Adds a slow-adapting terrain slope estimator (IIR tau=5s) that decouples
the robot's balance offset from genuine ground incline. The balance
controller subtracts the slope estimate from measured pitch so the PID
balances around the slope surface rather than absolute vertical.
- include/slope_estimator.h + src/slope_estimator.c: first-order IIR
filter clamped to ±15°; JLINK_TLM_SLOPE (0x88) telemetry at 1 Hz
- include/jlink.h + src/jlink.c: add JLINK_TLM_SLOPE (0x88),
jlink_tlm_slope_t (4 bytes), jlink_send_slope_tlm()
- include/balance.h + src/balance.c: integrate slope_estimator into
balance_t; update, reset on tilt-fault and disarm
- test/test_slope_estimator.c: 35 unit tests, all passing
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
sl-controls
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