feat: Reduce the number of slots on shoulder

Previously every shoulder joint was the same with two slots that specify
the neutral position. Experiment reveals this to be too fragile.

nhf/parts/joints.py

@@ -219,6 +219,8 @@ class TorsionJoint:
         assert self.groove_radius_inner > self.spring.radius > self.radius_axle
         assert self.spring.height > self.groove_depth, "Groove is too deep"
         assert self.groove_depth < self.spring.height - self.spring.thickness * 2
+        if self.rider_n_slots == 1:
+            assert self.rider_slot_span == 0.0, "Non-zero span is impossible with multiple riders"
 
     @property
     def total_height(self):
@@ -373,7 +375,9 @@ class TorsionJoint:
         )
         theta_begin = -math.radians(rider_slot_begin)
         theta_span = math.radians(self.rider_slot_span)
-        if abs(math.remainder(self.rider_slot_span, 360)) < TOL:
+        if self.rider_n_slots <= 1:
+            theta_step = 0
+        elif abs(math.remainder(self.rider_slot_span, 360)) < TOL:
             theta_step = theta_span / self.rider_n_slots
         else:
             theta_step = theta_span / (self.rider_n_slots - 1)

nhf/touhou/houjuu_nue/__init__.py

@@ -50,14 +50,14 @@ class Parameters(Model):
 
     wing_r1: MW.WingR = field(default_factory=lambda: MW.WingR(
         name="r1",
-        shoulder_joint=MJ.ShoulderJoint(directrix_id=1),
+        shoulder_angle_bias = 15.0,
     ))
     wing_r2: MW.WingR = field(default_factory=lambda: MW.WingR(
         name="r2",
     ))
     wing_r3: MW.WingR = field(default_factory=lambda: MW.WingR(
         name="r3",
-        shoulder_joint=MJ.ShoulderJoint(directrix_id=1),
+        shoulder_angle_bias = 15.0,
     ))
     wing_l1: MW.WingL = field(default_factory=lambda: MW.WingL(
         name="l1",
@@ -66,7 +66,7 @@ class Parameters(Model):
     wing_l2: MW.WingL = field(default_factory=lambda: MW.WingL(
         name="l2",
         wrist_angle=-30.0,
-        shoulder_joint=MJ.ShoulderJoint(directrix_id=1),
+        shoulder_angle_bias = 15.0,
     ))
     wing_l3: MW.WingL = field(default_factory=lambda: MW.WingL(
         name="l3",
@@ -84,6 +84,8 @@ class Parameters(Model):
         self.wing_l2.base_joint = self.harness.hs_hirth_joint
         self.wing_l3.base_joint = self.harness.hs_hirth_joint
 
+        self.wing_r1.shoulder_joint.torsion_joint
+
         assert self.wing_r1.hs_joint_axis_diam == self.harness.hs_joint_axis_diam
         assert self.wing_r2.hs_joint_axis_diam == self.harness.hs_joint_axis_diam
         assert self.wing_r3.hs_joint_axis_diam == self.harness.hs_joint_axis_diam

nhf/touhou/houjuu_nue/joints.py

@@ -32,8 +32,8 @@ class ShoulderJoint(Model):
             height=7.5,
         ),
         rider_slot_begin=0,
-        rider_n_slots=2,
+        rider_n_slots=1,
-        rider_slot_span=15,
+        rider_slot_span=0,
     ))
 
     # On the parent side, drill vertical holes

nhf/touhou/houjuu_nue/test.py

@@ -10,11 +10,21 @@ class TestJoints(unittest.TestCase):
         j = MJ.ShoulderJoint()
         assembly = j.torsion_joint.rider_track_assembly()
         self.assertEqual(pairwise_intersection(assembly), [])
+
     def test_shoulder_collision_0(self):
         j = MJ.ShoulderJoint()
         assembly = j.assembly()
         self.assertEqual(pairwise_intersection(assembly), [])
 
+    def test_shoulder_align(self):
+        j = MJ.ShoulderJoint()
+        a = j.assembly()
+        l_t_c0 = a.get_abs_location("parent_top/lip?conn0")
+        l_b_c0 = a.get_abs_location("parent_bot/lip?conn0")
+        v = l_t_c0 - l_b_c0
+        self.assertAlmostEqual(v.x, 0)
+        self.assertAlmostEqual(v.y, 0)
+
     def test_shoulder_joint_dist(self):
         """
         Tests the arm radius

nhf/touhou/houjuu_nue/wing.py

@@ -39,6 +39,7 @@ class WingProfile(Model):
 
     shoulder_joint: ShoulderJoint = field(default_factory=lambda: ShoulderJoint(
     ))
+    shoulder_angle_bias: float = 0.0
     shoulder_width: float = 36.0
     shoulder_tip_x: float = -200.0
     shoulder_tip_y: float = 160.0
@@ -94,7 +95,7 @@ class WingProfile(Model):
         self.elbow_top_loc = self.elbow_bot_loc * Cq.Location.from2d(0, self.elbow_height)
         self.wrist_top_loc = self.wrist_bot_loc * Cq.Location.from2d(0, self.wrist_height)
 
-        self.shoulder_joint.angle_neutral = -self.shoulder_angle_neutral
+        self.shoulder_joint.angle_neutral = -self.shoulder_angle_neutral - self.shoulder_angle_bias
 
     @submodel(name="shoulder-joint")
     def submodel_shoulder_joint(self) -> Model:
@@ -287,14 +288,14 @@ class WingProfile(Model):
         sw = self.shoulder_width
 
         axle_dist = self.shoulder_joint.parent_lip_ext
-        theta = math.radians(self.shoulder_joint.angle_neutral)
+        theta = math.radians(self.shoulder_angle_neutral)
-        c, s = math.cos(-theta), math.sin(-theta)
+        c, s = math.cos(theta), math.sin(theta)
         tags = [
             # transforms [axle_dist, -sw/2] about the centre (tip_x, tip_y - sw/2)
             ("shoulder", Cq.Location.from2d(
                 self.shoulder_tip_x          + axle_dist * c + (-sw/2) * s,
                 self.shoulder_tip_y - sw / 2 - axle_dist * s + (-sw/2) * c,
-                self.shoulder_joint.angle_neutral)),
+                -self.shoulder_angle_neutral)),
             ("base", Cq.Location.from2d(base_dx,  base_dy, 90)),
         ]
         result = extrude_with_markers(