From a33d089d3df5a18399c31fe5348fbaf3f4ff7be6 Mon Sep 17 00:00:00 2001 From: x12sa Date: Tue, 3 Nov 2026 12:34:01 +0100 Subject: [PATCH] feat(aerotech): trigger calibration aligns forward and backward lines The backward exposure centres are offset from the forward ones by a velocity dependent amount (DDG1: +2 um at 2 mm/s, +19 um at 10 mm/s, +26 um at 20 mm/s, -9 um at 40 mm/s backward - forward, independent of exp_time). With trigger_calibration=True (default) the scan shifts trigger_low by +h and trigger_high by -h, h = half of backward - forward from the table userParameter "trigger_calibration" of the fast axis: linear between the calibrated velocities, proportional below the lowest, none above the highest. The applied offset is stored in the scan info (trigger_offset, scan_velocity); the statistics print the table entry the scan measured, for training scans with trigger_calibration=False. Co-Authored-By: Claude Opus 5.5 Claude-Session: https://claude.ai/code/session_017NrH3poJsYBCTVq2Y9fuHZ --- .../scans/scans_v4/aerotech_cont_grid.py | 80 +++++++++++++++ docs/developer/aerotech_stages.md | 23 +++++ .../saxs/aerotech_stages/aerotech_stages.md | 41 ++++++++ .../test_aerotech_cont_grid_scan.py | 98 ++++++++++++++++++- 4 files changed, 240 insertions(+), 2 deletions(-) diff --git a/csaxs_bec/scans/scans_v4/aerotech_cont_grid.py b/csaxs_bec/scans/scans_v4/aerotech_cont_grid.py index 6a8c089e..6d61d26a 100644 --- a/csaxs_bec/scans/scans_v4/aerotech_cont_grid.py +++ b/csaxs_bec/scans/scans_v4/aerotech_cont_grid.py @@ -59,6 +59,19 @@ of motion for the moving fast axis). At the end the scan reports statistics of t centres of the fast axis (deviation from the nominal cell centres per direction, backward - forward offset and its slope along the line) and of the line times. +Trigger calibration: in a snake the backward exposure centres are offset from the forward +ones, by an amount that depends on the scan velocity (DDG1 at the beamline, 2026-11-03: +backward - forward +2 um at 2 mm/s, +19 um at 10 mm/s, +26 um at 20 mm/s, -9 um at +40 mm/s; independent of exp_time within the scatter). With trigger_calibration=True the +scan shifts the trigger positions by the calibrated offset h (half of backward - forward): +trigger_low by +h, trigger_high by -h, so that the centres of both directions are on the +same cells. h comes from the table userParameter "trigger_calibration" of the fast axis +(device config, a list of {velocity, offset [um]}): linear between the calibrated +velocities, proportional to the velocity below the lowest one, no correction above the +highest one. The statistics at the end show the applied offset and the table entry this +scan measured (applied + half of the remaining backward - forward), for new or better +calibration points; the applied offset is stored in the scan info (trigger_offset). + Run-up / run-out of each line: twice the ramp distance v^2 / (2 * acceleration) + v * settle_time beyond the trigger positions. The whole range including run-up / run-out is checked against the soft limits before the scan starts. The scan velocity may be higher @@ -122,6 +135,24 @@ class _DeviceExample(str): DDG_EXT_RISING_EDGE = 1 DDG_EXT_FALLING_EDGE = 2 DDG_SINGLE_SHOT = 5 + + +def interpolate_trigger_offset(table: list[dict], velocity: float) -> float | None: + """ + Trigger offset h [um] for a scan velocity from a calibration table of + {"velocity": ..., "offset": ...