From 5d76576a15c709309c9821c1100a23bcc4ca7976 Mon Sep 17 00:00:00 2001 From: Brian Hanson Date: Sun, 26 Apr 2026 12:31:10 -0500 Subject: [PATCH] sessions: document hyundai canfd steer torque bump Reference for the 270->324 change in commit 4058269. Covers what each constant means, the two-files-must-stay-in-lockstep rule, the path to push higher (324 -> 384, the community-consensus safe ceiling), risks and symptoms to watch for at higher values, verification steps, and rollback procedure. Co-Authored-By: Claude Opus 4.7 (1M context) --- .../README.md | 177 ++++++++++++++++++ 1 file changed, 177 insertions(+) create mode 100644 sessions/2026-04-26-1229-hyundai-canfd-steer-torque-bump/README.md diff --git a/sessions/2026-04-26-1229-hyundai-canfd-steer-torque-bump/README.md b/sessions/2026-04-26-1229-hyundai-canfd-steer-torque-bump/README.md new file mode 100644 index 0000000..a66953d --- /dev/null +++ b/sessions/2026-04-26-1229-hyundai-canfd-steer-torque-bump/README.md @@ -0,0 +1,177 @@ +# Session: 2026-04-26 — Hyundai CAN-FD steering torque bump + +Documentation for commit `4058269` on `clearpilot`. Reference for any +future re-tuning. + +## What changed + +Bumped this Tucson HDA2 (CAN-FD platform) from comma's conservative +steer ceiling to a value that gives more headroom on tighter on-ramp +clovers, plus a small rate-limit nudge so the controller can actually +reach the new ceiling within reasonable transient time. + +| Constant | Before (comma default for CAN-FD) | After (this commit) | Comma's non-CAN-FD HKG default | +|---|---:|---:|---:| +| `max_steer` / `STEER_MAX` | 270 | **324** | 384 | +| `max_rate_up` / `STEER_DELTA_UP` | 2 | **3** | 3 | +| `max_rate_down` / `STEER_DELTA_DOWN` | 3 | **5** | 7 | +| `max_rt_delta` | 112 | **134** | ~150 | + +## Where the change lives — TWO files in lockstep + +The panda safety firmware enforces these limits **independently** of +openpilot. If only one side is bumped, panda rejects the larger +commands and you get cut-out / `commIssue` behavior. **Always change +both, always to the same numbers, in the same commit.** + +1. **`panda/board/safety/safety_hyundai_canfd.h`** (lines 3-19) + - `HYUNDAI_CANFD_STEERING_LIMITS` struct: `max_steer`, `max_rate_up`, + `max_rate_down`, `max_rt_delta`. + - This is C; modifying it changes the panda firmware hash, which + forces an automatic re-flash on next `pandad` start. No manual + panda flash command needed. + +2. **`selfdrive/car/hyundai/values.py`** (CAN-FD branch of + `CarControllerParams.__init__`, lines 29-36) + - `STEER_MAX`, `STEER_DELTA_UP`, `STEER_DELTA_DOWN`. + - Pure Python; picked up on next `controlsd` start. + +## What each constant does + +- **`max_steer` / `STEER_MAX`** — peak torque magnitude the controller + can request. Hard ceiling. Going past this is the headline "more + torque" knob. +- **`max_rate_up` / `STEER_DELTA_UP`** — per-100Hz-cycle upward slew + cap. Higher = faster ramp into a turn. With `max_rate_up = 3` and + `max_steer = 324`, time from 0 to ceiling is 324 / 3 = 108 cycles = + 1.08 s. +- **`max_rate_down` / `STEER_DELTA_DOWN`** — per-cycle downward slew + cap. Higher = faster release back toward straight. We chose 5 (vs + comma's 7) for a smoother release feel. +- **`max_rt_delta`** — cumulative torque change allowed across a + rolling 250 ms window (`max_rt_interval`). It's a long-window + envelope check, separate from the per-cycle rate. Should scale with + `max_steer` — we used `max_steer × ~0.41` to mirror comma's ratio. +- **`driver_torque_allowance` / `STEER_DRIVER_ALLOWANCE`** — driver + wheel torque (Nm read off the wheel) that's tolerated before the + system starts derating its own command. Left at 250. +- **`driver_torque_factor` / `STEER_DRIVER_MULTIPLIER`** — how + aggressively the system fights driver input above the allowance. + Left at 2. + +## How to go higher (path to 384) + +`384` is the community-consensus safe ceiling for HKG. Comma uses it +as the default for every non-CAN-FD HKG that isn't on the explicit +255-blacklist, and they merged it for HDA1 CAN-FD (EV6 / Ioniq 5) in +[openpilot PR #25723](https://github.com/commaai/openpilot/pull/25723). +The PR author noted "max steer needed to be 384 to make basic turns." +Tucson NX4 HDA2 is **not** on the 255-blacklist (see +[issue #24122](https://github.com/commaai/openpilot/issues/24122) for +the verified blacklist). + +To go from 324 → 384: + +```c +// panda/board/safety/safety_hyundai_canfd.h +.max_steer = 384, +.max_rt_delta = 158, // ~max_steer × 0.41 +.max_rate_up = 3, +.max_rate_down = 5, // or 7 for comma-matched aggressive release +``` + +```python +# selfdrive/car/hyundai/values.py CAN-FD branch +self.STEER_MAX = 384 +self.STEER_DELTA_UP = 3 +self.STEER_DELTA_DOWN = 5 # or 7 +``` + +Beyond 384 is uncharted for HKG — comma has not tested past it. Some +forks (sunnypilot has discussions) try higher for very heavy vehicles +but with mixed results. Don't go past 384 without an explicit reason. + +## Things to watch for / community-flagged risks at higher values + +1. **EPS time-out cut every ~90 frames.