| """Push and retract a STEP-derived wedge under a guided spring follower.""" |
|
|
| 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("Wedge volume must be positive") |
| bounds = shape.BoundingBox() |
| inertia = props.MatrixOfInertia() |
| density = setup["material_density_kg_m3"] |
| envelope = cq.Solid.makeBox(500, 100, 50, cq.Vector(-250, 0, -25)) |
| mount = cq.Solid.makeBox(10, 10, 50, cq.Vector(-250, 0, -25)) |
| 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], |
| "external_added_mm3": shape.cut(envelope).Volume(), |
| "mount_missing_mm3": mount.cut(shape).Volume(), |
| "collision_vertices_mm": [[v.X, v.Y, v.Z] for v in shape.Vertices()], |
| } |
|
|
|
|
| def dynamics(properties: dict, setup: dict) -> dict: |
| import pychrono as ch |
|
|
| ch.ChCollisionModel.SetDefaultSuggestedEnvelope(1e-5) |
| ch.ChCollisionModel.SetDefaultSuggestedMargin(1e-5) |
| system = ch.ChSystemNSC() |
| system.SetCollisionSystemType(ch.ChCollisionSystem.Type_BULLET) |
| system.SetGravitationalAcceleration(ch.ChVector3d(0, -setup["gravity_m_s2"], 0)) |
| material = ch.ChContactMaterialNSC() |
| material.SetFriction(setup["contact_friction"]) |
| ground = ch.ChBody() |
| ground.SetFixed(True) |
| system.Add(ground) |
|
|
| radius = setup["follower_radius_m"] |
| follower_mass = setup["follower_mass_kg"] |
| follower = ch.ChBodyEasySphere( |
| radius, follower_mass / (4 * math.pi * radius ** 3 / 3), |
| False, True, material) |
| reference_height = setup["follower_reference_height_m"] |
| follower.SetPos(ch.ChVector3d(0, reference_height, 0)) |
| system.Add(follower) |
| follower_guide = ch.ChLinkLockPrismatic() |
| follower_guide.Initialize(follower, ground, ch.ChFramed( |
| ch.ChVector3d(0, reference_height, 0), |
| ch.QuatFromAngleAxis(-math.pi / 2, ch.VECT_X))) |
| system.Add(follower_guide) |
| spring = ch.ChForce() |
| follower.AddForce(spring) |
| spring.SetMode(ch.ChForce.FORCE) |
| spring.SetDir(ch.ChVector3d(0, 1, 0)) |
|
|
| center = [value / 1000 for value in properties["center_of_mass_mm"]] |
| origin = setup["wedge_initial_cad_origin_m"] |
| wedge = ch.ChBody() |
| wedge.SetMass(properties["mass_kg"]) |
| inertia = ch.ChMatrix33d() |
| inertia.SetMatr(properties["inertia_tensor_kg_m2"]) |
| wedge.SetInertia(inertia) |
| wedge.SetPos(ch.ChVector3d(*(origin[i] + center[i] for i in range(3)))) |
| points = ch.vector_ChVector3d() |
| for x, y, z in properties["collision_vertices_mm"]: |
| points.push_back(ch.ChVector3d(x / 1000 - center[0], |
| y / 1000 - center[1], |
| z / 1000 - center[2])) |
| wedge.AddCollisionShape(ch.ChCollisionShapeConvexHull(material, points)) |
| wedge.EnableCollision(True) |
| system.Add(wedge) |
| wedge_guide = ch.ChLinkLockPrismatic() |
| wedge_guide.Initialize(wedge, ground, ch.ChFramed( |
| ch.ChVector3d(*origin), ch.QuatFromAngleAxis(math.pi / 2, ch.VECT_Y))) |
| system.Add(wedge_guide) |
| push = ch.ChForce() |
| wedge.AddForce(push) |
| push.SetMode(ch.ChForce.FORCE) |
| push.SetDir(ch.ChVector3d(1, 0, 0)) |
|
|
| 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("Invalid simulation duration or time step") |
| peak_height = reference_height |
| peak_wedge_x = origin[0] |
| first_lift_s = None |
| for i in range(steps): |
| t = i * dt |
| spring.SetMforce(follower_mass * setup["gravity_m_s2"] - |
| setup["follower_spring_stiffness_N_m"] * |
| (follower.GetPos().y - reference_height)) |
| push.SetMforce(setup["push_force_N"] if t < setup["push_duration_s"] |
| else -setup["reverse_force_N"]) |
| system.DoStepDynamics(dt) |
| height = follower.GetPos().y |
| cad_x = wedge.GetPos().x - center[0] |
| if not math.isfinite(height + cad_x): |
| raise ValueError("Nonfinite wedge or follower trajectory") |
| if t < setup["push_duration_s"]: |
| peak_height = max(peak_height, height) |
| peak_wedge_x = max(peak_wedge_x, cad_x) |
| if height >= setup["target_follower_height_m"] and first_lift_s is None: |
| first_lift_s = (i + 1) * dt |
| return { |
| "peak_push_follower_height_m": peak_height, |
| "peak_push_wedge_cad_origin_x_m": peak_wedge_x, |
| "first_target_lift_s": first_lift_s, |
| "returned_follower_height_m": follower.GetPos().y, |
| "retracted_wedge_cad_origin_x_m": wedge.GetPos().x - center[0], |
| } |
|
|
|
|
| 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"] |
| bs = before["simulation_result"] |
| gs = after["simulation_result"] |
| checks = { |
| "baseline_below_target": bs["first_target_lift_s"] is None, |
| "target_lift_reached": gs["first_target_lift_s"] is not None, |
| "lift_gain": gs["peak_push_follower_height_m"] - |
| bs["peak_push_follower_height_m"] >= setup["minimum_lift_gain_m"], |
| "wedge_retracted": gs["retracted_wedge_cad_origin_x_m"] |
| <= setup["maximum_retracted_wedge_x_m"], |
| "follower_returned": gs["returned_follower_height_m"] |
| <= setup["maximum_returned_follower_height_m"], |
| "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"], bp["bounds_mm"])), |
| "outer_envelope_kept": ap["external_added_mm3"] |
| <= setup["maximum_external_added_mm3"], |
| "mounting_foot_intact": ap["mount_missing_mm3"] |
| <= setup["maximum_mount_missing_mm3"], |
| } |
| after["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"Peak follower height: {bs['peak_push_follower_height_m']} -> " |
| f"{gs['peak_push_follower_height_m']} m") |
| print(f"Task passed: {after['comparison_to_before']['passed']}") |
| if not after["comparison_to_before"]["passed"]: |
| raise SystemExit(1) |
|
|
|
|
| if __name__ == "__main__": |
| main() |
|
|
