Smart questions
Smart answers
Smart people
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Member Login




Remember Me
Forgot Password?
Join Us!

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips now!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

Join Eng-Tips
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Donate Today!

Do you enjoy these
technical forums?
Donate Today! Click Here

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.
Jobs from Indeed

Link To This Forum!

Partner Button
Add Stickiness To Your Site By Linking To This Professionally Managed Technical Forum.
Just copy and paste the
code below into your site.

Clyde38 (Electrical)
15 Jan 09 13:36
This is a simple spreadsheet to manipulate four physical quantities associated with motion calculations: position (x); its first derivative, velocity (v); its second derivative, acceleration (a), and of course, time (t). These quantities are related by several familiar equations, which can in turn be expanded by substitution to cover any combination.  The spreadsheet is protected without a password to avoid inadvertent destruction of the formulas.  Keep units consistent.
PNachtwey (Electrical)
11 Apr 09 17:32
Can you modify the spread sheet after you have posted it?   I have two equations that you might like to add.   I think it is best that the work sheet be kept in a place where it will not get lost in all the posts.

I use these equations when doing tech support when the customer says he wants to move a distance in so much time.   I can quickly calculate the velocity and average acceleration.

v=1.5*∆s/∆t
a=4.5*∆s/∆t2

These equations that the acceleration and deceleration ramp are 1/4 of the total distance, ∆s and that acceleration and deceleration ramp times are about 1/3 the total movement time, ∆t.   These equations assume the motion profile uses linear ramps.   However, most motion controllers use s curves so there are modifiers to use the average acceleration/deceleration  to calculate the peak values.
3rd order s curves 2.0 x average acceleration or deceleration
5th order s curves 1.5
7th order s curves 1.875
cosine      s curves 1.57 or PI/2

I have memorized so I can quickly bang out estimates on a calculator when talking on the phone.
Helpful Member!  Clyde38 (Electrical)
14 Apr 09 7:10
PNachtwey,
I'm not sure if the spread sheet can be modified after posting.  Does anyone know?  I have attached a spread sheet that addresses the "travel" portion of the velocity profile.  I'm not sure where I downloaded this from, so if you recognize it please give or take credit.
 

View Clyde Hancock's profile on LinkedIn

PNachtwey (Electrical)
14 Apr 09 11:05
Clyde, you should find a FTP site or some similar site where you can post your files and update them. I have my own FTP site so that I can correct and improve files.

This one needs some improvement.  This shows how one can generate 3rd order motion profiles using symbolic processing.  I used wxMaxima to generate the html. If you have wxMaxima installed you can just cut, paste and run the code.

Try doing this in a spread sheet:
ftp://ftp.deltacompsys.com/public/Maxima/Seg1234567.html
You need to wait a while for the images to download at the bottom of the file.  If you have your own website then you can easily add html files to it.

wxMaxima is not perfect but it is free and can do most math required to generate motion profiles.
 
Clyde38 (Electrical)
14 Apr 09 15:22
I remembered where I came across the spread sheet (Motion_Profile(1).xls).  It is from the "Mechanical engineering other topics" forum.  The post was from "volpegrigia (Mechanical)".  It was in response to a spread sheet I had offered (see attached).


thread404-238396: Linear Motion equations for trapezoidal move

PNachtwey,
I'm afraid that I'm not in a position to have my own FTP site, nor am I able to take advantage of the software you suggest (Scilab & wxMaxima).  Maybe some day, sounds interesting. .  

View Clyde Hancock's profile on LinkedIn

PNachtwey (Electrical)
14 Apr 09 15:56
Get a google or gmail account and post in your documents section.  Mine says I have used 65 mb out of 7350 mb.  That is a lot of storage that I have left.  You can even selectively provide access rights to each file.

wxMaxima and Scilab are free.

PLC people may use linear ramps but motion control people normally use s curves. 3rd order profiles are the lowest order to provide s curves.


 
Clyde38 (Electrical)
17 Apr 09 7:03
PNachtwey,
My willingness to embrace your suggestions about free software and ease of distribution is not the problem.  "IT" is the problem.  And I know it's hard to believe, I do not have personal access to the internet.  Alas, I must live within the guidelines established by the all wise "IT" department.  As for your comments about motion control, I think you have a lot to contribute and look forward to your participation.
yinyang

View Clyde Hancock's profile on LinkedIn

PNachtwey (Electrical)
17 Apr 09 11:21
I don't understand the problem.   IT is exists to serve engineering, production and marketing/sales, not the other way around.  You just need to make it clear to the IT guys and the management what IT's purpose is.
 
Clyde38 (Electrical)
17 Apr 09 13:07

Quote (Peter):

I don't understand the problem.
Neither do I.

Quote (Peter):

IT is exists to serve engineering, production and marketing/sales, not the other way around.  You just need to make it clear to the IT guys and the management what IT's purpose is.
Well said.  I'm off to set them (IT) straight!
 

View Clyde Hancock's profile on LinkedIn

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!

Back To Forum

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close