FA-88115 / Inverse kinematics solvers / Member archive

Delta rod horizontal distance uses the square of the summed offsets · case 05

Diagonal offsets produce wrong carriage heights while axis-aligned ones look correct.

Member previewVariant 5 · 3 implementations · 7 checks per implementation

Case contract

Input [R,e,L,x,y,z,hmax]: linear delta printer, towers at 90, 210 and 330 degrees (in that output order) on radius R, effector joints offset e toward the centre so the effective radius is R-e, diagonal rods of length L. Carriage height is z+sqrt(L^2-dx^2-dy^2); a negative radicand returns "unreachable", a carriage above hmax returns "out-of-travel". Return heights rounded to 4.

Why this case matters

Inverse kinematics code turns task-space goals into joint commands; a wrong branch, sign, limit or update order sends a real arm to the wrong pose.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
centre	`[13.9443, 9.9573, 16.6373]`	`[13.9443, 13.9443, 13.9443]`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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