FA-93676 / Solar tracker geometry / Open access

Overcast diffuse flat stow: blend band edge · case 01

At the lower edge of the blend band status reports blend while the angle is unchanged.

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

ROOT CAUSE

The blend band includes its lower edge.

VERIFIED REPAIR

Blend only when df is strictly inside the band.

Unsuccessful approach: Placing the band above the threshold disables blending.

Case contract

ghi <= 0 returns [0.0, night]. Diffuse fraction df = dhi*100/ghi percent (may exceed 100 with sensor noise). df >= thresh_pct: [0.0, 'diffuse']. If blend > 0 and df > thresh_pct - blend the angle is ideal*(thresh_pct - df)/blend ('blend'). Otherwise [ideal, 'track']. Angles rounded to 3.

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
import math
N = 1
observations = []
def solve(ghi, dhi, ideal, thresh_pct, blend):
    if ghi <= 0:
        return [0.0, 'night']
    df = dhi * 100 / ghi
    if df >= thresh_pct:
        return [0.0, 'diffuse']
    if blend > 0 and df >= thresh_pct - blend:
        return [round(ideal * (thresh_pct - df) / blend, 3), 'blend']
    return [round(float(ideal), 3), 'track']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['boundary: diffuse fraction at threshold', [400, 280, 30, 70, 10], [0.0, 'diffuse']],
  ['boundary: blend band lower edge', [400, 240, 30, 70, 10], [30.0, 'track']],
  ['normal: clear sky', [800, 80, -45, 70, 10], [-45.0, 'track']],
  ['regression: blend band edge', [200, 100, 25, 60, 10], [25.0, 'track']],
  ['regression: blend band edge (partial repair)', [100, 60, 0, 70, 20], [0.0, 'blend']],
  ['control 1', [100, 400, -30, 70, 20], [0.0, 'diffuse']],
  ['control 2', [0, 80, 0, 70, 0], [0.0, 'night']]],
 [['boundary: diffuse fraction at threshold', [400, 280, 30, 70, 10], [0.0, 'diffuse']],
  ['boundary: blend band lower edge', [400, 240, 30, 70, 10], [30.0, 'track']],
  ['normal: clear sky', [800, 80, -45, 70, 10], [-45.0, 'track']],
  ['regression: blend band edge', [200, 100, 0, 70, 20], [0.0, 'track']],
  ['regression: blend band edge (partial repair)', [100, 60, 45, 70, 20], [22.5, 'blend']],
  ['control 1', [100, 400, -30, 70, 0], [0.0, 'diffuse']],
  ['control 2', [100, 0, 0, 70, 0], [0.0, 'track']]],
 [['boundary: diffuse fraction at threshold', [400, 280, 30, 70, 10], [0.0, 'diffuse']],
  ['boundary: blend band lower edge', [400, 240, 30, 70, 10], [30.0, 'track']],
  ['normal: clear sky', [800, 80, -45, 70, 10], [-45.0, 'track']],
  ['regression: blend band edge', [200, 100, 25, 60, 10], [25.0, 'track']],
  ['regression: blend band edge (partial repair)', [100, 60, 45, 70, 20], [22.5, 'blend']],
  ['control 1', [200, 160, 25, 70, 0], [0.0, 'diffuse']],
  ['control 2', [800, 160, -50, 80, 20], [-50.0, 'track']]],
 [['boundary: diffuse fraction at threshold', [400, 280, 30, 70, 10], [0.0, 'diffuse']],
  ['boundary: blend band lower edge', [400, 240, 30, 70, 10], [30.0, 'track']],
  ['normal: clear sky', [800, 80, -45, 70, 10], [-45.0, 'track']],
  ['regression: blend band edge', [200, 100, 25, 60, 10], [25.0, 'track']],
  ['regression: blend band edge (partial repair)', [100, 60, 45, 70, 20], [22.5, 'blend']],
  ['control 1', [400, 80, -30, 80, 0], [-30.0, 'track']],
  ['control 2', [0, 60, 25, 80, 0], [0.0, 'night']]],
 [['boundary: diffuse fraction at threshold', [400, 280, 30, 70, 10], [0.0, 'diffuse']],
  ['boundary: blend band lower edge', [400, 240, 30, 70, 10], [30.0, 'track']],
  ['normal: clear sky', [800, 80, -45, 70, 10], [-45.0, 'track']],
  ['regression: blend band edge', [200, 100, 25, 60, 10], [25.0, 'track']],
  ['regression: blend band edge (partial repair)', [100, 60, 45, 70, 20], [22.5, 'blend']],
  ['control 1', [400, 400, 0, 80, 10], [0.0, 'diffuse']],
  ['control 2', [100, 400, -30, 70, 0], [0.0, 'diffuse']]]]
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 fixture	Actual	Expected	Outcome
boundary: diffuse fraction at threshold	`[0.0, 'diffuse']`	`[0.0, 'diffuse']`	Passed
boundary: blend band lower edge	`[30.0, 'blend']`	`[30.0, 'track']`	Failed
normal: clear sky	`[-45.0, 'track']`	`[-45.0, 'track']`	Passed
regression: blend band edge	`[25.0, 'blend']`	`[25.0, 'track']`	Failed
regression: blend band edge (partial repair)	`[0.0, 'blend']`	`[0.0, 'blend']`	Passed
control 1	`[0.0, 'diffuse']`	`[0.0, 'diffuse']`	Passed
control 2	`[0.0, 'night']`	`[0.0, 'night']`	Passed

