part modify equation transfer_function
Allows you to modify a user-defined transfer function.
You can use transfer functions to define an arbitrary set of constant-coefficient, differential and algebraic equations that can be expressed in the Laplace domain as the following where m, k:
Transfer functions are especially useful for describing elements from control-system block diagrams. The characteristic equation for a single transfer function can be a polynomial of degree less than 30. Internal to Adams Solver, there is an algorithm to automatically convert the list of fixed numerator and denominator coefficients to the following elements:
■Canonical state-space form
■Set of coupled, linear, constant-coefficient differential equations
■Single algebraic equation
You define the arrays for a transfer function using array data elements. The arrays define the transfer function input and let you reference the states and output of the transfer function. Initial conditions for a transfer function are assumed to be identically zero.
Format:
part modify equation transfer_function | |
|---|---|
transfer_function_name= | existing tfsiso |
new_transfer_function_name = | new name for the transfer function |
adams_id= | integer |
comments= | string |
x_state_array_name= | existing array |
u_input_array_name= | existing array |
y_output_array_name= | existing array |
ic_array_name= | existing adams array |
static_hold= | on_off |
numerator_coefficients= | real |
denominator_coefficients= | real |
Description:
Parameter | Value Type | Description |
|---|---|---|
transfer_function_name | Existing TFSISO | Specifies the name of the equation to be modified |
New_transfer_function_name | New Transfer Function Name | Specify the new name for the transfer function |
adams_id | Integer | Assigns a unique ID number to the equation. |
comments | String | Adds any comments about the equation to help you manage and identify it. |
x_state_array_name | Existing Array | Specifies the array that defines the state variable array for the transfer function. |
u_input_array_name | Existing Array | Specifies the array that defines the input (or control) for the transfer function. The array must be an inputs (U) array. If you specified the size of the array when you created it, it must be one. |
y_output_array_name | Existing Array | Specifies the array that defines the output for the transfer function. |
static_hold | On/Off | Indicates that equation states are not permitted to change during static and quasi-static simulations (on). |
numerator_coefficients | Real | Specifies the coefficients of the polynomial in the numerator of the transfer function. |
denominator_coefficients | Real | Specifies the coefficients of the polynomial in the denominator of the transfer function. |
Ic_array_name | Existing Adams array | Specifies an existing Adams array. |
Extended Definition:
1. When using the Adams View command language and naming entities, you can use the name later to refer to this entity. Adams View does not allow you to have two entities with the same name, so you must provide a unique name. Normally, entity names are composed of alphabetic, numeric, or '_' (underscore) characters, and start with an alphabetic or '_' character. They may be of any length. For more information, see Using Extended Names.
By enclosing the name in double quotes, you can use other printable characters, or start the name with a numeral. If a name contains characters, or starts with a numeral, you must always quote the name when entering it.
Note that you can specify the parentage of an entity (for example, what part "owns" a marker or a geometry element) when you create it by changing the name. If you enter just the entity name, then Adams View assigns the default parent. If you type in the full name, then you can override the default parent. In most cases, when creating an entity, Adams View provides a default name. The default name that Adams View provides specifies the parentage that it has assumed. You can, of course, delete this name and use your own. The form of a full name is:
"...._NAME.GRAND_PARENT_NAME.PARENT_NAME.ENTITY_NAME"
The number of levels used varies from case to case and the parentage must exist before an entity can be assigned to it.
Comments:
1. For comments, you can enter any alphanumeric characters. The comments that you create appear in the Information window when you select to display information about the object, in the Adams View log file and in a command or dataset file when you export your model to these types of files. (Note that design variables are not output to datasets; therefore, neither are their comments.)
2. The array specified in the x_state_array_name must be a states (X) array, and it cannot be used in any other linear state equation, general state equation, or transfer function. If you specified the size of the array when you created it, it must be one less than the number of coefficients in the denominator.
3. The array specified in the y_state_array_name must be an outputs (Y) array, and it cannot be used in any other linear state equation, general state equation, or transfer function. If you specify the size of the array when you created it, its size must be one.
4. For the static_hold parameter, the user-specified initial conditions are retained as the static equilibrium values. Note that this does not guarantee that the time derivatives of the user-defined variable will be zero after static analysis.
During a static simulation, Adams Solver finds equilibrium values for user-defined differential variables (differential equations, general state equations, linear state equations, and transfer functions), as well as for the displacement and force variables. The equilibrium values it finds change the initial conditions for subsequent simulations. To help you control the static simulation results, Adams View provides an option that you can set to keep the values constant. This option is called static hold. Static hold retains the user-specified initial conditions as the static equilibrium values.
If you do not set static hold, Adams Solver sets the time derivatives of the user-defined variables to zero during a static simulation, and uses the user-supplied initial-condition values only as initial guesses for the static solution. Generally, the final equilibrium values are not the same as the initial condition values. Adams Solver then uses the equilibrium values of the user-defined variables as the initial values for any subsequent simulation, just as with the equilibrium displacement and force values.
If you do set static hold, Adams Solver retains the user-specified initial conditions as the static equilibrium values. Therefore, the final equilibrium values are the same as the user-specified initial conditions. Note that this does not guarantee that the time derivatives of the user-defined variable are zero after a static simulation.
5. For the numerator_coefficients and the denominator_coefficients, list the coefficients in order of ascending power of s, starting with s to the zero power, including any intermediate zero coefficients. The number of coefficients for the denominator must be greater than or equal to the number of coefficients for the numerator.