Go to Post Some people need the 2x4. - Ether [more]
Home
Go Back   Chief Delphi > Technical > Technical Discussion
CD-Media   CD-Spy  
portal register members calendar search Today's Posts Mark Forums Read FAQ rules

 
 
 
Thread Tools Rate Thread Display Modes
Prev Previous Post   Next Post Next
  #6   Spotlight this post!  
Unread 01-11-2004, 11:56
Woodie Flowers Award
Ken Patton Ken Patton is offline
purple
FRC #0051 (Wings of Fire)
Team Role: Engineer
 
Join Date: Jul 2001
Rookie Year: 1997
Location: Pontiac, MI
Posts: 338
Ken Patton has a reputation beyond reputeKen Patton has a reputation beyond reputeKen Patton has a reputation beyond reputeKen Patton has a reputation beyond reputeKen Patton has a reputation beyond reputeKen Patton has a reputation beyond reputeKen Patton has a reputation beyond reputeKen Patton has a reputation beyond reputeKen Patton has a reputation beyond reputeKen Patton has a reputation beyond reputeKen Patton has a reputation beyond repute
Re: Manipulator designs

Some comments/advice:

If you can figure out a way to use springs (I suggest surgical tubing - its lightweight, durable, cheap, easy to install, fits a lot of designs) to counterbalance the mechanism, then the motor has a lot less work to do and you can gear it for the speed/accuracy tradeoff that you need. Think about springing the arm so that its weight is compensated for by the spring.

Friction is your enemy. Make sure you try to eliminate any sliding contacts and that you use bearings where possible or properly lubed bushings if you must.

When the robot tips over or runs into something, sometimes an arm might take extreme loads. Think about what is going to bend/break in that sort of situation, and make some spares. Lots of times the shaft on which the arm pivots is going to be the weak link.

There's nothing wrong with some deflections of the arm as it is being operated, but make sure the deflections don't screw up gear alignment or sprocket alignment.

We have used both gears and chain+sprockets as arm drive mechanisms, and both have worked satisfactorily. When selecting the motor and ratio, make sure to consider the counterbalancing.

Think about the need to hold position under situations where power is on and power is off. Do you need the arm to hold position or is it acceptable for the arm to sag? Some motors may be able to hold position by themselves, some may not. Some motors (van door and Globe come to mind) may seem "tight" at first but after use they are back-driveable and will probably not hold position under load.

Think about the need for very precise positioning of the arm - do you need to add a potentiometer or encoder to provide feedback to the controller? Can you write a control loop to take this feedback signal and convert it into a motor command? (search for threads on arm positioning and I think you'll find some good info on people's preferred methods)

Hopefully some of the experienced designers/builders of multi-segment arms might have some comments for us mere mortals....

hth,
Ken
 


Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -5. The time now is 03:46.

The Chief Delphi Forums are sponsored by Innovation First International, Inc.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright © Chief Delphi