Inline Joint

This section describes the Inline Joint entity of MotionView and shows the various usage, creation, and editing methods.

Theory/Background

An Inline joint is a four degree-of-freedom primitive constraint. The constraint is imposed such that the origin of a reference marker on one body (Body 2) translates along the Z axis of a reference marker on the other body (Body 1) connected by the joint. Three rotations are free along with one translation along the Z marker defining the joint orientation. Joint primitives like Inline joints may not have a physical existence. They can be used to impose unique constraints where using a regular joint would not be possible.

inline_joint_diagram_mv

Inline joint construction

Joint Definition

The Inline joint is represented using Markers when exported to an MBD Solver. The representation can be visualized as shown in the two figures below:

inline_joint_marker_diagram_coincident_mv

Inline joint - coincident origins

inline_joint_marker_diagram_non-coincident_mv

Inline joint - non-coincident origins

The bodies that are constrained by an Inline Joint are represented using two markers: Marker I and Marker J. Marker I belongs to Body 1 and Marker J belongs to Body 2. The constraints are applied on Marker I with respect to Marker J. While defining the joint, the markers can either have coincident origins or they can be non-coincident. The vertex of Marker I will be constrained to remain along the Z axis of Marker J, however Marker I can rotate about any of its axes.

Entity Data Members

The topological information required to define an Inline Joint is shown in the figure below:

inline_joint_diagram2_mv

The data members of the Inline Joint can be classified into the following members:

Connectivity

An Inline Joint needs the following:

•	Body 1 and Body 2 - Specify two Bodies between which the joint is to be created.

•	Origin - Specify Point, which defines the location of the joint.

•	Alignment Method - An axis needs to be specified for the constraint to be imposed. This can be done by specifying a Vector or by a Point which acts as the origin of Marker J. The Z axis of the Marker J will point to the joint origin, thus representing the constraint axis.

•

Compliant Mode (Optional) - If the Allow Compliance option is selected while adding the joint to a model, the joint's compliance state can be toggled between Compliant and Non-Compliant. If the joint is made Compliant, it no longer remains a rigid connection and the joint will then be treated as a bushing.

The joint can be modeled as a Single entity or as a Pair entity.

Properties

There are no editable properties for an Inline Joint.

Creating and Editing Joints

To learn how to add a Inline Joint to a model, please see the Joints topic.

1.	Once an Inline Joint has been added to the model using any of the "entity" creation methods, the panel for the joint will automatically be displayed in the panel area (see the panel examples below):

inline_joint_panel_conn_tab_mv

Joints Panel (Inline Joint) – Connectivity Tab - Single Entity

inline_joint_panel_conn_tab_pair_mv

Joints Panel (Inline Joint) – Connectivity Tab - Pair Entity

2.	The joint definition needs two bodies which are connected by the joint. Select Body 1 by picking the body from the graphics area, or double click the Body 1 collector to open to the model tree (from which the desired body can be selected).

3.	Similarly, pick Body 2 from the graphics area by clicking on the desired body (or use the collector and model tree method).

4.	Select the Origin Point from the Project Browser, or the graphics area, to specify a location for the joint.

5.	The axis defining the constraint of the joint can be defined by specifying an Axis or another point (Origin 2), which will define the axis along with the Origin. Use the drop-down menu located on the lower right side of the panel to select the alignment axis:

If Axis is used, the axis defining the constraint needs to be specified using a Vector or Point to define the direction. If the alignment axis for the joint is along any of the Global Axes, then the Global X, Y,or Z axis can be selected by clicking on the desired axis in the graphics area (or by browsing through the model tree).

alignment_axis_vector_example_mv

-	If Origin 2 is used, a point which acts as the point of origin of Marker J of the joint can be specified. The Z axis of Marker J, which defines the axis of the constraint, will automatically point to the joint Origin.

6.	When defining a Pair Inline Joint, use pair entities for Body 1, Body 2, Origin, etc.

Note - The same steps as shown above can also be used to define Pair Inline Joint entities.

1.	Left click the Joints panel icon on the Constraint toolbar.

The Project Browser will filter the entities and display only the Joints in the model.

2.	Select the desired joint in the Project Browser.

The corresponding panel is automatically displayed.

3.	From the Connectivity tab, use the Joint type drop-down menu to change the joint type, or use the collectors to change the bodies and origins/alignment points of the joint.

inline_joint_drop_down_menu_mv_ug

Joints panel - Connectivity tab - joint type drop-down menu

Inline Joint in MDL and XML Formats

The model containing the Inline Joint can be saved in MDL format from MotionView and exported in the MotionSolve XML format.

