<< Click to Display Table of Contents >> Navigation: Getting Started Tutorials - MechDesigner > Tutorial 16: Motion-Path FB and Blend-Curves > Step 16.4: Compare XY Piggyback Sliders and Blend-Curve |
We will use two ways to design a path that moves up and over an obstacle.
•Piggyback Sliders in the X-axis and Y-axis direction
•Sketch-Path and Motion-Path FB
STEP 1: Add an Obstacle to the Base-Part To see the obstacle, we will add a rectangle.
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STEP 2: Add Piggyback Sliders
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STEP 3: Design Motions for the X-axis Slider.
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STEP 4: Design Motions for the Y-axis Slider.
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STEP 5: Add Function-Blocks
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STEP 6: Add a Trace-Point to see the Path
<<< click to play video
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STEP 7: Open the Point Properties dialog
The Point Properties dialog is now open. STEP 8: Select the Vectors to show
Magnitude = √(X2 + Y2) STEP 9: Cycle the model
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The Maximum Vertical and Horizontal velocity and acceleration vectors are equal those of the X and Y Velocity and Acceleration graphs in MotionDesigner. This maximum acceleration Magnitude can be found any of these methods: •Move the MMA until the Acceleration Vector is a maximum value - see left •Use a Point-Data FB and a Graph FB to measure and plot motion-values •Use a Stats FB to review the statistical data values |
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We will imagine that this motion is to guide a Pick and Place Robot. We may want the Robot to move more rapidly in the Pick direction (say from right-to-left) as compared with the Place direction (say from the left-to-right direction) STEP 10: Edit the Motions to Return more quickly.
It takes a while to create suitable motions with Piggyback Sliders. Small changes to the motion can give large changes to the Path. There is a different approach. You will notice that it is not easy to make the 'Place' and 'Pick' paths the same. |
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Alternative, and easier strategy: |
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Motion to modify the MMA |
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Output of Motion FB is input to Motion FB |
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STEP 1: Add an Obstacle
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STEP 2: Add a sketch in the Base-Part to give the XY-Path
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STEP 3: Look in the Blend-Curve dialog
The image is the Start-Point separator, only |
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STEP 4: Add a Motion-Path FB to the sketch of the XY-Path.
The Motion-Path FB is in the graphic-area. The Motion-Point is at the start-Point of the Line. |
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STEP 5: Add a Motion FB and Linear-Motion FB
The Motion-Point does not move all the way along the XY-Path. |
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STEP 6: Edit the Motion that is linked to the Motion FB There are two ways to make sure the Motion-Point moves along all of the XY-Path, and returns. Method A
Use Method b) |
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Note: Make the motion value equal to 359.999 (not 360) to make sure the Motion-Point does not, for an instant, appear at the start of the first sketch-element when it should be at the end of the last sketch-element. This is because it is possible that the motion-value that should be 360 is actually 360.000001. |
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STEP 7: Edit the Motion so the first segment is longer than the second segment.
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