def setUp(self):
joint = PrismaticJoint('joint', [0, 0, 1])
joint.stiffness = self.K
joint.damping = 2 * self.damping_coeff * (self.K * self.M)**0.5
body = RigidBody('body', self.M)
system = System()
system.add_leaf(joint)
joint.add_leaf(body)
system.setup()
system.update_kinematics()
self.joint, self.body, self.system = joint, body, system
def setUp(self):
joint = PrismaticJoint('joint', [0, 0, 1])
joint.stiffness = self.K
joint.damping = 2 * self.damping_coeff * (self.K * self.M) ** 0.5
body = RigidBody('body', self.M)
system = System()
system.add_leaf(joint)
joint.add_leaf(body)
system.setup()
system.update_kinematics()
self.joint, self.body, self.system = joint, body, system
def test_1dof_linear_system(self):
s = System()
j = PrismaticJoint('joint', [0, 0, 1])
j.stiffness = 5.0
j.damping = 2.3
b = RigidBody('body', 10)
s.add_leaf(j)
j.add_leaf(b)
s.setup()
linsys = LinearisedSystem.from_system(s)
assert_array_equal(linsys.M, [[10.0]])
assert_array_equal(linsys.C, [[2.3]])
assert_array_equal(linsys.K, [[5.0]])
def test_1dof_linear_system(self):
s = System()
j = PrismaticJoint('joint', [0, 0, 1])
j.stiffness = 5.0
j.damping = 2.3
b = RigidBody('body', 10)
s.add_leaf(j)
j.add_leaf(b)
s.setup()
linsys = LinearisedSystem.from_system(s)
assert_array_equal(linsys.M, [[10.0]])
assert_array_equal(linsys.C, [[2.3]])
assert_array_equal(linsys.K, [[5.0]])
def test_find_equilibrium(self):
g = 9.81
m = 23.1
k = 45.2
s = System(gravity=g)
slider = PrismaticJoint('slider', [0, 0, 1])
slider.stiffness = k
body = RigidBody('body', mass=m)
s.add_leaf(slider)
slider.add_leaf(body)
s.setup()
# Initially position should be zero and acceleration nonzero
s.solve_accelerations()
assert_aae(slider.xstrain, 0)
assert_aae(slider.astrain, -g)
# At equilibrium, position should be nozero and force on body zero
s.find_equilibrium()
s.update_matrices() # recalculate stiffness force
s.solve_accelerations()
assert_aae(slider.xstrain, -m * g / k)
assert_aae(slider.astrain, 0)
