Orientation Joint

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

Theory/Background

An Orientation Joint is a three degree-of-freedom kinematic pair. The joint constrains the three rotational degrees of freedom while all three translations are free. Effectively, the orientations of the two bodies connected by the joint remain the same.

orientation_joint_diagram_mv

Orientation joint construction

Joint Definition

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

orientation_joint_marker_diagram_mv_ug

Orientation joint marker representation

The bodies that are constrained by the Orientation 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 the Marker I with respect to Marker J. While defining the joint, the markers can either have coincident origins or they can be non-coincident. Marker I is free to translate along the X, Y, and Z axis of Marker J.

Entity Data Members

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

orientation_joint_diagram2_mv

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

Connectivity

An Orientation Joint needs the following:

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

•	Origin 1 - Specify Point, which defines the location where a Marker on Body 1 is to be created.

•	Origin 2 - Specify Point, which defines the location where a Marker on Body 2 is to be created. Origin 1 and Origin 2 can be located at the same point.

•	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.

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

Properties

There are no editable properties for an Orientation joint.

Creating and Editing Joints

To learn how to add a Orientation joint to a model, please see the Joints topic.

1.	Once an Orientation 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:

orientation_joint_panel_conn_tab_mv

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

orientation_joint_panel_conn_tab__pair_mv

Joints Panel (Orientation 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, click Body 2 from the graphics area by clicking on the desired body (or use the collector and model tree method).

4.	Select the Origin 1 point for the joint that defines the point where the an implicit Marker (Marker I) is created on Body 1. Click the Point collector and select the desired point in the graphics area (or double click the collector and use the model tree to select the point).

5.	Select the Origin 2 point for the joint that defines the point where the an implicit Marker (Marker J) is created on Body 2. Click the Point collector and select the desired point in the graphics area (or double click the collector and use the model tree to select the point).

6.	When defining a Pair Orientation 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 Orientation 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 origin points of the joint.

orientation_joint_drop_down_menu_mv_ug

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

Orientation Joint in MDL and XML Formats

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

The Orientation Joint can be of the following types:

1.	Non-Compliant - Single and Pair

2.	Compliant – Single and Pair

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

Syntax:

*OrientJoint(joint_name, "joint_label", body_1,

body_2,

origin_1,

origin_2,

[ALLOW_COMPLIANCE])

To understand the complete syntax of the MDL statement please refer to the *OrientJoint() topic.

Syntax:

*OrientJointPair(joint_name, "joint_label", body_1,

body_2,

origin_1,

origin_2,

[ALLOW_COMPLIANCE])

To understand the complete syntax of the MDL statement please refer to the *OrientJointPair() topic.

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

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

Syntax:

<Constraint_Joint [or Constraint_Jprim]

id = "integer"

label = "Name of Joint"

type = "JOINT TYPE"

i_marker_id = "integer"

j_marker_id = "integer"

Example:

<Constraint_Joint [or Constraint_Jprim]

id= "301001"

label = "Orientation Joint"

type = "ORIENTATION"

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 or Constraint_Jprim.

Creating an Orientation 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 Orientation Joint the statement will look as shown below:

mdlmodel_handle InterpretEntity joint_Orientation_handle OrientJoint j_Orientation "\"Orientation Joint\"" b_1 B_Ground p_0 p_1 "ALLOW_COMPLIANCE";

*This command is not applicable for Orientation 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 an Orientation joint connecting two bodies:

*BeginMDL( the_model, "Model", "12.0.110.40" )

*StandardInclude(FILE)

*Point( p_0, "Point 0" )

*PointPair( p_1, "Point 1" )

*Body( b_0, "Body 0", p_0, , , , )

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

//Orientation joint definition

*OrientJoint( j_Orijsingle, "Orient Joint Single", b_0, B_Ground, p_0, p_0 )

//Orientation joint pair definition

*OrientJointPair( j_Orijpair, "Orient Joint pair", b_1, B_Ground, p_1, p_0 )

*SetPoint( p_1, LEFT, , -100 )

*EndMDL()