FAILURE MAP
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FA-93536 / Solar tracker geometry / Open access

Tracker actuator step command: reported position · case 01

The reported position drifts away from what the motor actually did.

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

ROOT CAUSE

The position is advanced by the requested move rather than the executed steps.

THE FAILURE

The position is advanced by the requested move rather than the executed steps.

Unsuccessful approach: Reporting the target when no step was possible claims motion that never happened.

Case contract

Angles in millidegrees. The target is clamped to [lo, hi]. If |target - current| < deadband no move is made. Otherwise the move is limited to +-max_step, converted to whole motor steps of dps millidegrees truncated toward zero. Return [new position, signed steps].

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(target, current, deadband, max_step, dps, lo, hi):
    tgt = min(max(target, lo), hi)
    err = tgt - current
    if abs(err) < deadband:
        return [current, 0]
    move = max(-max_step, min(max_step, err))
    steps = abs(move) // dps
    if move < 0:
        steps = -steps
    return [current + move, steps]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['boundary: error equal to deadband', [1500, 1000, 500, 2000, 125, -60000, 60000], [1500, 4]],
  ['boundary: target past west stop', [80000, 59000, 250, 5000, 7, -60000, 60000], [59994, 142]],
  ['normal: negative move truncation', [-10000, 0, 250, 2000, 300, -60000, 60000], [-1800, -6]],
  ['regression: move smaller than one step', [1200, 1000, 0, 2000, 300, -60000, 60000], [1000, 0]],
  ['regression: reported position', [87, 3902, 250, 500, 90, -52000, 55000], [3452, -5]],
  ['control 1', [-57417, -56117, 500, 2000, 300, -52000, 60000], [-54317, 6]],
  ['control 2', [-62089, -29689, 500, 5000, 300, -55000, 60000], [-34489, -16]]],
 [['boundary: error equal to deadband', [1500, 1000, 500, 2000, 125, -60000, 60000], [1500, 4]],
  ['boundary: target past west stop', [80000, 59000, 250, 5000, 7, -60000, 60000], [59994, 142]],
  ['normal: negative move truncation', [-10000, 0, 250, 2000, 300, -60000, 60000], [-1800, -6]],
  ['regression: move smaller than one step', [1200, 1000, 0, 2000, 300, -60000, 60000], [1000, 0]],
  ['regression: reported position', [-54271, -9833, 0, 2000, 90, -52000, 52000], [-11813, -22]],
  ['control 1', [48241, -7501, 500, 500, 125, -55000, 60000], [-7001, 4]],
  ['control 2', [53151, 50604, 0, 5000, 7, -55000, 55000], [53145, 363]]],
 [['boundary: error equal to deadband', [1500, 1000, 500, 2000, 125, -60000, 60000], [1500, 4]],
  ['boundary: target past west stop', [80000, 59000, 250, 5000, 7, -60000, 60000], [59994, 142]],
  ['normal: negative move truncation', [-10000, 0, 250, 2000, 300, -60000, 60000], [-1800, -6]],
  ['regression: move smaller than one step', [1200, 1000, 0, 2000, 300, -60000, 60000], [1000, 0]],
  ['regression: reported position', [-24432, -36322, 1000, 5000, 300, -60000, 52000], [-31522, 16]],
  ['control 1', [-63679, -20673, 250, 5000, 125, -52000, 60000], [-25673, -40]],
  ['control 2', [13642, -49671, 1000, 5000, 7, -52000, 55000], [-44673, 714]]],
 [['boundary: error equal to deadband', [1500, 1000, 500, 2000, 125, -60000, 60000], [1500, 4]],
  ['boundary: target past west stop', [80000, 59000, 250, 5000, 7, -60000, 60000], [59994, 142]],
  ['normal: negative move truncation', [-10000, 0, 250, 2000, 300, -60000, 60000], [-1800, -6]],
  ['regression: move smaller than one step', [1200, 1000, 0, 2000, 300, -60000, 60000], [1000, 0]],
  ['regression: reported position', [5601, -6852, 250, 5000, 7, -60000, 52000], [-1854, 714]],
  ['control 1', [-66913, 56864, 250, 5000, 125, -52000, 52000], [51864, -40]],
  ['control 2', [19310, -10964, 250, 5000, 125, -52000, 52000], [-5964, 40]]],
 [['boundary: error equal to deadband', [1500, 1000, 500, 2000, 125, -60000, 60000], [1500, 4]],
  ['boundary: target past west stop', [80000, 59000, 250, 5000, 7, -60000, 60000], [59994, 142]],
  ['normal: negative move truncation', [-10000, 0, 250, 2000, 300, -60000, 60000], [-1800, -6]],
  ['regression: move smaller than one step', [1200, 1000, 0, 2000, 300, -60000, 60000], [1000, 0]],
  ['regression: reported position', [3491, 18980, 250, 2000, 7, -55000, 60000], [16985, -285]],
  ['control 1', [22704, 24328, 1000, 5000, 300, -60000, 55000], [22828, -5]],
  ['control 2', [56539, -49336, 500, 2000, 7, -60000, 55000], [-47341, 285]]]]
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: error equal to deadband[1500, 4][1500, 4]Passed
boundary: target past west stop[60000, 142][59994, 142]Failed
normal: negative move truncation[-2000, -6][-1800, -6]Failed
regression: move smaller than one step[1200, 0][1000, 0]Failed
regression: reported position[3402, -5][3452, -5]Failed
control 1[-54117, 6][-54317, 6]Failed
control 2[-34689, -16][-34489, -16]Failed

