Driven Motion¶
Driven motion refers to the combination of both translational and rotational movements of an object, where either or both can be predefined (prescribed) or governed by dynamic forces (driven). It can involve free movement in all directions, fixed axis rotation, or a combination of both, depending on the specified conditions.
Driven Motion Mode¶
Translation¶
The motion along each global axis (X, Y, Z) can be set to driven or prescribed motion using the “Driven Translation X/Y/Z” option. The object does not rotate.
Download Sample File: Translation
- Driven Translation X
The motion along this axis can be set to free (driven) or prescribed.
- Prescribed
- Displacement X UDF
m | This UDF defines the x-displacement of the mount point about the initial position. Values may be positive or negative. The initial value of the UDF should be zero. This is a System UDF.
- Free
- Additional Force X UDF
N | Other forces to apply on the object as a time-varying expression that can be a function of the instantaneous position and velocity of the object. This is used for forces such as friction and damping. This is a System UDF.
- Initial Velocity X
m/s | Initial velocity along the axis at time 0.
- Driven Translation Y
The motion along this axis can be set to free (driven) or prescribed.
- Prescribed
- Displacement Y UDF
m | This UDF defines the y-displacement of the mount point about the initial position. Values may be positive or negative. The initial value of the UDF should be zero. This is a System UDF.
- Free
- Additional Force Y UDF
N | Other forces to apply on the object as a time-varying expression that can be a function of the instantaneous position and velocity of the object. This is used for forces such as friction and damping. This is a System UDF.
- Initial Velocity Y
m/s | Initial velocity along the axis at time 0.
- Driven Translation Z
The motion along this axis can be set to free (driven) or prescribed.
- Prescribed
- Displacement Z UDF
m | This UDF defines the z-displacement of the mount point about the initial position. Values may be positive or negative. The initial value of the UDF should be zero. This is a System UDF.
- Free
- Additional Force Z UDF
N | Other forces to apply on the object as a time-varying expression that can be a function of the instantaneous position and velocity of the object. This is used for forces such as friction and damping. This is a System UDF.
- Initial Velocity Z
m/s | Initial velocity along the axis at time 0.
- Mass
kg | Total mass of the moving body.
- Center of Mass
m | Position of the center of mass in the global coordinate system.
Rotation 1 Axis¶
The object has a fixed axis of rotation while there is no translation. This axis of rotation is defined by the moving body’s motion axis point and motion axis vector. The rotation can be driven or prescribed, which is designated using the “Driven Rotation” option. If prescribed, set the following parameters:
Download Sample File: Rotation 1 Axis
- Mass
kg | Total mass of the moving body.
- Center of Mass
m | Position of the center of mass in the global coordinate system.
- Driven Rotation
Designate if rotation can be driven or prescribed.
- Prescribed
- Prescribed Rotation UDF
rad | This UDF defines the rotational position of the object about the rotation axis. This is a System UDF.
Download Sample File:
Prescribed Rotation- Free
- Free 1 Axis Moment of Inertia
Moment of inertia about the axis of rotation.
- External Torque UDF
Nm | This UDF defines an additional external torque applied about the rotating axis for driven objects with free rotation about one axis. This torque is superimposed on any fluid or particle forces acting on the moving body. This is a System UDF.
Download Sample File:
External Torque- Free 1 Axis Initial Omega
rad/s | Initial angular velocity about rotation axis at time 0.
Prescribed Translation Free Rotation¶
The object translates according to predefined expressions while rotation occurs freely in all directions.
Download Sample File: Prescribed Translation Free Rotation
- Displacement X UDF
m | This UDF defines the x-displacement of the mount point about the initial position. Values may be positive or negative. The initial value of the UDF should be zero. This is a System UDF.
- Displacement Y UDF
m | This UDF defines the y-displacement of the mount point about the initial position. Values may be positive or negative. The initial value of the UDF should be zero. This is a System UDF.
- Displacement Z UDF
m | This UDF defines the z-displacement of the mount point about the initial position. Values may be positive or negative. The initial value of the UDF should be zero. This is a System UDF.
- Ixx
kg-m 2 | Components of the moment of inertia matrix calculated about the center of mass at the object’s initial position and orientation.
