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Jim Riggs


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Missile Defense Agency - Advanced Technology Group

230 total contributions since 2017

Developing simulations for the Missile Defense Agency - Advanced Technology group
30+ years experience in missiles, smart munitions and other aerodynamic systems. Specializing in systems engineering, aerospace systems design, simulation and modeling, aerodynamics, and numerical analysis.

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Answered
Why is ode45 changing the value of the state variable between calls to my dynamics function?
ode45 implements the Dormand-Prince method which is an embedded 4th / 5th order Runge-Kutta method. For every "step" in the sol...

1 day ago | 0

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Answered
Implement friction into a model, related to the velocity. (Missile Launch)
This question is familiar. look here.

3 days ago | 0

Answered
How to make a marker circle bold?
plot(x, y, 'ro', 'linewidth',2);

4 days ago | 0

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Answered
how can i resolve this equation Runge kutta method
Ths is the equation for a parabola. y'' = -1 y' = -y y = -1/2 y^2 No need for a numerical approximation.

6 days ago | 0

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Missile Lauch friction gamma factor - Output deviating from desired output, please help!
Step 1: Draw a free body diagram that shows the body with all of the forces that act on it and the coordinate frame(s) that are...

8 days ago | 0

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Answered
How to calculate the slope from geopraphical coordinates?
First of all, you should consider the relationship between the WGS84 lat/lon/alt and the ECEF frame. Altitude is perpendicular ...

10 days ago | 1

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calculate rotation matrix in 3D
I'll assume that we make the reference frame right-handed by negating the axis_3 vector such that axis_1 = [2.7239 -0.2014 -...

20 days ago | 1

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Translational motion of a rotating object.
To begin, Chasles' theorem states that translational motion and rotational motion obey the law of superposition. Therefore, you...

28 days ago | 0

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change variable value based on other variable in if loop
Your input command is requesting a string input: in1 = input('first: ','s'); in2 = input('second: ','s'); This results in in1...

28 days ago | 1

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Answered
I don't know the problem involved Backward difference.
I am assuming that your question is that you don't understand Simpson's rule. Below is an exerpt from Wikipedia: Simoson'...

1 month ago | 0

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Answered
1-2-1 or X-Y-X rotation matrix not supported
I recently cataloged all of the permutations of the 2 and 3 axis planar rotations. It is easy to write your own functions. See...

1 month ago | 0

Answered
Extracting data from simout MATLAB work space
simout is a timeseries structure. I like to extract separate vectors from the structure, for example: t = timout.time(simout.t...

1 month ago | 0

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Where can I publish Matlab-compiled software?
If you want to share the source code, you can post it on Matlab File Exchange

1 month ago | 0

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In my Simulink model I would like to conditionally write output data to selectable .mat files in different relative directories.
This sounds like a rather sophisticated way of constructing output. I'm not sure if that is easily acomplished with the "to fil...

1 month ago | 0

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Answered
minimum feret diameter of particle
https://blogs.mathworks.com/steve/2018/02/20/minimum-feret-diameter/?s_tid=answers_rc2-1_p4_MLT

1 month ago | 0

Answered
Vlookup equivalent function for matlab
If your data is in a 2D table (matrix) and you want to locate a column that matches the exact value from another column, then lo...

1 month ago | 0

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Answered
How calculate the second and third numerical derivative of one variable f(x)
The Matlab "diff" function is basically the Backward difference formula. There are much more accurate ways to compute numerical...

1 month ago | 0

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Runge kutta order 2 by hand
In the statement Y(1) = [t(1);y(1)] the simi-colon ";" indicates you are attempting to put 2 rows of numbers into a single ro...

2 months ago | 0

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Correct way to detect Zero crossing
A thought you might want to consider: if you multiply the current value, y(i) by the previous value y(i-1), this product is on...

2 months ago | 1

Answered
How to add optional outport to simulink model?
You can use a switch to select between the two different output options that you want, and there are a number of ways to activat...

2 months ago | 0

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Answered
Ralston's method function
There is an error in your function in the k2 term. For Ralstons method, it should be: k1 = h*f(t(i), y(i)); k2 = h*( f( t(i) ...

2 months ago | 0

Answered
First and Second Order Central Difference
For starters, the formula given for the first derivative is the FORWARD difference formula, not a CENTRAL difference. (here, ...

2 months ago | 0

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Answered
How can I integral Acceleration-time data to Velocity with removing drift?
It seems that what you are asking cannot be done. More information is needed. In order to remove an error in the data, you nee...

2 months ago | 1

Answered
circle with three points
Try this.

2 months ago | 0

Answered
Unit step function explanation
Double is simply the data type , i.e. double precision. (T>=0) is a logical 0 or 1. double converts the answer to double preci...

2 months ago | 1

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Answered
Solving Linear System of Equations with a Real Parameter
Using the symbolic toolbox, you can solve it as follows: 1) Define symbolic quantities; syms A B x1 x2 x3 x4 lamda 2) Write t...

2 months ago | 1

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Answered
Not sure why vector changes assignment when using ode45
I dont think that the statement out3=(3,1) is a valid statement. It may be that out3 is not the size that you intend. try o...

2 months ago | 1

Answered
Why ,the quaternion values from sensor fusion toolbox are switched ?
There are two different ways that are commonly used to represent quaternions. Q = [a,b,c,d] with d being the scalar part, and a...

2 months ago | 0

Answered
Euler's method for two first order differential equations?
Try preallocating x and y nsteps = (b-a)/h + 1; % this is the number of elements in t(a:h:b) (It is = N+1) x=zeros(1,nsteps);...

2 months ago | 0

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Answered
How do i create a projectile?
Always start by making a drawing of the problem. Define the coordinate system (which way is positive/negative) What are the pa...

2 months ago | 0

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