** The CAN-FD safety already + forces a brief torque cut to stop the EPS from faulting (the + `min_valid_request_frames = 89`, `max_invalid_request_frames = 2`, + `min_valid_request_rt_interval = 810000` block of + `HYUNDAI_CANFD_STEERING_LIMITS`). This is independent of + `max_steer`. Bumping the ceiling does not lengthen the cut-free + window — you just hold the higher torque for the same ~890 ms before + the brief cut. If you're getting `Steering Temporarily Unavailable` + *during sustained turns*, the issue is this cut, not the ceiling, + and it can't be tuned without risking a real EPS fault. + +2. **`steerTempUnavailable` / "Cruise Fault: Restart the Car".** Has + been reported on cars in the 255-blacklist when pushed to 384. + Tucson NX4 is not blacklisted, so 324–384 is normally safe — but if + you see this alert during slow sweeping turns, that's the symptom. + Roll back to 270 and confirm. + +3. **Lateral accel retune.** Higher torque headroom can cause the + torque controller to overshoot if `latAccelFactor` was tuned for + the old ceiling. EV6/Ioniq 5 testing in PR #25723 had to drop + lateral accel to 2.5 m/s² when bumping from 270 to 384. Watch for + over-correction (zig-zag in lane center) after a bump and retune + `latAccelFactor` in `selfdrive/locationd/torqued.py` or via the + torque-tune Params if needed. + +4. **Driver-fight feel.** `driver_torque_allowance = 250` / + `driver_torque_factor = 2` is the blending knob. Most "openpilot + fights my hands" complaints come from people who lowered allowance + or raised factor. Don't touch these without a specific reason. + +5. **Panda safety hash mismatch.** Changing + `safety_hyundai_canfd.h` regenerates the panda firmware binary with + a different signed hash. On the next `pandad` start, pandad detects + the mismatch and re-flashes the panda automatically (see + `pandad.log`: "Panda firmware out of date" → "flash: flashing" → + "Done flashing"). Takes ~10 s. No manual action needed; just expect + a brief delay before controls come up. + +## Verifying the change took effect + +```bash +# 1. Confirm the rebuild happened and panda firmware was re-signed. +grep "panda/board/obj/panda_h7" /tmp/build_only.log 2>/dev/null # or run build_only.sh and watch for "signing N bytes" + +# 2. Watch for re-flash on launch. +tail -f /data/log2/current/pandad.log +# Should see: "Panda firmware out of date, update required" +# "flash: flashing" +# "Done flashing" + +# 3. Confirm the openpilot side is using the new value. +su - comma -c 'PYTHONPATH=/data/openpilot python3 -c " +from cereal import car +from openpilot.common.params import Params +cp_bytes = Params().get(\"CarParams\") +with car.CarParams.from_bytes(cp_bytes) as cp: + print(\"safetyConfig safetyParam:\", [c.safetyParam for c in cp.safetyConfigs]) +"' + +# 4. Live-check the actual commanded torque ceiling (drive a moderate turn). +# carControl.actuators.steer should now be able to peak above 0.79 (270/255 normalized) +# but stay under 1.0 (full saturation at the new ceiling). +``` + +## Rollback + +If anything misbehaves, revert just the two-file commit: + +```bash +git revert 4058269 +chown -R comma:comma /data/openpilot +su - comma -c "bash /data/openpilot/build_only.sh" +# Next pandad launch will re-flash back to 270. +``` + +## Sources + +- [openpilot PR #25723 — HDA1 EV6/Ioniq 5 270 → 384](https://github.com/commaai/openpilot/pull/25723) +- [openpilot issue #24122 — HKG torque blacklist verification](https://github.com/commaai/openpilot/issues/24122) +- [openpilot PR #26427 — Hyundai Tucson 2023 support](https://github.com/commaai/openpilot/pull/26427) +- [sunnypilot — increasing torque help](https://community.sunnypilot.ai/t/increasing-torque-help-needed/2082) +- [sunnypilot — raising torque for heavier vehicles](https://community.sunnypilot.ai/t/raising-the-torque-for-heavier-vehicles/862)