Daniele Salatti http://www.salatti.net The unhandled exception Sat, 12 Nov 2011 18:06:19 +0000 en hourly 1 http://wordpress.org/?v=3.3.1 Bode Plots Little Tutorial – Part 1 http://www.salatti.net/bode-plots-little-tutorial/ http://www.salatti.net/bode-plots-little-tutorial/#comments Sat, 12 Nov 2011 18:06:19 +0000 Daniele Salatti http://www.salatti.net/?p=36 Continue reading →]]> While working as a consultant I’m struggling trying to finish my studies in Computer Engineering. The Bachelor degree seems so far away…
Anyway, I’m preparing for an exam right now and I would like to share with you a bit of what I learn along the road, so I’m going to write down a little tutorial on how to draw a bode plot. The transfer function comes from an actual exercise I found in a book.

Given the following transfer function:

G(s) = \frac{50(s+100)}{s(s+1)(s^2+10s+100)}

Plot the Bode diagram and determine the gain and phase margins.

Step 1 – Extract the constituent parts of the transfer function

That’s easy. In practice we are going to decompose the transfer function into its constituent parts. To simplify that process, we are going to rewrite the transfer function in the Bode form.

G(s) = \frac{50 \cdot 100(1+\frac{s}{100})}{s(1+s)100(1+\frac{1}{10}s+\frac{s^2}{100})}=50 \frac{(1+\frac{s}{100})}{s(1+s)(1+\frac{1}{10}s+\frac{s^2}{100})}

As I said that’s an easy step. Now we need to extract the following parts from the transfer function:

  1. A constant (K)
  2. Poles at the origin
  3. Zeros at the origin
  4. Real Poles
  5. Real Zeros
  6. Complex conjugate Poles
  7. Complex conjugate Zeros

1 – A constant (K)

A no-brainer. The value of K is 50.

K = 50

Write it down and let’s move forward.

2 – Poles at the origin

For a definition of what a pole is, please refer to the page on wikipedia. We need to find out if there are poles in zero, and of course there’s one. It’s easy to spot it at a glance: just give a look at the denominator:

s(1+s)(1+\frac{1}{10}s+\frac{s^2}{100})

So, we got a pole in 0, let’s write it down and move to the next step.

P = \left\{{0}\right\}

3 - Zeros at the origin

Again, for a definition of what a zero is, please refer to the page on wikipedia. This time we have no luck: it’s easy to see that there aren’t zeroes in 0.

Nothing to write this time…just move to the next step.

4 – Real Poles

We got one! Give a look at the denominator again:

s(1+s)(1+\frac{1}{10}s+\frac{s^2}{100})

We have a pole in -1.

P = \left\{{0, -1}\right\}

5 - Real Zeros

Looking at our numerator it is easy to spot: there’s a zero in -100.

(1+\frac{s}{100})

Write it down and…yeah, you guessed it: move to the next step.

P = \left\{{-100}\right\}

6 - Complex conjugate Poles

Finally, the fun begins! But you have to wait for this part…

To be continued…

]]> http://www.salatti.net/bode-plots-little-tutorial/feed/ 0 Catching the Sunset http://www.salatti.net/catching-the-sunset/ http://www.salatti.net/catching-the-sunset/#comments Tue, 18 Oct 2011 12:28:12 +0000 Daniele Salatti http://www.salatti.net/?p=118 Continue reading →]]> On Sunday evening I went out with my camera and tried to practice sunset photography. I took more than 130 pictures.
Some of them are good, others…well, not that much!
Here are a couple of those pictures.

Sunset in Leghorn 2 Sunset in Leghorn Sunset in Livorno

Location: Terrazza Mascagni, Livorno

]]> http://www.salatti.net/catching-the-sunset/feed/ 0 No more spam? http://www.salatti.net/no-more-spam/ http://www.salatti.net/no-more-spam/#comments Fri, 30 Sep 2011 18:38:22 +0000 Daniele Salatti http://www.salatti.net/?p=78 Continue reading →]]> You can’t even imagine how many spammy comments I got in the last few days…
To stop these annoying folks (or bots) from throwing their rubbish in my comments form I completely removed the “website” field, so anyone can still enter a comment but he/she will not get a link back anymore. Let’s see if it works…

]]> http://www.salatti.net/no-more-spam/feed/ 0 How to setup XCode 4 and GHUnit to do TDD on iOS http://www.salatti.net/how-to-setup-xcode-4-and-ghunit-to-do-tdd-on-ios/ http://www.salatti.net/how-to-setup-xcode-4-and-ghunit-to-do-tdd-on-ios/#comments Thu, 29 Sep 2011 20:03:32 +0000 Daniele Salatti http://www.salatti.net/?p=79

A very interesting video where Robert van Loghem, shows you how to setup GHUnit in XCode 4 to do Test Driven Development for iOS.
There’s also a blog post here.

]]> http://www.salatti.net/how-to-setup-xcode-4-and-ghunit-to-do-tdd-on-ios/feed/ 0 Luck is an abstract class http://www.salatti.net/luck-is-an-abstract-class/ http://www.salatti.net/luck-is-an-abstract-class/#comments Tue, 27 Sep 2011 19:47:22 +0000 Daniele Salatti http://www.salatti.net/?p=70

Luck in life always exists in the form of an abstract class that cannot be instantiated directly and needs to be inherited by hard work and dedication.

Y. Shetty, S. Jayaswal
Practical .NET for Financial Markets

]]> http://www.salatti.net/luck-is-an-abstract-class/feed/ 0 Back to blogging (again) http://www.salatti.net/back-to-blogging-again/ http://www.salatti.net/back-to-blogging-again/#comments Mon, 19 Sep 2011 02:01:04 +0000 Daniele Salatti http://www.salatti.net/?p=29 Continue reading →]]> It’s been a while since I last wrote on a blog. Real life commitments kept me busy for quite a bit but I think it’s time to revert to old habits. However, the topics will be completely new.

Hope to see you soon, here on my blog. In the mean time you can learn more about who I am by checking my LinkedIn profile (well, I got a Stack Overflow Careers profile if you prefer) or reading my tweets.

]]> http://www.salatti.net/back-to-blogging-again/feed/ 0