| """Measure both STEP blocks and test tipping under the same sideways load.""" |
|
|
| 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, density: float) -> 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(): |
| raise ValueError(f"Expected one valid solid: {step}") |
| props = GProp_GProps() |
| BRepGProp.VolumeProperties_s(shape.wrapped, props) |
| box = shape.BoundingBox() |
| inertia = props.MatrixOfInertia() |
| return { |
| "step_sha256": hashlib.sha256(step.read_bytes()).hexdigest(), |
| "volume_mm3": props.Mass(), |
| "mass_kg": props.Mass() * density * 1e-9, |
| "width_mm": box.xlen, |
| "height_mm": box.ylen, |
| "depth_mm": box.zlen, |
| "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) |
| ], |
| } |
|
|
|
|
| def dynamics(p: dict, setup: dict) -> dict: |
| import pychrono as ch |
|
|
| if max(abs(v) for v in p["center_of_mass_mm"]) > 1e-6: |
| raise ValueError("Block must be centered on the origin") |
| width = p["width_mm"] / 1000 |
| height = p["height_mm"] / 1000 |
| system = ch.ChSystemNSC() |
| system.SetGravitationalAcceleration(ch.ChVector3d(0, -setup["gravity_m_s2"], 0)) |
| floor = ch.ChBody() |
| floor.SetFixed(True) |
| system.Add(floor) |
| block = ch.ChBody() |
| block.SetMass(p["mass_kg"]) |
| inertia = ch.ChMatrix33d() |
| inertia.SetMatr(p["inertia_tensor_kg_m2"]) |
| block.SetInertia(inertia) |
| block.SetPos(ch.ChVector3d(-width / 2, height / 2, 0)) |
| system.Add(block) |
|
|
| |
| |
| hinge = ch.ChLinkLockRevolute() |
| hinge.Initialize(block, floor, ch.ChFramed(ch.ChVector3d(0, 0, 0))) |
| limit = hinge.LimitRz() |
| limit.SetActive(True) |
| limit.SetMin(-math.pi) |
| limit.SetMax(0) |
| system.Add(hinge) |
|
|
| |
| force = ch.ChForce() |
| block.AddForce(force) |
| force.SetMode(ch.ChForce.FORCE) |
| force.SetAlign(ch.ChForce.WORLD_DIR) |
| force.SetDir(ch.ChVector3d(1, 0, 0)) |
| force.SetVrelpoint(ch.ChVector3d(0, height / 2, 0)) |
| force.SetMforce(setup["sideways_force_at_top_N"]) |
|
|
| dt = setup["time_step_s"] |
| steps = round(setup["duration_s"] / dt) |
| if dt <= 0 or abs(steps * dt - setup["duration_s"]) > 1e-12: |
| raise ValueError("Duration must contain whole time steps") |
| greatest = 0.0 |
| tip_time = None |
| for i in range(1, steps + 1): |
| system.DoStepDynamics(dt) |
| q = block.GetRot() |
| angle = -math.degrees(2 * math.atan2(q.e3, q.e0)) |
| if not math.isfinite(angle): |
| raise ValueError("Nonfinite tipping angle") |
| greatest = max(greatest, angle) |
| if angle >= setup["tip_angle_deg"]: |
| tip_time = i * dt |
| break |
| return { |
| "tipped_within_window": tip_time is not None, |
| "time_to_tip_s": tip_time, |
| "maximum_tip_angle_deg": greatest, |
| "steps_run": i, |
| } |
|
|
|
|
| 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}") |
| 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) |
| print(json.dumps( |
| measure(Path(payload["step"]), payload["density"]) |
| if args.phase == "measure" |
| else dynamics(payload["properties"], payload["setup"]) |
| )) |
| return |
|
|
| setup_path = ROOT / "setup.json" |
| setup = json.loads(setup_path.read_text()) |
| hashes = { |
| "setup_sha256": hashlib.sha256(setup_path.read_bytes()).hexdigest(), |
| "simulation_sha256": hashlib.sha256(Path(__file__).read_bytes()).hexdigest(), |
| "engine": setup["engine"], |
| "engine_version": setup["engine_version"], |
| } |
| results = {} |
| for name in ("before", "after"): |
| step = ROOT / f"{name}.step" |
| p = invoke(args.cad_python, "measure", { |
| "step": str(step), "density": setup["material_density_kg_m3"], |
| }) |
| results[name] = { |
| "step": step.name, "setup": "setup.json", "simulation": "simulate.py", |
| "step_properties": p, |
| "simulation_result": invoke(args.physics_python, "dynamics", { |
| "properties": p, "setup": setup, |
| }), |
| "provenance": hashes, |
| } |
|
|
| b, a = results["before"], results["after"] |
| bp, ap = b["step_properties"], a["step_properties"] |
| checks = { |
| "before_tips": b["simulation_result"]["tipped_within_window"], |
| "after_resists_tip": not a["simulation_result"]["tipped_within_window"], |
| "mass_fixed": abs(ap["mass_kg"] / bp["mass_kg"] - 1) |
| <= setup["maximum_relative_mass_change"], |
| } |
| a["comparison_to_before"] = {"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"Tipped within {setup['duration_s']} s: " |
| f"{b['simulation_result']['tipped_within_window']} -> " |
| f"{a['simulation_result']['tipped_within_window']}" |
| ) |
| print(f"Task passed: {a['comparison_to_before']['passed']}") |
| if not a["comparison_to_before"]["passed"]: |
| raise SystemExit(1) |
|
|
|
|
| if __name__ == "__main__": |
| main() |
|
|