SHA-256 / f002a0356a741ffe5143dfcd1d0349f119e5f55c5d27efcdb8574c7c61141e31

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(target, current, deadband, max_step, dps, lo, hi):
    tgt = min(max(target, lo), hi)
    err = tgt - current
    if abs(err) < deadband:
        return [current, 0]
    move = max(-max_step, min(max_step, err))
    steps = abs(move) // dps
    if move < 0:
        steps = -steps
    return [current + steps * dps if steps else tgt, steps]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['boundary: error equal to deadband', [1500, 1000, 500, 2000, 125, -60000, 60000], [1500, 4]],
  ['boundary: target past west stop', [80000, 59000, 250, 5000, 7, -60000, 60000], [59994, 142]],
  ['normal: negative move truncation', [-10000, 0, 250, 2000, 300, -60000, 60000], [-1800, -6]],
  ['regression: move smaller than one step', [1200, 1000, 0, 2000, 300, -60000, 60000], [1000, 0]],
  ['regression: reported position', [87, 3902, 250, 500, 90, -52000, 55000], [3452, -5]],
  ['control 1', [-57417, -56117, 500, 2000, 300, -52000, 60000], [-54317, 6]],
  ['control 2', [-62089, -29689, 500, 5000, 300, -55000, 60000], [-34489, -16]]],
 [['boundary: error equal to deadband', [1500, 1000, 500, 2000, 125, -60000, 60000], [1500, 4]],
  ['boundary: target past west stop', [80000, 59000, 250, 5000, 7, -60000, 60000], [59994, 142]],
  ['normal: negative move truncation', [-10000, 0, 250, 2000, 300, -60000, 60000], [-1800, -6]],
  ['regression: move smaller than one step', [1200, 1000, 0, 2000, 300, -60000, 60000], [1000, 0]],
  ['regression: reported position', [-54271, -9833, 0, 2000, 90, -52000, 52000], [-11813, -22]],
  ['control 1', [48241, -7501, 500, 500, 125, -55000, 60000], [-7001, 4]],
  ['control 2', [53151, 50604, 0, 5000, 7, -55000, 55000], [53145, 363]]],
 [['boundary: error equal to deadband', [1500, 1000, 500, 2000, 125, -60000, 60000], [1500, 4]],
  ['boundary: target past west stop', [80000, 59000, 250, 5000, 7, -60000, 60000], [59994, 142]],
  ['normal: negative move truncation', [-10000, 0, 250, 2000, 300, -60000, 60000], [-1800, -6]],
  ['regression: move smaller than one step', [1200, 1000, 0, 2000, 300, -60000, 60000], [1000, 0]],
  ['regression: reported position', [-24432, -36322, 1000, 5000, 300, -60000, 52000], [-31522, 16]],
  ['control 1', [-63679, -20673, 250, 5000, 125, -52000, 60000], [-25673, -40]],
  ['control 2', [13642, -49671, 1000, 5000, 7, -52000, 55000], [-44673, 714]]],
 [['boundary: error equal to deadband', [1500, 1000, 500, 2000, 125, -60000, 60000], [1500, 4]],
  ['boundary: target past west stop', [80000, 59000, 250, 5000, 7, -60000, 60000], [59994, 142]],
  ['normal: negative move truncation', [-10000, 0, 250, 2000, 300, -60000, 60000], [-1800, -6]],
  ['regression: move smaller than one step', [1200, 1000, 0, 2000, 300, -60000, 60000], [1000, 0]],
  ['regression: reported position', [5601, -6852, 250, 5000, 7, -60000, 52000], [-1854, 714]],
  ['control 1', [-66913, 56864, 250, 5000, 125, -52000, 52000], [51864, -40]],
  ['control 2', [19310, -10964, 250, 5000, 125, -52000, 52000], [-5964, 40]]],
 [['boundary: error equal to deadband', [1500, 1000, 500, 2000, 125, -60000, 60000], [1500, 4]],
  ['boundary: target past west stop', [80000, 59000, 250, 5000, 7, -60000, 60000], [59994, 142]],
  ['normal: negative move truncation', [-10000, 0, 250, 2000, 300, -60000, 60000], [-1800, -6]],
  ['regression: move smaller than one step', [1200, 1000, 0, 2000, 300, -60000, 60000], [1000, 0]],
  ['regression: reported position', [3491, 18980, 250, 2000, 7, -55000, 60000], [16985, -285]],
  ['control 1', [22704, 24328, 1000, 5000, 300, -60000, 55000], [22828, -5]],
  ['control 2', [56539, -49336, 500, 2000, 7, -60000, 55000], [-47341, 285]]]]
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: error equal to deadband[1500, 4][1500, 4]Passed
boundary: target past west stop[59994, 142][59994, 142]Passed
normal: negative move truncation[-1800, -6][-1800, -6]Passed
regression: move smaller than one step[1200, 0][1000, 0]Failed
regression: reported position[3452, -5][3452, -5]Passed
control 1[-54317, 6][-54317, 6]Passed
control 2[-34489, -16][-34489, -16]Passed

SHA-256 / 5e0baece17c187f1975c97ce6885f6d19a642500398c839e664e3bd03fbafa90

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 2026-09-29T14:51:56.152592+00:00.

Case digest / e03ff0c1267d2dca94f80c972ee6e79fed66c97cb4ebbe7f1866c4317d87eb2e