Added a much more robust displacement tool for the GZ computation
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Jose Luis Cercos Pita
parent
a5d7344f5a
commit
3644dcbcab
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@ -57,7 +57,7 @@ class TaskPanel:
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gz = Tools.solve(self.ship,
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self.weights,
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self.tanks
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self.tanks,
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rolls,
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form.var_trim.isChecked())
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@ -36,6 +36,7 @@ from shipHydrostatics import Tools as Hydrostatics
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G = 9.81
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MAX_EQUILIBRIUM_ITERS = 10
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DENS = 1.025 # [tons/m3], salt water
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TRIM_RELAX_FACTOR = 10.0
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def solve(ship, weights, tanks, rolls, var_trim=True):
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@ -68,14 +69,15 @@ def solve(ship, weights, tanks, rolls, var_trim=True):
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# t[2] = filling level
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vol = t[0].Proxy.setFillingLevel(t[0], t[2]).getValueAs('m^3').Value
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TW += vol * t[1]
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TW = TW.getValueAs('kg').Value * G
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TW = TW * G
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gzs = []
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for roll in rolls:
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for i,roll in enumerate(rolls):
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App.Console.PrintMessage("{0} / {1}\n".format(i + 1, len(rolls)))
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gz = solve_point(W, COG, TW, ship, tanks, roll, var_trim)
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if gz is None:
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return []
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gzs.append(solve_point(W, COG, TW, ship, tanks, roll, var_trim))
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gzs.append(gz)
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return gzs
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@ -92,9 +94,9 @@ def solve_point(W, COG, TW, ship, tanks, roll, var_trim=True):
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gz = 0.0
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# Look for the equilibrium draft (and eventually the trim angle too)
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max_draft = ship.Shape.BoundBox.ZMax
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draft = max_draft
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max_disp = ship.Shape.Volume.getValueAs('m^3').Value * DENS * 1000.0 * G
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max_draft = ship.Shape.BoundBox.ZMax / Units.Metre.Value
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draft = ship.Draft.getValueAs('m').Value
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max_disp = ship.Shape.Volume / Units.Metre.Value**3 * DENS * 1000.0 * G
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if max_disp < W + TW:
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msg = QtGui.QApplication.translate(
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"ship_console",
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@ -109,35 +111,32 @@ def solve_point(W, COG, TW, ship, tanks, roll, var_trim=True):
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# Get the displacement, and the bouyance application point
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disp, B, Cb = Hydrostatics.displacement(ship, draft, roll, trim)
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disp *= 1000.0 * G
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# Get the empty ship weight transformed application point
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p = Part.makePoint(COG)
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p.translate(Vector(0.0, 0.0, -draft))
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m = Matrix()
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m.rotateX(math.radians(roll))
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m.rotateY(-math.radians(trim))
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p.rotate(Placement(m))
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# Add the tanks
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# Add the tanks effect on the center of gravity
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# TODO
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# ---
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# Compute the errors
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draft_error = abs(disp - W - TW) / max_disp
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draft_error = -(disp - W - TW) / max_disp
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R = COG - B
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if not var_trim:
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trim_error = 0.0
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else:
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dx = B.x - p.X
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dz = B.z - p.Z
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if abs(dx) < 0.001 * ship.Length.getValueAs('m').Value:
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trim_error = 0.0
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else:
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trim_error = math.degrees(math.atan2(dz, dx))
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trim_error = -TRIM_RELAX_FACTOR * R.x / ship.Length.getValueAs('m').Value
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# Check if we can tolerate the errors
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if draft_error < 0.01 and trim_error < 1.0:
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if abs(draft_error) < 0.01 and abs(trim_error) < 0.05:
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break
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# Get the new draft and trim
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draft += draft_error * max_draft
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trim += 0.5 * trim_error
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trim += trim_error
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return B.y - p.Y
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App.Console.PrintMessage("draft and trim: {}, {}\n".format(draft, trim))
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App.Console.PrintMessage(R)
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App.Console.PrintMessage("\n")
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c = math.cos(math.radians(roll))
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s = math.sin(math.radians(roll))
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App.Console.PrintMessage(c * R.y - s * R.z)
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App.Console.PrintMessage("\n")
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return c * R.y - s * R.z
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@ -22,13 +22,20 @@
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#***************************************************************************
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import math
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from FreeCAD import Vector, Matrix, Placement
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import random
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from FreeCAD import Vector, Rotation, Matrix, Placement
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import Part
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import Units
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import FreeCAD as App
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import FreeCADGui as Gui
