| """Measure radial load at two bearings from a STEP-derived rotor.""" |
|
|
| import argparse |
| import hashlib |
| import json |
| import math |
| import subprocess |
| import sys |
| from pathlib import Path |
|
|
|
|
| ROOT = Path(__file__).resolve().parent |
|
|
|
|
| def measure(step: Path, setup: dict) -> dict: |
| import cadquery as cq |
| from OCP.BRepGProp import BRepGProp |
| from OCP.GProp import GProp_GProps |
|
|
| shape = cq.importers.importStep(str(step)).val() |
| if shape.ShapeType() != "Solid" or not shape.isValid() or len(shape.Solids()) != 1: |
| raise ValueError(f"Expected one valid solid: {step}") |
| props = GProp_GProps() |
| BRepGProp.VolumeProperties_s(shape.wrapped, props) |
| if props.Mass() <= 0: |
| raise ValueError("Rotor volume must be positive") |
| density = setup["material_density_kg_m3"] |
| inertia = props.MatrixOfInertia() |
| bounds = shape.BoundingBox() |
| radius = setup["shaft_radius_mm"] |
| half_thickness = setup["half_thickness_mm"] |
| bore = cq.Solid.makeCylinder(radius, 2 * half_thickness, cq.Vector(0, 0, -half_thickness)) |
| hub = cq.Solid.makeCylinder(setup["hub_radius_mm"], 2 * half_thickness, |
| cq.Vector(0, 0, -half_thickness)).cut(bore) |
| return { |
| "step_sha256": hashlib.sha256(step.read_bytes()).hexdigest(), |
| "volume_mm3": props.Mass(), |
| "mass_kg": props.Mass() * density * 1e-9, |
| "center_of_mass_mm": list(props.CentreOfMass().Coord()), |
| "inertia_tensor_kg_m2": [ |
| [inertia.Value(i, j) * density * 1e-15 for j in (1, 2, 3)] |
| for i in (1, 2, 3) |
| ], |
| "bounds_mm": [bounds.xmin, bounds.xmax, bounds.ymin, bounds.ymax, |
| bounds.zmin, bounds.zmax], |
| "bore_intrusion_mm3": shape.intersect(bore).Volume(), |
| "hub_interface_missing_mm3": hub.cut(shape).Volume(), |
| } |
|
|
|
|
| def dynamics(properties: dict, setup: dict) -> dict: |
| import pychrono as ch |
|
|
| cx, cy, cz = (value / 1000 for value in properties["center_of_mass_mm"]) |
| speed = setup["angular_speed_rad_s"] |
| system = ch.ChSystemNSC() |
| system.SetGravitationalAcceleration(ch.ChVector3d(0, 0, 0)) |
| ground = ch.ChBody() |
| ground.SetFixed(True) |
| system.Add(ground) |
| rotor = ch.ChBody() |
| rotor.SetMass(properties["mass_kg"]) |
| inertia = ch.ChMatrix33d() |
| inertia.SetMatr(properties["inertia_tensor_kg_m2"]) |
| rotor.SetInertia(inertia) |
| rotor.SetPos(ch.ChVector3d(cx, cy, cz)) |
| rotor.SetLinVel(ch.ChVector3d(-speed * cy, speed * cx, 0)) |
| rotor.SetAngVelParent(ch.ChVector3d(0, 0, speed)) |
| system.Add(rotor) |
|
|
| lower = ch.ChLinkLockSpherical() |
| lower.Initialize(rotor, ground, ch.ChFramed(ch.ChVector3d(0, 0, |
| setup["bearing_z_mm"][0] / 1000))) |
| system.Add(lower) |
| upper = ch.ChLinkLockPointLine() |
| upper.Initialize(rotor, ground, ch.ChFramed(ch.ChVector3d(0, 0, |
| setup["bearing_z_mm"][1] / 1000))) |
| system.Add(upper) |
|
|
| dt = setup["time_step_s"] |
| steps = round(setup["duration_s"] / dt) |
| settle = round(setup["settling_s"] / dt) |
| if dt <= 0 or steps <= settle or abs(steps * dt - setup["duration_s"]) > 1e-12: |
| raise ValueError("Invalid simulation duration or time step") |
| sums = [0.0, 0.0] |
| count = 0 |
| speeds = [] |
| for i in range(steps): |
| system.DoStepDynamics(dt) |
| if i < settle: |
| continue |
| for j, bearing in enumerate((lower, upper)): |
| force = bearing.GetReaction1().force |
| radial_squared = force.x * force.x + force.y * force.y |
| if not math.isfinite(radial_squared): |
| raise ValueError("Nonfinite bearing reaction") |