SHA-256 / cef0b8b1b39ca90592e13bbda1898e814ffd1071db6cdfe0a3ae8fa1bfdf20c2

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(ghi, dhi, ideal, thresh_pct, blend):
    if ghi <= 0:
        return [0.0, 'night']
    df = dhi * 100 / ghi
    if df >= thresh_pct:
        return [0.0, 'diffuse']
    if blend > 0 and df > thresh_pct + blend:
        return [round(ideal * (thresh_pct - df) / blend, 3), 'blend']
    return [round(float(ideal), 3), 'track']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['boundary: diffuse fraction at threshold', [400, 280, 30, 70, 10], [0.0, 'diffuse']],
  ['boundary: blend band lower edge', [400, 240, 30, 70, 10], [30.0, 'track']],
  ['normal: clear sky', [800, 80, -45, 70, 10], [-45.0, 'track']],
  ['regression: blend band edge', [200, 100, 25, 60, 10], [25.0, 'track']],
  ['regression: blend band edge (partial repair)', [100, 60, 0, 70, 20], [0.0, 'blend']],
  ['control 1', [100, 400, -30, 70, 20], [0.0, 'diffuse']],
  ['control 2', [0, 80, 0, 70, 0], [0.0, 'night']]],
 [['boundary: diffuse fraction at threshold', [400, 280, 30, 70, 10], [0.0, 'diffuse']],
  ['boundary: blend band lower edge', [400, 240, 30, 70, 10], [30.0, 'track']],
  ['normal: clear sky', [800, 80, -45, 70, 10], [-45.0, 'track']],
  ['regression: blend band edge', [200, 100, 0, 70, 20], [0.0, 'track']],
  ['regression: blend band edge (partial repair)', [100, 60, 45, 70, 20], [22.5, 'blend']],
  ['control 1', [100, 400, -30, 70, 0], [0.0, 'diffuse']],
  ['control 2', [100, 0, 0, 70, 0], [0.0, 'track']]],
 [['boundary: diffuse fraction at threshold', [400, 280, 30, 70, 10], [0.0, 'diffuse']],
  ['boundary: blend band lower edge', [400, 240, 30, 70, 10], [30.0, 'track']],
  ['normal: clear sky', [800, 80, -45, 70, 10], [-45.0, 'track']],
  ['regression: blend band edge', [200, 100, 25, 60, 10], [25.0, 'track']],
  ['regression: blend band edge (partial repair)', [100, 60, 45, 70, 20], [22.5, 'blend']],
  ['control 1', [200, 160, 25, 70, 0], [0.0, 'diffuse']],
  ['control 2', [800, 160, -50, 80, 20], [-50.0, 'track']]],
 [['boundary: diffuse fraction at threshold', [400, 280, 30, 70, 10], [0.0, 'diffuse']],
  ['boundary: blend band lower edge', [400, 240, 30, 70, 10], [30.0, 'track']],
  ['normal: clear sky', [800, 80, -45, 70, 10], [-45.0, 'track']],
  ['regression: blend band edge', [200, 100, 25, 60, 10], [25.0, 'track']],
  ['regression: blend band edge (partial repair)', [100, 60, 45, 70, 20], [22.5, 'blend']],
  ['control 1', [400, 80, -30, 80, 0], [-30.0, 'track']],
  ['control 2', [0, 60, 25, 80, 0], [0.0, 'night']]],
 [['boundary: diffuse fraction at threshold', [400, 280, 30, 70, 10], [0.0, 'diffuse']],
  ['boundary: blend band lower edge', [400, 240, 30, 70, 10], [30.0, 'track']],
  ['normal: clear sky', [800, 80, -45, 70, 10], [-45.0, 'track']],
  ['regression: blend band edge', [200, 100, 25, 60, 10], [25.0, 'track']],
  ['regression: blend band edge (partial repair)', [100, 60, 45, 70, 20], [22.5, 'blend']],
  ['control 1', [400, 400, 0, 80, 10], [0.0, 'diffuse']],
  ['control 2', [100, 400, -30, 70, 0], [0.0, 'diffuse']]]]
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 fixture	Actual	Expected	Outcome
boundary: diffuse fraction at threshold	`[0.0, 'diffuse']`	`[0.0, 'diffuse']`	Passed
boundary: blend band lower edge	`[30.0, 'track']`	`[30.0, 'track']`	Passed
normal: clear sky	`[-45.0, 'track']`	`[-45.0, 'track']`	Passed
regression: blend band edge	`[25.0, 'track']`	`[25.0, 'track']`	Passed
regression: blend band edge (partial repair)	`[0.0, 'track']`	`[0.0, 'blend']`	Failed
control 1	`[0.0, 'diffuse']`	`[0.0, 'diffuse']`	Passed
control 2	`[0.0, 'night']`	`[0.0, 'night']`	Passed

