<< Click to Display Table of Contents >> Navigation: Getting Started Tutorials - MotionDesigner > Motion Design: Tutorial 1: Indexing Motion |
This tutorial designs an indexing motion. After this tutorial you should be able to: •delete segments •make sure the Motion-Width is 360º •change the motion-law of a segment •edit the X-axis value of a Blend-Point •edit the Y-axis Position of a Blend-Point |
Terminology and Index Motions Index Motions usually have two segments‡: SEGMENT 1: Index Segment. We specify its: •Index-Period: the rotational angle of the input-shaft (X-axis) as the output shaft also rotates •Index-Angle: the rotational angle of the output-shaft (Y-axis) during the Index-Period. •Motion-Law: the mathematical function for the rotational angle of the output-shaft as a function of the rotational angle of the input-shaft . SEGMENT 2: Dwell Segment. We must specify its: •Dwell-Period†: the number-of-degrees the input-shaft rotates during the dwell segment. •Dwell Period = 360 - Index-Period Note: ‡ When you design a 3D-Cam, it is frequently better to use three segments : Dwell–Index–Dwell, to be symmetrical at 180° (360/2). †: Period = Time-Period, Duration, or Interval. |
Video : Motion Tutorial 1: Design an Indexing Motion
Motion Tutorial 1: Design an Indexing Motion
![]() Default Motion: Four Flexible-Polynomial Segment |
Default Motion: Number-of-Segments = 4 Motion-Width = 360º Motion Rise = 90º Motion-Laws = All 4 are Flexible Polynomial Notes: The X-axis is the horizontal axis. You can see its units are degrees. The Position, Velocity, Acceleration and Jerk graphs are above each other. They are the same motion, but at different motion-derivatives. The X-axis is the same for all of the motion graphs. Segment Names Selected-Segment - is the segment that you select to edit with the Segment Editor or Blend-Point Editor. The Selected-Segment is a different color to the others, typically, it is RED. Previous-Segment - is to the left of the Selected-Segment. Next-Segment - is to the right of the Selected-Segment. |
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If the Y-axis units are not 'degrees' then, to make them 'degrees': 1.Click the Edit toolbar > Active Motion-Settings 2.Click the Active Motion-Settings > Motion tab > Motion Units separator : Y-axis Position units 3.Select degree in the drop-down box. |
Indexing motions usually have 2 segments. Thus, we must delete two segments from the default motion. Before we can delete a segment, we must make it the Selected-Segment 1.Click in the motion-graph area above or below the last segment The RED Selected-Segment is the last segment. |
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To delete the RED Selected-Segment 2.Click the Blend-Point & Segment Editor toolbar > Delete Segment See toolbar above •The last segment stretches. •The total Motion-Width does not change; it remains at 360º. •The first segment becomes the RED Selected-Segment. |
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We want to delete the last segment. 3.Do again Steps 1 and 2 That is: Click the last segment, and then Blend-Point-Segment toolbar >Delete Segment, |
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The motion is to the left. •There are two segments. Terminology: •Period (time period): also applies to a number-of-degrees along the X-axis. •Index-Period: The number-of-degrees along the X-axis during which the Y-axis is in motion. •Dwell-Period: The number-of-degrees along the X-axis during which the Y-axis is not in motion. •Index-Angle: The range of the output motion - in Y-axis units. |
The motion we have: •Segment 1: X-axis Segment-Width = 90º ( the Index-Period) •Segment 2: X-axis Segment-Width = 270º (the Dwell-Period) The Motion-Width 90 + 270 = 360º The motion Y-axis •Segment 1: Y-axis 0-90º (called the Index-Angle) The motion we want: •Segment 1: X-axis Segment-Width = 120º ( the Index-Period) •Segment 2: X-axis Segment-Width = 240º (the Dwell-Period) The Motion-Width 120 + 240 = 360º (as before) The motion Y-axis •Segment 1: Y-axis 0-120º (called the Index-Angle). |
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We must edit the Segment-Width of the segments, but we must not change Motion-Width. We can: •Use the Blend-Point Editor to the move the Blend-Point to the right. •Use the Segment-Editor to make the first segment longer and then make the last segment shorter. The best tool to edit the Segment-Width, when we do not want to edit the Motion-Width, is the Blend-Point Editor. STEP 1.Open the Blend-Point Editor Click: Blend-Point and Segment toolbar > Open Blend-Point Editor. |
![]() Blend-Point Editor button |
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STEP 2.Make sure the active Blend-Point is #2 1.Use the Previous / Next buttons to move the active Blend-Point to #2 You can see the X-axis position is at 90º Note: You can also make sure the second segment is the RED Selected-Segment before you open the Blend-Point Editor. The Next / Previous buttons are important when you want to edit (or find) a 'very short' segment in the motion that you cannot click (or see) in the motion graph. |
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STEP 3.Edit the X-axis value Note: The Blend-Point Editor can edit the the motion-values at the left (the start) of the RED Selected-Segment We can use the spin-box tool to edit the X-axis value of the Blend-Point. 1.Click the bottom arrow-buttons in the spin-box control to increase the Spin-Increment from 1 to 10. 2.Click the top arrow-buttons in the spin-box control to increase X-axis motion-value from 90º to 120º. Or: 1.Use your keyboard to enter a value in the X-axis box (enter 120) 2.Use the 'Enter' key on your keyboard to update to the new value (120) General Reminder: The Blend-Point Editor edits the active Blend-Point. The active Blend-Point is at the left of the RED Selected-Segment. As you edit the X-axis value of the active Blend-Point, the duration (period) of the Previous- Segment and the RED Selected-Segment change at the same time. The Motion-Width does not change. |
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STEP 4.Change the Motion-Law of the last segment (#2) to a Dwell The default motion uses Flexible-Polynomial Motion-Laws for each segment. 1.Click the last segment so that it becomes the RED Selected-Segment 2.Click the Motion-Law Selector in the Motion toolbar (below the motion plots) 3.Select Dwell to change it from a Flexible-Polynomial to a Dwell motion-law STEP 5.Change the Motion-Law of the first segment (#1) to a Modified-Sinusoid 1.Click the first segment so that it becomes the RED Selected-Segment 2.Click the Motion-Law Selector in the Motion toolbar (below the motion plots) 3.Select Modified-Sinusoid to change the motion-law from a Flexible-Polynomial to a Modified-Sinusoid motion-law. IMPORTANT: Click in the graph area (not on the segment) to remove the 'focus' from the Motion-Law selector. Otherwise, if you use your scroll mouse button, you will scroll through the motions! Not good! |
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STEP 6.Edit the Index-Angle (Y-axis-Values) If necessary, open the Blend-Point Editor again - see STEP 1 Make sure the second segment is the RED Selected-Segment - see STEP 2 In the Y-axis values separator, edit the 'End-Position' of the Blend-Point. We want to increase it from 90 to 120º 1.Click the spin-box of the End-Position - see image to the left - to increase the Y-axis value of the Blend-Point from 90 to 120º The graph auto-scales. Thus, look at the Y-axis scale of the Position graph (left of motion graph) to see the change to the motion. Question: What if you do not change the 'Motion-Law' of the second segment to a Dwell? Answer: The second Blend-Point moves up or down along the Y-axis, but the last Blend-Point does not move. You will need to edit the End-Position of the last segment. To do this, you must first make Blend-Point #1 the active Blend-Point. To edit the End-Position of the motion, you must click the FIRST SEGMENT. |