} entries: linear between the calibrated velocities, + proportional to the velocity below the lowest one (no offset at rest), None above the + highest one or without a table. + """ + points = sorted((float(e["velocity"]), float(e["offset"])) for e in table) + if not points: + return None + velocities, offsets = zip(*points) + if velocity > velocities[-1] * (1 + 1e-9): + return None + if velocity <= velocities[0]: + return offsets[0] * velocity / velocities[0] + return float(np.interp(velocity, velocities, offsets)) DDG_TRIGGER_EDGES = {"rising": DDG_EXT_RISING_EDGE, "falling": DDG_EXT_FALLING_EDGE} # Extra run-up / run-out beyond the ramp distance, as a fraction of it (headroom for the @@ -136,6 +167,9 @@ MIN_RUN_UP = 0.01 TRIGGER_SOURCES = ("ddg", "panda", None) +# userParameter of the fast axis with the trigger calibration table, see the module docstring +TRIGGER_CALIBRATION_PARAMETER = "trigger_calibration" + # Poll interval of the fast axis position while waiting for the end of the exposures, s STEP_POLL_INTERVAL = 0.01 @@ -178,6 +212,7 @@ class AerotechContGrid(ScanBase): "relative", "trigger_source", "minimal_run_up", + "trigger_calibration", ], } @@ -201,6 +236,7 @@ class AerotechContGrid(ScanBase): settle_time: float = 0.15, minimal_run_up: bool = False, capture_device: str = "aerocapture", + trigger_calibration: bool = True, **kwargs, # fmt: on ): @@ -226,6 +262,7 @@ class AerotechContGrid(ScanBase): settle_time (float): Run-up at constant velocity before the trigger position, in s. Default is 0.15. minimal_run_up (bool): Run-up / run-out only the ramp distance v^2 / (2 * acceleration), at least 0.01, without the 2x margin and settle_time: faster lines, but the exposures start right after the ramp while the fast axis may still oscillate, so the captured positions are less evenly spaced. Default is False. capture_device (str): Name of the A3200PositionCapture device (always used). Default is "aerocapture". + trigger_calibration (bool): Shift the trigger positions by the calibrated offset of the fast axis for the scan velocity, so that forward and backward exposure centres are on the same cells (userParameter "trigger_calibration"). False for training scans of new calibration points. Default is True. Returns: ScanReport @@ -282,6 +319,7 @@ class AerotechContGrid(ScanBase): self._ddg1_shutter_delay = None # DDG1 value to restore after the scan self.settle_time = settle_time self.minimal_run_up = minimal_run_up + self.trigger_calibration = trigger_calibration devices = self.device_manager.devices self.ddg1 = self.ddg2 = self.mcs = self.panda = None @@ -358,6 +396,8 @@ class AerotechContGrid(ScanBase): computed_positions=positions, num_lines=num_lines, readout_time=self._line["readout_time"], + scan_velocity=self._line["target_velocity"], + trigger_offset=self._line["trigger_offset"], ) # progress bar in the client, which also prints the statistics at the end: the @@ -598,6 +638,7 @@ class AerotechContGrid(ScanBase): f" backward - forward [um]: mean {diff.mean():+.2f}, slope {slope:+.2f} / mm," f" peak-peak {np.ptp(diff):.2f}", ] + text.append(self._calibration_summary(diff.mean())) if self._line_starts and self._last_line_end is not None: # line period: start to start of the next line (motion, trigger check, capture # readout, wait for the step); the last line ends with its capture readout @@ -614,6 +655,40 @@ class AerotechContGrid(ScanBase): ) return "\n".join(text) + def _trigger_offset(self, velocity: float) -> float | None: + """Calibrated trigger offset [um] for the velocity, None if not applied.""" + if not self.trigger_calibration: + return None + # the device config, as user_parameter of DeviceBaseWithConfig (not on every device class) + config = getattr(self.fast_axis, "_config", None) # pylint: disable=protected-access + parameters = config.get("userParameter") if isinstance(config, dict) else None + table = ( + parameters.get(TRIGGER_CALIBRATION_PARAMETER) if isinstance(parameters, dict) else None + ) + offset = interpolate_trigger_offset(table or [], velocity) + if offset is None: + logger.warning( + f"aerotech_cont_grid: no trigger calibration of {self.fast_axis.name} for" + f" {velocity:g} / s, forward and backward exposures are not aligned." + ) + return offset + + def _calibration_summary(self, backward_minus_forward: float) -> str: + """Applied