def onAutoTrim(self):
""" Called when trim angle must be auto computed.
"""
# Start at null trim angle
trim = 0.0
# Get center of gravity
disp = self.computeDisplacement(trim)
G = [disp[1], disp[2], disp[3]]
disp = disp[0]
# Get bouyancy center
draft = self.computeDraft(disp)
xcb = draft[1]
draft = draft[0]
KBT = Hydrostatics.KBT(self.ship, draft, trim)
B = [xcb, KBT[0], KBT[1]]
# Get stability initial condition
BG = [G[0]-B[0], G[1]-B[1], G[2]-B[2]]
x = BG[0]*math.cos(math.radians(trim)) - BG[2]*math.sin(math.radians(trim))
y = BG[1]
z = BG[0]*math.sin(math.radians(trim)) + BG[2]*math.cos(math.radians(trim))
var = math.degrees(math.atan2(x,z))
# Iterate looking stability point
dVar = math.copysign(0.0033, var)
while True:
if (dVar*math.copysign(dVar, var) < 0.0):
break
trim = trim - math.copysign(dVar, var)
# Get center of gravity
disp = self.computeDisplacement(trim)
G = [disp[1], disp[2], disp[3]]
disp = disp[0]
# Get bouyancy center
draft = self.computeDraft(disp, trim)
xcb = draft[1]
draft = draft[0]
KBT = Hydrostatics.KBT(self.ship, draft, trim)
B = [xcb, KBT[0], KBT[1]]
# Get stability initial condition
BG = [G[0]-B[0], G[1]-B[1], G[2]-B[2]]
x = BG[0]*math.cos(math.radians(trim)) - BG[2]*math.sin(math.radians(trim))
y = BG[1]
z = BG[0]*math.sin(math.radians(trim)) + BG[2]*math.cos(math.radians(trim))
var = math.degrees(math.atan2(x,z))
self.form.trim.setValue(trim)
def computeGZ(self, draft, trim, roll):
""" Compute GZ value.
@param draft Ship draft.
@param trim Ship trim angle [degrees].
@param roll Ship roll angle [degrees].
@return GZ value [m].
"""
# Get center of gravity (x coordinate not relevant)
disp = self.computeDisplacement(trim, roll)
G = [disp[2], disp[3]]
disp = disp[0]
# Get bouyancy center (x coordinate not relevant)
KBT = Hydrostatics.KBT(self.ship, draft, trim, roll)
B = [KBT[0], KBT[1]]
# GZ computation
BG = [G[0] - B[0], G[1] - B[1]]
y = BG[0]*math.cos(math.radians(-roll)) - BG[1]*math.sin(math.radians(-roll))
z = BG[0]*math.sin(math.radians(-roll)) + BG[1]*math.cos(math.radians(-roll))
return -y
