FA-12111 / Robotics frame conventions / Open access

A mounted sensor offset is added in the world frame · case 01

A mounted sensor offset is added in the world frame.

Verified by executionVariant 1 · 6 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Child extrinsic translation is added directly to the parent world translation.

THE FAILURE

Child extrinsic translation is added directly to the parent world translation.

Unsuccessful approach: Rotating the offset by its own child heading uses the wrong parent frame.

Case contract

Given parent world translation a and quarter-turn heading qa, and child translation b in parent coordinates with heading qb, return child world translation. qb does not affect its own origin.

Why this case matters

Robot adapters must preserve the declared frame, reference point, and representation conventions across interfaces.

1 / The failure

Exit 1

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

def rot(v, q):
    x,y = v
    return [(x,y),(-y,x),(-x,-y),(y,-x)][q%4]

N = 1
observations = []
def solve(a, qa, b, qb):
    return [a[i]+b[i] for i in range(2)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('rotated mount', solve([N,N],1,[N,0],0), [N,2*N])
check('child orientation irrelevant', solve([N,N],0,[N,0],1), [2*N,N])
check('half turn parent', solve([N,N],2,[N,2*N],1), [0,-N])
check('zero mount', solve([N,N],1,[0,0],3), [N,N])
check('world origin', solve([0,0],-1,[N,2*N],2), [2*N,-N])
check('identity chain', solve([N,-N],0,[2*N,N],0), [3*N,0])
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
rotated mount	`[2, 1]`	`[1, 2]`	Failed
child orientation irrelevant	`[2, 1]`	`[2, 1]`	Passed
half turn parent	`[2, 3]`	`[0, -1]`	Failed
zero mount	`[1, 1]`	`[1, 1]`	Passed
world origin	`[1, 2]`	`[2, -1]`	Failed
identity chain	`[3, 0]`	`[3, 0]`	Passed

SHA-256 / 40bec626cf309d699cc515d93242ed0083278643c2241872794443ee898a40c2

2 / The unsuccessful fix

Exit 1

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

def rot(v, q):
    x,y = v
    return [(x,y),(-y,x),(-x,-y),(y,-x)][q%4]

N = 1
observations = []
def solve(a, qa, b, qb):
    r=rot(b,qb)
    return [a[i]+r[i] for i in range(2)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('rotated mount', solve([N,N],1,[N,0],0), [N,2*N])
check('child orientation irrelevant', solve([N,N],0,[N,0],1), [2*N,N])
check('half turn parent', solve([N,N],2,[N,2*N],1), [0,-N])
check('zero mount', solve([N,N],1,[0,0],3), [N,N])
check('world origin', solve([0,0],-1,[N,2*N],2), [2*N,-N])
check('identity chain', solve([N,-N],0,[2*N,N],0), [3*N,0])
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
rotated mount	`[2, 1]`	`[1, 2]`	Failed
child orientation irrelevant	`[1, 2]`	`[2, 1]`	Failed
half turn parent	`[-1, 2]`	`[0, -1]`	Failed
zero mount	`[1, 1]`	`[1, 1]`	Passed
world origin	`[-1, -2]`	`[2, -1]`	Failed
identity chain	`[3, 0]`	`[3, 0]`	Passed

SHA-256 / 03213818cb505acf8248b03730089142814ee30d62c3cf93128179d8835a2f97

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 6 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.

Member access is invitation-based. Sign in with your invited account to inspect the repair.

Verification & scope

Small exact offline frame model; not a robot middleware implementation or continuous pose estimator. 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 2026-09-29T14:38:53.947009+00:00.

Case digest / caf8c80e175ca28616f48d846489c46b2c802dcb223996bce12f404246c05d7a