Example modules

Examples, which can be run locally. For instructions on how to use openTorsion, please refer to Tutorials.

opentorsion.examples.forced_response

opentorsion.examples.forced_response.forced_response(): First a model of a windmill is created as a system of three lumped masses connected by two shafts. The assembly is given harmonic excitation as input. Finally, the system response is calculated and plotted.

opentorsion.examples.forced_response.generator_torque(rpm): Generator torque as a function of rotor rotating speed.

opentorsion.examples.forced_response.get_windmill_excitation(rpm): Cogging torque and torque ripple as harmonic excitation. (Table III from https://doi.org/10.1109/TIE.2010.2087301)

opentorsion.examples.roll

opentorsion.examples.roll.back_to_back_testbench(): Example of a powertrain with shaft, lumped mass and gear elements.

opentorsion.examples.windmill

opentorsion.examples.windmill.windmill_assembly(): A shaft-line Finite Element Model of a windmill based on model presented in https://doi.org/10.1109/TIE.2010.2087301. A mechanical shaft-line FEM consists of shaft elements, disk elements/lumped masses (optional) and gear elements (optional). Elements are initiated by calling Shaft(), Disk() or Gear(). The elements take as inputs the element node number and element parameter values (refer to shaft_element.py, disk_element.py and gear_element.py documentation).

opentorsion.examples.ICE_example

Calculates the steady-state torsional vibration in the crankshaft of an internal combustion engine. Torque produced by each cylinder is calculated from the force produced by the pressure from ignition which is scaled according to the rotation speed of the crankshaft. Torsional vibration analysis based on https://doi.org/10.1243/14644193JMBD126 The model is based on Fig.4 of the original article.

opentorsion.examples.ICE_example.ICE_example.calculate_cylinder_torque(speed_rpm, num_points=500)

Calculates the torque produced by a single cylinder at given rpm. Torque is based on the tangential force caused by the pressure in the cylinder and the tangential component of the oscillating inertial force from the crankshaft spinning.

Parameters:

speed_rpm: float: Current rotation speed in rpm
num_points: float, optional: Number of points for the x-axis

Returns:

M_t: ndarray: The torque produced by the cylinder
alpha: ndarray: Angles for which the cylinder torques are given

opentorsion.examples.ICE_example.ICE_example.calculate_dft_components(signal, t, num_harmonics)

Calculates dft components and harmonics (0,0.5,1,…) for the given signal, to be used at stedy-state vibration calculations.

Parameters:

signal: ndarray: Cylinder torque
t: ndarray: Crankshaft rotation angle
num_harmonics: float: Number of harmonics considered

Returns:

complex ndarray: The first num_harmonics complex components of the Fourier transform
complex ndarray: The first num_harmonics components of the harmonics

opentorsion.examples.ICE_example.ICE_example.calculate_response(crankshaft, rpm)

Calculates the crankshaft’s response to excitation at given rpm.

Parameters:

crankshaft: openTorsion Assembly class instance: Opentorsion Assembly of the crankshaft
rpm: float: Current rotation speed in rpm

Returns:

sum_response: ndarray: Array containing maximum vibratory torque at current rotation speed for each shaft

opentorsion.examples.ICE_example.ICE_example.crankshaft_assembly()

A shaft-line Finite Element Model of a crankshaft based on model presented in https://doi.org/10.1243/14644193JMBD126 Fig.4.

Returns:

assembly: openTorsion Assembly class instance: The created opentorsion assembly

opentorsion.examples.ICE_example.ICE_example.peak_pressures(): Load digitized peak pressure from csv and pass it to interpolator

opentorsion.examples.ICE_example.ICE_example.plot_results(rpms, vibratory_torque)

Plots the vibratory torque in wanted shafts for each considered engine speed.

Parameters:

rpms: ndarray: All considered engine speeds in rpm
vibratory_torque: ndarray: Matrix containing maximum vibratory torque at each rotation speed for each shaft. Each row correspond to an engine speed and each column to a shaft.

Returns:

shaft_8: ndarray: Array containing maximum vibratory torque at all considered engine speeds for shaft between flywheel and 6th cylinder
shaft_1: ndarray: Array containing maximum vibratory torque at all considered engine speeds for shaft between crankshaft pulley and gear train

opentorsion.examples.ICE_example.ICE_example.pressure_curve(): Load digitized pressure curve from csv and pass it to interpolator

opentorsion.examples.ICE_example.ICE_example.relative_damping_C(assembly, d, w)

Updates the damping matrix C of assembly when using frequency dependent relative damping.

Parameters:

assembly: openTorsion Assembly class instance: The assembly of whose damping matrix is to be updated
d: float: Loss factor property, used to calculate relative damping
w: float: Angular frequency of the system, used to calculate relative damping

Returns:

C: ndarray: The damping matrix assembled with new component specific damping coefficients

opentorsion.examples.ICE_example.ICE_example.scaled_cylinder_pressure(rpm, num_points)

Scales the cylinder pressure curve based on the variation of peak pressure with engine speed.

Returns:

angles: np.ndarray: Angles for which the cylinder pressures are given
scaled_curve: np.ndarray: The scaled pressure curve scaled to the given rpm corresponding to the angles. (Pa)