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# Jim Riggs

### Missile Defense Agency - Advanced Technology Group

262 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.

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Numerical Integration in Matlab
There seem to be two problems: 1) your function "fun" returns "NaN" at zero, so you cannot integrate starting from zero. You n...

19 hours ago | 0

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Simulink counter block having an initial starting value of -1
Yes, the two counter blocks in the library do not allow you to set the initial value. Whenever I need to use a counter, I usual...

3 days ago | 1

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Finding the roots of an equation using Newton-Raphson method but I don't know the equation!
You use a numerical approximation for the derivative. Start at some initial guess for x & y. take a small step, and compute th...

6 days ago | 1

Implementing Angles as an input in Simulink
It appears (based on the icon on the block) that the block labeled "Robot Controler" is a Matlab function block. In order to a...

15 days ago | 0

Pendulum using Runge Kutta
Yes, there are a few things wrong with this code. James Tursa has identified one obvious error. Another problem is with the lo...

29 days ago | 0

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How to return the index of time steps in Simulink?
One way to do this is to put a step counter in the block. This will keep track of the number of times the block is executed. T...

1 month ago | 0

Why is my code not working?
Not entirely sure if this is the reference in the error message, but this line has unballanced parentheses: f = (1/(t-t^(-1))*...

2 months ago | 0

In the Simulink library browser, on the "sources" pallet, you will find a "clock" function. Use this to create a time signal. ...

4 months ago | 0

How can one do this calculation?
Look into using logical indexing. Not my strong point, but for example, if A is the 3 x 10 matrix, you can select all cases whe...

4 months ago | 0

Kalman Filtering for smoothing GPS speed data
The problem is with this line: P = (1-KG)*P; This causes the gain P to continuously decrease. After a while, the gain P is ve...

6 months ago | 1

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numerical derivate and central difference
Here are some Numerical difference formulas using the central difference method (substitute dt = h). You can find more formulas...

7 months ago | 1

Meaning of the following: function [y1,...yn] = input()
It simply means that there are no user inputs to this function. The long list of variable names are returned from the function....

8 months ago | 0

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Angle Between two vectors.
Given two vectors A and B, the dot product of the two vectors (A dot B) gives the product ABcos(ang), so to get just the angle, ...

8 months ago | 0

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Is it possible to summarize this code?
You could use a switch case structure, that would be a bit more compact. it would look like this: switch davar1.CC_CHECK ...

8 months ago | 2

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help fixing the Heuns method
Heun's method is otherwise known as "explicit trapezoidal method", "improved Euler's method" or "modified Euler's method". Th...

8 months ago | 0

I need help coding a human cannonball ignoring air resistance
Assuming zero drag and relatively low muzzle velocity ( acceleration due to gravity = constant), the point-mass trajectory can b...

9 months ago | 1

Runge Kutta 4th Order Method
I think the problem is the T argument. in k1 you have a capital T, which is a 3-vector in k2, k3, and k4 it is a lower case t,...

9 months ago | 0

Matlab Homework that im struggling with
To prompt a user to enter a value, try: x = input('Enter the number of equations (from 2 to 5): \n')

9 months ago | 0

I need help with this script
Try this: T = input('Enter your temperature') if T<=96 disp('You are either hypothermic or a zombie') elseif T<99 d...

9 months ago | 0

Ballstic Impact of Bullets on armor
I don't know af any specific ballistics tools. You should browse the a list of Matlab products at this link: Matlab Products

10 months ago | 0

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How to find theta and theta dot in a simple pendulum simulation in MATLAB.
I'm not sure at all what your system equations are. The first rule of dynamics is where you have translational modes of motion ...

10 months ago | 0

What is a "system variable" in a Simulink model?
In this context, the "system" is the device that you are modelling. Therefore, a "system variable" is one of the variables in y...

10 months ago | 1

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Undefined function 'simset' for input arguments of type 'char'.
simset is an obsolete function. See documentation here. It says to use the Configuration Parameters dialog box.

10 months ago | 0

Newtons method for finding minimum of a function.
Here is another variation; function [f,g,h] = myfunction(x) f1 = @(z) exp(2*sin(z))-z; %function dx ...

10 months ago | 0

help me in trying to solve the secant method
Try preallocating x, right after you define n: n = 100; x = nan(1,n); ...

10 months ago | 0

trying to calculate the central diff approximation
There is a Matlab function "diff" which will do this. Otherwise, your subscripts must all match (2:end-1) Adi_1 = diff(Vdi_1...

10 months ago | 0

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Performing calculations (Newton's method) over values in loop
Yes, your loop is not quite right. Notice your placement of the three lines i=1; converge = false; po = p_init(1); These t...

10 months ago | 0

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Draw a circle for arbitrary orientation on spherical surface
My approach is to define the circle around the X-axis, then rotate it into the desired position through a Yaw-Pitch rotation. ...

10 months ago | 1

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the meaning of basic matlab words
an argument is a constant or variable that you provide to a function; e.g. sin(x) % here x is the argument to the function sin...

10 months ago | 0

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