offset and the calibration entry measured by this scan.""" + line = self._line + applied = line.get("trigger_offset") + measured = (applied or 0.0) + backward_minus_forward / 2 + if applied is not None: + state = f"offset {applied:+.2f} um applied" + elif self.trigger_calibration: + state = "no calibration for this velocity" + else: + state = "off" + return ( + f" trigger calibration [um]: {state}; this scan measured" + f" {{velocity: {line['target_velocity']:g}, offset: {measured:.2f}}}" + ) + def _trigger_window(self, line_index: int) -> tuple[float, float]: """PSO window of a line: entered at the trigger position, open beyond the line end.""" line = self._line @@ -711,6 +786,11 @@ class AerotechContGrid(ScanBase): line["exposure_end"] = self.fast_start + self.frames_per_line * self.fast_step_size line["trigger_low"] = self.fast_start - lead + gap line["trigger_high"] = line["exposure_end"] + lead - gap + # calibrated offset [um]: later trigger in the direction of motion, both directions + line["trigger_offset"] = self._trigger_offset(velocity) + shift = (line["trigger_offset"] or 0.0) * 1e-3 + line["trigger_low"] += shift + line["trigger_high"] -= shift line["line_start"] = line["trigger_low"] - ramp_distance - margin line["line_end"] = line["trigger_high"] + ramp_distance + margin diff --git a/docs/developer/aerotech_stages.md b/docs/developer/aerotech_stages.md index b12d22d4..c1d12019 100644 --- a/docs/developer/aerotech_stages.md +++ b/docs/developer/aerotech_stages.md @@ -108,6 +108,29 @@ of -24 / +10 / +4.5 / -21 um (2026-10-29). against the soft limits before anything moves. The message separates the scan range from the run-up so a user can see why a scan inside the limits does not fit. +### Trigger calibration + +The backward exposure centres are offset from the forward ones by a velocity +dependent amount (DDG1 at the beamline, 2026-11-03, scans 4897-4917: backward minus +forward +0.9 / +2.1 / +9.3 / +18.6 / +25.7 / +3.0 / -8.8 um at 1 / 2 / 4 / 10 / 20 / 30 / +40 mm/s; 5 vs 20 ms exposure time the same within the scatter; repeats within 0.1 um +at 1 mm/s and 0.2 um at 40 mm/s). It is not a constant delay: about 0.5-1 ms up to +20 mm/s, then it falls and changes sign. With the PandA (2026-10-29) it was below 1 um at +20 mm/s. + +`trigger_calibration=True` (default) shifts `trigger_low` by `+h` and `trigger_high` +by `-h` (later in the direction of motion), with `h` = half of backward minus forward +from the table `userParameter.trigger_calibration` of the fast axis +(`interpolate_trigger_offset`: linear between the points, proportional to the velocity +below the lowest one, `None` above the highest one). The device config is read from +`_config` of the fast axis (the scan server's devices are `DeviceBaseWithConfig`, +whose `user_parameter` reads the same). The applied `h` is in the scan info +(`trigger_offset`, with `scan_velocity`); the statistics print the entry the scan +measured, `h_applied + (backward - forward) / 2`. Only the mean offset per direction is +corrected; the variation along the line at high velocity (oscillation after the ramp) +remains. The calibration is for the configured acceleration (500 mm/s^2) and +`settle_time` 0.15 s. + ### Step during the run-out As soon as X has left the exposure range of a line, the PSO window of the next line diff --git a/docs/user/saxs/aerotech_stages/aerotech_stages.md b/docs/user/saxs/aerotech_stages/aerotech_stages.md index c6f8185b..f5d22ede 100644 --- a/docs/user/saxs/aerotech_stages/aerotech_stages.md +++ b/docs/user/saxs/aerotech_stages/aerotech_stages.md @@ -74,6 +74,7 @@ scans.aerotech_cont_grid( | `settle_time` | constant velocity time before the first exposure of a line, default 0.15 s (leave it) | | `shutter_delay` | time from the line trigger to the first exposure, for the shutter to open. Default: the value of DDG1 (8 ms); a given value is set on