Ballscrew drive¶
Description¶
The Ballscrew drive block models the mechanical transmission between a rotary spindle and a translatory nut-side structure. It is intended for drive chains in which the motor, coupling or gearbox can be represented by separate rotary auxiliary subsystems, while this block represents the screw transmission, the spindle rotary inertia and the axial compliance of the screw support path.
The subsystem represents a rotating ballscrew spindle whose axial motion is modeled by a dedicated spindle mass between the nut-side and bearing-side compliances.
Functional principle¶
The block converts relative rotary motion between spindle and nut into an axial motion according to the screw pitch. In the current convention, a positive spindle rotation produces a negative axial nut motion tendency. This matches a right-hand screw.
The nut-side axial compliance generates the axial nut force. The same nut-side force also generates a torque reaction on the nut-side rotary structural port. The opposite screw torque acts internally on the spindle rotary dynamics.
The bearing or mount-side axial compliance supports the axial spindle motion. It generates an axial mount force, but the ballscrew block does not create an additional explicit motor reaction torque on the mount. Motor reaction torque needs to be applied separately. It usually matches the negative motor torque value.
Input signals¶
Signal |
Description |
Unit |
|---|---|---|
Drive torque |
Torque applied to the ballscrew spindle. |
Nm |
Nut position |
Translatory displacement of the nut-side structural port. |
m |
Nut velocity |
Translatory velocity of the nut-side structural port. |
m/s |
Mount position |
Translatory displacement of the mount-side structural port. |
m |
Mount velocity |
Translatory velocity of the mount-side structural port. |
m/s |
Nut angle |
Rotary displacement of the nut-side structural port. |
rad |
Nut angular velocity |
Rotary velocity of the nut-side structural port. |
rad/s |
Output signals¶
Signal |
Description |
Unit |
|---|---|---|
Spindle angle |
Rotary displacement of the ballscrew spindle. |
rad |
Spindle angular velocity |
Rotary velocity of the ballscrew spindle. |
rad/s |
Spindle position |
Axial displacement of the ballscrew spindle. |
m |
Spindle velocity |
Axial velocity of the ballscrew spindle. |
m/s |
Nut force |
Axial force applied to the nut-side structural port. |
N |
Mount force |
Axial force applied to the mount-side structural port. |
N |
Nut torque |
Torque applied to the nut-side rotary structural port. |
Nm |
Parameters¶
Parameter |
Description |
Unit |
|---|---|---|
Pitch |
Ballscrew pitch, i.e. translatory displacement per spindle revolution. |
m/rev |
Spindle inertia |
Rotary inertia of the ballscrew spindle. |
kg m² |
Spindle mass |
Axial mass of the ballscrew spindle. |
kg |
Nut axial stiffness |
Axial stiffness between spindle and nut-side structure. |
N/m |
Nut axial damping |
Viscous axial damping between spindle and nut-side structure. |
Ns/m |
Bearing axial stiffness |
Axial stiffness between spindle and mount-side structure. |
N/m |
Bearing axial damping |
Viscous axial damping between spindle and mount-side structure. |
Ns/m |
Coupling with rotary inertia blocks¶
The block is commonly connected to a rotary inertia, motor or geared inertia block. The rotary inertia block provides the drive torque and receives the spindle angle and angular velocity as coupling coordinates.