Point-Cloud FB

See Add Point-Cloud


Why use a Point-Cloud?

Use a Point Cloud to:

Import-data as a text-file.

The Point-Cloud dialog-box can import data.

Typically, the data are coordinates of a cam-profile, which is measured with a Coordinate Measurement Machine (CMM). The measurement data is taken 'as is'. Numerical techniques approximate motion-derivatives, which are usually noisy.

Fit-a-Curve to the imported-data.

The Point-Cloud dialog-box can fit a Curve to the Imported-Data.

The Curve is a continuous-function that is a good-fit to the imported-data. We use the continuous-function to evaluate motion-derivatives, which are usually smooth.


Open the Point-Cloud dialog-box

Icon-FB-PointCloud

To open the Point-Cloud dialog-box:

1.Double-click a Point-Cloud FB in the graphic-area

-or -

...see How to open a Dialog-Box


Point-Cloud dialog-box

Dialog-PointCloudFB-tabs

There are two tabs:

STEP 1: Import Data

STEP 2: Fit Curve to Data

tog_minusSTEP 1: Import Data

Import a text file of data that you want to use as the Point-Cloud.

Do A, B, and C

Dialog-Point-CloudFB-Import-BrowseImportbuttonsDialog-Point-CloudFB-Import-FileFormat

Dialog-Point-CloudFB-Import-DataUnitsOffset

A. Browse...

Click the Browse... button to select data-file you want to import.

The file-name will show in the File-name to Import (Read-Only) box

B. Edit File-Format

Each row of data in the data-file must include:

X & Y coordinates, or
R & Θ coordinates.

Each data-point must be on a new line, and ideally only two columns of data.

However, not all data-files have only two columns of data.

Use the Edit File-Format box to remove extra columns of data from the data-file

See Data-File Formats below.

The File Format must include at least these terms:

(x) and (y) if the data is X–axis and Y–axis coordinates.
(Radius) and (Angle) if the data is Radius and Angle coordinates.

These other characters and are ignored in the data-file:

Header lines, when entered as text.
ASCII characters that are NOT: . , -, 09

c. Import button

Click the Import button to import the Point-Cloud data file.

If successful, the Point-Cloud will show as a continuous line in the graphic-area immediately.

Messages:

FA-Point-Cloud Message

Options:

x , y

When you add a Point-Cloud, you select a Part. The Part has an Origin where its coordinates are X=0 and Y=0.

If the Point-Cloud data has an offset to it, then remove the offset with the X and Y data boxes.

File Rotary Units ; File Linear Units

Select the units that matches the units of the original Point-Cloud data-file


Data-File Formats:

Pre-Select a File Format

To help you with the formatting, you can use the Pre-Select a File Format drop-down list-box.

MD-Point-Cloud-Text-Format

When any of these formats do not represent the format of the data in your data-file, then edit the format in the Edit File Format box directly.

Example Data-Files & File-Formats.

Example1: Data-File:

Example data-file to import as a Point-Cloud

Example format of a data-file to import as a Point-Cloud

Enter File Format: () () (x) (y)

Why:

Line 1: is ignored because it only has letters

Line 2: is ignored because it only has letters

Line 3: The Edit File Format has () () (x) (y) to filter our Column 1 and Column2...

Line 3...: Column 3 and Column4 are imported as the X-axis and Y-axis data.


Example 2: Data-File

Format: N100 G00 X10 Y25 Z27

Enter File Format: () () (x) (y) ()

Why:

All letters are automatically ignored, which reduces the data to: N100 G00 X10 Y25 Z27

Column 1, Column2 Column 5 are ignored. This reduces the format to N100 G00 X10 Y25 Z27

Thus, the data that is left to import is: 10 25 - which will be the X-axis and Y-axis coordinates you want to import as the Point-Cloud.


tog_minusSTEP 2: Fit Curve to Data

When you successfully import a Point-Cloud, the chartRed-14-1b shows the Point-Cloud in (Dark Blue) and the Continuous Curve in (Light-Blue).

Information-24

In the chart below, the Continuous Curve does not follow the Point-Cloud!

It shows the charts separately, for this help documentation ONLY.

The two charts will show as one chart after you successfully 'Fit the Curve to the Point-Cloud'.

Do these steps:

A.Edit the Original Data Accuracy to match the CMM accuracy - see below for more thoughts
B.Make sure the Auto-Fit check-box is checked.
C.Increase the # Harmonics
D.When Fit Quality is, or near to, 1 ; or the Traffic-Light is Green., then the curve 'good'.
E.Click one of the Display Options

Dialog-FB-PointCloud-FitCurvetoData=LH3

Fit a Continuous Curve to the Point-Cloud Data

A.Original Data AccuracyRed-14-2

This is a judgement you must make. I enter 0.1, then reduce it to approximately 0.01 - see below for more thoughts.

B.Auto-Fit check-box and Fit Curve buttonRed-14-4

Usually, you can click the Auto-Fit... check-box to put a tick in the check-box - see options

C.Increase the # HarmonicsRed-14-3

Edit the # HarmonicsRed-14-3

The Continuous-Curve improves each time you edit the # HarmonicRed-14-3.

D.Fit-Quality =~1 ? Red-14-5

When Fit Quality Traffic Light becomes Green, STOP, or

When the number in the Fit-Quality Number boxRed-14-5 is near to, or equal to, one (1), STOP

If you add more harmonics, the fitted-curve may oscillate with an amplitude equal to the Original Data Accuracy.

E.Display OptionsRed-14-6

Click one of the four radio buttons:

Show Nothing
Points only
Point and Curve
Curve Only

Options

Auto-Fit Check-box

Clear the Auto-Fit check-box if the Point-Cloud has many points. E.g. > 10000 points / lines.

You must click use the Fit CurveRed-14-4 button to update the Fitted-Curve,

Repeat until the Fit-Quality and the Traffic-Light becomes Green or Orange

Velocity and Acceleration Filter Width

The default plot is for Position.  I do not use the V or the A buttons as I cannot find a good use to do so.

However:

If you want to look at the plot of the Point-Cloud as Velocity or Acceleration (Red-14-8), then click the V or the A icons.
If the Point-Cloud Data is noisy you can smooth the Velocity or Acceleration data. Use the Filter WidthRed-14-7 to remove some of the noise from the data. This may help you identify the original Motion-Law.

Original Data Accuracy

Thoughts:

Consider 0.1, then reduce it to approximately 0.01.
Do not enter an accuracy that is less than the data. For example, if the data has 3d.p. , then 0.005 is a sensible minimum entry.
Is the skill of the person that measured the Cam-Profile a factor?
Was the cam clean? Is the cam worn? Is the cam damaged?

Machine Measurement Accuracy Approximations: per 100mm of Cam Diameter:

Temperature-Controlled (18-22ºC) CMM is ~0.2 - 5µm
Non-temperature-controlled CMM is ~2 - 10µm
Portable CMM is ~5 - 20µm, and
Test Rig is variable, but you should aim for 20 - 100µm.

 

Tutorials and Reference Help Files for MechDesigner and MotionDesigner 14.2 + © Machine, Cam, Mechanism, and Motion Design Software by PSMotion Ltd