Go to Post We can help FIRST improve the system, but we can't just blame them and wait. - Siri [more]
Home
Go Back   Chief Delphi > ChiefDelphi.com Website > Extra Discussion
CD-Media   CD-Spy  
portal register members calendar search Today's Posts Mark Forums Read FAQ rules

 
Reply
Thread Tools Rate Thread Display Modes
  #1   Spotlight this post!  
Unread 17-01-2017, 18:42
Ari423's Avatar
Ari423 Ari423 is offline
LabVIEW aficionado and robot addict
AKA: The guy with the yellow hat
FRC #5987 (Galaxia)
Team Role: Mentor
 
Join Date: Mar 2015
Rookie Year: 2012
Location: Haifa, Israel
Posts: 656
Ari423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud of
paper: Optimal Gear Ratio Calculator

Thread created automatically to discuss a document in CD-Media.

Optimal Gear Ratio Calculator by Ari423
Reply With Quote
  #2   Spotlight this post!  
Unread 17-01-2017, 19:59
Ari423's Avatar
Ari423 Ari423 is offline
LabVIEW aficionado and robot addict
AKA: The guy with the yellow hat
FRC #5987 (Galaxia)
Team Role: Mentor
 
Join Date: Mar 2015
Rookie Year: 2012
Location: Haifa, Israel
Posts: 656
Ari423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud of
Re: paper: Optimal Gear Ratio Calculator

With an hour and a shower spent thinking of motor curves, I am prepared to release v1.5. The new spreadsheet is effectively the same, except these calculations are exact instead of guess and check. This makes the spreadsheet more efficient and slightly more accurate, but there is effectively no change in the output.
__________________
2017-present: Mentor FRC 5987
2017-present: CSA for FIRST in Israel
2012-2016: Member FRC 423
2013: Programmer
2014: Head Programmer, Wiring
2015: Head Programmer, Wiring
2016: Captain, Head Programmer, Wiring, Manipulator, Chassis, CAD, Business, Outreach (basically everything)


Reply With Quote
  #3   Spotlight this post!  
Unread 17-01-2017, 21:37
jojoguy10's Avatar
jojoguy10 jojoguy10 is offline
Programming/Controls Mentor
AKA: Joe Kelly
FRC #0997 (Spartan Robotics) and FRC #2990 (Hotwire Robotics)
Team Role: Mentor
 
Join Date: Jan 2013
Rookie Year: 2010
Location: Corvallis, OR
Posts: 296
jojoguy10 has a brilliant futurejojoguy10 has a brilliant futurejojoguy10 has a brilliant futurejojoguy10 has a brilliant futurejojoguy10 has a brilliant futurejojoguy10 has a brilliant futurejojoguy10 has a brilliant futurejojoguy10 has a brilliant futurejojoguy10 has a brilliant futurejojoguy10 has a brilliant futurejojoguy10 has a brilliant future
Re: paper: Optimal Gear Ratio Calculator

This is amazing and very simple to use! Thanks!
__________________

2013 and 2014 - Student (FRC#2990), Programmer (LabVIEW)
2015 and 2016 - Mentor (FRC#2990), Programming (LabVIEW)
2017-Current - Mentor (FRC#997), Controls/Programming (Java)
2015-Current - A/V Volunteer at Oregon events
Reply With Quote
  #4   Spotlight this post!  
Unread 18-01-2017, 09:41
Monochron's Avatar
Monochron Monochron is offline
Engineering Mentor
AKA: Brian O'Sullivan
FRC #4561 (TerrorBytes)
Team Role: Engineer
 
Join Date: Feb 2007
Rookie Year: 2002
Location: Research Triangle Park, NC
Posts: 917
Monochron has a reputation beyond reputeMonochron has a reputation beyond reputeMonochron has a reputation beyond reputeMonochron has a reputation beyond reputeMonochron has a reputation beyond reputeMonochron has a reputation beyond reputeMonochron has a reputation beyond reputeMonochron has a reputation beyond reputeMonochron has a reputation beyond reputeMonochron has a reputation beyond reputeMonochron has a reputation beyond repute
Re: paper: Optimal Gear Ratio Calculator

Do you have a good way to estimate load for a system? For instance, if you were building a flywheel for the Fuel, what is appropriate load? And would that load chance as you increase throughput?

