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-   -   2012 FRC Team 1717 Uncut (http://www.chiefdelphi.com/forums/showthread.php?t=106880)

MichaelBick 13-06-2012 20:42
Re: 2012 FRC Team 1717 Uncut
 
Quote:
Originally Posted by JamesTerm (Post 1173759)
Thanks for the heads up and this was an idea we considered for last year's game (especially since most of the time the robot was facing you), but given what is said here... I feel there is a missing piece to the puzzle... A gyro can give delta's of angular acceleration but what can ensure the robot's heading is calibrated? Is there some point of reference that can be sensed dynamically while rotating?

I'll be anxious to hear how/if they solved that problem. :)
Yes magnetometer. But it lags, so you have to run it through a filter.

1717 has inspired me. They are truly one of the best teams in FIRST, and I am so glad that they have finally found the spotlight(if they had not already by showing up on Einstein in 2009). The quality of each and every robot they make is amazing.

Swerve is a very hard drivetrain. They make it look very easy. However, even if they do not release their CAD, I highly recommend to any teams looking into swerve that you look at 973's Emperor Swerve. I feel that it is mechanically equal to 1717's drivetrain. You should furthermore look at 973's CADs regardless, because they are an example of how to make a competitive robot.

Again, to all teams looking into swerve: it is a very hard drivetrain. Adam has even said that they are likely not going to compete with a swerve again next year. The amount of driver practice, programming, and build time required just to get a competitive swerve, is unachievable than 95% of teams, and furthermore not worth the return on investment those teams. Prototyping in the offseason is a must, and don't expect to compete with it after only a year of prototyping. 6/8 wheel drive is an absolutely competitive drivetrain, that I and many other teams, including powerhouses, will recommend.

Akash Rastogi 13-06-2012 21:10
Re: 2012 FRC Team 1717 Uncut
 
Quote:
Originally Posted by MICHAELABICK (Post 1173824)
Yif they had not already by showing up on Einstein in 2009)
Small correction, they were Galileo finalists and the CMP quality award winners.

akoscielski3 13-06-2012 21:25
Re: 2012 FRC Team 1717 Uncut
 
Quote:
Originally Posted by Akash Rastogi (Post 1173828)
Small correction, they were Galileo finalists and the CMP quality award winners.
yea, if you read their book... lol

jakemochas 13-06-2012 21:47
Re: 2012 FRC Team 1717 Uncut
 
Quote:
Originally Posted by msimon785 (Post 1173619)
I know from our mentors that they utilize their gyro to make the controls driver-relative and thus location-aware. In other words, regardless of the orientation of the robot, if the driver moves the joystick forward, the robot will travel away from him. This was done to make it more intuitive to the driver. With that said, I only know this of their 2011 (non-independent) swerve system, and even then you will need a 1717 student to confirm and expand on that.
Last year and in all previous years, we did not utilize a gyro with our swerve drivetrain. As a result, all previous robots have been driven from a robot-centric view.

Quote:
Originally Posted by JamesTerm (Post 1173613)
All of this is absolutely amazing... I gotta ask... would you mind sharing how the controls are mapped to the drive. In particular the spin and pivot. (We like to call this slide turning). Was it intuitive to the driver and useful to have and use?

Because the drivetrain was capable of such complex maneuvers, a goal for the programming team this year was to make the robot as easy to drive as possible. This was incredibly important because we are all seniors and our team has rookie drivers every year. Almost everyone on our team has been capable of driving the robot in a rudimentary fashion when using the joysticks for the first time. They really enjoy the simplicity and the intuitive nature of the controls.

This year, the simplicity of the driver’s controls were particularly important. Our drivers had never driven a FIRST robot because we were moving into our new facility. As a result, we were not able to give them the proper introduction to driving a robot. The first time our drivers were able to drive a robot was 2 weeks after build season ended when we finished our practice robot. Before the LA Regional, our drivers had less than 10 hours of driving practice.

The layout for the driver’s controls and programming implementation are as follows:

The driver has 2 joysticks to control the drivetrain. Like last year, the left is used to translate the robot in any direction and the right joystick’s x-axis is used for rotating the robot. Unlike last year, however, this year we used a gyro to make the controls for the drive field-centric. If our driver pushes the joystick away from himself, the robot moves away from him regardless of the robot’s orientation.

