Actuators
We provide several actuator options with the Template Builder. An actuator lets you define an element that can apply a force or motion function to a collection of modeling components. For example, you might want to create a motion on a valvetrain system, or steer a vehicle around a corner. These components include joints and parts but are not limited only to these.
Learn more about actuators:
About Actuators
When used with appropriate
feedback channels, actuators provide a very powerful method to control your system.
Actuators differ from adjustable forces due to their behavior during dynamic analyses, with actuators remaining active, whereas adjustable forces are either locked in place or replaced by a fixed joint.
If you create actuators as a symmetrical pair, then you can define separate left and right functions. You can use the
Function Builder to define functions.
Each actuator can have an application area and an identifier. The application area provides information about the intended purpose of the actuator. The identifier should be used to describe the actuator instance for this application area. A typical example would be:
Application area = steering
Identifier = steering_wheel_angle (e.g. for a motion type actuator)
These two additional parameters support a more dynamic use of actuators. For example, to allow de-/activation and function assignment on the assembly level by adding additional means for browsing and filtering. Note that they are currently not required by your template-based product.
You can define limits for each actuator in the same way that you would define limits in a test laboratory to prevent damage caused by excessive actuator force or travel. Although you can define limits for force, displacement, velocity, and acceleration, it is not required that you do so.
Learn more about using the actuator limits.
You can define the activity of the actuator as either active or not active. You can define the activity either from the dialog box or from the menu option Set Activity located under the Actuators menu.
Learn about defining the activity.
Joint-Force Actuators
A joint-force actuator defines either a translational or rotational
Single-Component Force acting between two parts that a user-defined joint connects. You can select three types of joints:
■Revolute joint: Selecting a revolute joint causes the Template Builder to automatically switch to rotational and disable the Type of Freedom option. The single-component force will be a rotational force acting between the two bodies that the revolute joint connects.
■Translational joint: Selecting a translational joint causes the Template Builder to automatically switch to translational and disable the Type of Freedom option. The single-component force will be a translational force acting between the two bodies that the translation joint connects.
■Cylindrical joint: Selecting a cylindrical joint makes an additional text box active. Because either the rotational or translational degree of freedom of the cylindrical joint can be used, you must specify if the rotational or translational force will be used. This allows you to decide between the creation of a torque or a force, based on the selection of either the rotational or translational type of freedom.
Learn more about actuators, such as creating symmetrical pairs, using application area and identifier attributes, and defining limits.
To create/modify a joint-force actuator:
1. From the Build menu, point to Actuators, point to Joint Force, and then select New/Modify.
3. Select OK.
Point-Force Actuators
A point-force actuator defines a translational single-component force acting between the two parts that I Part and J Part parameters specify. Three different types of force orientation are supported:
■Line of Sight: The action-reaction force will act along the line of sight between the I and J markers. You define the direction of the force by selecting the two points of force application, which can be either hardpoint or construction frame locations.
■Moving with Body: The action-only force will act on the I part, and the orientation of the force will depend on the motion of the J part. You may use the same body for both the I and J part. You define the initial location and orientation of the force by selecting any of the standard
Location Dependency and
Orientation Dependency options.
■Space Fixed: The action-only force will act on the I part and the orientation will remain fixed. You define the initial location and orientation of the force by selecting any of the standard
Location Dependency and
Orientation Dependency options.
Learn more about actuators, such as creating symmetrical pairs, using application area and identifier attributes, and defining limits.
To create/modify a point-force actuator:
1. From the Build menu, point to Actuators, point to Point Force, and then select New/Modify.
3. Select OK.
Joint-Motion Actuators
A joint-motion actuator defines either a translational or rotational motion acting between two parts that a user-defined joint connects. You can select three types of joints:
■Revolute joint: Selecting a revolute joint causes the Template Builder to automatically switch to rotational and disable the Type of Freedom option. The motion will be a rotational motion acting between the two bodies that the revolute joint connects.
■Translational joint: Selecting a translational joint causes the Template Builder to automatically switch to translational and disable the Type of Freedom option. The motion will be a translational motion acting between the two bodies that the translational joint connects.
■Cylindrical joint: Selecting a cylindrical joint makes an additional text box active. Because either the rotational or translational degree of freedom of the cylindrical joint can be used, you must specify if the rotational or translational motion will be used. This allows you to decide between the creation of a rotational or a translational motion based on selection of either the rotational or translational type of freedom.
Learn more about actuators, such as creating symmetrical pairs, using application area and identifier attributes, and defining limits.
