Point-Cloud dialog-box

See Modelling FB toolbar > Add Point-Cloud


Why use a Point-Cloud?

Use a Point Cloud to:

Import-data as a text-file.

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

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 function to evaluate the 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 data-file [text file] you want to use as the Point-Cloud.

Do these steps:

A.Use the Browse button to pre-select a data-file
B.Enter a File-Format in the Edit File Format box - see below for Options and Data-File Formats Examples
C.Click the Import button

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 data-point in the data-file must include:

X & Y coordinates, or
R & Θ coordinates.

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

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

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

See Data-File Formats below.

The format must include at least:

(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 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.

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 FB, 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 chart1s-red 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 Accuracy2s

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 button4s

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

C.Increase the # Harmonics3s

Edit the # Harmonics3s

The Continuous-Curve improves each time you edit the # Harmonic3s.

D.Fit-Quality =~1 ? 5s

When Fit Quality Traffic Light becomes Green, STOP, or

When the number in the Fit-Quality Number box5s 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 Options6s

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 Curve4s 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 (8s), 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 Width7s 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.

 

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