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Search took 0.04 seconds. search: Posts Made By: Jared Russell
Forum: Programming 01-01-2017, 05:47 PM
Replies: 3
Views: 511
Posted By Jared Russell
Re: Theoretical Motion Profiling

You can obtain the equations and switching times necessary to compute any arbitrary trajectory point in constant time (per degree of freedom). (EDIT: Assuming your constraints (min/max velocity and...
Forum: Control System 12-31-2016, 09:59 PM
Replies: 5
Views: 336
Posted By Jared Russell
Re: Full State Feedback Question

What does your state space look like?

Problem #1 (integral windup on a unit step) is a fundamental limitation of linear feedback control; you can implement some sort of anti-windup mechanism if you...
Forum: Programming 12-29-2016, 07:12 PM
Replies: 34
Views: 2,279
Posted By Jared Russell
Re: Drivetrain PID tuning

Yep this makes sense and is a problem if you have large errors that the gyro needs to correct (which would also be a problem if you didn't have a gyro present). Usually, though, your yaw errors will...
Forum: Electrical 12-29-2016, 01:09 AM
Replies: 10
Views: 1,013
Posted By Jared Russell
Re: Wiring Talon SRX PID w/ Beam Break Sensor

The RoboRIO can timestamp pulses to about 25ns accuracy (in FPGA hardware, with no CPU overhead). With 3ms between pulses, this is an absolute ton (O(10^-6)) of precision.
Forum: General Forum 12-28-2016, 04:55 PM
Replies: 11
Views: 746
Posted By Jared Russell
Re: CIM Like motors for non-FRC use

Many BattleBots teams swear by Magmotors: http://magmotor.com/brushed/brushed.html
Forum: Programming 12-28-2016, 04:46 PM
Replies: 34
Views: 2,279
Posted By Jared Russell
Re: Drivetrain PID tuning

Do you mean angular displacement? (Gyros measure angular rate, which then must be integrated to obtain angular displacement). With commonly available FRC gyros based on an Invensense MPU-9250...
Forum: Programming 12-28-2016, 04:27 PM
Replies: 34
Views: 2,279
Posted By Jared Russell
Re: Drivetrain PID tuning

This is very common for mecanum drives. The rollers don't need to spin for forward movement or turns in place (depending on your drivebase geometry), but do need to spin for sideways translation. ...
Forum: Programming 12-28-2016, 02:13 PM
Replies: 34
Views: 2,279
Posted By Jared Russell
Re: Drivetrain PID tuning

You can definitely do motion profiling with a gyro.
Forum: Programming 12-21-2016, 11:36 PM
Replies: 34
Views: 2,279
Posted By Jared Russell
Re: Drivetrain PID tuning

Sensitivity to carpet variation is somewhat dependent on your drivetrain geometry and dynamics. A 6 wheel drive, dropped-center robot with a roughly central CoM and hard wheels is going to turn...
Forum: Electrical 12-18-2016, 08:06 PM
Replies: 10
Views: 1,013
Posted By Jared Russell
Re: Wiring Talon SRX PID w/ Beam Break Sensor

One quick word of warning...the Talon SRX calculates velocity as "change in position per 100ms". This works well for providing smooth velocity measurements with quadrature encoders (where you are...
Forum: Programming 12-16-2016, 12:03 PM
Replies: 6
Views: 738
Posted By Jared Russell
Re: Feed-forward coefficient for motion-constrained system

A feedforward gain is useful if you are doing velocity control, motion profiling, or compensating for some known external force (e.g. gravity). The latter two applications are applicable to an arm...
Forum: Pneumatics 12-14-2016, 11:11 AM
Replies: 19
Views: 1,575
Posted By Jared Russell
Re: Andymark 1.1 Compressor Data

Just curious...why 80-120?
Forum: Programming 12-11-2016, 06:00 PM
Replies: 22
Views: 2,537
Posted By Jared Russell
Re: Velocity PID(F) Best Practices - To Integrate, or Not To Integrate?