SHA-256 / b4312d3203df5e16d4605152c42092e808f5e3c7c35bb0780d03dedea013cfad

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(ghi, dhi, ideal, thresh_pct, blend):
    if ghi <= 0:
        return [0.0, 'night']
    df = dhi * 100 / ghi
    if df >= thresh_pct:
        return [0.0, 'diffuse']
    if blend > 0 and df > thresh_pct - blend:
        return [round(ideal * (thresh_pct - df) / blend, 3), 'blend']
    return [round(float(ideal), 3), 'track']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['boundary: diffuse fraction at threshold', [400, 280, 30, 70, 10], [0.0, 'diffuse']],
  ['boundary: blend band lower edge', [400, 240, 30, 70, 10], [30.0, 'track']],
  ['normal: clear sky', [800, 80, -45, 70, 10], [-45.0, 'track']],
  ['regression: blend band edge', [200, 100, 25, 60, 10], [25.0, 'track']],
  ['regression: blend band edge (partial repair)', [100, 60, 0, 70, 20], [0.0, 'blend']],
  ['control 1', [100, 400, -30, 70, 20], [0.0, 'diffuse']],
  ['control 2', [0, 80, 0, 70, 0], [0.0, 'night']]],
 [['boundary: diffuse fraction at threshold', [400, 280, 30, 70, 10], [0.0, 'diffuse']],
  ['boundary: blend band lower edge', [400, 240, 30, 70, 10], [30.0, 'track']],
  ['normal: clear sky', [800, 80, -45, 70, 10], [-45.0, 'track']],
  ['regression: blend band edge', [200, 100, 0, 70, 20], [0.0, 'track']],
  ['regression: blend band edge (partial repair)', [100, 60, 45, 70, 20], [22.5, 'blend']],
  ['control 1', [100, 400, -30, 70, 0], [0.0, 'diffuse']],
  ['control 2', [100, 0, 0, 70, 0], [0.0, 'track']]],
 [['boundary: diffuse fraction at threshold', [400, 280, 30, 70, 10], [0.0, 'diffuse']],
  ['boundary: blend band lower edge', [400, 240, 30, 70, 10], [30.0, 'track']],
  ['normal: clear sky', [800, 80, -45, 70, 10], [-45.0, 'track']],
  ['regression: blend band edge', [200, 100, 25, 60, 10], [25.0, 'track']],
  ['regression: blend band edge (partial repair)', [100, 60, 45, 70, 20], [22.5, 'blend']],
  ['control 1', [200, 160, 25, 70, 0], [0.0, 'diffuse']],
  ['control 2', [800, 160, -50, 80, 20], [-50.0, 'track']]],
 [['boundary: diffuse fraction at threshold', [400, 280, 30, 70, 10], [0.0, 'diffuse']],
  ['boundary: blend band lower edge', [400, 240, 30, 70, 10], [30.0, 'track']],
  ['normal: clear sky', [800, 80, -45, 70, 10], [-45.0, 'track']],
  ['regression: blend band edge', [200, 100, 25, 60, 10], [25.0, 'track']],
  ['regression: blend band edge (partial repair)', [100, 60, 45, 70, 20], [22.5, 'blend']],
  ['control 1', [400, 80, -30, 80, 0], [-30.0, 'track']],
  ['control 2', [0, 60, 25, 80, 0], [0.0, 'night']]],
 [['boundary: diffuse fraction at threshold', [400, 280, 30, 70, 10], [0.0, 'diffuse']],
  ['boundary: blend band lower edge', [400, 240, 30, 70, 10], [30.0, 'track']],
  ['normal: clear sky', [800, 80, -45, 70, 10], [-45.0, 'track']],
  ['regression: blend band edge', [200, 100, 25, 60, 10], [25.0, 'track']],
  ['regression: blend band edge (partial repair)', [100, 60, 45, 70, 20], [22.5, 'blend']],
  ['control 1', [400, 400, 0, 80, 10], [0.0, 'diffuse']],
  ['control 2', [100, 400, -30, 70, 0], [0.0, 'diffuse']]]]
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 fixture	Actual	Expected	Outcome
boundary: diffuse fraction at threshold	`[0.0, 'diffuse']`	`[0.0, 'diffuse']`	Passed
boundary: blend band lower edge	`[30.0, 'track']`	`[30.0, 'track']`	Passed
normal: clear sky	`[-45.0, 'track']`	`[-45.0, 'track']`	Passed
regression: blend band edge	`[25.0, 'track']`	`[25.0, 'track']`	Passed
regression: blend band edge (partial repair)	`[0.0, 'blend']`	`[0.0, 'blend']`	Passed
control 1	`[0.0, 'diffuse']`	`[0.0, 'diffuse']`	Passed
control 2	`[0.0, 'night']`	`[0.0, 'night']`	Passed

SHA-256 / f5c787dfd69e026d07809e34dfb0d28ff90c64873cc9fb276a3e0eca55ca06c8

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 2026-09-29T14:51:57.415875+00:00.

Case digest / 932eb7d877df3f6b41dde82b8b30b67fb5138c53378fed547053bf7209e185d9