The gyro makes basic driving easier, but it also makes it possible to spin while driving. All the driver does to spin while driving, or “slide turn”, is move the left and right joysticks together. The robot moves with the direction and speed of the left joystick. The robot’s spin speed and spin direction are dictated by the right joystick. Spinning while driving has become an integral part of all of our driver’s maneuvers. The spinning while driving made it much easier to avoid defensive robots, collect balls, lineup for shots, and make final adjustments on the bridge.

To pivot around a specific wheel, we used 4 buttons that each correspond to one of the wheel modules on the robot. When the driver holds down one of those buttons, the right joystick’s spin commands adjust to pivot around that wheel. The pivots about a single wheel were used less frequently, but helped in situations where we wanted to maneuver around a robot that was pushing us or line up at the fender after collecting a ball from in front of the fender.

Spinning while driving became natural for our drivers because of its implementation and joystick mapping. Our robot was able to perform maneuvers in the game that were not possible in previous years. An example of our robot’s maneuverability can be seen in the slalom swerve video from our original post.

http://www.youtube.com/watch?v=p9WHMssEF4U

CalTran 13-06-2012 22:05
Re: 2012 FRC Team 1717 Uncut
 
Well...they technically showed up on Einstein as the Galileo back up bot, and sat on the side of the field...

jakemochas 14-06-2012 13:18
Re: 2012 FRC Team 1717 Uncut
 
Quote:
Originally Posted by msimon785 (Post 1173619)
I know from our mentors that they utilize their gyro to make the controls driver-relative and thus location-aware. In other words, regardless of the orientation of the robot, if the driver moves the joystick forward, the robot will travel away from him. This was done to make it more intuitive to the driver. With that said, I only know this of their 2011 (non-independent) swerve system, and even then you will need a 1717 student to confirm and expand on that.
Last year and in all previous years, we did not utilize a gyro with our swerve drivetrain. As a result, all previous robots have been driven from a robot-centric view.

Quote:
Originally Posted by JamesTerm (Post 1173613)
All of this is absolutely amazing... I gotta ask... would you mind sharing how the controls are mapped to the drive. In particular the spin and pivot. (We like to call this slide turning). Was it intuitive to the driver and useful to have and use?
Because the drivetrain was capable of such complex maneuvers, a goal for the programming team this year was to make the robot as easy to drive as possible. This was incredibly important because we are all seniors and our team has rookie drivers every year. Almost everyone on our team has been capable of driving the robot in a rudimentary fashion when using the joysticks for the first time. They really enjoy the simplicity and the intuitive nature of the controls.

This year, the simplicity of the driver’s controls were particularly important. Our drivers had never driven a FIRST robot because we were moving into our new facility. As a result, we were not able to give them the proper introduction to driving a robot. The first time our drivers were able to drive a robot was 2 weeks after build season ended when we finished our practice robot. Before the LA Regional, our drivers had less than 10 hours of driving practice.

The layout for the driver’s controls and programming implementation are as follows:

The driver has 2 joysticks to control the drivetrain. Like last year, the left is used to translate the robot in any direction and the right joystick’s x-axis is used for rotating the robot. Unlike last year, however, this year we used a gyro to make the controls for the drive field-centric. If our driver pushes the joystick away from himself, the robot moves away from him regardless of the robot’s orientation.

The gyro makes basic driving easier, but it also makes it possible to spin while driving. All the driver does to spin while driving, or “slide turn”, is move the left and right joysticks together. The robot moves with the direction and speed of the left joystick. The robot’s spin speed and spin direction are dictated by the right joystick. Spinning while driving has become an integral part of all of our driver’s maneuvers. The spinning while driving made it much easier to avoid defensive robots, collect balls, lineup for shots, and make final adjustments on the bridge.

To pivot around a specific wheel, we used 4 buttons that each correspond to one of the wheel modules on the robot. When the driver holds down one of those buttons, the right joystick’s spin commands adjust to pivot around that wheel. The pivots about a single wheel were used less frequently, but helped in situations where we wanted to maneuver around a robot that was pushing us or line up at the fender after collecting a ball from in front of the fender.

Spinning while driving became natural for our drivers because of its implementation and joystick mapping. Our robot was able to perform maneuvers in the game that were not possible in previous years. An example of our robot’s maneuverability can be seen in the slalom swerve video from our original post.

CalTran 14-06-2012 14:09
Re: 2012 FRC Team 1717 Uncut
 
Quote:
Originally Posted by jakemochas (Post 1173933)
Spinning while driving has become an integral part of all of our driver’s maneuvers. The spinning while driving made it much easier to avoid defensive robots, collect balls, lineup for shots, and make final adjustments on the bridge.