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from PySide import QtGui, QtCore
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import Instance
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from shipUtils import Math
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import shipUtils.Units as USys
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DENS = 1.025 # [tons/m3], salt water
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COMMON_BOOLEAN_ITERATIONS = 10
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def areas(ship, draft, roll=0.0, trim=0.0, yaw=0.0, n=30):
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@ -148,50 +155,72 @@ def displacement(ship, draft, roll=0.0, trim=0.0, yaw=0.0):
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L = xmax - xmin
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B = ymax - ymin
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H = zmax - zmin
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p = Vector(xmin - L, ymin - B, zmin - H)
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try:
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box = Part.makeBox(3.0 * L, 3.0 * B, - zmin + H, p)
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except Part.OCCError:
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return [0.0, Vector(), 0.0]
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Part.show(box)
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box_shape = App.ActiveDocument.Objects[-1]
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box = App.ActiveDocument.addObject("Part::Box","Box")
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length_format = USys.getLengthFormat()
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box.Placement = Placement(Vector(xmin - L, ymin - B, zmin - H),
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Rotation(App.Vector(0,0,1),0))
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box.Length = length_format.format(3.0 * L)
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box.Width = length_format.format(3.0 * B)
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box.Height = length_format.format(- zmin + H)
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App.ActiveDocument.recompute()
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common = App.activeDocument().addObject("Part::MultiCommon",
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"DisplacementHelper")
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common.Shapes = [ship_shape, box_shape]
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common.Shapes = [ship_shape, box]
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App.ActiveDocument.recompute()
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if len(common.Shape.Solids) == 0:
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# The common operation is failing, let's try moving a bit the free
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# surface
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msg = QtGui.QApplication.translate(
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"ship_console",
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"Boolean operation failed. The tool is retrying that slightly"
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" moving the free surface position",
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None,
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QtGui.QApplication.UnicodeUTF8)
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App.Console.PrintWarning(msg + '\n')
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random_bounds = 0.01 * H
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i = 0
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while len(common.Shape.Solids) == 0 and i < COMMON_BOOLEAN_ITERATIONS:
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i += 1
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box.Height = length_format.format(
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- zmin + H + random.uniform(-random_bounds, random_bounds))
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App.ActiveDocument.recompute()
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vol = 0.0
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cog = Vector()
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for solid in common.Shape.Solids:
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vol += solid.Volume / Units.Metre.Value**3
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sCoG = solid.CenterOfMass
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cog.x = cog.x + sCoG.x * solid.Volume / Units.Metre.Value**4
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cog.y = cog.y + sCoG.y * solid.Volume / Units.Metre.Value**4
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cog.z = cog.z + sCoG.z * solid.Volume / Units.Metre.Value**4
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cog.x = cog.x / vol
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cog.y = cog.y / vol
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cog.z = cog.z / vol
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if len(common.Shape.Solids) > 0:
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for solid in common.Shape.Solids:
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vol += solid.Volume / Units.Metre.Value**3
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sCoG = solid.CenterOfMass
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cog.x = cog.x + sCoG.x * solid.Volume / Units.Metre.Value**4
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cog.y = cog.y + sCoG.y * solid.Volume / Units.Metre.Value**4
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cog.z = cog.z + sCoG.z * solid.Volume / Units.Metre.Value**4
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cog.x = cog.x / vol
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cog.y = cog.y / vol
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cog.z = cog.z / vol
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Vol = L * B * abs(bbox.ZMin) / Units.Metre.Value**3
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App.ActiveDocument.removeObject(common.Name)
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App.ActiveDocument.removeObject(ship_shape.Name)
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App.ActiveDocument.removeObject(box_shape.Name)
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App.ActiveDocument.removeObject(box.Name)
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App.ActiveDocument.recompute()
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# Undo the transformations
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B = Part.Point(Vector(cog.x, cog.y, cog.z))
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m = Matrix()
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m.move(Vector(0.0, 0.0, _draft))
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m.move(Vector(0.0, 0.0, draft))
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m.rotateZ(-math.radians(yaw))
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m.move(Vector(-_draft * math.sin(math.radians(roll)), 0.0, 0.0))
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m.move(Vector(-draft * math.sin(math.radians(roll)), 0.0, 0.0))
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m.rotateY(math.radians(trim))
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m.move(Vector(0.0, -_draft * math.sin(math.radians(trim)), base_z))
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m.move(Vector(0.0,
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-draft * math.sin(math.radians(trim)),
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base_z / Units.Metre.Value))
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m.rotateX(-math.radians(roll))
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B.transform(m)
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# Return the computed data
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dens = 1.025 # [tons/m3], salt water
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return [dens*vol, Vector(B.X, B.Y, B.Z), vol/Vol]
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return [DENS*vol, Vector(B.X, B.Y, B.Z), vol/Vol]
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def wettedArea(shape, draft, trim):
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