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FA-93426 / Solar tracker geometry / Open access

Dual-axis azimuth cable-wrap slew: range inclusivity · case 01

A target exactly at the mechanical stop is reached the long way round.

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

ROOT CAUSE

The upper stop is excluded from the candidate range.

THE FAILURE

The upper stop is excluded from the candidate range.

Unsuccessful approach: Excluding the lower stop instead just moves the error.

Case contract

The azimuth drive has a continuous mechanical range [min_az, max_az] (may exceed 360 span). target_az is 0..359. Candidates are target + 360k inside the range; pick the smallest |move| from cur_az, ties to the candidate nearest the range centre, then the smaller. If none is in range, go to the limit with the smaller angular distance (mod 360) to the target, ties to min_az, status 'limit'. Return [position, move, status].

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(cur_az, target_az, min_az, max_az):
    cands = []
    k0 = math.floor((min_az - target_az) / 360)
    for k in range(k0, k0 + 4):
        c = target_az + 360 * k
        if min_az <= c < max_az:
            cands.append(c)
    center = (min_az + max_az) / 2
    if not cands:
        def ang(a):
            d = (a - target_az) % 360
            return min(d, 360 - d)
        lim = min_az if ang(min_az) <= ang(max_az) else max_az
        return [lim, lim - cur_az, 'limit']
    best = min(cands, key=lambda c: (abs(c - cur_az), abs(c - center), c))
    return [best, best - cur_az, 'ok']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['boundary: target exactly at max stop', [0, 270, -270, 270], [-90, -90, 'ok']],
  ['normal: short way through north', [350, 10, -270, 270], [10, -340, 'ok']],
  ['boundary: target outside narrow range', [180, 0, 90, 270], [90, -90, 'limit']],
  ['regression: range inclusivity', [450, 90, -90, 450], [450, 0, 'ok']],
  ['regression: range inclusivity (partial repair)', [90, 0, 0, 180], [0, -90, 'ok']],
  ['control 1', [180, 0, -90, 450], [0, -180, 'ok']],
  ['control 2', [180, 315, 0, 360], [315, 135, 'ok']]],
 [['boundary: target exactly at max stop', [0, 270, -270, 270], [-90, -90, 'ok']],
  ['normal: short way through north', [350, 10, -270, 270], [10, -340, 'ok']],
  ['boundary: target outside narrow range', [180, 0, 90, 270], [90, -90, 'limit']],
  ['regression: range inclusivity', [270, 270, 90, 270], [270, 0, 'ok']],
  ['regression: range inclusivity (partial repair)', [-135, 180, -180, 180], [-180, -45, 'ok']],
  ['control 1', [45, 225, -90, 450], [225, 180, 'ok']],
  ['control 2', [180, 180, -90, 450], [180, 0, 'ok']]],
 [['boundary: target exactly at max stop', [0, 270, -270, 270], [-90, -90, 'ok']],
  ['normal: short way through north', [350, 10, -270, 270], [10, -340, 'ok']],
  ['boundary: target outside narrow range', [180, 0, 90, 270], [90, -90, 'limit']],
  ['regression: range inclusivity', [360, 90, -90, 450], [450, 90, 'ok']],
  ['regression: range inclusivity (partial repair)', [-225, 90, -270, 270], [-270, -45, 'ok']],
  ['control 1', [0, 45, -90, 450], [45, 45, 'ok']],
  ['control 2', [360, 45, 0, 360], [45, -315, 'ok']]],
 [['boundary: target exactly at max stop', [0, 270, -270, 270], [-90, -90, 'ok']],
  ['normal: short way through north', [350, 10, -270, 270], [10, -340, 'ok']],
  ['boundary: target outside narrow range', [180, 0, 90, 270], [90, -90, 'limit']],
  ['regression: range inclusivity', [135, 270, -270, 270], [270, 135, 'ok']],
  ['regression: range inclusivity (partial repair)', [270, 45, 45, 315], [45, -225, 'ok']],
  ['control 1', [315, 135, 45, 315], [135, -180, 'ok']],
  ['control 2', [45, 135, 45, 315], [135, 90, 'ok']]],
 [['boundary: target exactly at max stop', [0, 270, -270, 270], [-90, -90, 'ok']],
  ['normal: short way through north', [350, 10, -270, 270], [10, -340, 'ok']],
  ['boundary: target outside narrow range', [180, 0, 90, 270], [90, -90, 'limit']],
  ['regression: range inclusivity', [180, 270, 90, 270], [270, 90, 'ok']],
  ['regression: range inclusivity (partial repair)', [-270, 90, -270, 270], [-270, 0, 'ok']],
  ['control 1', [45, 315, 0, 180], [0, -45, 'limit']],
  ['control 2', [315, 180, 0, 360], [180, -135, 'ok']]]]
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: target exactly at max stop[-90, -90, 'ok'][-90, -90, 'ok']Passed
normal: short way through north[10, -340, 'ok'][10, -340, 'ok']Passed
boundary: target outside narrow range[90, -90, 'limit'][90, -90, 'limit']Passed
regression: range inclusivity[90, -360, 'ok'][450, 0, 'ok']Failed
regression: range inclusivity (partial repair)[0, -90, 'ok'][0, -90, 'ok']Passed
control 1[0, -180, 'ok'][0, -180, 'ok']Passed
control 2[315, 135, 'ok'][315, 135, 'ok']Passed

