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Search took 0.04 seconds. search: Posts Made By: Ether
Forum: Rules/Strategy Today, 02:58 PM
Replies: 6
Views: 345
Posted By Ether
Re: paper: Comparison of Statistical Prediction Models

If you haven't read the following thread in a while, you might want to revisit it and see if any of wgardner's suggestions might be worth comparing to your other...
Forum: Programming 01-01-2017, 08:40 PM
Replies: 2
Views: 364
Posted By Ether
Re: fast OPR computation with R using sparse matrix technology

Look at the timings in the log file in the ZIP file (https://www.chiefdelphi.com/media/papers/download/4810).

Then compare those to this (https://www.chiefdelphi.com/forums/showpost.php?p=1612051).
Forum: Programming 01-01-2017, 06:17 PM
Replies: 2
Views: 364
Posted By Ether
fast OPR computation with R using sparse matrix technology

Thread created for discussion of this paper (https://www.chiefdelphi.com/media/papers/3310).
Forum: Programming 01-01-2017, 05:56 PM
Replies: 3
Views: 511
Posted By Ether
Re: Theoretical Motion Profiling

For students who may be interested: There's a recent thread here (https://www.chiefdelphi.com/forums/showthread.php?t=152790) which has a discussion and some simple examples of solving Initial Value...
Forum: Scouting 12-31-2016, 09:26 PM
Replies: 29
Views: 2,935
Posted By Ether
Re: R Package for Downloading FIRST API Data

Your results look about right for R code that uses dense matrix...
Forum: Scouting 12-31-2016, 09:23 PM
Replies: 6
Views: 449
Posted By Ether
Re: R, OPR, etc

If you need any links to posts and threads here on CD that explain the math underlying the computation of OPR let me know.
Forum: Scouting 12-31-2016, 09:11 PM
Replies: 29
Views: 2,935
Posted By Ether
Re: R Package for Downloading FIRST API Data

I am getting ~0.93 seconds on a 10-year-old Pentium D desktop running 32-bit XP with 1G RAM.
Forum: Scouting 12-31-2016, 07:06 PM
Replies: 6
Views: 449
Posted By Ether
Re: R, OPR, etc

https://www.chiefdelphi.com/forums/showpost.php?p=1624147&postcount=24
Forum: Scouting 12-31-2016, 04:48 PM
Replies: 29
Views: 2,935
Posted By Ether
Re: R Package for Downloading FIRST API Data

@ Stacy: thanks for posting this. I just send you a PM.
Forum: Programming 12-31-2016, 11:39 AM
Replies: 34
Views: 2,279
Posted By Ether
Re: Drivetrain PID tuning

It might be helpful to slightly modify one line of code:

float delta_angle = desired_heading - gyro_heading; // This is our error in alignment

float delta_angle = MATH.IEEEremainder(desired_heading...
Forum: Math and Science 12-30-2016, 10:42 AM
Replies: 31
Views: 835
Posted By Ether
Re: numerical solution of differential equations

It's not clear what the point of that spreadsheet is. You are using the analytical solution for x' to compute an Euler step.

You weren't intending to compare that result to the Midpoint method,...
Forum: Electrical 12-29-2016, 09:37 PM
Replies: 10
Views: 1,013
Posted By Ether
Re: Wiring Talon SRX PID w/ Beam Break Sensor

Hi neilh.. I see this is your first post. Welcome to Chief Delphi !
Forum: Math and Science 12-26-2016, 12:03 AM
Replies: 31
Views: 835
Posted By Ether
Re: numerical solution of differential equations

You're still struggling with this, but I can't point out your error since you didn't post your spreadsheet.

I think you may have overlooked my earlier post #24...
Forum: Math and Science 12-25-2016, 07:50 AM
Replies: 31
Views: 835
Posted By Ether
Re: numerical solution of differential equations

Yes, but you got x and t confused.

given:

x(t) = 1/4*t^3 + 1

... take time derivative of x(t) to get:

x'(t) = (3/4)*t^2
Forum: Math and Science 12-24-2016, 09:04 PM
Replies: 31
Views: 835
Posted By Ether
Re: numerical solution of differential equations

OK.

x(t) = 1/4*t^3 + 1 is the analytical solution to the Initial Value Problem

a(t) = sqrt(3*v(t))

with initial values*

x(0.01) = 1.00000025
Forum: Math and Science 12-24-2016, 05:21 PM
Replies: 31
Views: 835
Posted By Ether
Re: numerical solution of differential equations

In post14 you wrote:


I am assuming what you actually meant by that is

x(t) = 1/4*t^3 + 1

Is that correct?

If so, then in order to investigate the performance of Euler vs Midpoint numerical...
Forum: Math and Science 12-23-2016, 09:57 PM
Replies: 31
Views: 835
Posted By Ether
Re: numerical solution of differential equations

where did you get the revised accel formula?
Forum: Math and Science 12-23-2016, 09:19 PM
Replies: 31
Views: 835
Posted By Ether
Re: numerical solution of differential equations

@Mark: Where did you get the accel formula for columns D and G.
Forum: Math and Science 12-23-2016, 03:00 PM
Replies: 31
Views: 835
Posted By Ether
Re: numerical solution of differential equations

derivation of k1 k2 k3
Forum: Math and Science 12-23-2016, 12:41 PM
Replies: 31
Views: 835
Posted By Ether
Re: numerical solution of differential equations

Vn+1 = Vn + An∙dt;
Xn+1 = Xn + Vn+1∙dt;

Maybe provides some insight: the above is algebraically equivalent to

Vn+1 = Vn + An∙dt;
Xn+1 = Xn + dt∙(Vn+Vn+1)/2 + ½∙An∙dt2
Forum: Math and Science 12-23-2016, 12:45 AM
Replies: 31
Views: 835
Posted By Ether
Re: numerical solution of differential equations

Unless I was careless with the algebra (it happens when I'm tired),
Steve's catapult (https://www.chiefdelphi.com/forums/showthread.php?t=152739) can be modeled with an ODE of the form

θ'' =...
Forum: Java 12-23-2016, 12:26 AM
Replies: 7
Views: 303
Posted By Ether
Re: Confusing Issues with Swerve

An easy way to test your swerve inverse kinematics code to confirm that it is doing the computations correctly is to feed it several [fwd,str,rcw] triplets and compare the resulting wheel speeds and...
Forum: Java 12-22-2016, 11:48 PM
Replies: 7
Views: 303
Posted By Ether
Re: Confusing Issues with Swerve

FTFY.
Forum: Math and Science 12-22-2016, 10:44 PM
Replies: 31
Views: 835
Posted By Ether
Re: numerical solution of differential equations

Where did you come by this understanding?



You could easily modify the XLS I posted to test this hypothesis :)
Forum: Math and Science 12-22-2016, 04:52 PM
Replies: 31
Views: 835
Posted By Ether
Re: numerical solution of differential equations

Yes I am very much looking forward to the Kickoff.

And I have some long-overdue hardware to return to you :)
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