I assume flat moving average, but not positive.
Forum: Programming 12-11-2016, 04:21 PM
Replies: 22
Views: 2,537
Posted By Jared Russell
Re: Velocity PID(F) Best Practices - To Integrate, or Not To Integrate?

Note that the Talon SRX does velocity filtering for you (IIRC a 64-tap FIR filter, where each value is the change in position over the preceding 100 milliseconds, and the filter is updated at 1KHz).
Forum: Programming 12-08-2016, 01:45 AM
Replies: 22
Views: 2,537
Posted By Jared Russell
Re: Velocity PID(F) Best Practices - To Integrate, or Not To Integrate?

This is totally reasonable, and in practice you need an integrator if your loop rate is slow or you are concerned about the effects of rapid oscillation on the lifetime of your mechanical...
Forum: Programming 12-07-2016, 07:11 PM
Replies: 22
Views: 2,537
Posted By Jared Russell
Re: Velocity PID(F) Best Practices - To Integrate, or Not To Integrate?

We didn't use integral gain, but we did use some derivative gain to lessen the initial overshoot, and a 36V/s rate limit to smooth things out a...
Forum: Programming 12-05-2016, 11:48 PM
Replies: 22
Views: 2,537
Posted By Jared Russell
Re: Velocity PID(F) Best Practices - To Integrate, or Not To Integrate?

I agree wholeheartedly...I'm hopeful that this will be improved for 2017.
Forum: Technical Discussion 11-30-2016, 11:36 PM
Replies: 108
Views: 28,152
Posted By Jared Russell
Re: Team 254 Presents: Dropshot Technical Binder 2016

Whoa, this thread died before I saw these questions



Nothing too polished here, just prototype-driven iteration. We knew that our overall design concept would not result in a whole lot of contact...
Forum: Motors 11-21-2016, 10:03 PM
Replies: 59
Views: 5,499
Posted By Jared Russell
Re: NeveRest 60 in FRC

NeveRest 60 is 11.5W max power.

Globe Motor was 47W.

BAG motor is 149W.
Forum: Programming 11-17-2016, 03:49 PM
Replies: 22
Views: 2,537
Posted By Jared Russell
Re: Velocity PID(F) Best Practices - To Integrate, or Not To Integrate?

Bang-bang control is a proven and effective method of velocity control (especially for systems with considerable inertia, like flywheels). The second method (which is more common in mobile robotics)...
Forum: Programming 11-17-2016, 11:57 AM
Replies: 1
Views: 1,144
Posted By Jared Russell
Re: Team 254 Motion Profiling Variables

Yes, these are 2d coordinate points. The robot starts at (0, 0). Positive x is straight ahead, positive y is to the left. We used inches for units, but as long as you are consistent throughout,...
Forum: Programming 11-16-2016, 12:13 PM
Replies: 31
Views: 2,834
Posted By Jared Russell
Re: 30fps Vision Tracking on the RoboRIO without Coprocessor

Full HSV requires evaluating conditions to compute hue, but if you use (ex.) a green LED ring, you can pretty well assume that if green is not the most abundant component for any given pixel then hue...
Forum: Programming 11-16-2016, 12:07 PM
Replies: 31
Views: 2,834
Posted By Jared Russell
Re: 30fps Vision Tracking on the RoboRIO without Coprocessor

Most industrial vision system applications use a pretty controlled background, so intensity-based detection and segmentation works well and has few false positives. Pointing a camera towards the...
Forum: Programming 11-14-2016, 11:57 AM
Replies: 31
Views: 2,834
Posted By Jared Russell
Re: 30fps Vision Tracking on the RoboRIO without Coprocessor

This is definitely true. The resolution you need is a function of range, target geometry, angle of incidence, camera field of view, the frequency and type of non-target objects that pass the...
Forum: Programming 11-14-2016, 11:49 AM
Replies: 31
Views: 2,834
Posted By Jared Russell
Re: 30fps Vision Tracking on the RoboRIO without Coprocessor

This is very cool, though I'm not (yet) convinced that you can get 30fps @ 640x480 with an RGB USB camera using a "conventional" FRC vision algorithm. But now you have me thinking...

Why I think...
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