OCCRA
Go to Post Winning, the objective, the thing you can point to and say "See that? We want to do that. What can we do to make our program better, to improve our chances at that?" is what has grown FIRST from 28 teams in a high school gym to where it is today. - Joe G. [more]
Home
Go Back   Chief Delphi > FIRST > General Forum
CD-Media   CD-Spy  
portal register members calendar search Today's Posts Mark Forums Read FAQ rules

 
Reply
Thread Tools Rate Thread Display Modes
  #91   Spotlight this post!  
Unread 11-14-2017, 04:33 PM
Ether's Avatar
Ether Ether is offline
systems engineer (retired)
no team
 
Join Date: Nov 2009
Rookie Year: 1969
Location: US
Posts: 8,723
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: FRC Blog - 2018 Beta Teams, Brushless Motors, and More!


Does anybody know how many stator pole pairs and rotor pole pairs this 2018 FRC BLDC motor has??

Does anybody know if it's trapezoidally or sinusoidally wound?

Does it use 3 Hall sensors for commutation?

If so, is the tach signal derived from the 3 Hall sensors, or is there a separate tach sensor?


Oh... @Mark: what's causing the jerking in the video?





Last edited by Ether : 11-14-2017 at 04:58 PM.
Reply With Quote
  #92   Spotlight this post!  
Unread 11-14-2017, 04:45 PM
Mark McLeod's Avatar
Mark McLeod Mark McLeod is offline
Just Itinerant
AKA: Hey dad...Father...MARK
FRC #0358 (Robotic Eagles)
Team Role: Engineer
 
Join Date: Mar 2003
Rookie Year: 2002
Location: Hauppauge, Long Island, NY
Posts: 9,353
Mark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond repute
Re: FRC Blog - 2018 Beta Teams, Brushless Motors, and More!

Quote:
Originally Posted by Richard Wallace View Post
I can confirm that teams can purchase the crimp terminal that fits the harness connector housing (terminal is Molex 16-02-0103), and connect the Pin 1 Tachometer to a digital I/O.
Thanks, I ordered some terminals to use in testing.
__________________
2018 Beta Testing Results

Reply With Quote
  #93   Spotlight this post!  
Unread 11-14-2017, 04:48 PM
Mark McLeod's Avatar
Mark McLeod Mark McLeod is offline
Just Itinerant
AKA: Hey dad...Father...MARK
FRC #0358 (Robotic Eagles)
Team Role: Engineer
 
Join Date: Mar 2003
Rookie Year: 2002
Location: Hauppauge, Long Island, NY
Posts: 9,353
Mark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond repute
Re: FRC Blog - 2018 Beta Teams, Brushless Motors, and More!

Quote:
Originally Posted by Ether View Post
Oh... @Mark: what's causing the jerking in the video?
The torque of full reversal of shaft direction-full forward to full reverse and back again.
__________________
2018 Beta Testing Results


Last edited by Mark McLeod : 11-14-2017 at 04:50 PM.
Reply With Quote
  #94   Spotlight this post!  
Unread 11-14-2017, 04:56 PM
Ether's Avatar
Ether Ether is offline
systems engineer (retired)
no team
 
Join Date: Nov 2009
Rookie Year: 1969
Location: US
Posts: 8,723
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: FRC Blog - 2018 Beta Teams, Brushless Motors, and More!

Quote:
Originally Posted by Mark McLeod View Post
The torque of full reversal of shaft direction-full forward to full reverse and back again.
Judging from the relatively small reaction, the ratio of the moment of inertia of the rotor to the moment of inertia of the remaining (static) parts of the motor appears to be significantly smaller than other FRC motors... probably due to the lightweight rotor typical of brushless motors compared to the apparently more massive static parts of this BLDC motor compared to equivalently powerful brushed FRC motors.



Last edited by Ether : 11-14-2017 at 05:25 PM.
Reply With Quote
  #95   Spotlight this post!  
Unread 11-15-2017, 12:18 PM
Richard Wallace's Avatar
Richard Wallace Richard Wallace is offline
I live for the details.
FRC #3620 (Average Joes)
Team Role: Engineer
 
Join Date: Jan 2003
Rookie Year: 1996
Location: Southwestern Michigan
Posts: 4,061
Richard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond repute
Re: FRC Blog - 2018 Beta Teams, Brushless Motors, and More!

Quote:
Originally Posted by Ether View Post

Does anybody know how many stator pole pairs and rotor pole pairs this 2018 FRC BLDC motor has??

Does anybody know if it's trapezoidally or sinusoidally wound?