And just to clarify, using the flywheel example, if you reduce voltage to a motor at this gear ratio to allow headroom to keep your flywheel speed steady, would this change the required gear ratio? Or are you still able to hit peak power with this given ratio at each voltage? My question is really, is the ratio needed for peak power at 12V the same ratio needed for peak power at 6V?
__________________


2016 | Innovation In Controls, Industrial Design, Quality Award, NC District - 4th Seed
Reply With Quote
  #5   Spotlight this post!  
Unread 18-01-2017, 10:41
Ari423's Avatar
Ari423 Ari423 is offline
LabVIEW aficionado and robot addict
AKA: The guy with the yellow hat
FRC #5987 (Galaxia)
Team Role: Mentor
 
Join Date: Mar 2015
Rookie Year: 2012
Location: Haifa, Israel
Posts: 656
Ari423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud of
Re: paper: Optimal Gear Ratio Calculator

Quote:
Originally Posted by Monochron View Post
Do you have a good way to estimate load for a system? For instance, if you were building a flywheel for the Fuel, what is appropriate load? And would that load chance as you increase throughput?

And just to clarify, using the flywheel example, if you reduce voltage to a motor at this gear ratio to allow headroom to keep your flywheel speed steady, would this change the required gear ratio? Or are you still able to hit peak power with this given ratio at each voltage? My question is really, is the ratio needed for peak power at 12V the same ratio needed for peak power at 6V?
For a system like an arm or a conveyor belt, you can usually find the load using a simple free body diagram. For a flywheel, however, the load depends on a lot of factors (including ball weight, wheel MoI, compression, ball compressability, wheel compressability, time in contact with ball, etc). You can guess the load for a given set up by gearing the flywheel 1:1 and measuring how much the wheel slows down when a ball is launched, but AFAIK there is no good way to calculate the load on a flywheel. I usually set up a prototype with an easily-changeable ratio (e.g. easily accessible belt/chain/gear reduction or VersaPlanetary) and change the gear ratio until I'm satisfied with the top speed and spin-up time.

In an ideal DC motor, doubling the voltage doubles the free speed, stall torque, free current, and stall current, and quadruples the max power. This also doubles the torque where max power occurs, so your gear ratio should be halved to remain at the max power point on the motor curve. Halving your gear ratio, combined with a doubling of the free speed, will result in a 4x increase in speed at that point. Conversely, if you only provide your motor with 6V instead of 12V, you should double your gear ratio to remain at max power, and your speed at that point will be quartered. JVN's first calculator allowed users to specify input voltage, but he took away this ability in the later versions. I think this is an important feature to have, so I will add it into the next version of my spreadsheet.
__________________
2017-present: Mentor FRC 5987
2017-present: CSA for FIRST in Israel
2012-2016: Member FRC 423
2013: Programmer
2014: Head Programmer, Wiring
2015: Head Programmer, Wiring
2016: Captain, Head Programmer, Wiring, Manipulator, Chassis, CAD, Business, Outreach (basically everything)


Reply With Quote
  #6   Spotlight this post!  
Unread 18-01-2017, 11:46
Ether's Avatar
Ether Ether is offline
systems engineer (retired)
no team
 
Join Date: Nov 2009
Rookie Year: 1969
Location: US
Posts: 8,104
Ether has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond repute
Re: paper: Optimal Gear Ratio Calculator

Quote:
Originally Posted by Monochron View Post
are you still able to hit peak power with this given ratio at each voltage? My question is really, is the ratio needed for peak power at 12V the same ratio needed for peak power at 6V?
Suppose you have a motor whose free speed is 6000 rpm at 12 volts when connected 1:1 with an unloaded flywheel.

Suppose your desired flywheel operating speed is 3000 rpm.

For the sake of simplicity, ignore parasitic losses and say it takes 6 volts to keep the motor (and flywheel) running at the desired 3000 rpm when the flywheel is unloaded.

If you have 12 volts available, you can get max power output from the motor (to respond to a load being applied to the flywheel) by changing the motor voltage from 6 volts to 12 volts.

But if all you have available is 6 volts (because of weak battery and heavy current draw elsewhere), then you cannot supply any additional power to the motor at 3000 rpm.



Reply With Quote
  #7   Spotlight this post!  
Unread 20-01-2017, 11:07
Ari423's Avatar
Ari423 Ari423 is offline
LabVIEW aficionado and robot addict
AKA: The guy with the yellow hat
FRC #5987 (Galaxia)
Team Role: Mentor
 
Join Date: Mar 2015
Rookie Year: 2012
Location: Haifa, Israel
Posts: 656
Ari423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud of
Re: paper: Optimal Gear Ratio Calculator

I just uploaded version 1.6.

