21-08-2012, 03:31 PM
[u]Adams/Vibration Theory Manual[/u]
[attachment=32310]
Introduction to Adams/Vibration
Using Adams/Vibration, you can compute system response in the frequency domain. You can perform
two types of analyses:
1. Normal-modes analysis
2. Forced response analysis
A normal modes analysis computes eigen-values and eigenvectors of your model at an operating point
you specify. This analysis is effective in understanding natural modes of vibration for the model and to
determine the basic dynamic characteristics of your model. Although the result of an eigenvalue analysis
is independent of specific excitation, they are useful in predicting the effects of applying dynamic loads
on your model.
Normal modes analysis is relevant in many scenarios. In one scenario you may need to assess dynamic
interaction between parts in an MD Adams model. For example, if you are designing a washing machine,
it is necessary to determine if the operating rotational frequency of the tub is close to one or more natural
frequencies of the supporting structure and electronic components. If they are then ordinary operation of
the washing machine may lead to damage of the supporting structure and/or premature failure of
electrical and electronic components in the machine.
If you are setting up a physical test, a normal-modes analysis is useful in determining the best location
on your systems to attach strain gauges and/or accelerometers. After the test, test results can be correlated
with the results of the normal-modes analysis.
Frequency-response analysis is an efficient method for finding the steady-state model response to
sinusoidal excitation. In this analysis the loading is in the form of a sine wave for which you specify the
frequency, amplitude, and phase. Adams/Vibration performs frequency response analysis using
linearized MD Adams models. Several different types of inputs can be applied to the model and force
and kinematic output measured.
Forced-Response Analysis
Inputs and outputs to the linear model are defined by means of input and output channels in
Adams/Vibration. Input channels contribute to the B matrix. Output channels contribute to the C matrix.
The D matrix represents direct interaction between input and output channels. For more details, see
Modeling of Vibration Entities.
Vibration Input Channels
A vibration input channel defines the location, orientation, and type of forcing function to be applied.
There are three types of input channels you can specify in Adams/Vibration:
1. Force-type input channel applies a force at the specified marker. The expression for the force is
as specified by the vibration actuator.
2. User-specified state variable applies the vibration actuator to a state variable that you may have
created in your model. This input channel is useful in applying vibratory input to models that are
represented by general dynamical elements, such as GSE/LSE/TFSISO.
3. Kinematic input channel applies displacement, velocity, or acceleration input. This form of the
input channel imposes a kinematic constraint in the frequency domain at the specified marker.
This constraint will result in removal of one degree of freedom at the maker at which it is applied.
Vibration Actuators
A vibration actuator defines the magnitude and phase of the applied forcing function. Vibration actuators
are required for modeling forcing function in forced response analysis. Phase angle, as defined in a
vibration actuator, is with respect to the positive direction of the marker in the vibration input channel on
which this actuator is defined.
Vibration actuators are applied at the input channel after the model is linearized. Therefore, vibration
actuators are only in effect for frequency domain analysis and have no effect on the operation point
analysis for the model.
[attachment=32310]
Introduction to Adams/Vibration
Using Adams/Vibration, you can compute system response in the frequency domain. You can perform
two types of analyses:
1. Normal-modes analysis
2. Forced response analysis
A normal modes analysis computes eigen-values and eigenvectors of your model at an operating point
you specify. This analysis is effective in understanding natural modes of vibration for the model and to
determine the basic dynamic characteristics of your model. Although the result of an eigenvalue analysis
is independent of specific excitation, they are useful in predicting the effects of applying dynamic loads
on your model.
Normal modes analysis is relevant in many scenarios. In one scenario you may need to assess dynamic
interaction between parts in an MD Adams model. For example, if you are designing a washing machine,
it is necessary to determine if the operating rotational frequency of the tub is close to one or more natural
frequencies of the supporting structure and electronic components. If they are then ordinary operation of
the washing machine may lead to damage of the supporting structure and/or premature failure of
electrical and electronic components in the machine.
If you are setting up a physical test, a normal-modes analysis is useful in determining the best location
on your systems to attach strain gauges and/or accelerometers. After the test, test results can be correlated
with the results of the normal-modes analysis.
Frequency-response analysis is an efficient method for finding the steady-state model response to
sinusoidal excitation. In this analysis the loading is in the form of a sine wave for which you specify the
frequency, amplitude, and phase. Adams/Vibration performs frequency response analysis using
linearized MD Adams models. Several different types of inputs can be applied to the model and force
and kinematic output measured.
Forced-Response Analysis
Inputs and outputs to the linear model are defined by means of input and output channels in
Adams/Vibration. Input channels contribute to the B matrix. Output channels contribute to the C matrix.
The D matrix represents direct interaction between input and output channels. For more details, see
Modeling of Vibration Entities.
Vibration Input Channels
A vibration input channel defines the location, orientation, and type of forcing function to be applied.
There are three types of input channels you can specify in Adams/Vibration:
1. Force-type input channel applies a force at the specified marker. The expression for the force is
as specified by the vibration actuator.
2. User-specified state variable applies the vibration actuator to a state variable that you may have
created in your model. This input channel is useful in applying vibratory input to models that are
represented by general dynamical elements, such as GSE/LSE/TFSISO.
3. Kinematic input channel applies displacement, velocity, or acceleration input. This form of the
input channel imposes a kinematic constraint in the frequency domain at the specified marker.
This constraint will result in removal of one degree of freedom at the maker at which it is applied.
Vibration Actuators
A vibration actuator defines the magnitude and phase of the applied forcing function. Vibration actuators
are required for modeling forcing function in forced response analysis. Phase angle, as defined in a
vibration actuator, is with respect to the positive direction of the marker in the vibration input channel on
which this actuator is defined.
Vibration actuators are applied at the input channel after the model is linearized. Therefore, vibration
actuators are only in effect for frequency domain analysis and have no effect on the operation point
analysis for the model.