"""Differentiable cylinder-segment magnet source."""
from __future__ import annotations
import jax.numpy as jnp
from magpylib_jax._types import ArrayLike
from magpylib_jax.constants import MU0
from magpylib_jax.core.base import BaseSource, MagpylibMissingInput
[docs]
class CylinderSegment(BaseSource):
"""Uniformly polarized cylinder segment (r1, r2, h, phi1_deg, phi2_deg)."""
_source_type = "cylindersegment"
def __init__(
self,
dimension: ArrayLike | None = None,
polarization: ArrayLike | None = None,
magnetization: ArrayLike | None = None,
position: ArrayLike = (0.0, 0.0, 0.0),
orientation: ArrayLike | None = None,
style=None,
style_label: str | None = None,
**kwargs,
) -> None:
self.dimension = dimension
self.polarization = polarization
self.magnetization = magnetization
if self.dimension is not None:
dim = jnp.asarray(self.dimension, dtype=float)
if dim.shape != (5,):
raise ValueError(
f"CylinderSegment `dimension` must have shape (5,), got {dim.shape}."
)
r1, r2, _, phi1, phi2 = dim
if not (r1 >= 0 and r2 > r1 and phi2 > phi1):
raise ValueError("CylinderSegment `dimension` must satisfy r2>r1>=0 and phi2>phi1.")
super().__init__(
position=position,
orientation=orientation,
style=style,
style_label=style_label,
**kwargs,
)
@property
def _polarization(self) -> jnp.ndarray:
if self.polarization is not None:
return jnp.asarray(self.polarization, dtype=float)
if self.magnetization is not None:
return MU0 * jnp.asarray(self.magnetization, dtype=float)
raise MagpylibMissingInput("Input polarization of CylinderSegment must be set.")
@property
def volume(self) -> float:
if self.dimension is None:
return 0.0
r1, r2, h, phi1, phi2 = jnp.asarray(self.dimension, dtype=float)
return float((r2 * r2 - r1 * r1) * jnp.pi * h * (phi2 - phi1) / 360.0)
@property
def barycenter(self) -> jnp.ndarray:
if self.dimension is None:
return jnp.zeros((3,), dtype=float)
r1, r2, _, phi1, phi2 = jnp.asarray(self.dimension, dtype=float)
alpha = jnp.deg2rad((phi2 - phi1) / 2.0)
phi = jnp.deg2rad((phi1 + phi2) / 2.0)
centroid_x = (2.0 / 3.0) * jnp.sin(alpha) / alpha * (r2**3 - r1**3) / (r2**2 - r1**2)
cent = jnp.array([centroid_x * jnp.cos(phi), centroid_x * jnp.sin(phi), 0.0])
return cent
@property
def centroid(self) -> jnp.ndarray:
return self.barycenter + jnp.asarray(self.position, dtype=float)
def _require_inputs(self) -> None:
if self.dimension is None:
raise MagpylibMissingInput("Input dimension of CylinderSegment must be set.")
if self.polarization is None and self.magnetization is None:
raise MagpylibMissingInput("Input polarization of CylinderSegment must be set.")
def _field_kwargs(self) -> dict:
"""Geometry + excitation arguments for the field engine."""
return {"dimension": self.dimension, "polarization": self._polarization}