sdynpy.fem.sdynpy_shaker.Shaker4DoF

• Module: sdynpy.fem.sdynpy_shaker

• Source: GitHub

Signature¶

class sdynpy.fem.sdynpy_shaker.Shaker4DoF(m_armature, m_body, m_forcegauge, k_suspension, k_stinger, c_suspension, c_stinger, resistance, inductance, force_factor)

A class defining a four degree-of-freedom model of a shaker

Methods¶

__init__¶

• Source: GitHub

def sdynpy.fem.sdynpy_shaker.Shaker4DoF.__init__(self, m_armature, m_body, m_forcegauge, k_suspension, k_stinger, c_suspension, c_stinger, resistance, inductance, force_factor)

Creates a four degree of freedom electromechanical model of a shaker

Parameters¶

• m_armature : float Mass of the armature

• m_body : float Mass of the body and trunion of the shaker

• m_forcegauge : float Mass of the force gauge at the tip of the stinger

• k_suspension : float Stiffness of the spring between the body and armature

• k_stinger : float Stiffness of the stinger between the armature and force gauge

• c_suspension : float Damping of the spring between the body and armature

• c_stinger : float Damping of the stinger between the armature and force gauge

• resistance : float Coil resistance of the electronics portion of the shaker

• inductance : float Coil inductance of the electronics portion of the shaker

• force_factor : float Force factor BL of the magnet and coil

MCK¶

• Source: GitHub

def sdynpy.fem.sdynpy_shaker.Shaker4DoF.MCK(self)

Returns mass, damping, and stiffness matrices for the shakers.

Returns¶

• M : np.ndarray The mass matrix of the shaker

• C : np.ndarray The damping matrix of the shaker

• K : np.ndarray The stiffness matrix of the shaker

Notes¶

The dof order of the responses are: Displacement of Armature, Displacement of Body, Displacement of Force Gauge, Shaker Current.

The dof order of the inputs are: Force into Armature Force into Body Force into Force Gauge Shaker Voltage.

The force imparted by the shaker can be computed as the stinger stiffness times the difference in displacement of the armature and force gauge plus the stinger damping times the difference in the velocity of the armature and force gauge.

modal_shop_100lbf¶

• Source: GitHub

def sdynpy.fem.sdynpy_shaker.Shaker4DoF.modal_shop_100lbf(cls)

Returns a shaker model for a Modal Shop Model 2100E11 100lbf modal shaker.

Returns¶

• shaker_model : Shaker4DoF A 4 degree of freedom model of the Modal Shop 2100E11 100lbf modal shaker.

Notes¶

The shaker uses the following parameters

• m_armature = 0.44 kg

• m_body = 15 kg

• m_forcegauge = 1e-2 kg

• k_suspension = 1.1e5 N/m

• k_stinger = 9.63e6 N/m

• c_suspension = 9.6 Ns/m

• c_stinger = 0.42 Ns/m

• resistance = 4 Ohm

• inductance = 6e-4 Henry

• force_factor = 36 (-)

plot_electrical_impedance¶

• Source: GitHub

def sdynpy.fem.sdynpy_shaker.Shaker4DoF.plot_electrical_impedance(self, frequencies=array([   1,    2,    3, ..., 3998, 3999, 4000], shape=(4000,)), test_data=None)

Plots the electrical impedance voltage/current for the shaker model and compares to test data if supplied

Parameters¶

• frequencies : np.array, optional Frequency lines. The default is np.arange(4000).

• test_data : np.ndarray, optional Test data defined at frequencies. The default is None.

state_space¶

• Source: GitHub

def sdynpy.fem.sdynpy_shaker.Shaker4DoF.state_space(self)

Returns the state space formulation of the shaker model of the form

x_dot = A@x + B@u y = C@x + D@u

Returns¶

• A : np.ndarray State (system) Matrix.

• B : np.ndarray Input Matrix

• C : np.ndarray Output Matrix

• D : np.ndarray Feedthrough (feedforward) Matrix

Notes¶

The dof order of the state matrix is 0. armature displacement

1. body displacement

2. forcegauge displacement,

3. armature velocity

4. body velocity

5. forcegauge velocity

6. current.

The dof order of the input matrix is 0. external force on armature

1. external force on body

2. external force on forcegauge

3. shaker voltage

The dof order for the output matries is 0. Displacement of armature

1. Velocity of armature

2. Acceleration of armature

3. External force on armature

4. Displacement of body

5. Velocity of body

6. Acceleration of body

7. External force on body

8. Displacement of forcegauge

9. Velocity of forcegauge

10. Acceleration of forcegauge

11. External force on forcegauge

12. Shaker voltage

13. Shaker current

14. Current change per time

15. Force on coil due to electronics

16. Force in stinger

transfer_function¶

• Source: GitHub

def sdynpy.fem.sdynpy_shaker.Shaker4DoF.transfer_function(self, frequencies)

Computes the shaker transfer function matrix

Returns¶

• H : np.ndarray A transfer function matrix.