def test_body_add_force():
# Body with RigidBody.
rigidbody_masscenter = Point('rigidbody_masscenter')
rigidbody_mass = Symbol('rigidbody_mass')
rigidbody_frame = ReferenceFrame('rigidbody_frame')
body_inertia = inertia(rigidbody_frame, 1, 0, 0)
rigid_body = Body('rigidbody_body', rigidbody_masscenter, rigidbody_mass,
rigidbody_frame, body_inertia)
l = Symbol('l')
Fa = Symbol('Fa')
point = rigid_body.masscenter.locatenew('rigidbody_body_point0',
l * rigid_body.frame.x)
point.set_vel(rigid_body.frame, 0)
force_vector = Fa * rigid_body.frame.z
# apply_force with point
rigid_body.apply_force(force_vector, point)
assert len(rigid_body.loads) == 1
force_point = rigid_body.loads[0][0]
frame = rigid_body.frame
assert force_point.vel(frame) == point.vel(frame)
assert force_point.pos_from(force_point) == point.pos_from(force_point)
assert rigid_body.loads[0][1] == force_vector
# apply_force without point
rigid_body.apply_force(force_vector)
assert len(rigid_body.loads) == 2
assert rigid_body.loads[1][1] == force_vector
# passing something else than point
raises(TypeError, lambda: rigid_body.apply_force(force_vector, 0))
raises(TypeError, lambda: rigid_body.apply_force(0))
def test_custom_rigid_body():
# Body with RigidBody.
rigidbody_masscenter = Point("rigidbody_masscenter")
rigidbody_mass = Symbol("rigidbody_mass")
rigidbody_frame = ReferenceFrame("rigidbody_frame")
body_inertia = inertia(rigidbody_frame, 1, 0, 0)
rigid_body = Body(
"rigidbody_body",
rigidbody_masscenter,
rigidbody_mass,
rigidbody_frame,
body_inertia,
)
com = rigid_body.masscenter
frame = rigid_body.frame
rigidbody_masscenter.set_vel(rigidbody_frame, 0)
assert com.vel(frame) == rigidbody_masscenter.vel(frame)
assert com.pos_from(com) == rigidbody_masscenter.pos_from(com)
assert rigid_body.mass == rigidbody_mass
assert rigid_body.inertia == (body_inertia, rigidbody_masscenter)
assert hasattr(rigid_body, "masscenter")
assert hasattr(rigid_body, "mass")
assert hasattr(rigid_body, "frame")
assert hasattr(rigid_body, "inertia")
def test_particle_body_add_force():
# Body with Particle
particle_masscenter = Point('particle_masscenter')
particle_mass = Symbol('particle_mass')
particle_frame = ReferenceFrame('particle_frame')
particle_body = Body('particle_body', particle_masscenter, particle_mass,
particle_frame)
a = Symbol('a')
force_vector = a * particle_body.frame.x
particle_body.apply_force(force_vector, particle_body.masscenter)
assert len(particle_body.loads) == 1
point = particle_body.masscenter.locatenew(particle_body._name + '_point0',
0)
point.set_vel(particle_body.frame, 0)
force_point = particle_body.loads[0][0]
frame = particle_body.frame
assert force_point.vel(frame) == point.vel(frame)
assert force_point.pos_from(force_point) == point.pos_from(force_point)
assert particle_body.loads[0][1] == force_vector
def test_default():
body = Body('body')
assert body.name == 'body'
assert body.loads == []
point = Point('body_masscenter')
point.set_vel(body.frame, 0)
com = body.masscenter
frame = body.frame
assert com.vel(frame) == point.vel(frame)
assert body.mass == Symbol('body_mass')
ixx, iyy, izz = symbols('body_ixx body_iyy body_izz')
ixy, iyz, izx = symbols('body_ixy body_iyz body_izx')
assert body.inertia == (inertia(body.frame, ixx, iyy, izz, ixy, iyz,
izx), body.masscenter)
def test_default():
body = Body("body")
assert body.name == "body"
assert body.loads == []
point = Point("body_masscenter")
point.set_vel(body.frame, 0)
com = body.masscenter
frame = body.frame
assert com.vel(frame) == point.vel(frame)
assert body.mass == Symbol("body_mass")
ixx, iyy, izz = symbols("body_ixx body_iyy body_izz")
ixy, iyz, izx = symbols("body_ixy body_iyz body_izx")
assert body.inertia == (
inertia(body.frame, ixx, iyy, izz, ixy, iyz, izx),
body.masscenter,
)
def test_particle_body():
# Body with Particle
particle_masscenter = Point('particle_masscenter')
particle_mass = Symbol('particle_mass')
particle_frame = ReferenceFrame('particle_frame')
particle_body = Body('particle_body', particle_masscenter, particle_mass,
particle_frame)
com = particle_body.masscenter
frame = particle_body.frame
particle_masscenter.set_vel(particle_frame, 0)
assert com.vel(frame) == particle_masscenter.vel(frame)
assert com.pos_from(com) == particle_masscenter.pos_from(com)
assert particle_body.mass == particle_mass
assert not hasattr(particle_body, "_inertia")
assert hasattr(particle_body, 'frame')
assert hasattr(particle_body, 'masscenter')
assert hasattr(particle_body, 'mass')
def test_custom_rigid_body():