Does it use 3 Hall sensors for commutation?

If so, is the tach signal derived from the 3 Hall sensors, or is there a separate tach sensor?


Oh... @Mark: what's causing the jerking in the video?

The Dynamo has five electrical cycles per mechanical rotation; i.e., ten magnetic poles (5N, 5S).

It is single-tooth wound. There are twelve stator slots (thus twelve teeth) and each coil is wound on one tooth.

The resulting back-EMF and flux-linkage are sinusoidal functions of angular shaft position.

There are three Hall-effect sensors (surface mounted on the Greendrive circuit card) that produce commutation signals in response to a magnetized disc on the shaft, just below the card.

The Tachometer signal is derived from the Hall sensors; thus there are 15 Tach pulses per mechanical rotation (3 Halls x 5 pole-pairs).

Mark is right about the jerking seen in the video; it indicates relatively quick reversals. You are correct about the ratio of reversing torque to rotor inertia; this is an inherent advantage of in-runner type brushless PM motors, compared with conventional brush-type PMDC motors.

Mark, can you measure the transient DC supply current during rapid reversal? A 'scope trace would be nice to see. I can do that myself, but due to travel I will be away from my lab for a couple of weeks.
__________________
Richard Wallace

Mentor since 2011 for FRC 3620 Average Joes (St. Joseph, Michigan)
Mentor 2002-10 for FRC 931 Perpetual Chaos (St. Louis, Missouri)
since 2003

I believe in intuition and inspiration. Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution. It is, strictly speaking, a real factor in scientific research.
(Cosmic Religion : With Other Opinions and Aphorisms (1931) by Albert Einstein, p. 97)
Reply With Quote
  #96   Spotlight this post!  
Unread 11-15-2017, 02:26 PM
gerthworm's Avatar
gerthworm gerthworm is offline
Making the 1's and 0's
FRC #1736 (Robot Casserole)
Team Role: Mentor
 
Join Date: Jan 2015
Rookie Year: 2015
Location: Peoria, IL
Posts: 228
gerthworm is a glorious beacon of lightgerthworm is a glorious beacon of lightgerthworm is a glorious beacon of lightgerthworm is a glorious beacon of lightgerthworm is a glorious beacon of lightgerthworm is a glorious beacon of light
Re: FRC Blog - 2018 Beta Teams, Brushless Motors, and More!

Quote:
Originally Posted by MrRoboSteve View Post
Stronghold is a good example. You might have had a string that looked like:

ACEBF 00120 BADCE 02210

Where the letters represent the defense configuration and the digits represent the current crossing state, for both alliances.
This is what I was assuming as well when I first read it. Maybe something to indicate which goal is "Hot" and gets a bonus, maybe something right before autonomous which might make you change what strategy you use....

I predict the string will have the following properties:
1) Not be required to use to score points
2) Impart some advantage if you can display it to the driver, and allow the human to make decisions
3) Impart lots of advantage if you can parse it and use it to control the robot automatically

For the sake of crowd interaction, you'd probably also want the same data displayed to them (somehow) so they can understand why robots are doing certain things, or why (perhaps) the same action has different point values. It would definitely require some creativity to make the teams use the string, and not whatever the audience gets.

In any case, I fully plan on having our team log all strings received to file for later analysis.
Reply With Quote
  #97   Spotlight this post!  
Unread 11-15-2017, 03:01 PM
Waz Waz is offline
Strategy and programming mentor
AKA: Steve
FRC #2357 (System Meltdown)
Team Role: Mentor
 
Join Date: Feb 2013
Rookie Year: 2009
Location: Raymore, MO
Posts: 60
Waz will become famous soon enough
Re: FRC Blog - 2018 Beta Teams, Brushless Motors, and More!

Quote:
Originally Posted by gerthworm View Post
For the sake of crowd interaction, you'd probably also want the same data displayed to them (somehow) so they can understand why robots are doing certain things...
I think the ghosts the robots are chasing changing color will be sufficient.

Anyway.... I do think you are on the right track.

Steve

Edit: Hmmm.... human players in color changing ghost costumes....
Reply With Quote
  #98   Spotlight this post!  
Unread 11-15-2017, 06:06 PM
Ether's Avatar
Ether Ether is offline
systems engineer (retired)
no team
 
Join Date: Nov 2009
Rookie Year: 1969
Location: US
Posts: 8,723
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: FRC Blog - 2018 Beta Teams, Brushless Motors, and More!

