fix(hardware): minimum movement displacement of 0.05mm (#13052)

* Displacement must be at least 0.05mm to move an axis * need an approx --------- Co-authored-by: Seth Foster <[email protected]>
Opentrons · Jul 6, 2023 · bbffb4a · bbffb4a
1 parent 37609fd
commit bbffb4a
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Showing 2 changed files with 8 additions and 2 deletions.
diff --git a/api/tests/opentrons/hardware_control/test_ot3_calibration.py b/api/tests/opentrons/hardware_control/test_ot3_calibration.py
@@ -184,8 +184,8 @@ async def test_find_edge(
     # all other moves should only move in the search axis
     for call in checked_calls:
         assert call[0][0] == OT3Mount.RIGHT
-        assert _other_axis_val(call[0][1], search_axis) == _other_axis_val(
-            Point(0, 0, 0), search_axis
+        assert _other_axis_val(call[0][1], search_axis) == pytest.approx(
+            _other_axis_val(Point(0, 0, 0), search_axis)
         )
 
 

diff --git a/hardware/opentrons_hardware/hardware_control/motion_planning/move_utils.py b/hardware/opentrons_hardware/hardware_control/motion_planning/move_utils.py
@@ -24,6 +24,8 @@
 
 FLOAT_THRESHOLD = 0.001  # TODO: re-evaluate this value based on system limitations
 
+MINIMUM_DISPLACEMENT = 0.05
+
 
 class MoveConditionNotMet(ValueError):
     """Error raised if a move does not meet its stop condition before finishing."""
@@ -47,6 +49,10 @@ def get_unit_vector(
     initial_vectorized = vectorize({k: np.float64(v) for k, v in initial.items()})
     target_vectorized = vectorize({k: np.float64(v) for k, v in target.items()})
     displacement: "NDArray[np.float64]" = target_vectorized - initial_vectorized
+    # minimum distance of 0.05mm
+    for i in range(len(displacement)):
+        if abs(displacement[i]) < MINIMUM_DISPLACEMENT:
+            displacement[i] = 0
     distance = np.linalg.norm(displacement)  # type: ignore[no-untyped-call]
     if not distance or np.array_equal(initial_vectorized, target_vectorized):
         raise ZeroLengthMoveError(initial, target)