# Body with RigidBody.
rigidbody_masscenter = Point('rigidbody_masscenter')
rigidbody_mass = Symbol('rigidbody_mass')
rigidbody_frame = ReferenceFrame('rigidbody_frame')
body_inertia = inertia(rigidbody_frame, 1, 0, 0)
rigid_body = Body('rigidbody_body', rigidbody_masscenter, rigidbody_mass,
rigidbody_frame, body_inertia)
com = rigid_body.masscenter
frame = rigid_body.frame
rigidbody_masscenter.set_vel(rigidbody_frame, 0)
assert com.vel(frame) == rigidbody_masscenter.vel(frame)
assert com.pos_from(com) == rigidbody_masscenter.pos_from(com)
assert rigid_body.mass == rigidbody_mass
assert rigid_body.inertia == (body_inertia, rigidbody_masscenter)
assert hasattr(rigid_body, 'masscenter')
assert hasattr(rigid_body, 'mass')
assert hasattr(rigid_body, 'frame')
assert hasattr(rigid_body, 'inertia')
def __init__(self,
name,
masscenter=None,
mass=None,
frame=None,
central_inertia=None):
self.name = name
self.loads = []
if frame is None:
frame = ReferenceFrame(name + '_frame')
if masscenter is None:
masscenter = Point(name + '_masscenter')
if central_inertia is None and mass is None:
ixx = Symbol(name + '_ixx')
iyy = Symbol(name + '_iyy')
izz = Symbol(name + '_izz')
izx = Symbol(name + '_izx')
ixy = Symbol(name + '_ixy')
iyz = Symbol(name + '_iyz')
_inertia = (inertia(frame, ixx, iyy, izz, ixy, iyz,
izx), masscenter)
else:
_inertia = (central_inertia, masscenter)
if mass is None:
_mass = Symbol(name + '_mass')
else:
_mass = mass
masscenter.set_vel(frame, 0)
# If user passes masscenter and mass then a particle is created
# otherwise a rigidbody. As a result a body may or may not have inertia.
if central_inertia is None and mass is not None:
self.frame = frame
self.masscenter = masscenter
Particle.__init__(self, name, masscenter, _mass)
else:
RigidBody.__init__(self, name, masscenter, frame, _mass, _inertia)
names : str
Names of the dynamic symbols you want to create; works the same way as
inputs to symbols
level : int
Level of differentiation of the returned function; d/dt once of t,
twice of t, etc.
Examples
========
>>> from sympy.physics.vector import dynamicsymbols
>>> from sympy import diff, Symbol
>>> q1 = dynamicsymbols('q1')
>>> q1
q1(t)
>>> diff(q1, Symbol('t'))
Derivative(q1(t), t)
"""
esses = symbols(names, cls=Function)
t = dynamicsymbols._t
if iterable(esses):
esses = [reduce(diff, [t] * level, e(t)) for e in esses]
return esses
else:
return reduce(diff, [t] * level, esses(t))
dynamicsymbols._t = Symbol('t')
dynamicsymbols._str = '\''
>>> q1 = dynamicsymbols('q1')
>>> q1
q1(t)
>>> q2 = dynamicsymbols('q2', real=True)
>>> q2.is_real
True
>>> q3 = dynamicsymbols('q3', positive=True)
>>> q3.is_positive
True
>>> q4, q5 = dynamicsymbols('q4,q5', commutative=False)
>>> bool(q4*q5 != q5*q4)
True
>>> q6 = dynamicsymbols('q6', integer=True)
>>> q6.is_integer
True
>>> diff(q1, Symbol('t'))
Derivative(q1(t), t)
"""
esses = symbols(names, cls=Function, **assumptions)
t = dynamicsymbols._t
if iterable(esses):
esses = [reduce(diff, [t] * level, e(t)) for e in esses]
return esses
else:
return reduce(diff, [t] * level, esses(t))
dynamicsymbols._t = Symbol('t') # type: ignore
dynamicsymbols._str = '\'' # type: ignore
>>> q1 = dynamicsymbols('q1')
>>> q1
q1(t)
>>> q2 = dynamicsymbols('q2', real=True)
>>> q2.is_real
True
>>> q3 = dynamicsymbols('q3', positive=True)
>>> q3.is_positive
True
>>> q4, q5 = dynamicsymbols('q4,q5', commutative=False)
>>> bool(q4*q5 != q5*q4)
True
>>> q6 = dynamicsymbols('q6', integer=True)
>>> q6.is_integer
True
>>> diff(q1, Symbol('t'))
Derivative(q1(t), t)
"""
esses = symbols(names, cls=Function, **assumptions)
t = dynamicsymbols._t
if iterable(esses):
esses = [reduce(diff, [t] * level, e(t)) for e in esses]
return esses
else:
return reduce(diff, [t] * level, esses(t))
dynamicsymbols._t = Symbol("t") # type: ignore
dynamicsymbols._str = "'" # type: ignore