- Iyy
kg-m 2 | Components of the moment of inertia matrix calculated about the center of mass at the object’s initial position and orientation.
- Izz
kg-m 2 | Components of the moment of inertia matrix calculated about the center of mass at the object’s initial position and orientation.
- Ixy
kg-m 2 | Components of the moment of inertia matrix calculated about the center of mass at the object’s initial position and orientation.
- Ixz
kg-m 2 | Components of the moment of inertia matrix calculated about the center of mass at the object’s initial position and orientation.
- Iyz
kg-m 2 | Components of the moment of inertia matrix calculated about the center of mass at the object’s initial position and orientation.
Free 6 DOF¶
The object is allowed to freely rotate and translate in all directions.
Download Sample File: Additional Force UDF
- Mass
kg | Total mass of the moving body.
- Center of Mass
m | Position of the center of mass in the global coordinate system.
- Additional Force X UDF
N | Other forces to apply on the object as a time-varying expression that can be a function of the instantaneous position and velocity of the object. This is used for forces such as friction and damping. This is a System UDF.
- Additional Force Y UDF
N | Other forces to apply on the object as a time-varying expression that can be a function of the instantaneous position and velocity of the object. This is used for forces such as friction and damping. This is a System UDF.
- Additional Force Z UDF
N | Other forces to apply on the object as a time-varying expression that can be a function of the instantaneous position and velocity of the object. This is used for forces such as friction and damping. This is a System UDF.
- Initial Velocity X
m/s | Initial velocity along the axis at time 0.
- Initial Velocity Y
m/s | Initial velocity along the axis at time 0.
- Initial Velocity Z
m/s | Initial velocity along the axis at time 0.
- Ixx
kg-m 2 | Components of the moment of inertia matrix calculated about the center of mass at the object’s initial position and orientation.
- Iyy
kg-m 2 | Components of the moment of inertia matrix calculated about the center of mass at the object’s initial position and orientation.
- Izz
kg-m 2 | Components of the moment of inertia matrix calculated about the center of mass at the object’s initial position and orientation.
- Ixy
kg-m 2 | Components of the moment of inertia matrix calculated about the center of mass at the object’s initial position and orientation.
- Ixz
kg-m 2 | Components of the moment of inertia matrix calculated about the center of mass at the object’s initial position and orientation.
- Iyz
kg-m 2 | Components of the moment of inertia matrix calculated about the center of mass at the object’s initial position and orientation.
Prescribed Translation Free Rotation 1 Axis¶
The object translates according to predefined expressions while rotation occurs about a fixed axis. This axis is defined by the moving body’s motion axis point and motion axis vector.
Download Sample File: Prescribed Translation Free Rotation 1 Axis
- Mass
kg | Total mass of the moving body.
- Center of Mass
m | Position of the center of mass in the global coordinate system.
- Displacement X UDF
m | This UDF defines the x-displacement of the mount point about the initial position. Values may be positive or negative. The initial value of the UDF should be zero. This is a System UDF.
- Displacement Y UDF
m | This UDF defines the y-displacement of the mount point about the initial position. Values may be positive or negative. The initial value of the UDF should be zero. This is a System UDF.
- Displacement Z UDF
m | This UDF defines the z-displacement of the mount point about the initial position. Values may be positive or negative. The initial value of the UDF should be zero. This is a System UDF.
- Free 1 Axis Moment of Intertia
kg-m 2 | Moment of inertia about the axis of rotation.
- External Torque UDF
Nm | This UDF defines an additional external torque applied about the rotating axis for driven objects with free rotation about one axis. This torque is superimposed on any fluid or particle forces acting on the moving body. This is a System UDF.
Download Sample File: External Torque
- Free 1 Axis Initial Omega
rad/s | Initial angular velocity about rotation axis at time 0.
- Lower Rotation Limit
deg | These limits prevent the object from rotating beyond lower limits. When a limit is hit, the object will rotate in the opposite direction again once it receives a torque in the opposite direction.
- Upper Rotation Limit
deg | These limits prevent the object from rotating beyond upper limits. When a limit is hit, the object will rotate in the opposite direction again once it receives a torque in the opposite direction.
Note
You can automatically calculate the moments of intertia using the Moments form or you can extract them from the Diagnostics form.