The Inline Joint can be of the following types:

1.	Non-Compliant - Single and Pair

2.	Compliant – Single and Pair

And these four types of entities can be added to the model using MDL Statements shown below:

Syntax:

*InlineJoint(joint_name, "joint_label", body_1,

body_2,

origin,

AXIS,

POINT|VECTOR,

point_1|vector_1)

[ALLOW_COMPLIANCE])

To understand the complete syntax of the MDL statement please refer to the *InlineJoint() - inline joint (coincident origins) topic.

Syntax:

*InlineJoint(joint_name, "joint_label", body_1,

body_2,

origin_1,

ORIGIN,

POINT,

origin_2)

[ALLOW_COMPLIANCE]

To understand the complete syntax of the MDL statement please refer to the *InlineJoint() - inline joint (non-coincident origins) topic.

Syntax:

*InlineJointPair(joint_name, "joint_label", body_1,

body_2,

origin,

AXIS,

POINT|VECTOR,

point_1|vector_1)

[ALLOW_COMPLIANCE]

To understand the complete syntax of the MDL statement please refer to the *InlineJointPair() - inline joints (coincident origins) topic.

Syntax:

*InlineJointPair(joint_name, "joint_label", body_1,

body_2,

origin_1,

ORIGIN,

POINT,

origin_2)

[ALLOW_COMPLIANCE]

To understand the complete syntax of the MDL statement please refer to the *InlineJointPair() - inline joints (non-coincident origins) topic.

To learn how to create a complete model using MDL Statements please refer to tutorial MV-1060: Introduction to MDL.

The Inline joint when exported to the MotionSolve XML format is defined as a Constraint_Joint statement.

Syntax:

<Constraint_Joint

id = "integer"

label = "Name of Joint"

type = "JOINT TYPE"

i_marker_id = "integer"

j_marker_id = "integer"

In case of the Inline joint the model statement will be as shown below:

<Constraint_Joint

id = "301001"

label = "Inline Joint"

type = "INLINE"

i_marker_id = "30103050"

j_marker_id = "30101050"

In the above XML Model statement the i_marker_id and j_marker_id represent the I and J markers of the Joint which belong to Body 1 and Body 2 respectively. To understand the complete syntax of the Constraint_Joint XML model statement, please refer to the MotionSolve Reference Guide Page for Constraint_Joint.

Creating an Inline Joint using the Tcl Command Layer

In MotionView, the Tcl command layer can be used to add any MDL entities to the model. There are two Tcl commands that can be used to add an entity:

Syntax:

mdlmodel_handle InterpretEntity new_handle keyword varname label

In case of the Inline joint with coincident origins, the statement will look as shown below:

mdlmodel_handle InterpretEntity InlineJt_handle InlineJoint j_Inline "\"Inline Joint\"" b_1 B_Ground p_ori "AXIS" "VECTOR" "V_Global_Z" "ALLOW_COMPLIANCE";

In case of the Inline joint with non-coincident origins, the statement will look as shown below:

mdlmodel_handle InterpretEntity InlineJt_handle InlineJoint j_Inline "\"Inline Joint\"" b_1 B_Ground p_ori_1 "ORIGIN" "POINT" p_ori_2 "ALLOW_COMPLIANCE";

*This command is not applicable for Inline joint entities.

The InterpretEntity command is used to add entities to the model and the InterpretSet command is used to set the entity properties (which is not applicable for this type of joint). Extended definitions for InterpretEntity and InterpretSet can be found in the HyperWorks Desktop Reference Guide.

Note - When using the InterpretEntity and InterpretSet commands, it is important to also use the Evaluate command in order for the changes to take effect immediately.

To learn how to create a complete model using Tcl commands, please refer to tutorial MV-1040: Model Building Using Tcl.

Example Model

The example file below shows a Inline joint connecting two bodies:

*BeginMDL( the_model, "Model",)

*StandardInclude(FILE)

*Point( p_0, "Single Joint Origin" )

*PointPair( p_1, "Pair Joint Origin" )

*SetPoint( p_2, 0.0, 50.0, 0.0 )

*SetPoint( p_1, LEFT, , -100 )

*Body( b_0, "Single Body 1", p_0, , , , )

*BodyPair( b_1, "Pair Body 1", p_1, , , , )

//Inline joint definition

*InlineJoint( j_Inlinejsingle, "Inline Joint Single", b_0, B_Ground, p_0, AXIS, VECTOR, V_Global_X )

//Inline joint pair definition

*InlineJointPair( j_Inlinejpair, "Inline Joint pair", b_1, B_Ground, p_1, AXIS, VECTOR, V_Global_Z )

*Point( p_2, "Point for ori" )

*EndMDL