def test_multi_mass_spring_damper_inputs():
c0, k0, m0 = symbols("c0 k0 m0")
g = symbols("g")
v0, x0, f0 = dynamicsymbols("v0 x0 f0")
kane1 = models.multi_mass_spring_damper(1)
massmatrix1 = Matrix([[m0]])
forcing1 = Matrix([[-c0*v0 - k0*x0]])
assert simplify(massmatrix1 - kane1.mass_matrix) == Matrix([0])
assert simplify(forcing1 - kane1.forcing) == Matrix([0])
kane2 = models.multi_mass_spring_damper(1, True)
massmatrix2 = Matrix([[m0]])
forcing2 = Matrix([[-c0*v0 + g*m0 - k0*x0]])
assert simplify(massmatrix2 - kane2.mass_matrix) == Matrix([0])
assert simplify(forcing2 - kane2.forcing) == Matrix([0])
kane3 = models.multi_mass_spring_damper(1, True, True)
massmatrix3 = Matrix([[m0]])
forcing3 = Matrix([[-c0*v0 + g*m0 - k0*x0 + f0]])
assert simplify(massmatrix3 - kane3.mass_matrix) == Matrix([0])
assert simplify(forcing3 - kane3.forcing) == Matrix([0])
kane4 = models.multi_mass_spring_damper(1, False, True)
massmatrix4 = Matrix([[m0]])
forcing4 = Matrix([[-c0*v0 - k0*x0 + f0]])
assert simplify(massmatrix4 - kane4.mass_matrix) == Matrix([0])
assert simplify(forcing4 - kane4.forcing) == Matrix([0])
def test_multi_mass_spring_damper_higher_order():
c0, k0, m0 = symbols("c0 k0 m0")
c1, k1, m1 = symbols("c1 k1 m1")
c2, k2, m2 = symbols("c2 k2 m2")
v0, x0 = dynamicsymbols("v0 x0")
v1, x1 = dynamicsymbols("v1 x1")
v2, x2 = dynamicsymbols("v2 x2")
kane1 = models.multi_mass_spring_damper(3)
massmatrix1 = Matrix([[m0 + m1 + m2, m1 + m2, m2], [m1 + m2, m1 + m2, m2],
[m2, m2, m2]])
forcing1 = Matrix([[-c0 * v0 - k0 * x0], [-c1 * v1 - k1 * x1],
[-c2 * v2 - k2 * x2]])
assert simplify(massmatrix1 - kane1.mass_matrix) == zeros(3)
assert simplify(forcing1 - kane1.forcing) == Matrix([0, 0, 0])
def test_multi_mass_spring_damper_higher_order():
c0, k0, m0 = symbols("c0 k0 m0")
c1, k1, m1 = symbols("c1 k1 m1")
c2, k2, m2 = symbols("c2 k2 m2")
v0, x0 = dynamicsymbols("v0 x0")
v1, x1 = dynamicsymbols("v1 x1")
v2, x2 = dynamicsymbols("v2 x2")
kane1 = models.multi_mass_spring_damper(3)
massmatrix1 = Matrix([[m0 + m1 + m2, m1 + m2, m2],
[m1 + m2, m1 + m2, m2],
[m2, m2, m2]])
forcing1 = Matrix([[-c0*v0 - k0*x0],
[-c1*v1 - k1*x1],
[-c2*v2 - k2*x2]])
assert simplify(massmatrix1 - kane1.mass_matrix) == zeros(3)
assert simplify(forcing1 - kane1.forcing) == Matrix([0, 0, 0])
