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Measure FourPost static balance from executed signals - #155
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The static-balance summary derived the spring force from the target load and compared the target with itself. static_balance_max_abs_fz_error_n was 0 and static_balance_pass was True for every car. Now FourPost reads the contact-patch forces, spring forces and chassis actuator reaction. It checks force and moment closure on every zero-command row, the spring force against the executed table with the signed BobLib rule, and the measured contact Fz against the target sprung corner load. static_balance_max_abs_fz_error_n keeps its name and now means measured contact Fz minus target. A run without the signals is 'unavailable', not 'fail'. The spring free length no longer comes from a metrics CSV of an earlier run. It comes from the config or the vehicle file. The static balance loop, which always stopped after one run, is removed with its two config keys.
The page gives the rows each check uses, the metrics CSV keys, the tolerance basis with the closure residual that grows with time on the default car, the limits, and the behavior change.
rhorvath02
approved these changes
Oct 29, 2026
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What
The static-balance summary derived the spring force from the target load and compared the target with itself.
static_balance_max_abs_fz_error_nwas 0 andstatic_balance_passwas True for every car. The balance loop always stopped after one run.Changes
unavailable, never a pass._static_balance_iterations, whose default you set to 4. The executed behavior was one run either way. Please confirm.docs/four-post-static-balance.mdexplains the checks and tolerances.How to check
tests/test_four_post_static_balance.py.LinearSegmentstables. In OpenModelica 1.27.1 the actuator acceleration then grows as k·t on flat segments, and the rig link masses turn it into force. BobLib 093952a (BobVis: easier controls, LLTD, friction circles and a metrics tab #48) switches toMonotoneContinuousDerivative2and a quasi-static rig. FourPostSim there closes to 7e-13 N over 118 s. The check passes once BobSim pins BobLib 093952a or later.Notes
Stack
4 of 7.