Step 16.4: Compare XY Piggyback Sliders and Blend-Curve

<< 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

Compare Piggyback Sliders and Blend-Curve

We will use the two ways to design a path that moves up and over an obstacle.

Piggyback Sliders i9n the X-axis and Y-axis direction

Sketch-Path and Motion-Path FB

Piggyback Sliders

GST-16-4-Motion-Path-A

STEP 1: Add an Obstacle to the Base-Part

To see the obstacle, we will add a rectangle.

1.Part-Editor: Geometry toolbar > Add 4 × Lines

2.Part-Editor: Constraints toolbar > Add 3 × Perpendicular

3.Part-Editor: Geometry toolbar > Add 1 × Horizontal to a Line

4.Part-Editor: Geometry toolbar > Add Dimension (70mm wide, 50mm tall )

5.Exit Part-Editor

GST-16-4-Motion-Path-B

STEP 2: Add Piggyback Sliders

1.Edit Base-Part: Geometry toolbar > Add Line, Vertical Constraint, Dimension

2.Exit Part-Editor

3.Mechanism-Editor: Kinematic elements toolbar, Add Part, Add Slide-Joint

4.Mechanism-Editor: Kinematic FB toolbar, Add Motion-Dimension FB (Y-axis)

5.Edit Sliding-Part: Add vertical Line (Horizontal in Mechanism-Plane),

6.Exit Part-Editor

7.Mechanism-Editor: Kinematic elements toolbar, Add Part, Add Slide-Joint

8.Mechanism-Editor: Kinematic FB toolbar, Add Motion-Dimension FB (X-axis)

X-axis motion

STEP 3: Design Motions for the X-axis Slider.

1.Motion-Designer: Right-Click the motion graph. Rename to X

2.Motion-Designer: Blend-Point Editor. All Blend-Point Position=0,

3.Motion-Designer: Close Blend-Point Editor

4.Motion-Designer: Insert Blend-Point: Click the Motion graph

5.Motion-Designer: Blend-Point Editor. Edit X-axis values of all Blend-Points.

6.Motion-Designer: Blend-Point Editor. Edit Y-axis values of all Blend-Points.

Y-axis motion

STEP 4: Design Motions for the Y-axis Slider.

1.Motion-Designer: File toolbar > Add new Motion

2.Motion-Designer: Right-click the motion graph Rename to Y

3.Motion-Designer: Blend-Point Editor. Edit X-axis values of all Blend-Points.

4.Motion-Designer: Blend-Point Editor. Edit Y-axis values of all Blend-Points.

GST16-4-Motion-Path-E

STEP 5: Add Function-Blocks

1.Mechanism-Editor: Kinematic FB toolbar, Linear-Motion FB, Click Graphic-area

2.Mechanism-Editor: Kinematic FB toolbar, Motion FB, Click Graphic-area

3.Mechanism-Editor: Kinematic FB toolbar, Add Motion FB AGAIN, Click Graphic-area

4.Mechanism-Editor: Edit a Motion FB - select Y in Select-Motion drop-down.

5.Mechanism-Editor : Drag wires to connect FBs to the Motion-Dimension FBs

t16.4-piggybackslider_zoom38

STEP 6: Add a Trace-Point to see the Path

1.Mechanism-Editor: Kinematic elements toolbar > Add Trace-Point

2.Graphic-area: Click a Point on the X-axis Slider.

3.Command-Manager: Click OK-tiny-11-15 to close

<<< click to play video

 

GST-16-4-Motion-Path-G-Point-Properties

STEP 7: Open the Point Properties dialog-box

1.Mechanism-Editor: Filters toolbar > Filter for Points

2.Mechanism-Editor: Double-Click the Point with the Trace-Point

The Point Properties dialog-box is now open.

STEP 8: Select the Vectors to show

1.Click Show Velocity Vector

2.Click Show Acceleration Vector

3.Click Velocity Vector Options: Mag. (Magnitude)

4.Click OK-tiny-11-15 to close the Point Properties dialog-box

Magnitude = √(X2 + Y2)

STEP 9: Cycle the model

1.Click Run toolbar > Cycle

or

1.Press ALT+C on your keyboard

 

GST-16-4-Motion-Path-H

The Maximum Vertical and Horizontal velocity and acceleration vectors will equal those of the X and Y Velocity and Acceleration graphs in MotionDesigner.

This maximum acceleration Magnitude can be found by:  

Moving 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


t16.4-piggybackslider-asymmetrical_zoom38

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 9: Edit the Motions to Return more quickly.

1.Try to edit the X and Y motions to move the Sliders quickly in the Pick direction as compared to the Place direction

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 very easy to make the 'Place' and 'Pick' paths the same.

Alternative, and easier strategy:

Motion to modify the MMA

Motion to modify the MMA

When you want a fast Pick and slow Place, it is easier change the input function to the X-Y-axis Slider motions.

In the standard motion strategy - as above - the output from the Linear-Motion FB is the input-function to the X-Y-axis motions. Its output mirrors the MMA.

This is motion-function is indicated in the image with the Linear-Motion FB motion (in the top image, left)

The alternative motion increases slowly until its output reaches 180, and then increases rapidly until its output reaches 360.

See again, the top image, left, with the Blue then Orange segments

The output of this motion is connected to the X and Y-axis Motion FBs in exactly the same way as the output from a Linear-Motion FB in the examples above - see middle image, left

With this technique, XY-path does not change, buy you change the speed along it - this is often the best strategy.

Output of Motion FB is input to Motion FB

Output of Motion FB is input to Motion FB

t16.4-piggyback-symmmotions-asymmtiming_zoom35

tog_minus        A Motion-Path FB.