Quote:
Originally Posted by Richard Wallace View Post
The Dynamo has five electrical cycles per mechanical rotation ... There are three Hall-effect sensors (surface mounted on the Greendrive circuit card) that produce commutation signals ... The Tachometer signal is derived from the Hall sensors; thus there are 15 Tach pulses per mechanical rotation (3 Halls x 5 pole-pairs).
5 electrical cycles per mechanical rotation
times
6 commutation steps per electrical cycle
equals
30 commutation steps per mechanical rotation
which means
30 Hall edge detections per mechanical rotation

So therefore the tach rating of "15" must mean 15 complete lo/hi cycles per mechanical rotation, or 30 rising+falling edges per mechanical rotation... so the edge-edge resolution would be 12 motor shaft degrees. Yes?

Quote:
The resulting back-EMF and flux-linkage are sinusoidal functions of angular shaft position.
I'm guessing the motor is sinusoidally commutated when it has an encoder?


Reply With Quote
  #99   Spotlight this post!  
Unread 11-15-2017, 08:45 PM
Richard Wallace's Avatar
Richard Wallace Richard Wallace is offline
I live for the details.
FRC #3620 (Average Joes)
Team Role: Engineer
 
Join Date: Jan 2003
Rookie Year: 1996
Location: Southwestern Michigan
Posts: 4,061
Richard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond repute
Re: FRC Blog - 2018 Beta Teams, Brushless Motors, and More!

Quote:
Originally Posted by Ether View Post
so the edge-edge resolution would be 12 motor shaft degrees. Yes?
Yes, if the Hall sensor signals are exactly 50% duty and exactly 24 degrees apart.

Quote:
Originally Posted by Ether View Post
I'm guessing the motor is sinusoidally commutated when it has an encoder?
Reasonable guess. We had in mind to do that when the motor was initially developed, many years ago. I will ask the engineers who support this motor now, when I see them.
__________________
Richard Wallace

Mentor since 2011 for FRC 3620 Average Joes (St. Joseph, Michigan)
Mentor 2002-10 for FRC 931 Perpetual Chaos (St. Louis, Missouri)
since 2003

I believe in intuition and inspiration. Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution. It is, strictly speaking, a real factor in scientific research.
(Cosmic Religion : With Other Opinions and Aphorisms (1931) by Albert Einstein, p. 97)
Reply With Quote
  #100   Spotlight this post!  
Unread 11-15-2017, 09:17 PM
Ether's Avatar
Ether Ether is offline
systems engineer (retired)
no team
 
Join Date: Nov 2009
Rookie Year: 1969
Location: US
Posts: 8,723
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: FRC Blog - 2018 Beta Teams, Brushless Motors, and More!

Quote:
Quote:
Originally Posted by Ether View Post
I'm guessing the motor is sinusoidally commutated when it has an encoder?
Reasonable guess. We had in mind to do that when the motor was initially developed, many years ago.
Ah. I was wondering about that.


Quote:
Originally Posted by Richard Wallace View Post
Quote:
Originally Posted by Ether View Post
... 6 commutation steps per electrical cycle ... so the edge-edge resolution would be 12 motor shaft degrees. Yes?
Yes, if the Hall sensor signals are exactly 50% duty and exactly 24 degrees apart.
Commutation accuracy affects motor efficiency. Like everything else in engineering it's a tradeoff I guess. What's a typical design goal for 6-step commutation accuracy? Or better yet, do you have access to the specs for the edge tolerances for the tach signal?


Reply With Quote
  #101   Spotlight this post!  
Unread 11-15-2017, 09:34 PM
Mark McLeod's Avatar
Mark McLeod Mark McLeod is offline
Just Itinerant
AKA: Hey dad...Father...MARK
FRC #0358 (Robotic Eagles)
Team Role: Engineer
 
Join Date: Mar 2003
Rookie Year: 2002
Location: Hauppauge, Long Island, NY
Posts: 9,353
Mark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond repute
Re: FRC Blog - 2018 Beta Teams, Brushless Motors, and More!

Tested the pins that aren't part of the cable harness.
The Tach (fast & slow traces below) and Direction pins work.

