Wednesday, February 24, 2010
Having grown up about 30 minutes south of New Haven, I know some of its history, but whatever of it I did learn was from its early days as a colony and major port. I had no idea of the more recent history of the Connector, though I've driven on it many times. I always enjoy seeing little bits and pieces of local history. When I was first able to walk around Derby, where I now live, I made sure to stop to read the few monuments in town. Sure, every town has history, and I'm not saying any one place is truly special, but knowing the local history, for me, is more interesting than reading something about Europe or somewhere that's often experienced in a 7 day tourist trip. It's also much cheaper.
Tuesday, February 23, 2010
I am hosting, for the second year going, a St. Patrick's Day celebration. You're welcome to come, by the way. Starts at 8:00PM on Friday the 12th, at my place.
I sent out the invites for this celebration last Friday, and have been seeing the usual trickling in of responses. A couple of these responses are the dreaded "Maybe." This, my friends, I do not like. I don't know who invented the "Maybe" response on Google Calendar, but I hope that employee has either been fired or has moved on to better things (like Google Buzz), because I hate it. And, since I haven't gone on a good rant for a while, I'll explain to you, dear reader, why the "Maybe" response has no real use.
My concern as the host is if you, the invited, will attend my party. This should be a binary response: "Yes" or "No." When I see a "Yes" response, I think "This person is planning at least part of their day to attend my party." When I see a "No" response, I think "This person already has plans and is kind enough to take the time to let me know they are definitely not showing up." Both responses are perfectly fine, and appreciated. When I see a "Maybe" response, I think "This person is letting me know that they know I'm having the party, but that it is not one of their top priorities."
Let's go back to my role as the host: is this person attending or are they not. I really don't need to know what this person's priorities are. I want to know, one way or the other, if they're planning to show up. The "Maybe" response, to me, is NOT a "Maybe" for attendance, it's simply a "Soft No" unless it turns into a "Yes." A true "Maybe" is the simple non-response. A lot of people employ that technique, which I like less than a "Yes" or "No," but more so than a "Maybe" response. Please, if you are a legitimate "Maybe", just don't respond. That is totally understandable. I don't expect you to drop everything you're planning just to attend my party. It's not a big deal. But, whatever you do, don't respond "Maybe." It doesn't help me.
And Google Calendar employees: if there is any way to prevent possible attendees from responding "Maybe," please let me know. Thanks.
Sunday, February 21, 2010
Thursday, February 18, 2010
The question was simple: how does one derive the transfer function to a simple closed loop system?
Take the following system as an example:
The system components are the Reference input R(s), what you want the system's output to be, M(s), the Controller, G(s), the Plant or model of the system, Y(s), the output of the system, and H(s), the Sensor. In addition, I have added X(s), which is the output of the Sensor, and W(s), which is after the summing block.
Last night I "walked around the loop" with my fellow student to help him understand how to get the transfer function, which is Y(s) / R(s), or simply the ratio of the output to the reference input.
Let's start by finding W(s) and X(s) in terms of the system components.
(1) W(s) = R(s) – X(s) the output of the summing block
(2) X(s) = H(s) * Y(s) remember that Y(s) is fed back through H(s)
Now let's find Y(s) in terms of W(s):
(3) Y(s) = W(s) * M(s) * G(s)
Now insert Equation 1 to eliminate W(s) from Equation 3 above.
(4) Y(s) = [R(s) – X(s)] * M(s) * G(s)
Now insert Equation 2 to eliminate X(s)
(5) Y(s) = [R(s) – [H(s) * Y(s)] ] * M(s) * G(s)
Now we have an equation for Y(s) in terms of all the other system components. Now we just need to get Y(s) / R(s):
(6) Y(s) = R(s) * M(s) * G(s) – H(s) * Y(s) * M(s) * G(s)
(7) Y(s) + H(s) * Y(s) * M(s) * G(s) = R(s) * M(s) * G(s)
(8) Y(s) * [1 + H(s) * M(s) * G(s)] = R(s) * M(s) * G(s)
And the finale:
(9) Y(s) / R(s) = [ M(s) * G(s)] / [1 + H(s) * M(s) * G(s)]
Saturday, February 13, 2010
Tuesday, February 9, 2010
Sent to you by Pat via Google Reader:
Google's Street View team shoots the slopes of Canada's Whistler mountain using cameras with extra hard drives attached to a snowmobile and an SUV. Ski downhill on the Olympic runs for a real off-Street View.
Things you can do from here:
Sunday, February 7, 2010
We got there a little before 9:00AM, and were on the slopes by 9:15. We started with a nice little trip from the top on Pied Piper across to Cruiser to check out the easier of the two terrain parks (which is also free to use). Nice little warm-up. The rest of the day was spent on the various blue and black trails. Butternut only has a few black diamond runs, and none of them are particularly steep or difficult. I actually had my best run on Lucifer's Leap, a short black diamond run at the top. Scott tried Downspout, which was the toughest of the runs because it has some decent bumps at the top. I decided to take some runs down Freewheeler, which was the toughest of the blue runs all the way to the skier's left of the mountain. Nice rollers on that trail.
One of the things Scott suggested was for me to keep my feet a little closer together while turning. This is something I've heard different things about, but, to be honest, it definitely helped. I felt better turning to the right, and have started to do a little better at actually making S turns as opposed to "Z turns" that look more like hockey stops. My only spill of the day was in the afternoon when I was going way too fast on a flat and caught an edge. Nothing major.
Over the course of about six hours of skiing, we had hit almost every trail at least once or twice. The lines got to get longer in the afternoon, so we ended up leaving at around 3:00PM. Nice little day on the slopes. I'm feeling more confident each time I hit the harder terrain. Now I just need to work more on my edges during turns and I think I'll be good to go for the really steep stuff.