Recent content by asgerbj

oh god... i can't believe i spend so much time on this... .. thanks, that solved it :)

I need to solve this circuit using nodal analysis (find the voltage in all nodes), but i need the actual equations used to solve it. http://dl.dropbox.com/u/202411/p2/circuit328.png All supplied information is there. What I've done is to create 2 supernodes, like this...

Just as a note, you can try to use LTSpice to help you solve these circuits, and also to create better drawings :-) Its free and easy to use. Just to avoid any questions about the circuit itself.

Yes, I agree, there are big changes with just a little change in the data used. To determine it more accurately we need measurements at much higher speeds (70-100 km/h)... However, we are modelling and simulating an electric car, which means that our calculations will only need to satisfy speeds...

OK, Thanks for the help everybody. Just to close this topic, here's what we did. (I hate when there are no ending answers when looking around internet forums, so here we go :D) Here is an example of data we gathered using GPS (something similar is already presented in the topic). We...

Yes, if you just use Crr there won't be any curvature. Can you tell me how you made the calculations/graphs using both rolling and air resistance, and tried changing the drag coefficient?

OK, We will take a look there. I can't deny that there might be a slope of 0.1%, but it should be more or less as level as it can be... So you might recommend us doing calculations at higher speeds?

Frontal area is: A = 1.425m \cdot 1.462m = 2.08 m^2 We use the density of air at 17 degree celsius: ρ = 1.2250 \frac{kg}{m^3} The mass of the car is 740 kg, and weight of our 2 passengers approx 75kg each: m = 740kg + 2 \cdot 75kg = 890kg

We seem to get a function a(v), where as the other function is v(t), and something here messes up. However, when we do the calculations manually with just Δa at the time Δt, we seem to get approx values that sound plausible. But we want to use it mathematicly right in MATLAB.

Oh yea, so, there are no force from engine or anything else, just the wheels and airdrag. The rolling resistance is; F_{rr} = C_{rr} \cdot m \cdot g C_{rr} is the coefficent of rolling resistance, m the mass and g the gravitational constant (9,82 m/s^2). and the air resistance is F_{air} =...

This should be straight forward using only digital electronics. Using a microcontroller (maybe using a PC and USB-connected board would make it easier) you can control the different holes, that light up just using several LEDs. To detect human interaction with the holes, i believe the easiest...

So, we're trying to simulate an electric car running with a DC-engine. To get the calculations right we must determine the rolling resistance coefficient and airdrag coefficient. (We've already determined the rolling resistance to about 0.014, doing some linear calculations at low speeds <...