Hi Blackhole, I use Adobe Photoshop with a black background and draw on it using a Wacom Bamboo tablet. I capture the screen using a built in function in Quicktime, edit the video in iMovie, and do the voice over in garageband. The last three programs were all standard on my iMac. I copied the style of the videos from Kahn Academy, which I think is a fantastic online source of free educational videos. Thanks for watching.
Hey Brian! Just wanted to say your videos are helping a whole class of electrical control systems students in Oslo understand what the heck we're doing. Our professor has actually listed your youtube-channel as alternative curriculum since, quote, "Brian Douglas explains it at lot better than I ever could". Good work! And thanks!
+Lars Martin Jensvoll Wow, you must have really humble professors. My EE controls professor is a haughty MIT graduate and he'd never think that someone was better at instructing controls than him. It's a shame too because he's taught me in such a pedantic way that enforces nothing but rote memory. So much so that I literally didn't know the difference between a close loop or open loop system or what stability was until I started watching these videos. I made it all the way to senior year not learning anything practical about controls. I kind of feel embarrassed that I paid dozens of thousands of dollars to go to a "highly ranked school" when Brian Douglas has taught me more in less time for free :-/
I have one video this week and one next week to finish a few backgroup topics first. The third video this year will begin Root locus drawing. Stayed tuned!
Hello Naze, thanks for the comment. I'm working on a stability theme right now but I like your suggestion. In the near future I'll put out a series on signal processing and cover topics like high and low pass filters, band pass, butterworth filters, Kalman filters etc.
Amateur mathematician, retired programmer, WOW this stuff is really interesting! Thank you so much for making it available! You have a talent for making everything clear! By focusing on the graphical! Thank you! Great stuff!
As a student in Germany your videos are helping to a degree that I can't even express at this point. Seriously, you are the best. I thank you to the moon and back :)
first of all this is extremely helpful , thank you very much secondly, i wound use a curved up (positive slope) slides that would convert the unstable system into a stable one like the example of stable system, and that is triggered by a sensor when the ball comes near it
Thank you sir very much! I'm an undergraduate student from China. I feel so grateful that I can learn such great and free control system course on youtube. Teaching with PhotoShop is really cool! You make some knowledge point like convolution so clear and easy to understand.
Sensor - strain guage Actuators - that ball is connected to two motors placed at each bottom sides with a Rope whenever the ball is falling that opposite side motor will start and get the ball back to stable position
A silly idea that only works on metal ball: Place electromagnet as an actuator on the top of the mountain to return the ball to its original position. Still use radar as sensors. :) Nice video as always!
Great idea! And if the ball is magnetic you could also use induction sensors that registers if the ball creates a current by its motion. Just taking up on your idea ;) Nice videos, Brian! The're really awesome! Helps me alot for my control theory exams at the end of the week :)
Many aircraft types display this stability by having either a high wing, so the centre of gravity is below and acts like a pendulum, or a low wing with dihedral which tends to make the plane fly wings level when there is no control input and to recover from a disturbance. This is also why the tailplane and fin are called "stabilizers" I love your videos and am learning all the time as I associate your ideas with other experiences encouraging me to go deeper into this subject, thanks very much.
In the beginning i felt control systems was somewhat difficult and none explained with a proper example. This video was very much useful. Thank you sir. I was searching for videos like this. 👌
Brian, I should say, one of the best lecture series I watched on control systems. God bless you for helping us understanding difficult things in a very effective way. Now I dont need to go through the books. Great!
Your Dart explanation is the first thing that has really made me interested in this class! I never realized that the center of pressure was a thing but it makes so much sense and is really dang cool!!
Hi Freddy, MIMO systems are typically covered in modern control theory classes because state space representation just lends itself so nicely to linear MIMO systems. On the other hand, you can use classical methods to design linear MIMO control systems (root locus, bode, nyquist, etc.) but it starts to get really cumbersome. I hope to cover modern control one day but it's still several months away.
Hey ! Your lectures are too good for an beginner in the Control Theory. I would like to answer the question that you mentioned at the last in this video. I think that actuators/ sensors have individual transfer functions and we should theoretically model our system ,then consider various control techniques for finding the extent of stability of that system. Once we have done these analysis then we can actually think of whether the transfer functions of actuators/sensors considered were correct or not (as per our requirement). Please comment about my analogy. Cheers !!
Your explanation and the way you did it is a new high level before 9 years ago !!!!!! How it would be if you start now ! I think you are a brilliant person. Thx for your efforts ❤️
Thanks, Brian!! My idea to solve this problem could be to put two sonar sensors to get the measure of the ball and then trigger one side actuator until I don't have the same distance from each sensor to the ball. On the actuator solution, I don't have much more idea than yours, then everything depends on the ball material to dimension wich actuator performs betters to bring the ball to the stable position. Thanks for your videos!
You're amazing sir I will donate as soon as I will start earning. Your lectures are making it interesting as hell! keep up the good work and don't ever stop.
Thanks for the comment Satish. If you go to my RU-vid Channel home page (just click on my name) and then click on playlists they are in the correct order there. If you want to see the correct order for all of the videos then click on the playlist for all lecture videos. Otherwise if you're interested in just a particular topic I have playlists for that as well.