Tach video (stop->slow->fast)

There isn't a Quad encoder on the FIRST model, so nothing from those pins.
Attached Thumbnails
Click image for larger version

Name:	Tach-fast.jpg
Views:	55
Size:	1.14 MB
ID:	22665  Click image for larger version

Name:	Tach-slow.jpg
Views:	39
Size:	1.06 MB
ID:	22666  
__________________
2018 Beta Testing Results


Last edited by Mark McLeod : 11-16-2017 at 12:48 PM.
Reply With Quote
  #102   Spotlight this post!  
Unread 11-15-2017, 09:47 PM
marshall's Avatar
marshall marshall is offline
Discerning and exacting individual
FRC #0900 (The Zebracorns)
Team Role: Mentor
 
Join Date: Jan 2012
Rookie Year: 2003
Location: North Carolina
Posts: 2,073
marshall has a reputation beyond reputemarshall has a reputation beyond reputemarshall has a reputation beyond reputemarshall has a reputation beyond reputemarshall has a reputation beyond reputemarshall has a reputation beyond reputemarshall has a reputation beyond reputemarshall has a reputation beyond reputemarshall has a reputation beyond reputemarshall has a reputation beyond reputemarshall has a reputation beyond repute
Re: FRC Blog - 2018 Beta Teams, Brushless Motors, and More!

The shaft does come through the back side (once you remove the housing) and would make connecting an encoder on the rear easy enough but I'm not sure what will be legal to modify in terms of the housing for this motor... Definitely room for an aftermarket encoder though.
__________________
"La mejor salsa del mundo es la hambre" - Miguel de Cervantes
"The future is unwritten" - Joe Strummer
"Simplify, then add lightness" - Colin Chapman
Clarke's Laws
Reply With Quote
  #103   Spotlight this post!  
Unread 11-15-2017, 10:02 PM
Mark McLeod's Avatar
Mark McLeod Mark McLeod is offline
Just Itinerant
AKA: Hey dad...Father...MARK
FRC #0358 (Robotic Eagles)
Team Role: Engineer
 
Join Date: Mar 2003
Rookie Year: 2002
Location: Hauppauge, Long Island, NY
Posts: 9,353
Mark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond repute
Re: FRC Blog - 2018 Beta Teams, Brushless Motors, and More!

Quote:
Originally Posted by Richard Wallace View Post
Mark, can you measure the transient DC supply current during rapid reversal? A 'scope trace would be nice to see.
This was the trace on the DC supply during a rapid reversal.
(I was without a single thumbdrive, because I came from a sponsor event, so it's a real snapshot.)
Attached Thumbnails
Click image for larger version

Name:	P1100769.jpg
Views:	58
Size:	1.11 MB
ID:	22664  
__________________
2018 Beta Testing Results

Reply With Quote
  #104   Spotlight this post!  
Unread 11-15-2017, 10:31 PM
Richard Wallace's Avatar
Richard Wallace Richard Wallace is offline
I live for the details.
FRC #3620 (Average Joes)
Team Role: Engineer
 
Join Date: Jan 2003
Rookie Year: 1996
Location: Southwestern Michigan
Posts: 4,061
Richard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond reputeRichard Wallace has a reputation beyond repute
Re: FRC Blog - 2018 Beta Teams, Brushless Motors, and More!

Quote:
Originally Posted by Mark McLeod View Post
This was the trace on the DC supply during a rapid reversal.
(I was without a single thumbdrive, because I came from a sponsor event, so it's a real snapshot.)
Looks like the 'scope trace transient ranges +/- 40 mV. What does that correspond to, in Amperes? What kind of probe did you use?
__________________
Richard Wallace

Mentor since 2011 for FRC 3620 Average Joes (St. Joseph, Michigan)
Mentor 2002-10 for FRC 931 Perpetual Chaos (St. Louis, Missouri)
since 2003

I believe in intuition and inspiration. Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution. It is, strictly speaking, a real factor in scientific research.
(Cosmic Religion : With Other Opinions and Aphorisms (1931) by Albert Einstein, p. 97)
Reply With Quote
  #105   Spotlight this post!  
Unread 11-15-2017, 10:35 PM
Mark McLeod's Avatar
Mark McLeod Mark McLeod is offline
Just Itinerant
AKA: Hey dad...Father...MARK
FRC #0358 (Robotic Eagles)
Team Role: Engineer
 
Join Date: Mar 2003
Rookie Year: 2002
Location: Hauppauge, Long Island, NY
Posts: 9,353
Mark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond repute
Re: FRC Blog - 2018 Beta Teams, Brushless Motors, and More!

It was a 1x passive probe. I may have had the scope set on AC though.
I don't know what the input impedance of the probe was. It was borrowed.
I can play with it again tomorrow.

P.S.
I only have a stand-alone clamp meter. I'll have to borrow a probe to measure current.
__________________
2018 Beta Testing Results


Last edited by Mark McLeod : 11-16-2017 at 06:11 AM.
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 03:26 AM.

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