Change log:
  • Added ability to vary motor voltage
  • Added more motors

Normally I would wait longer to include more changes before pushing an update, but I think this calculator is very useful when designing mechanisms so anyone who wants it should have the most recent version. Again, if you have any more suggestions, please let me know.
__________________
2017-present: Mentor FRC 5987
2017-present: CSA for FIRST in Israel
2012-2016: Member FRC 423
2013: Programmer
2014: Head Programmer, Wiring
2015: Head Programmer, Wiring
2016: Captain, Head Programmer, Wiring, Manipulator, Chassis, CAD, Business, Outreach (basically everything)


Reply With Quote
  #8   Spotlight this post!  
Unread 20-01-2017, 11:38
JesseK's Avatar
JesseK JesseK is offline
Expert Flybot Crasher
FRC #1885 (ILITE)
Team Role: Mentor
 
Join Date: Mar 2007
Rookie Year: 2005
Location: Reston, VA
Posts: 3,712
JesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond repute
Re: paper: Optimal Gear Ratio Calculator

This is a nifty calculator! Personally I appreciate quick updates based upon feedback. Release away!

I was apprehensive at first, since some of the other papers that come out which try to improve upon JVN's Calcuator often come at a price of complexity and/or mathematical results that don't match what JVN's models or what I've modeled/measured. Yet I put our 2017 climber setup into this spreadsheet and validated the 'optimum' and 'current-limited' gearing values match JVN's and also my own models.

So now that it's validated, it definitely saves a little bit of time when trying to figure out what gearing to aim for. Thanks for putting in the voltage changes - that helps when determining end-of-match characteristics.
__________________

Drive Coach, 1885 (2007-present)
CAD Library Updated 5/1/16 - 2016 Curie/Carver Industrial Design Winner
GitHub
Reply With Quote
  #9   Spotlight this post!  
Unread 20-01-2017, 18:49
Ari423's Avatar
Ari423 Ari423 is offline
LabVIEW aficionado and robot addict
AKA: The guy with the yellow hat
FRC #5987 (Galaxia)
Team Role: Mentor
 
Join Date: Mar 2015
Rookie Year: 2012
Location: Haifa, Israel
Posts: 656
Ari423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud of
Re: paper: Optimal Gear Ratio Calculator

Wow two updates in one day! It was brought to my attention that one of my formulas was slightly off (only noticeable for very small radii). The problem has been fixed and version 1.7 is now available. Please let me know if you find any more bugs or have any more suggestions.
__________________
2017-present: Mentor FRC 5987
2017-present: CSA for FIRST in Israel
2012-2016: Member FRC 423
2013: Programmer
2014: Head Programmer, Wiring
2015: Head Programmer, Wiring
2016: Captain, Head Programmer, Wiring, Manipulator, Chassis, CAD, Business, Outreach (basically everything)



Last edited by Ari423 : 20-01-2017 at 18:51.
Reply With Quote
  #10   Spotlight this post!  
Unread 28-01-2017, 20:31
CyborgBear CyborgBear is offline
Registered User
AKA: Ari
FRC #1677
Team Role: Mechanical
 
Join Date: Jan 2016
Rookie Year: 2011
Location: Michigan
Posts: 2
CyborgBear is an unknown quantity at this point
Re: paper: Optimal Gear Ratio Calculator

Would this work for calculating a gear ratio for a winch?
Reply With Quote
  #11   Spotlight this post!  
Unread 28-01-2017, 21:35
Ari423's Avatar
Ari423 Ari423 is offline
LabVIEW aficionado and robot addict
AKA: The guy with the yellow hat
FRC #5987 (Galaxia)
Team Role: Mentor
 
Join Date: Mar 2015
Rookie Year: 2012
Location: Haifa, Israel
Posts: 656
Ari423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud ofAri423 has much to be proud of
Re: paper: Optimal Gear Ratio Calculator

Quote:
Originally Posted by CyborgBear View Post
Would this work for calculating a gear ratio for a winch?
Absolutely! Use the spool's radius as the radius and the robot's weight as the load. Don't forget that the spool's radius will get bigger as the rope wraps and you probably want some factor of safety in the robot weight to account for dynamic loading. You will probably also want to use ~10V applied because the robot's battery can drop that low under load by the end of the match and you want to make sure you will still be able to climb even with a low battery. Once you set all the parameters, you can vary the number and type of motors to see how that affects your climbing speed (i.e. speed @ edge), optimal gear ratio, and stall current. Divide 5.8ft (height of climb sensor) minus the height of your climber on the ground (in feet) by the climbing speed to get the time it takes to climb. If you know what motors you want but the optimal gear ratio gives too high of a stall current, you can use the current limited column to calculate the gear ratio based on your desired stall current. Feel free to reach out if you have any more questions on how to use the spreadsheet or suggestions for improvements.
__________________
2017-present: Mentor FRC 5987
2017-present: CSA for FIRST in Israel
2012-2016: Member FRC 423
2013: Programmer
2014: Head Programmer, Wiring
2015: Head Programmer, Wiring
2016: Captain, Head Programmer, Wiring, Manipulator, Chassis, CAD, Business, Outreach (basically everything)


Reply With Quote
Reply


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 03:39.

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