DDG1 for this scan only | | `minimal_run_up` | `True`: run-up only the acceleration distance (at least 10 um), no settling. Faster lines, but the exposures are less evenly spaced; use the captured positions. Default `False` | +| `trigger_calibration` | `True` (default): forward and backward lines are aligned with the calibration of `aerox` (see below). `False` only for training scans of new calibration points | The number of points per line is `ceil(|fast_end - fast_start| / fast_step_size) + 1`, the number of lines `ceil(|stepper_stop - stepper_start| / stepper_step_size) + 1`. @@ -97,6 +98,46 @@ csaxs.aerotech.stop_plot() # stop following (the plot stays) Every exposure is shown as a marker. Forward and backward lines alternate, so the two colours alternate in Y by one line spacing. +### Forward and backward alignment (trigger calibration) + +Without correction the backward lines are offset from the forward lines along X, by +an amount that depends on the scan velocity (measured 2026-11-03 at the beamline, +backward minus forward): + +| Velocity [mm/s] | 0.5 | 1 | 2 | 4 | 8 | 10 | 20 | 30 | 40 | +|---|---|---|---|---|---|---|---|---|---| +| Offset [um] | -0.6 | +0.9 | +2.1 | +9.3 | +15.8 | +18.6 | +25.7 | +3.0 | -8.8 | + +It does not depend on the exposure time and is reproducible. The scan therefore moves +the trigger positions of both directions by half of it, so that forward and backward +exposures land on the same cells. The calibration is a table in the device config of +`aerox` (`userParameter` `trigger_calibration`, velocity and offset), interpolated +between the calibrated velocities. Above 40 mm/s there is no calibration: the scan +runs uncorrected and says so in its summary. + +The summary of each scan shows the applied offset and the table entry the scan +measured, for example: + +```text +trigger calibration [um]: offset +9.29 um applied; this scan measured {velocity: 10, offset: 9.41} +``` + +A calibrated scan should show a backward - forward mean of a few um at most. What +remains along a line at high velocity (rms per direction 4-7 um from 10 mm/s on) is +the motion of X and cannot be corrected by the trigger. + +**New calibration point** (other acceleration, settle time, or a velocity outside the +table): run a short scan with `trigger_calibration=False` at that velocity, for example +X +-1 mm, 6 lines: + +```python +scans.aerotech_cont_grid(dev.aerox, -1.0, 1.0, 0.1, dev.aeroy, -0.1, 0.1, 0.04, exp_time=0.005, relative=True, trigger_calibration=False) # 20 mm/s +``` + +and add the printed `{velocity: ..., offset: ...}` to `trigger_calibration` of `aerox` +in `sastt_aerotech.yaml` (ask the beamline staff to commit it). For a quick test without +a config change: `dev.aerox.update_user_parameter({...})`. + ### Examples Fields of view centred on the current position (`relative=True`), X fast, Y step: diff --git a/tests/tests_scans/test_aerotech_cont_grid_scan.py b/tests/tests_scans/test_aerotech_cont_grid_scan.py index 6e59cdd0..b8bcae7d 100644 --- a/tests/tests_scans/test_aerotech_cont_grid_scan.py +++ b/tests/tests_scans/test_aerotech_cont_grid_scan.py @@ -4,6 +4,7 @@ import numpy as np import pytest from bec_server.scan_server.errors import LimitError from bec_server.scan_server.tests.scan_fixtures import MockCustomDevice +from csaxs_bec.scans.scans_v4.aerotech_cont_grid import interpolate_trigger_offset from bec_server.scan_server.tests.scan_hook_tests import ( DEFAULT_HOOK_TESTS, PREMOVE_HOOK_TESTS, @@ -18,7 +19,12 @@ def _signal(obj_name, kind="config"): def _add_devices( - device_manager, capture=True, acceleration=100.0, panda=True, max_scan_velocity=10.0 + device_manager, + capture=True, + acceleration=100.0, + panda=True, + max_scan_velocity=10.0, + user_parameter=None, ): aerox = MockCustomDevice( "aerox", @@ -37,6 +43,7 @@ def _add_devices( "aerox_wait_in_position": True, }, ) + aerox._config = {"userParameter": user_parameter or {}} aerox.arm_line_trigger = mock.MagicMock() aerox.disarm_line_trigger = mock.MagicMock() aerox.set_line_trigger_window = mock.MagicMock() @@ -101,7 +108,7 @@ def _assemble(v4_scan_assembler, device_manager, **kwargs): device_manager, **{ k: kwargs.pop(k) - for k in ("capture", "acceleration", "panda", "max_scan_velocity") + for k in ("capture", "acceleration", "panda", "max_scan_velocity", "user_parameter") if k in kwargs }, ) @@ -681,3 +688,90 @@ def test_progress_bar_from_the_capture_without_mcs(v4_scan_assembler, device_man scan = _assemble(v4_scan_assembler, device_manager, trigger_source="panda") scan.prepare_scan() assert _progress_devices(scan) == ["aerocapture"] + + +CALIBRATION = [ + {"velocity": 10.0, "offset": 4.0}, + {"velocity": 2.0, "offset": 1.0}, + {"velocity": 20.0, "offset": -2.0}, +] + + +@pytest.mark.parametrize( + ("velocity", "expected"), + [ + (0.0, 0.0), + (1.0, 0.5), # below the lowest point: proportional to the velocity + (2.0, 1.0), + (6.0, 2.5), # linear between the points (table unsorted) + (15.0, 1.0), + (20.0, -2.0), + (20.0 * (1 + 1e-12), -2.0), # rounding of fast_step_size / exp_time + (25.0, None), # above the highest point: not calibrated + ], +) +def test_interpolate_trigger_offset(velocity, expected): + offset = interpolate_trigger_offset(CALIBRATION, velocity) + if expected is None: + assert offset is None + else: + assert offset == pytest.approx(expected) + + +def test_interpolate_trigger_offset_without_table(): + assert interpolate_trigger_offset([], 5.0) is None + + +def _trigger_positions(v4_scan_assembler, device_manager, **kwargs): + scan = _assemble(v4_scan_assembler, device_manager, **kwargs) + scan.prepare_scan() + return scan, scan._line["trigger_low"], scan._line["trigger_high"] + + +def test_trigger_calibration_shifts_both_directions(v4_scan_assembler, device_manager): + # 5 / s: offset 2.125 um between the points at 2 and 10 / s + _, low, high = _trigger_positions(v4_scan_assembler, device_manager, trigger_calibration=False) + scan, low_cal, high_cal = _trigger_positions( + v4_scan_assembler, + device_manager, + user_parameter={"trigger_calibration": CALIBRATION}, + ) + # later in the direction of motion: forward triggers at a higher, backward at a lower position + assert low_cal - low == pytest.approx(2.125e-3) + assert high - high_cal == pytest.approx(2.125e-3) + info = scan.scan_info.additional_scan_parameters + assert info["trigger_offset"] == pytest.approx(2.125) + assert info["scan_velocity"] == pytest.approx(5.0) + + +def test_trigger_calibration_off_or_not_calibrated(v4_scan_assembler, device_manager): + _, low, high = _trigger_positions(v4_scan_assembler, device_manager) # no table + scan, low_off, high_off = _trigger_positions( + v4_scan_assembler, + device_manager, + user_parameter={"trigger_calibration": CALIBRATION}, + trigger_calibration=False, + ) + assert (low_off, high_off) == pytest.approx((low, high)) + assert scan._line["trigger_offset"] is None + # 5 / s is above a table that ends at 2 / s + scan, low_high, _ = _trigger_positions( + v4_scan_assembler, + device_manager, + user_parameter={"trigger_calibration": CALIBRATION[1:2]}, + ) + assert low_high == pytest.approx(low) + assert scan._line["trigger_offset"] is None + + +def test_calibration_summary_reports_the_measured_entry(v4_scan_assembler, device_manager): + scan, _, _ = _trigger_positions( + v4_scan_assembler, device_manager, user_parameter={"trigger_calibration": CALIBRATION} + ) + # applied 2.125 um, still +1 um backward - forward: the entry is 2.625 um + summary = scan._calibration_summary(1.0) + assert "offset +2.12 um applied" in summary + assert "{velocity: 5, offset: 2.62}" in summary + scan.trigger_calibration = False + scan._line["trigger_offset"] = None + assert "off; this scan measured {velocity: 5, offset: 0.50}" in scan._calibration_summary(1.0)