To create/modify a joint-motion actuator:
1. From the Build menu, point to Actuators, point to Joint Motion, and then select New/Modify.
3. Select OK.
Point-Motion Actuators
A point-motion actuator defines a translational or rotational single-component motion acting between the two parts that I Part and J Part parameters specify. The motion will act along (or about) the Z axis of the J marker. The motion function can be defined as displacement, velocity, or acceleration. Initial conditions may be specified if desired.
Learn more about actuators, such as creating symmetrical pairs, using application area and identifier attributes, and defining limits.
To create/modify a point-motion actuator:
1. From the Build menu, point to Actuators, point to Point Motion, and then select New/Modify.
3. Select OK.
Point-Torque Actuators
A point-torque actuator defines an action-reaction or action-only rotational single-component torque acting between the two parts that the I Part and J Part parameters specify. You define the direction of the resulting torque within the dialog box. Many of the parametric functions discussed in
Construction Frames are available to define the position and orientation of the resulting actuator.
If you define the actuator as action only, then the J Part text box is disabled and no reaction is exerted.
Learn more about actuators, such as creating symmetrical pairs, using application area and identifier attributes, and defining limits.
To create/modify a point-torque actuator:
1. From the Build menu, point to Actuators, point to Point Torque, and then select New/Modify.
3. Select OK.
Variable Actuators
A variable actuator is a user-defined element consisting of a data element variable and a series of additional elements, such as strings and arrays. A variable actuator can be particularly useful where either parts or joints cannot be referenced. An example of a variable actuator is the velocity of a vehicle: the function could define a changing velocity which is then referenced by several other modeling components.
Learn more about actuators, such as creating symmetrical pairs, using application area and identifier attributes, and defining limits.
To create/modify a variable actuator:
1. From the Build menu, point to Actuators, point to Variable, and then select New/Modify.
3. Select OK.
Set Function
You can use the set function menu item to modify or replace the function that you defined.
You can use the
Function Builder to define functions.
To set actuator function:
1. From the Build menu, point to Actuators, and then select Set Function.
3. Select OK.
Set Activity
You can use the set activity menu option to set the actuator to be either active or not active. The not active option is particularly useful when actuator elements are not required.
To set actuator activity:
1. From the Build menu, point to Actuators, and then select Set Activity.
3. Select OK.
Example of using actuator limits
Actuators are generic objects, used for many different purposes. The limits were added to satisfy suspension and full vehicle analysis. In general, use the limits where actuator functions are not directly applied by the user.
Note that General Actuation Analysis (GAA) does not support the actuator limits. Here the explicitly defined user function expressions take precedence over the limits.
For suspension analysis, the actuators limits are used for force actuators such as jack_force and motion actuators such as jack_motion defined in the suspension testrig. These limits won’t be used on their own, they are processed by the difsub dif903 (
DIFF 903).
For example, in the suspension testrig vertical controller is defined that does limits the travel and forces of the jack. The vertical controller is defined using differential equation using difsub dif903. In addition to vertical controller, steering_controller is defined in the suspension testrig that does makes use of dif903 without use of actuator limits.
Here is an example of creating differential equation and use of actuator limits:
part create equation differential_equation &
differential_equation_name = .__MDI_SUSPENSION_TESTRIG.left_vertical_controller &
user_function = &
903.0, &
1.0, &
0.0, &
(.__MDI_SUSPENSION_TESTRIG.jfl_jack_force.force.adams_id), &
(.__MDI_SUSPENSION_TESTRIG.left_vertical_input.adams_id), &
(.__MDI_SUSPENSION_TESTRIG.ffl_wheel_center_height.offset_channel.adams_id), &
(.__MDI_SUSPENSION_TESTRIG.jfl_jack_force.force_limits[1]), &
(.__MDI_SUSPENSION_TESTRIG.jfl_jack_force.force_limits[2]), &
(.__MDI_SUSPENSION_TESTRIG.jfl_jack_force.displacement_limits[1]), &
(.__MDI_SUSPENSION_TESTRIG.jfl_jack_force.displacement_limits[2]), &
1.0, &
1.0, &
1.0 &
routine = "acarSDM::dif903"
For full vehicle analysis, steering limits are specified by the parameter variables like pvs_max_steering_angle in the steering templates. These values are communicated to the testrig using a communicator. The limits for max_rack_displacement, max_rack_force and max_steering_torque can be set via environment variables MSC_SD_STDSP_MAX, MSC_SD_STFRC_MAX and MSC_SD_STTRQ_MAX respectively.