| sums[j] += radial_squared |
| speeds.append(rotor.GetAngVelParent().z) |
| count += 1 |
| return { |
| "bearing_rms_radial_load_N": [math.sqrt(value / count) for value in sums], |
| "mean_angular_speed_rad_s": sum(speeds) / count, |
| "maximum_relative_speed_drift": max(abs(value / speed - 1) for value in speeds), |
| "steps": steps, |
| } |
|
|
|
|
| def invoke(python: str, phase: str, payload: dict) -> dict: |
| run = subprocess.run( |
| [python, str(Path(__file__).resolve()), "--phase", phase], |
| input=json.dumps(payload), text=True, capture_output=True, check=False, |
| ) |
| if run.returncode: |
| raise RuntimeError(f"{phase} failed:\n{run.stderr[-1600:]}") |
| return json.loads(run.stdout) |
|
|
|
|
| def main() -> None: |
| parser = argparse.ArgumentParser() |
| parser.add_argument("--cad-python", default=sys.executable) |
| parser.add_argument("--physics-python", default=sys.executable) |
| parser.add_argument("--phase", choices=("measure", "dynamics")) |
| args = parser.parse_args() |
| if args.phase: |
| payload = json.load(sys.stdin) |
| result = (measure(Path(payload["step"]), payload["setup"]) |
| if args.phase == "measure" |
| else dynamics(payload["properties"], payload["setup"])) |
| print(json.dumps(result)) |
| return |
|
|
| setup = json.loads((ROOT / "setup.json").read_text()) |
| results = {} |
| for name in ("before", "after"): |
| properties = invoke(args.cad_python, "measure", { |
| "step": str(ROOT / f"{name}.step"), "setup": setup, |
| }) |
| results[name] = { |
| "step_properties": properties, |
| "simulation_result": invoke(args.physics_python, "dynamics", { |
| "properties": properties, "setup": setup, |
| }), |
| } |
| before = results["before"] |
| after = results["after"] |
| bp = before["step_properties"] |
| ap = after["step_properties"] |
| br = before["simulation_result"]["bearing_rms_radial_load_N"] |
| ar = after["simulation_result"]["bearing_rms_radial_load_N"] |
| target = setup["required_relative_bearing_load_reduction"] |
| envelope = [-setup["outer_radius_mm"], setup["outer_radius_mm"], |
| -setup["outer_radius_mm"], setup["outer_radius_mm"], |
| -setup["half_thickness_mm"], setup["half_thickness_mm"]] |
| checks = { |
| "baseline_load_measurable": min(br) > 0.001, |
| "both_bearing_loads_reduced": all(a <= (1 - target) * b for a, b in zip(ar, br)), |
| "mass_fixed": abs(ap["mass_kg"] / bp["mass_kg"] - 1) |
| <= setup["maximum_relative_mass_change"], |
| "envelope_fixed": all(abs(a - b) <= setup["maximum_envelope_change_mm"] |
| for a, b in zip(ap["bounds_mm"], envelope)), |
| "shaft_bore_clear": ap["bore_intrusion_mm3"] |
| <= setup["maximum_bore_intrusion_mm3"], |
| "shaft_interface_intact": ap["hub_interface_missing_mm3"] |
| <= setup["maximum_interface_missing_mm3"], |
| "speed_held": all(result["simulation_result"]["maximum_relative_speed_drift"] |
| <= setup["maximum_relative_speed_drift"] |
| for result in (before, after)), |
| } |
| after["comparison_to_before"] = { |
| "relative_bearing_load_reduction": [1 - a / b for a, b in zip(ar, br)], |
| "checks": checks, |
| "passed": all(checks.values()), |
| } |
| for name, result in results.items(): |
| (ROOT / f"{name}.results.json").write_text(json.dumps(result, indent=2) + "\n") |
| print(f"Bearing RMS radial loads: {br} -> {ar} N") |
| print(f"Task passed: {after['comparison_to_before']['passed']}") |
| if not after["comparison_to_before"]["passed"]: |
| raise SystemExit(1) |
|
|
|
|
| if __name__ == "__main__": |
| main() |
|
|
