"""Measure target speed after a STEP-derived striker impact.""" 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("Striker volume must be positive") density = setup["material_density_kg_m3"] inertia = props.MatrixOfInertia() bounds = shape.BoundingBox() outer = cq.Workplane("XY").box(20, 95, 10).translate((0, 37.5, 0)) bore = cq.Workplane("XY").circle(5).extrude(12).translate((0, 0, -6)) exterior = outer.cut(bore).val() if len(exterior.Solids()) == 1: exterior = exterior.Solids()[0] allowed = cq.Solid.makeBox(17, 71, 9, cq.Vector(-8.5, 7, -4.5)) vertices, _ = shape.tessellate(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(exterior).Volume(), "exterior_removed_mm3": exterior.cut(shape).cut(allowed).Volume(), "collision_vertices_mm": [[v.x, v.y, v.z] for v in vertices], } def dynamics(properties: dict, setup: dict) -> dict: import pychrono as ch center = [value / 1000 for value in properties["center_of_mass_mm"]] mass = properties["mass_kg"] inertia_tensor = properties["inertia_tensor_kg_m2"] pivot_inertia = inertia_tensor[2][2] + mass * (center[0] ** 2 + center[1] ** 2) speed = -math.sqrt(2 * setup["initial_rotational_energy_J"] / pivot_inertia) angle = math.radians(setup["initial_angle_deg"]) pivot_to_center = ( center[0] * math.cos(angle) - center[1] * math.sin(angle), center[0] * math.sin(angle) + center[1] * math.cos(angle), ) system = ch.ChSystemSMC() system.UseMaterialProperties(False) system.SetCollisionSystemType(ch.ChCollisionSystem.Type_BULLET) system.SetGravitationalAcceleration(ch.ChVector3d(0, 0, 0)) material = ch.ChContactMaterialSMC() material.SetFriction(setup["contact_friction"]) material.SetKn(setup["contact_stiffness_N_m"]) material.SetGn(setup["contact_damping_N_s_m"]) ground = ch.ChBody() ground.SetFixed(True) system.Add(ground) striker = ch.ChBody() striker.SetMass(mass) inertia = ch.ChMatrix33d() inertia.SetMatr(inertia_tensor) striker.SetInertia(inertia) striker.SetRot(ch.QuatFromAngleAxis(angle, ch.VECT_Z)) striker.SetPos(ch.ChVector3d(*pivot_to_center, center[2])) striker.SetAngVelParent(ch.ChVector3d(0, 0, speed)) striker.SetLinVel(ch.ChVector3d(-speed * pivot_to_center[1], speed * pivot_to_center[0], 0)) 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])) striker.AddCollisionShape(ch.ChCollisionShapeConvexHull(material, points)) striker.EnableCollision(True) system.Add(striker) hinge = ch.ChLinkLockRevolute() hinge.Initialize(striker, ground, ch.ChFramed(ch.ChVector3d(0, 0, 0))) system.Add(hinge) size = setup["target_size_m"] target = ch.ChBodyEasyBox( *size, setup["target_mass_kg"] / (size[0] * size[1] * size[2]), False, True, material) target.SetPos(ch.ChVector3d(*setup["target_center_m"])) system.Add(target) guide = ch.ChLinkLockPrismatic() guide.Initialize(target, ground, ch.ChFramed( ch.ChVector3d(*setup["target_center_m"]), ch.QuatFromAngleAxis(math.pi / 2, ch.VECT_Y))) system.Add(guide) dt = setup["time_step_s"] steps = round(setup["duration_s"] / dt) if dt <= 0 or steps <= 0 or abs(steps * dt - setup["duration_s"]) > 1e-12: raise ValueError("Invalid simulation duration or time step") contact_steps = 0 for _ in range(steps): system.DoStepDynamics(dt) if target.GetContactForce().Length() > 1e-8: contact_steps += 1 final_speed = target.GetLinVel().x if not math.isfinite(final_speed): raise ValueError("Nonfinite target speed") return { "target_final_speed_m_s": final_speed, "contact_steps": contact_steps, "initial_striker_angular_speed_rad_s": speed, "initial_striker_energy_J": 0.5 * pivot_inertia * speed * speed, "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": { "runs": [invoke(args.physics_python, "dynamics", { "properties": properties, "setup": {**setup, "target_center_m": [x, *setup["target_center_m"][1:]]}, }) for x in setup["target_center_x_cases_m"]], }, } before = results["before"] after = results["after"] bp = before["step_properties"] ap = after["step_properties"] bruns = before["simulation_result"]["runs"] aruns = after["simulation_result"]["runs"] baseline = [run["target_final_speed_m_s"] for run in bruns] candidate = [run["target_final_speed_m_s"] for run in aruns] checks = { "baseline_impact_measurable": all(speed > 0.01 for speed in baseline), "target_speed_gain": all(a >= b * (1 + setup["required_relative_target_speed_gain"]) for a, b in zip(candidate, baseline)), "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"])), "pivot_and_strike_surface_fixed": ap["external_added_mm3"] <= setup["maximum_external_added_mm3"] and ap["exterior_removed_mm3"] <= setup["maximum_exterior_removed_mm3"], "centered_on_swing_plane": max(abs(ap["center_of_mass_mm"][i]) for i in (0, 2)) <= setup["maximum_center_xz_offset_mm"], "target_contact_observed": all(run["contact_steps"] > 0 for run in (*bruns, *aruns)), } after["comparison_to_before"] = { "target_center_x_cases_m": setup["target_center_x_cases_m"], "relative_target_speed_gain": [a / b - 1 for a, b in zip(candidate, baseline)], "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"Target speed: {baseline} -> {candidate} m/s") print(f"Task passed: {after['comparison_to_before']['passed']}") if not after["comparison_to_before"]["passed"]: raise SystemExit(1) if __name__ == "__main__": main()