Modified-Trapezoidal Motion-Law

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Modified-Trapezoidal Motion-Law

Modified-Trapezoid Cam-Law, Motion-Law

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

You CAN specify the:


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


You CANNOT specify the:

Start-Velocity, End-Velocity

Start-Acceleration, End-Acceleration

Start-Jerk, End-Jerk

Segment Parameters




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.

Modified Trapezoid Cam-Law / Motion-Law

Modified Trapezoid Cam-Law / Motion-Law

Motion-Law Coefficients

Velocity Coefficient :

Acceleration Coefficient :

Jerk Coefficient :

Jerk at Cross-over :

Application Notes

The Modified Trapezoidal motion-law has finite jerk throughout the segment. It has an average peak nominal acceleration compared to the other Traditional Motion-Laws.

Dynamic Performance

This Motion-Law is a good general purpose type particularly in applications where the period ratio is above about 5. It is not good in applications where the input drive has backlash or is relatively flexible. As long as the drive satisfies these conditions, then this segment exhibits low residual vibrations.

Pressure Angle Considerations

This one of the Traditional Motion-Laws that produce a relatively large pressure angle - and so might need a large cam for a given lift and pre-prescribed maximum pressure angle.

Drive Torques

This Motion-Law exhibits a rapid reversal of acceleration at the cross-over (mid) point. Only the Constant-Acceleration Motion-Law is more rapid, of the Traditional Segments. It is unsuitable to drive heavy masses at high speeds. The rapid reversal of torque may give rise to severe vibrations and shock loading especially if the period ratio is less than 10.

More information:

The Acceleration function of the Modified-Trapezoidal is comprised of:

0.125 Segment-Width - 1/4 Sine function

0.250 Segment-Width - Constant-Acceleration

0.250 Segment-Width - 1/2 Cosine function

0.250 Segment-Width - Constant-Acceleration

0.125 Segment-Width - 1/4 Sine function