Table driven kinematics 1

[wrightti]

Hi,

Does anyone know of a method to drive a kinematic assembly from a lookup table of values instead of with laws. I have a mechanism with 3 commands and I want to simulate about 1000 discrete points. I have the command values already in excel, and it would be a pain to have to draw out a law for each command.

Any ideas?

Tim

 

[kirrer]

When you say it'd be a pain to draw out the law for each command, I assume you mean to do so in Sketcher. What you should be able to do is convert your excel data points to a TXT file with the following format (see attached from Catia V5 help) and import that to your mechanism - double click the first command, click 'import' and find your formatted TXT file.

If this helps, great. If this is what you were saying that it'd be a pain to do, then I don't know another method to make it easier - sorry!

By the way, the full help file is available at: Catia V5 help dir > DMU Kinematic Simulator > Advanced Tasks > Mechanism Design > Defining Laws in a V5 Mechanism > Defining Laws using a 2D Curve

Kevin Irrer
Powertrain Engineer
IAV Inc.

 

[wrightti]

Hi Kevin,

Thanks for that info. I actually did find this help file today in the end. I was avoiding the section called "Defining Laws using a 2D Curve" because I wanted to do it with a text file!

I have trialled the method with a basic input and it works as I want. I'm generating the text file with about 1000 points automatically from excel so its infinitely easier to make than drawing each law by hand.

cheers again

Tim

 

[jackk]

Tim. have you tried using a Design Table to drive the kinematic parameters?

 

[wrightti]

Hi Jack,

I havent tried this. Is there anything in the help documentation about this?

In the end I took the points from a text file and imported them as Kevin suggested. It worked well.

Id be interested in hearing how the design table metehod works.

Tim

 

[jackk]

Tim,

First of all, I'm assuming you have a kinematic mechanism with multiple inputs. And you want a table of those input values to plug into the mechanism and have it move to that into that particular configuration. Right?

The basic steps for doing this with a design table are:
1. create a parameter for each input
2. link the parameters the the appropriate assembly constraint
3. make a design table (and spreadsheet) based on the parameters
4. add additionsl colums with various values
5. choose a design table configuration to apply to your assembly and update the assembly.

(as I'm writing these steps, I realized that you really don't need to use the DMU Kinematic workbench for this. As long as your mechanism assembly is fully constrained, the design table will drive the mechanism.