wind': 20}, 4, 0, 60, -70], [0.0, 'wind']],
  ['regression: wind stow threshold (partial repair)',
   [{'wind': 20, 'hail_from': 180}, 1, 180, 50, 0], [0.0, 'wind']],
  ['control 1', [{}, 3, 0, 60, 65], [60.0, 'manual']],
  ['control 2', [{'wind': 21, 'hail_from': 225, 'snow': True}, 1, 180, 60, -70], [0.0, 'wind']]],
 [['boundary: wind exactly at stow limit', [{'wind': 20}, 0, 180, 60, 30], [0.0, 'wind']],
  ['boundary: hail along the axis', [{'hail_from': 180}, 1, 180, 60, None], [-60.0, 'hail']],
  ['normal: snow on odd row', [{'snow': True}, 3, 180, 60, None], [-60.0, 'snow']],
  ['regression: wind stow threshold', [{'wind': 20, 'snow': True}, 4, 0, 60, None], [0.0, 'wind']],
  ['regression: wind stow threshold (partial repair)', [{'wind': 21}, 4, 0, 50, -70],
   [0.0, 'wind']],
  ['control 1', [{}, 3, 180, 50, -20], [-20.0, 'manual']],
  ['control 2', [{'wind': 21, 'snow': False}, 1, 0, 60, 65], [0.0, 'wind']]],
 [['boundary: wind exactly at stow limit', [{'wind': 20}, 0, 180, 60, 30], [0.0, 'wind']],
  ['boundary: hail along the axis', [{'hail_from': 180}, 1, 180, 60, None], [-60.0, 'hail']],
  ['normal: snow on odd row', [{'snow': True}, 3, 180, 60, None], [-60.0, 'snow']],
  ['regression: wind stow threshold', [{'wind': 20, 'hail_from': 225}, 0, 0, 50, 65],
   [0.0, 'wind']],
  ['regression: wind stow threshold (partial repair)',
   [{'wind': 21, 'snow': True}, 1, 180, 50, -20], [0.0, 'wind']],
  ['control 1', [{'hail_from': None, 'snow': True}, 1, 180, 50, 30], [30.0, 'manual']],
  ['control 2', [{'wind': 15, 'snow': True}, 3, 0, 50, -20], [-20.0, 'manual']]],
 [['boundary: wind exactly at stow limit', [{'wind': 20}, 0, 180, 60, 30], [0.0, 'wind']],
  ['boundary: hail along the axis', [{'hail_from': 180}, 1, 180, 60, None], [-60.0, 'hail']],
  ['normal: snow on odd row', [{'snow': True}, 3, 180, 60, None], [-60.0, 'snow']],
  ['regression: wind stow threshold', [{'wind': 20, 'snow': True}, 4, 180, 50, -70], [0.0, 'wind']],
  ['regression: wind stow threshold (partial repair)',
   [{'wind': 21, 'hail_from': 45}, 5, 180, 50, 30], [0.0, 'wind']],
  ['control 1', [{'wind': 19, 'snow': False}, 1, 180, 60, None], [None, 'normal']],
  ['control 2', [{'snow': True}, 4, 0, 50, -20], [-20.0, 'manual']]]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
boundary: wind exactly at stow limit[30.0, 'manual'][0.0, 'wind']Failed
boundary: hail along the axis[-60.0, 'hail'][-60.0, 'hail']Passed
normal: snow on odd row[-60.0, 'snow'][-60.0, 'snow']Passed
regression: wind stow threshold[-50.0, 'manual'][0.0, 'wind']Failed
regression: wind stow threshold (partial repair)[0.0, 'manual'][0.0, 'wind']Failed
control 1[0.0, 'manual'][0.0, 'manual']Passed
control 2[-50.0, 'manual'][0.0, 'wind']Failed

