fixifixi (#6)

Author: OrtnerMichael

CHANGELOG.md

@@ -1,3 +1,7 @@
+# v0.1.10
+- improve docstrings
+- fix bad sign of torque
+
 # v0.1.9
 - fix docstrings
 - bugfix remove pint dependency from development

magpylib_force/__init__.py

@@ -5,7 +5,7 @@
 """
 
 # module level dunders
-__version__ = "0.1.9"
+__version__ = "0.1.10"
 __author__ = "SAL"
 __all__ = [
     "getFT",

magpylib_force/force.py

@@ -11,7 +11,8 @@
 
 def getFT(sources, targets, anchor=None, eps=1e-5, squeeze=True):
     """
-    Compute force and torque between sources and targets.
+    Compute magnetic force and torque acting on the targets that are exposed
+    to the magnetic field of the sources.
     SI units are assumed for all inputs and outputs.
 
     Parameters
@@ -181,7 +182,7 @@ def getFTmagnet(sources, targets, eps=1e-5, anchor=None):
     T = np.array([np.sum(Ts[insti[i]:insti[i+1]],axis=0) for i in range(tgt_number)])
     F = np.array([np.sum(Fs[insti[i]:insti[i+1]],axis=0) for i in range(tgt_number)])
 
-    return np.array((F, T))
+    return np.array((F, -T))
 
 
 
@@ -330,4 +331,4 @@ def getFTcurrent(sources, targets, anchor=None, eps=None):
     # sumup force for every target
     F = np.array([np.sum(F[insti[i]:insti[i+1]],axis=0) for i in range(tgt_number)])
 
-    return np.array((F, T))
+    return np.array((F, -T))

tests/test_FEM.py

@@ -35,6 +35,7 @@ def test_ANSYS_cube_cube():
     for i,poz in enumerate(tgt_pos):
         tgt.position = poz
         F,T = getFT(gen, tgt)
+        T *= -1 #bad sign in original implementation
 
         errF = np.linalg.norm(F - F_fe[i])/np.linalg.norm(F)
         assert errF < 0.04
@@ -144,7 +145,9 @@ def test_ANSYS_loop_magnet():
         loop.meshing = 1000
         magnet.meshing=(10,20,10)
         F3,T3 = getFT(sources=loop, targets=magnet, anchor=(0,0,0))
+        T3*=-1 #bad sign at initial test design
         F4,T4 = getFT(sources=magnet, targets=loop, anchor=(0,0,0))
+        T4*=-1 #bad sign at initial test design
         F3 *= 1e3
         F4 *= 1e3
         T3 *= 1e6
@@ -229,6 +232,7 @@ def test_ANSYS_magnet_current_close():
 
         F1,_ = getFT(wires, magnet, anchor=(0,0,0))
         F2,T2 = np.sum(getFT(magnet, wires, anchor=(0,0,0)), axis=0)
+        T2*=-1 #bad sign at initial test design
 
         assert np.linalg.norm(F1+F2)/np.linalg.norm(F1) < 1e-3
         assert np.linalg.norm(f2-F2)/np.linalg.norm(F2) < 1e-2

tests/test_physics.py

@@ -84,6 +84,7 @@ def func(field, observers):
 
     # with anchor
     F,T = getFT(hom, cloop, anchor=cloop.position)
+    T*=-1 #bad sign at initial test design
     assert np.amax(abs(F)) < 1e-14
     assert abs(T[0]) < 1e-14
     assert abs(T[1] - np.pi ) < 1e-3
@@ -106,6 +107,7 @@ def func(field, observers):
 
     # with anchor
     F,T = getFT(hom, rloop, anchor=rloop.position)
+    T*=-1 #bad sign at initial test design
     assert np.amax(abs(F)) < 1e-14
     assert abs(T[0]) < 1e-14
     assert abs(T[1] + 4 ) < 1e-3
@@ -262,3 +264,32 @@ def test_sphere_cube_at_distance():
 
     assert max(abs(errF)) < 1e-5
     assert max(abs(errT)) < 1e-5
+
+
+def test_torque_sign():
+    """ make sure that torque sign is in the right direction"""
+
+    # Cuboid -> Cuboid
+    mag1 = magpy.magnet.Cuboid(position=(2,0,0), polarization=(1,0,0), dimension=(2,1,1))
+    mag2 = magpy.magnet.Cuboid(position=(-2,0,0), polarization=(1,0,0), dimension=(2,1,1))
+
+    mag1.rotate_from_angax(15, "y")
+    mag1.meshing=(3,3,3)
+
+    _,T = getFT(mag2, mag1)
+
+    assert T[1] < 0
+
+    # Cuboid -> Polyline
+    mag = magpy.magnet.Cuboid(polarization=(0,0,1), dimension=(1,1,2))
+
+    ts = np.linspace(0,2*np.pi,10)
+    verts = [(2*np.cos(t), 2*np.sin(t),0) for t in ts]
+    loop = magpy.current.Polyline(vertices=verts, current=1)
+    loop.rotate_from_angax(15, "y")
+
+    loop.meshing=2
+
+    _,T = getFT(mag, loop, anchor=(0,0,0))
+
+    assert T[1] < 0