Joint Initial Velocity: Revolute

Model ElementThe Jointlnitialvel_Rev element defines the initial angular velocity for a revolute joint element.

Format

<JointInitial_Rev
joint_id    = "integer"
iv          = "real"
</JointInitial_Rev>

Attributes

joint_id
The ID of the revolute joint whose initial velocity is being specified.
iv
The initial rotational velocity of the revolute joint. The value specified is the rotational velocity of the I marker of the joint relative to the J marker of the joint. The unit is radians per model time unit.
A positive value specifies a velocity in the counterclockwise direction.

Example

Consider the simple 2-dimensional pendulum shown in the image below.

Assume that the pendulum body (shown in red) is pivoted at the global origin, denoted by point P, by a revolute joint, such that rotation is allowed about the global z-axis. The center-of-mass of the pendulum is at B.

At the start of the simulation, the pendulum is rotating counterclockwise about the global z-axis at 20 radians per second. The initial velocity of the revolute joint may be specified as follows:

<JointInitial_Rev
joint_id  = "1"
iv        = "20">
</JointInitial_Rev>