Polynomial 3-4-5 Motion-Law

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Polynomial 3-4-5 Motion-Law

Polynomial 3-4-5 Cam-Law, Motion-Law

Motion Description

A Traditional Motion-Law.  Its name is often reduced to Poly-345.

A motion with continuous Velocity and Acceleration, from start to end. The Jerk is finite at its start and end. It has finite Jerk throughout.

It gives a relatively low nominal peak velocity, but a relatively high peak nominal Acceleration. It has a relatively low Jerk value at the crossover point (the mid-point). It is commonly used in high-speed mechanisms.


You CAN control the:

Start Position

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

End Position

You CANNOT control the:

Start Velocity and End Velocity

Start Acceleration and End Acceleration

Start Jerk and End Jerk

Segment Parameters




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

Polynomial 3-4-5 Motion-Law / Cam-Law

Polynomial 3-4-5 Motion-Law / Cam-Law

Motion-Law Coefficients

Velocity Coefficient :

Acceleration Coefficient :

Jerk Coefficient :

Jerk at Crossover :

Application Notes

Dynamic Performance:

This Motion-Law is recommended for applications where the period ratio is between 5 and 10, particularly where the input drive is flexible and has backlash. It also performs relatively well from a residual vibration viewpoint.

Pressure Angle Considerations

This is a Traditional Motion-Law that produces a relatively small pressure angle - and so might allow a smaller cam for a given lift and pre-prescribed maximum pressure angle.

Drive Torques

Both the nominal drive torque characteristics and the actual drive torques for low period ratio values are reasonable for this law. The peak values and smooth variation of the drive torque during the motion segment makes it suitable in applications where the input drive is relatively flexible or exhibits backlash.