Constant-Velocity [or other 'Polynomial* Motion-Laws] with the Flexible-Polynomial Motion-Law

Polynomial' motion-laws include: Dwell, Constant-Velocity, Cubic, Quadratic, 345 Poly, 4567 Poly.

Flexible-Polynomial Motion-Law

You can make the Flexible-Polynomial Motion-Law the same as other 'Polynomial Motion-Laws'.

It is possible to make it the same as the Dwell, Constant Velocity, Cubic, Quadratic, Polynomial 345, Polynomial 4567 Motion-Laws, and others.

This tutorial shows you  how to use the Segment-Editor to:

1.Start the Segment-Editor
2.Edit the Motion-Law in the Segment-Editor
3.Edit the 'Start of the Segment'

The Default Motion


Number of Segments:

Four segments

Motion-Width (X-axis):



All four segments are Flexible-Polynomial


Only the bottom graph displays the X-axis values. All the motion-graphs (Position, Velocity, Acceleration, and Jerk) use the same X-axis values.

The Basic Flexible Polynomial


When you select a segment, it becomes red and it is the Selected-Segment.

The Steps to make the Flexible Polynomial Motion-Law appear like a Constant-Velocity Motion-Law:

STEP 1: Identify and select the segment you would like to be Constant-Velocity

STEP 2: Use the Motion-Law Selector to change it to a Constant Velocity motion-law.

STEP 3: Use the Blend-Point Editor to edit the Blend-Point at the start of the 'Constant-Velocity segment.

STEP 1: Make the segment you want to be Constant-Velocity, the 'Selected-Segment'.


In this case, I want to make the second segment a 'constant velocity' segment.

1.Click the graph area below the graph line of the second segment.

The segment should be RED. '1'

Note : If you click the graph line itself, you will open the Segment-Editor. Do not do this yet.

2.Use the 'Motion-Law Selector' to make the segment a 'Constant-Velocity' segment.

See the inset image '2'

3.You MUST click a different segment, to take the 'focus' from the Motion-Law Selector.




STEP 2: Edit the Motion-Values

Blend-Point Editor button

Blend-Point Editor button

1.Click the 'Start Blend-Point Editor' icon in the Segment & Blend-Point-Editor toolbar - see left

Now, we can edit the motion-values of the Selected-Segment.


The Blend-Point Editor, is open.

We use the Blend-Point Editor to edit the motion values at the:

'end' of the previous-segment
'start' of the selected-segment

The Control Buttons for the Position and Velocity motion-values are shown in the image.

We will focus on the Velocity Control-Buttons and Motion-Values.

Match Control-Button is active.

This means that, if we edit a motion-values at the end of the previous-segment, the motion-values at the start of the selected-segment will be the same.

Specify-End of Previous-Segment is active

This means that we can edit the motion-values.

Specify-Start Selected-Segment is NOT active.

When the 'Match' Control-Button is active, this control button is always 'not active'.

The motion-value in the 'End Velocity' box is '0 mm/s.

Thus, the velocity at the end and start of the selected-segment is '0' mm/s

Because the Selected-Segment is a 'Constant-Velocity' motion-law, the velocity of the whole segment is '0'. This means the Segment will be identical to a 'dwell'.


1.Use the 'End-Velocity spin-box to increase the Velocity of the Selected-Segment to 200mm/s.

Because, the Motion-Law is 'Constant-Velocity, the velocity of the whole segment is 200mm/s

See image.


Tutorial and Reference Help Files for MechDesigner and MotionDesigner 13.2 + © Machine, Mechanism, Motion and Cam Design Software by PSMotion Ltd