SHA-256 / c3ec8619a64a615870eb81c25affa6f8fffe73efc6f35c76375178d976749b32

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(cur_az, target_az, min_az, max_az):
    cands = []
    k0 = math.floor((min_az - target_az) / 360)
    for k in range(k0, k0 + 4):
        c = target_az + 360 * k
        if min_az < c <= max_az:
            cands.append(c)
    center = (min_az + max_az) / 2
    if not cands:
        def ang(a):
            d = (a - target_az) % 360
            return min(d, 360 - d)
        lim = min_az if ang(min_az) <= ang(max_az) else max_az
        return [lim, lim - cur_az, 'limit']
    best = min(cands, key=lambda c: (abs(c - cur_az), abs(c - center), c))
    return [best, best - cur_az, 'ok']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['boundary: target exactly at max stop', [0, 270, -270, 270], [-90, -90, 'ok']],
  ['normal: short way through north', [350, 10, -270, 270], [10, -340, 'ok']],
  ['boundary: target outside narrow range', [180, 0, 90, 270], [90, -90, 'limit']],
  ['regression: range inclusivity', [450, 90, -90, 450], [450, 0, 'ok']],
  ['regression: range inclusivity (partial repair)', [90, 0, 0, 180], [0, -90, 'ok']],
  ['control 1', [180, 0, -90, 450], [0, -180, 'ok']],
  ['control 2', [180, 315, 0, 360], [315, 135, 'ok']]],
 [['boundary: target exactly at max stop', [0, 270, -270, 270], [-90, -90, 'ok']],
  ['normal: short way through north', [350, 10, -270, 270], [10, -340, 'ok']],
  ['boundary: target outside narrow range', [180, 0, 90, 270], [90, -90, 'limit']],
  ['regression: range inclusivity', [270, 270, 90, 270], [270, 0, 'ok']],
  ['regression: range inclusivity (partial repair)', [-135, 180, -180, 180], [-180, -45, 'ok']],
  ['control 1', [45, 225, -90, 450], [225, 180, 'ok']],
  ['control 2', [180, 180, -90, 450], [180, 0, 'ok']]],
 [['boundary: target exactly at max stop', [0, 270, -270, 270], [-90, -90, 'ok']],
  ['normal: short way through north', [350, 10, -270, 270], [10, -340, 'ok']],
  ['boundary: target outside narrow range', [180, 0, 90, 270], [90, -90, 'limit']],
  ['regression: range inclusivity', [360, 90, -90, 450], [450, 90, 'ok']],
  ['regression: range inclusivity (partial repair)', [-225, 90, -270, 270], [-270, -45, 'ok']],
  ['control 1', [0, 45, -90, 450], [45, 45, 'ok']],
  ['control 2', [360, 45, 0, 360], [45, -315, 'ok']]],
 [['boundary: target exactly at max stop', [0, 270, -270, 270], [-90, -90, 'ok']],
  ['normal: short way through north', [350, 10, -270, 270], [10, -340, 'ok']],
  ['boundary: target outside narrow range', [180, 0, 90, 270], [90, -90, 'limit']],
  ['regression: range inclusivity', [135, 270, -270, 270], [270, 135, 'ok']],
  ['regression: range inclusivity (partial repair)', [270, 45, 45, 315], [45, -225, 'ok']],
  ['control 1', [315, 135, 45, 315], [135, -180, 'ok']],
  ['control 2', [45, 135, 45, 315], [135, 90, 'ok']]],
 [['boundary: target exactly at max stop', [0, 270, -270, 270], [-90, -90, 'ok']],
  ['normal: short way through north', [350, 10, -270, 270], [10, -340, 'ok']],
  ['boundary: target outside narrow range', [180, 0, 90, 270], [90, -90, 'limit']],
  ['regression: range inclusivity', [180, 270, 90, 270], [270, 90, 'ok']],
  ['regression: range inclusivity (partial repair)', [-270, 90, -270, 270], [-270, 0, 'ok']],
  ['control 1', [45, 315, 0, 180], [0, -45, 'limit']],
  ['control 2', [315, 180, 0, 360], [180, -135, 'ok']]]]
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: target exactly at max stop[-90, -90, 'ok'][-90, -90, 'ok']Passed
normal: short way through north[10, -340, 'ok'][10, -340, 'ok']Passed
boundary: target outside narrow range[90, -90, 'limit'][90, -90, 'limit']Passed
regression: range inclusivity[450, 0, 'ok'][450, 0, 'ok']Passed
regression: range inclusivity (partial repair)[0, -90, 'limit'][0, -90, 'ok']Failed
control 1[0, -180, 'ok'][0, -180, 'ok']Passed
control 2[315, 135, 'ok'][315, 135, 'ok']Passed

SHA-256 / 859b437305b931d279818387f51e9e7fcabeace4ccd83e1db4b3f021b7b75230

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 2026-09-29T14:51:54.986617+00:00.

Case digest / c78bd859f504fd9f9b45a7fe74562754b9447c6abf5610cd1794e185998c7996