I need to design a transfer function for a fixed wing UAV using the 1st order which give response based on step input. The input is PWM (thrust, drag) and the output response is airspeed. There are four cases, which areDo you have any information on the order of the transfer functions? My choices would be 1st order or overdamped 2nd order. I see no information in the problem statement that would give a clue. Is there more information that you're not showing us?
Yes, the input signals is PWM. How can I create a transfer function for low pass filter and inverted low pass filter?Looks like a low-pass filter and an inverted low-pass filter.
Your graphs show PWM on the vertical axis but I see no info on that.
Are those input signals PWM?
Since I need to model the transfer function to get the response, thus i just assume input, output and sampling time (Ts). for example for the ThrustUp isPretty nice. So they are all 1st order transfer functions. What was it that led you to those solutions?
It shouldn't be too hard to test all possible 1st order transfer functions. If that doesn't work you might try a damped 2nd order function for the denominator with a compensating zero in the numerator. You could also take the root locus approach. If the system is going to be first order all the poles will be on the negative real axis.Since I need to model the transfer function to get the response, thus i just assume input, output and sampling time (Ts). for example for the ThrustUp is
Input : 1200PWM
Output : 24m/s
Ts : 3s
for SpoilerUp, i almost got the solution but the amplitude should be in positive, so i think maybe i have the problem with the transfer function.
for ThrustDown, i don't know to find the correct transfer function
what are the first order system for step response?It shouldn't be too hard to test all possible 1st order transfer functions. If that doesn't work you might try a damped 2nd order function for the denominator with a compensating zero in the numerator. You could also take the root locus approach. If the system is going to be first order all the poles will be on the negative real axis.
With second order systems, the poles are conjugate pairs, and the zero is near the origin.
Whoaa... Thank you for your effort, i'm really appreciate it, but can you please write the transfer function equation that you used because i never used this kind of software. Is the green colour is the input? By the way, what software did you used?I think this is it for 1st order responses
You can use the transient analysis if you want to see the response with an applied PWM signal as well as a step.You can do either a transient analysis or Magnitude and Phase (Bode) plot
I had not thought of that but you are right.You can use the transient analysis if you want to see the response with an applied PWM signal as well as a step.
Do you know how to get this response if using transfer function block using simulink in matlab software?The transfer functions are on the schematic where the expression is Laplace = <Transfer Function> , and that is where I wrote them
The graphs are labeled V(out1) or Voltage at node OUT1
and V(out2) or voltage at node OUT2
It is a simulator (free download) that can simulate the response of arbitrary transfer functions expressed as their Lapalce transform.
It is called LTspice and it is a free download from the Analog Devices Inc. website. Many people on this site (AAC) use it for divers purposes
The E1 and E2 components are Voltage Dependent Voltage Sources
V1 is a positive step generator (0 --> 1) and V2 is a negative step generator (1 --> 0)
You can do either a transient analysis or Magnitude and Phase (Bode) plot
Nope. I haven't been able to afford that package since I was a graduate student for the 2nd time in the early part of this century. They let us have it for the low-low price of $99.00+tax -- of course.do
Do you know how to get this response if using transfer function block using simulink in matlab software?
Since a first order low pass filter has already been suggested, the general form of the transfer function is:View attachment 240762
How can i get these four transfer functions response based on the step input? What are the transfer function to get the output response?
by Aaron Carman
by Robert Keim
by Aaron Carman