SHA-256 / c202bb574e225deaee4c7d0d89a84b866aa743319d9cf604fe30624db6184d86

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(hazards, row, axis_az, max_angle, manual):
    wind = hazards.get('wind', 0)
    if wind >= 25:
        return [0.0, 'wind']
    if manual is not None:
        return [float(max(-max_angle, min(max_angle, manual))), 'manual']
    hail = hazards.get('hail_from')
    if hail is not None:
        rel = (hail - axis_az) % 360
        return [float(max_angle if 0 < rel < 180 else -max_angle), 'hail']
    if hazards.get('snow'):
        return [float(max_angle if row % 2 == 0 else -max_angle), 'snow']
    return [None, 'normal']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['boundary: wind exactly at stow limit', [{'wind': 20}, 0, 180, 60, 30], [0.0, 'wind']],
  ['boundary: hail along the axis', [{'hail_from': 180}, 1, 180, 60, None], [-60.0, 'hail']],
  ['normal: snow on odd row', [{'snow': True}, 3, 180, 60, None], [-60.0, 'snow']],
  ['regression: wind stow threshold', [{'wind': 20, 'hail_from': 270}, 2, 180, 50, -70],
   [0.0, 'wind']],
  ['regression: wind stow threshold (partial repair)', [{'wind': 20, 'hail_from': 90}, 4, 0, 50, 0],
   [0.0, 'wind']],
  ['control 1', [{'wind': 15, 'hail_from': 180}, 5, 180, 50, 0], [0.0, 'manual']],
  ['control 2', [{'wind': 20, 'hail_from': 90, 'snow': False}, 2, 180, 50, -70], [0.0, 'wind']]],
 [['boundary: wind exactly at stow limit', [{'wind': 20}, 0, 180, 60, 30], [0.0, 'wind']],
  ['boundary: hail along the axis', [{'hail_from': 180}, 1, 180, 60, None], [-60.0, 'hail']],
  ['normal: snow on odd row', [{'snow': True}, 3, 180, 60, None], [-60.0, 'snow']],
  ['regression: wind stow threshold', [{'wind': 20}, 4, 0, 60, -70], [0.0, 'wind']],
  ['regression: wind stow threshold (partial repair)',
   [{'wind': 20, 'hail_from': 180}, 1, 180, 50, 0], [0.0, 'wind']],
  ['control 1', [{}, 3, 0, 60, 65], [60.0, 'manual']],
  ['control 2', [{'wind': 21, 'hail_from': 225, 'snow': True}, 1, 180, 60, -70], [0.0, 'wind']]],
 [['boundary: wind exactly at stow limit', [{'wind': 20}, 0, 180, 60, 30], [0.0, 'wind']],
  ['boundary: hail along the axis', [{'hail_from': 180}, 1, 180, 60, None], [-60.0, 'hail']],
  ['normal: snow on odd row', [{'snow': True}, 3, 180, 60, None], [-60.0, 'snow']],
  ['regression: wind stow threshold', [{'wind': 20, 'snow': True}, 4, 0, 60, None], [0.0, 'wind']],
  ['regression: wind stow threshold (partial repair)', [{'wind': 21}, 4, 0, 50, -70],
   [0.0, 'wind']],
  ['control 1', [{}, 3, 180, 50, -20], [-20.0, 'manual']],
  ['control 2', [{'wind': 21, 'snow': False}, 1, 0, 60, 65], [0.0, 'wind']]],
 [['boundary: wind exactly at stow limit', [{'wind': 20}, 0, 180, 60, 30], [0.0, 'wind']],
  ['boundary: hail along the axis', [{'hail_from': 180}, 1, 180, 60, None], [-60.0, 'hail']],
  ['normal: snow on odd row', [{'snow': True}, 3, 180, 60, None], [-60.0, 'snow']],
  ['regression: wind stow threshold', [{'wind': 20, 'hail_from': 225}, 0, 0, 50, 65],
   [0.0, 'wind']],
  ['regression: wind stow threshold (partial repair)',
   [{'wind': 21, 'snow': True}, 1, 180, 50, -20], [0.0, 'wind']],
  ['control 1', [{'hail_from': None, 'snow': True}, 1, 180, 50, 30], [30.0, 'manual']],
  ['control 2', [{'wind': 15, 'snow': True}, 3, 0, 50, -20], [-20.0, 'manual']]],
 [['boundary: wind exactly at stow limit', [{'wind': 20}, 0, 180, 60, 30], [0.0, 'wind']],
  ['boundary: hail along the axis', [{'hail_from': 180}, 1, 180, 60, None], [-60.0, 'hail']],
  ['normal: snow on odd row', [{'snow': True}, 3, 180, 60, None], [-60.0, 'snow']],
  ['regression: wind stow threshold', [{'wind': 20, 'snow': True}, 4, 180, 50, -70], [0.0, 'wind']],
  ['regression: wind stow threshold (partial repair)',
   [{'wind': 21, 'hail_from': 45}, 5, 180, 50, 30], [0.0, 'wind']],
  ['control 1', [{'wind': 19, 'snow': False}, 1, 180, 60, None], [None, 'normal']],
  ['control 2', [{'snow': True}, 4, 0, 50, -20], [-20.0, 'manual']]]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
boundary: wind exactly at stow limit[30.0, 'manual'][0.0, 'wind']Failed
boundary: hail along the axis[-60.0, 'hail'][-60.0, 'hail']Passed
normal: snow on odd row[-60.0, 'snow'][-60.0, 'snow']Passed
regression: wind stow threshold[-50.0, 'manual'][0.0, 'wind']Failed
regression: wind stow threshold (partial repair)[0.0, 'manual'][0.0, 'wind']Failed
control 1[0.0, 'manual'][0.0, 'manual']Passed
control 2[-50.0, 'manual'][0.0, 'wind']Failed

SHA-256 / 1fb2dd52bf4a87123903918169e8eb94246ec59a5906a9424cf7774ee3fdd38f

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 7 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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Verification & scope

Deterministic stipulated toy contract for teaching; no claim of conformance with any standard, vendor protocol or production controller. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:51:58.148447+00:00.

Case digest / a335e74c00a2a50b5346597f51e88ce45bd8910a9d2c4dce8cbffb7ab5d9afe1