The pivots about a single wheel were used less frequently, but helped in situations where we wanted to maneuver around a robot that was pushing us or line up at the fender after collecting a ball from in front of the fender.

An example of our robot’s maneuverability can be seen in the slalom swerve video from our original post.
I've watched that video a few times, but do you happen to have a specific match that you think showcases this feature the best? I'd like to see not only how your team used it, but how a team would react to this maneuver happening.

JamesTerm 14-06-2012 15:38
Re: 2012 FRC Team 1717 Uncut
 
Quote:
Originally Posted by jakemochas (Post 1173933)
Unlike last year, however, this year we used a gyro to make the controls for the drive field-centric. If our driver pushes the joystick away from himself, the robot moves away from him regardless of the robot’s orientation.
Thanks for giving the layout and it makes sense given that it is possible to drive field centric.

I have to ask... what language are you using to program?
I looked into the gyro class (I use c++ wind-river) and found this:

Code:
/**
 * Reset the gyro.
 * Resets the gyro to a heading of zero. This can be used if there is significant
 * drift in the gyro and it needs to be recalibrated after it has been running.
 */
void Gyro::Reset()
How did you solve the problem for potential drift? Is there something you calibrated against to keep it in line? How reliable can it keep its heading? Does it matter where the gyro is placed on the robot?


Also I want to make a correction from the last entry... "spin and pivot" is different from "slide turns". Watch this video (sorry some of you have seen this before).

www.termstech.com/files/SwerveDriveDemo.wmv

The slide turns... are turns made in slide mode where slide mode is a toggle button pressed. This is robot-centric and does not require a gyro... the way it works is that there is a fundamental desired linear and angular velocity that get translated. The slide mode is a simpler case of not applying centripetal force to keep the robot driving in a straight line. It is like playing asteroids using the thrust button. Since we apply force for centripetal force we can be aware of how much force is applied at all times and dampen the overall velocity (without sacrificing direction) to stay within a limited amount of force. This helps prevent the robot from an accidental tip over... and with our high CG this year... that comes in handy.

jakemochas 14-06-2012 18:58
Re: 2012 FRC Team 1717 Uncut
 
Quote:
Originally Posted by MICHAELABICK (Post 1173824)
Yes magnetometer. But it lags, so you have to run it through a filter.
We did not use a magnetometer. We only used a gyro. Our implementation of field-centric swerve drive with a gyro can be seen below.

Quote:
Originally Posted by Jared341 (Post 1173648)
What gyro do you use for field-relative control?
Quote:
Originally Posted by JamesTerm (Post 1173952)
Does it matter where the gyro is placed on the robot?
We ended up using a SparkFun gyro (product# 9094), but we were not satisfied with performance of this gyro with the cRIO’s analog interface. It is important that you mount the gyro in a spot on the robot that has little vibration because it is very susceptible to noise. I would recommend mounting it to the frame of your robot.

Quote:
Originally Posted by JamesTerm (Post 1173759)
Thanks for the heads up and this was an idea we considered for last year's game (especially since most of the time the robot was facing you), but given what is said here... I feel there is a missing piece to the puzzle... A gyro can give delta's of angular acceleration but what can ensure the robot's heading is calibrated? Is there some point of reference that can be sensed dynamically while rotating?
I'll be anxious to hear how/if they solved that problem. :)
Quote:
Originally Posted by JamesTerm (Post 1173952)
I have to ask... what language are you using to program?

How did you solve the problem for potential drift? Is there something you calibrated against to keep it in line? How reliable can it keep its heading? Does it matter where the gyro is placed on the robot?
The gyro measures angular acceleration, which we use to determine the orientation of our robot. When the robot is booting up, it calibrates the sensor by measuring the analog voltage when the robot is motionless and establishes that as a baseline. We used the C++ Gyro class provided by WPILib to integrate the analog channel and show us our current angle. We know the orientation of the robot at the beginning of the match and zero it then.

Throughout the season, we tried a variety of 500 degree/second gyros that were attached to the analog port on the cRIO. In the end, though, we were not satisfied with any of the gyros. The gyros had significant drift, asymmetrical behavior, and were extremely sensitive to collisions on the field. In about 45 seconds, the gyro would drift by as much as 60 degrees and the advantages of the gyro would be lost.

