Control nodes

Note:

Control nodes are intended for advanced users.

For revolute, inline, cylindrical, slider, and slider-universal joints, you can define an optional third node, called a control node. The control node internally allows the solver to drive joints, and it stores results.

You can use control nodes to do the following:

• To move joints in sync, assign the same control node to CJOINTs of the same type (as set in PJOINT). Then, add the Kinematic Driver boundary condition to the CJOINT element of one of those joints. The joints that share the same control node are moved by the same Kinematic Driver.

• To view a curve of the relative displacement or relative rotation of a joint, create a Report simulation object for the first degree of freedom of the control node. For example, in the Report dialog box, select the control node, and from the Degree of Freedom list, select DOF1. When you solve the solution, you can access the displacement curve in the Solution Monitor by clicking Graph(s) and selecting the name of the report.

• To prevent a joint from moving in some subcases but not in others, assign the control node to the CJOINT that you want to stop moving.This is an alternative to using the Joint Time Constraint boundary condition, which can be used only once per joint, and at the solution-level only.

• To add additional physical properties to your joints, associate the control node with the physical properties you want to add to the joint. These physical properties are in addition to the friction, spring, and damping physical properties you can add to a CJOINT element (in PJOINT and PJOINT2).

Note:

If you don’t create control nodes, the solver creates them, but you cannot select them to assign to multiple joints, and so on. You can still move multiple joints in sync by applying the same Kinematic Driver to those joints.

Degrees of freedom for control nodes

The first degree of freedom of the control node represents the kinematic mode of the joint.

Cylindrical joints, however, use two degrees of freedom of the control node, one for the translation degree of freedom and one for the rotation degree of freedom.

Example

To add the same Kinematic Driver to multiple joints so that the movement of the joints is synchronized, create a control node, and select that same control node for each element that you want to use the Kinematic Driver.

For example, you might want two revolute joints (hinges) to open at the same time. To do that, you can:

1. Create a node in a free space in your model.

2. In the mesh-associated data of one of the revolute joints, create the control node by selecting the node you created.

3. In the mesh-associated data of the other revolute joint, create the control node by selecting the same node.

4. Add the Kinematic Driver to one of the revolute joints.Note: You cannot add the Kinematic Driver or other boundary conditions to a control node. You can add the Kinematic Driver only to the CJOINT element.

When you solve the model and animate the results, the revolute joints that share a control node move in sync.

How do I

Add joints to your kinematics model using universal connections

Create a flexible slider joint

Create and assign control nodes

Learn more

SOL 402 structural analysis with kinematics

1D connection elements for kinematic joints

Kinematic Driver boundary condition

Joint Time Constraint boundary condition

Flexible slider joint

Look up more details

Kinematic joints for SOL 402

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Control nodes, Simcenter 3D 2021.1 Series

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