Motion-Law: Constant-Acceleration and-Deceleration

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Motion-Law: Constant-Acceleration and-Deceleration

Constant-Acceleration and Constant-Deceleration Cam-Law, Motion-Law

A Traditional Motion-Law.  Its name is often reduced to Poly345


You CAN specify the:

Start-Position

The Start-Position usually flows from the End-Position of the Previous-Segment.

End-Position

You CANNOT specify the:

Start-Velocity, End-Velocity

Start-Acceleration, End-Acceleration

Start-Jerk, End-Jerk

Segment Parameters

None

Segment-Range

Start-Range

End- Range

0 ≤ Start-Range < End-Range ≤ 1


See also : MD-Globe-www-24 Tutorial 5: Edit the Start of a Traditional Motion-Law.

See also : MD-Globe-www-24 Tutorial 9: Asymmetrical Motions.

Constant-Acceleration - Constant-Deceleration Motion-Law - Parabolic Motion (Cam-Law)

Constant-Acceleration - Constant-Deceleration Motion-Law - Parabolic Motion (Cam-Law)

Motion-Law Coefficients

Velocity Coefficient :

Acceleration Coefficient :

Jerk Coefficient :

Jerk at Cross-over :

Application Notes

This Motion-Law was used in the past because it has the lowest nominal acceleration of the Traditional Motion-Laws. However, it has infinite-jerk at three points: at its start, end, and at its cross-over. This makes it a very poor choice form a dynamic viewpoint. Infinite-Jerk incites vibrations in any mechanical system. We do not recommend this motion-law if the Period-Ratio is less than 10, or even 20.

Dynamic Performance

The actual acceleration of the load being driven by Constant-Acceleration motion will be significantly higher than the nominal value because of induced vibrations.

For this reason, this segment should only be used in applications where inertia effects are small or even insignificant.

Pressure-Angle Considerations

This segment produces a relatively large pressure-angle - and so might need a large cam for a given lift. The pressure-angle for this segment varies quite severely throughout this Motion-Law indicating that it is unsuitable for roller follower applications because of the severe accelerations imposed on the roller that will tend to induce roller slip.

Drive-Torques

This law performs badly in terms of drive torque considerations. All of the torque factor curves for this law exhibit a discontinuity, indicating shock loading and noise in operation. Particularly notable is the sudden reversal of the inertia torque factor, and hence of the torsional strain energy, at the cross-over of the motion segment. These reversals will contribute further to noise, shock loading and vibration during operation.