In order to solve this problem, the drivers rezeroed the gyro every time they lined up for a shot at the fender or the key (the Reset() function). For all of our shots, the robot faced directly forward, which gave the perfect opportunity to rezero. Between each shot, the gyro was good enough to keep the robot oriented in the correct direction. Also, we trained our drivers in a no-gyro mode (robot-centric) in the event of a gyro failure. This training paid off. Even though we had gyro calibration failures in each regional event, the robot appeared like it was operating normally to the outside observer.

In the end, we were not satisfied with the performance of the gyro. One of our goals for next year is to find a better gyro solution for our swerve drive system.

AdamHeard 14-06-2012 20:08
Re: 2012 FRC Team 1717 Uncut
 
Quote:
Originally Posted by jakemochas (Post 1173967)
In order to solve this problem, the drivers rezeroed the gyro every time they lined up for a shot at the fender or the key (the Reset() function). For all of our shots, the robot faced directly forward, which gave the perfect opportunity to rezero. Between each shot, the gyro was good enough to keep the robot oriented in the correct direction. Also, we trained our drivers in a no-gyro mode (robot-centric) in the event of a gyro failure. This training paid off. Even though we had gyro calibration failures in each regional event, the robot appeared like it was operating normally to the outside observer.

In the end, we were not satisfied with the performance of the gyro. One of our goals for next year is to find a better gyro solution for our swerve drive system.
We used a gyro in the same fashion for pretty much the same drivetrain and agree 100% with your comments. We also zeroed on shots and are looking into better implementations for a gyro.

JamesTerm 14-06-2012 22:38
Re: 2012 FRC Team 1717 Uncut
 
Quote:
Originally Posted by MICHAELABICK (Post 1173824)
Yes magnetometer. But it lags, so you have to run it through a filter.
Woe! ok can you elaborate on this? So is there a particular part I can research, and is it legal? This is some exciting stuff! :)

JamesTerm 14-06-2012 23:04
Re: 2012 FRC Team 1717 Uncut
 
Quote:
Originally Posted by jakemochas (Post 1173967)
In order to solve this problem, the drivers rezeroed the gyro every time they lined up for a shot at the fender or the key (the Reset() function). For all of our shots, the robot faced directly forward, which gave the perfect opportunity to rezero. Between each shot, the gyro was good enough to keep the robot oriented in the correct direction.
Ah ha! Oh that's cool. When the robot faced directly forward, did you take that moment to have a keying solution? (see below)

We call a keying solution when we would find a good place to "key" our position and orientation. From that we calibrated where we were on the field, and then could use the feedback from the encoders to make it possible to move around the key to fender area for a little while and still be position aware. We'd interpolate evenly spaced key points in an error correction grid and calibrate shots from those points (i.e. 3x3 grid). IIRC I think Jared (341) used an error correction table as well.

While I'm here... I noticed the tune of the shooter speed sounded very consistent. Did you PID the rate of the shooter to an encoder, and did you use victors or Jags? It seems to lock on to the rate very well!


Quote:
Originally Posted by jakemochas (Post 1173967)
In the end, we were not satisfied with the performance of the gyro. One of our goals for next year is to find a better gyro solution for our swerve drive system.
So what are your thoughts on using a Magnetometer? I'm googling like crazy right now about this! ;)

rsisk 15-06-2012 00:10
Re: 2012 FRC Team 1717 Uncut
 
Something that I've been wondering, what on your bot was stabbing the fender in LA?

jakemochas 15-06-2012 02:22
Re: 2012 FRC Team 1717 Uncut
 
Quote:
Originally Posted by rsisk (Post 1174023)
Something that I've been wondering, what on your bot was stabbing the fender in LA?
Our barrier-crossing mechanism was deployed when we lined up for a fender shot. That only happened once in all of our competitions and driver practices. You can see the barrier-crossing mechanism in a video at the beginning of the thread.

Siri 15-06-2012 07:44
Re: 2012 FRC Team 1717 Uncut
 
Quote:
Originally Posted by jakemochas (Post 1173813)
This year, however, with the new motor allowance, we were able to allocate 8 motors to the drive and still have enough high quality/power motors remaining to effectively power all of our remaining mechanisms...
Can I ask what drive & steering motors did you use in 2009-2012?




Anyone who hasn't, read The New Cool. I keep remembering this one line as I read this thread:
"We're Team 1717. Nobody knows us here."
...1717 Coach Amir Abo-Shaeer at the 2009 FRC World Championship

How quickly things can change when you're truly dedicated.


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