IMU integration (WitMotion HWT905-RS232, doc/06-imu-integration-plan.md):
- Phase 1: raw accel/gyro/angle observation, power-on-relative yaw offset
- Phase 2: x,y odometry + wheel-vs-IMU omega residual, using a self-fused
heading (wheel encoder omega + raw gyro_z average) instead of the IMU's
own onboard fused yaw, which field logs showed disagreeing with its own
raw gyro sign ~30% of the time during turns
- Phase 3: straight-line heading-hold PI trim, active only when steering
is centered and no lidar dodge is in progress, capped and field-tuned
- Phase 4: whole-body slip detection (commanded vs IMU-measured omega
ratio) that temporarily scales down v_x/omega, independent of the
per-wheel current-based diagnostics
- Phase 5a: k_skid/effective_w replaced with values fitted from real
wheel-vs-IMU logs (0.406->0.51, 0.684->0.87) instead of the geometric
formula, which field data showed under-driving every turn
RC receiver: switched from ttyUSB* guessing to udev-stable device names
(ttyMOTOR/ttyRC/ttyIMU), wired through run_4wd.sh and set_low_latency.sh.
Motor driver: read motor/driver temperature registers (0x20A4/0x20B0)
for proactive overheat visibility in the HUD/CSV.
Control fixes:
- Airborne-wheel zeroing no longer applies during spin turns, where
reaction-torque-driven diagonal load transfer was misclassified as
wheels leaving the ground and cutting spin torque in half
- jerkLimitedStep's instant-acceleration path now only fires for
same-direction speed increases; sign reversals (RC noise/deadzone
jitter near a stop, or a genuine direction change) go through the
jerk-limited path instead of snapping across zero
Auto CSV logging (logs/, gitignored) extended with encoder ticks, IMU,
odometry, heading-hold, slip, and temperature columns for field analysis.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
robin
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