Use the Modal Reduction () solver to perform either parameter stepping (also called frequency response) or time stepping (also called transient response) using a reduced model. The modal reduction uses precomputed eigenvalues and eigenvectors. This solver is automatically used when a Time Dependent, Modal or Frequency Domain, Modal study is added to the model.

Also see The Modal Solver Algorithm for more information.

Use the Defined by study step list to specify if the settings are synchronized with the corresponding study step, or select User defined to specify all settings locally.

Use the Study type list to select the basic study type. Select:

For a Frequency Domain, Modal study, use the Parameter values field to enter a vector of parameter values that define the parameter value span for the frequency-domain simulation. Click the Range button () to define a range of parameter values using the Range dialog box.

Exactly how the vector of parameter values is used by the solver is determined by the option Parameter list type.

An alternative to specifying parameter values directly in the Parameters values field is to specify them in a text file. You can use the Load parameter values field and the Browse button () to specify such a text file. You can also click the downward arrow beside the Browse button and choose Browse From () to open the fullscreen Select File window. Click the downward arrow for the Location menu () to choose Show in Auxiliary Data () to move to the row for this file in the Auxiliary Data window, Copy Location (), and (if you have copied a file location) Paste Location (). Click the Read File button () to read the specified file. The read values appear in the Parameters values field.

Use the Parameter list type list to control how to interpret the parameter values entered in the Parameter values field. Select:

Use the Linearity list to specify the type of linear behavior. Select:

For a Time Dependent, Modal study, select a Time unit from the list. Then use the Output times field to enter a vector of times that define the time span for the simulation. Click the Range button () to define time values. Output from a simulation includes the times given in this field and the corresponding solutions.

Use the Relative tolerance field to enter a positive number (default value: 0.01). Depending on the selection in the Study type list in the General section, the tolerance means one of the following:

For the maximum time step, select an option from the Maximum step constraint list. By default, the solver chooses a maximum time step automatically. Select Constant as the maximum step constraint for manual specification of a fixed maximum time step in the Maximum step field. A constant maximum step constraint is a positive scalar value, which can be an expression that evaluates to a numerical value before entering the solver. The expression can include global parameters. Select Expression as the maximum step constraint for more general expressions of the allowed maximum time step. These expressions are evaluated while solving and can, for instance, depend on the time parameter itself.

From the Extend basis with initial data list choose Automatic, On, or Off. If it is On, it means that initial data will be considered in the base extension. You can use On for rare cases where the automatic method does not add the initial values to the basis but it makes sense to do so. If it is Off, then initial data will no be considered. The default is Automatic, which means that the initial data will be considered in the base extension only if it is large enough to make a difference.

Use the Solution list to specify a solver configuration to be used when constructing the reduced model.

Use the Eigenpairs list to specify which of the eigenpairs present in the solution to include when constructing the reduced model. The default setting is All and the solver uses all available eigenpairs. Select Manual to enter a space-separated list of Eigenpair numbers in the field.

Use the Damping ratios field to enter either a scalar value or a space-separated list with values. The total number of entered values must be one or equal to the number of eigenpairs in the reduced model. If one number is entered, that value becomes the damping ratio for all eigenpairs. If the field is empty (the default), no damping is applied by the solver.

Use the Solution list to specify which solution to be used when constructing the reduced model.

Use the Constraint modes list to specify which of the constraint modes present in the solution to include when constructing the reduced model. The default setting is All, and the solver then uses all available constraint modes. Select Manual to enter a space-separated list of constraint modes numbers in the Constraint modes numbers field.

A frequency-domain problem solved by the Modal Solver is assumed to be a linearization about a solution. You can specify such a solution (a linearization point) with the Prescribed by list. Select:

Select the Store linearization point and deviation in output check box to store the used linearization point in the output.

If Reduced matrices is selected, click to select the check boxes corresponding to matrices and vectors that should be stored in the output. The following matrices and vectors can be exported for all modal solvers: Stiffness matrix, Damping matrix, Damping ratio matrix, Mass matrix, Constraint modes to inputs map, Projection matrix, Load vector, Input matrix, Output matrix, Output bias, and Input feedback matrix. For Time Dependent, Modal studies the following can also be exported: Time derivative input matrix, Second time derivative input matrix, Initial value vector, Initial derivative vector, Initial value input matrix, Initial value time derivative input matrix, Stiffness matrix times ud, and state-space matrices (Mc, MA, MB, Null, D, C, ud, and x0). For Frequency Domain, Modal studies the following can also be exported: Mass matrix times particular solution, Damping matrix times particular solution, and All load vectors.

In this section you can define constants that can be used as temporary constants in the solver. You can use the constants in the model or to define values for internal solver parameters. These constants overrule any previous definition (for example, from Global Definitions). The constant values are expressions and can, for example, include the range() operator, units, and global expressions. The constant name can be a new or an existing global parameter. The constant is temporary in the sense that it is only defined during the solver run. You cannot override parameters used in the following parts of the model:

Click the Add button () to add a constant and then define its name in the Constant name column and its value (a numerical value or parameter expression) in the Constant value column. By default, any defined parameters are first added as the constant names, but you can change the names to define other constants. Click Delete () to remove the selected constant from the list.

Select the Keep warnings in stored log check box if you want the warnings to remain in the log for troubleshooting or other use.