SimMechanics

Weld

Represent a joint with no DoFs

Library

Joints

Description

The Weld block represents a joint with no degrees of freedom (DoFs). The two Bodies connected to either side of the Weld block are locked rigidly to one another, with no possible relative motion.

You must connect each side of the Joint block to a Body block at a Body coordinate system (CS) point. The Weld block is assembled: the origins of these Body CSs must lie along the primitive axes, within assembly tolerances. But the Body CS origins on either side of the Joint do not have to be spatially collocated points.

You can connect any Joint block to two and only two Body blocks, and Joints have a default of two Connector Ports for connecting to base and follower Bodies.

A Joint block represents only the abstract relative motion of two bodies, not the bodies themselves.

Dialog Box and Parameters

The dialog box has two active areas, Connection parameters and Parameters.

Connection Parameters

Current base

When you connect the base (B) Connector Port on the Weld block to a Body CS Port on a Body, this parameter is automatically reset to the name of this Body CS. See the following Weld base and follower Body Connector Ports figure.

The base Body is automatically connected to the joint primitive W in the primitive list in Parameters.

Current follower

When you connect the follower (F) Connector Port on the Bushing block to a Body CS Port on a Body, this parameter is automatically reset to the name of this Body CS. See the following Weld base and follower Body Connector Ports figure.

The follower Body is automatically connected to the joint primitive W in the primitive list in Parameters.

Number of sensor/actuator ports

Using this spinner menu, you can set the number of extra Connector Ports needed for connecting Joint Sensor blocks to this Joint. The default is 0.

You cannot actuate a Weld joint, and a Weld joint undergoes no motion. A Joint Sensor measures zero motion, but in general nonzero reaction forces, at this joint.

Weld base and follower Body Connector Ports

Parameters

Toggle between the Axes and Advanced panels with the tabs.

The entries on the Axes pane are inactive for Weld. This block has no DoF primitives.

Name - Primitive

The primitive list states the names and types of joint primitives that make up the Bushing block: a rigid primitive W representing no motion.

Axis of action [x y z]

This field is inactive.

Reference csys

Using the pull-down menu, choose the coordinate system (World, the base Body CS, or the follower Body CS) whose coordinate axes the vector axis of action is oriented with respect to. This CS also determines the absolute meaning of forces/torques and motion along/about the joint axis. The default is WORLD.

The Advanced pane is optional. You use it to control the way SimMechanics interprets the topology of your schematic diagram.

Mark as the preferred cut joint

In a closed loop, one and only one joint is cut during the simulation. SimMechanics does the cutting internally and automatically.

If you want this particular joint to be weighted preferentially for cutting during the simulation, select the check box. The default is unselected.

See Also

Distance Driver

See Modeling Joints for more on representing DoFs with Joints.

See Checking Schematic Topology and How SimMechanics Works for more on closed loops and cutting.

Velocity Driver

SimMechanics Command Reference