I think we could use pressure sensing resistors for position sensing which are aligned on the ground or we could use laser distance meters may be instead of radars. That was for position sensor. For actuator may be a moving floor huh? If ball moves to the right floor will move to the left trying to keep initial position of the ball. Thank you for your great lectures Mr. Douglas they are really helpful! :) I wish you continue posting new lectures...
this series lecture is very useful to study control system ,and combine signal and system knowledage contains such as fourier transform ,Laplace Transform and so on ,thanks ,
Thanks for the fast answer =) The reason I asked is because I am on my masters in satellite engineering, and the last control theory subject (out of 3 control theory subjects) is kinda hard and is the last subject I need to be able to start writing my masters. :P But I think I'll get there. I looked att all your 17 videos so far, and it refreshed my background a bit, so thank you!! I will definately be watching more of your videos in the future!
I wish my curiosity lead me to this channel bit earlier I am in the endgame of the semester now, I will watch it anyways (after the tests )but would've loved to understand the concept rather than just solving everything without intuitivation in the test
Hi Brian the lecture series is very nice and i was going through it you concluded that too stable system will be rigid but when system is too stable then the time constant will be small so the response will be faster so how can it be unresponsive .Could you please let me know ur thoughts
I think if we consider it in terms of two way feedback system with one at sending end (Generation) and second at Receiving end (Distribution) but missing part here is transmission system so take reference when ball is at zero position in centre of crest then it will shift either way sensor at both ends and one at centre to measure if there is any disturbance in the position of ball the feedback system acts between the three sensors then we can bring the system in its stable position more accurately the fans at both ends response to feedback from center and either end on which side ball is moving after disturbance.
Excellent video. I don't mean to be pedantic, but for BIBO stability you need to ensure that the impulse response not only goes to zero, but goes to zero fast enough (its energy is finite). Granted for linear systems this distinction won't matter, but math D:
Hey Brian, I really wanna say hat's off to the way you're helping people with such videos... I'm a under - grad student in EEE ( completed 2 yrs back) and now planning to take up masters in EE (control systems). Can you please tell me the order in which i should approach your videos to brush my basics. Thanks in advance.
I would place my "hill" on a stage that can tilt in all possible directions and cover the "hill" with a very dense set of electrodes to preform capacitative sensing of the position of the ball. I would feed the signal into my controller and output a signal to control a hydraulic lifts to reduce the error term. There would have to be many lifts to have a great deal stability.
PLEASE COME AND WORK AT THE UNIVERSITY OF LIVERPOOL!!! That could not have been explained more clearly. Also I like the extreme examples you use, they really get the point across.
Hello Brian!! Your videos are really helpful and helps us to visualize the whole thing. I have almost seen all of your videos in RU-vid by now. I wanted to know if you could make a video on state space control and explain on the controllability and observability of a system, which still to me is a bit unclear. Thank you.
shooting off a first idea to that question which popped up in my mind. Maybe I would try to introduce electro-magnetic surfaces on my mountain and ball so that as soon as it starts tumbling down either side, a similar polarity can be induced and the ball would be repelled to come back to the equilibrium point.
note that the 1st segment (Stability) disagrees with the second (Darts). When the dart's initial orientation is sideways the system doesn't return to zero, it goes to some finite value.
One could actually build that mountain ball system, little tabletop one. I would detect the ball position with a camera looking down on the ball and "mountain" could be moved a little bit on xy axes. Might be a very good educational model, as ball&mountain must be the most used stability example(besides the pendelum maybe)
Very great video, very intuitive. I have one long pending doubt on small signal analysis, Is it possible to include one intuitive video on the meaning of small signal model, and also can you explain the intuitive link of small signal model to the control problem of keeping the ball on mountain top that you have described in the above video. Thanks for the video and thanks in advance
on both left and right id put a conveyor belt (both moving towards the equilibrium position) this would only activate if the sensors are triggered though.
Hi, I was a little confused on why shooting a dart backward produces an unstable system... The motion of the dart is the same (except its flipped) to the stable system
As for a solution to the problem proposed at the end: I'm sure this may be trivial and silly, but I want my actuator to be a motor attached to a string which comes out of the opening at the top and attaches to the ball. The sensor senses the length say of the string, so that at minimum length the ball is at equilibrium and you can let the string loose when you want to enter astable state. A variation on the sensor could be one that senses the tension in the string, but then we'll also require a differentiator to measure the change in tension in order to achieve observability in the system, if I am not wrong?
Why not just tied to a string, as you said. With a maximum length(stretched) that is a fraction of the hill's semi hemi-sphere arc length in any direction. And a small motor to pull the string back to it's original place. Two sensors, one stimulated by attaining maximum length, and signals to a motor(actuator), which can be a simple pressure sensor. And another for guiding the ball back to the calibrated reference point and resetting the the parameters to reference positions, which can either be a pressure sensor or a light sensor. Simple and cheap, but very discrete in data collection and poor control flexibility.
build gps and motors into the ball? that'd be potentially expensive electromagnet at the top of the hill with a pressure pad, with the ball made of or coated in iron, when the ball leaves the pressure pad the magnet turns on and draws the ball back? Would require lots of fine tuning. only 2 ideas i could come up with on short notice that other people may not have said
I would use Hall Sensors assuming that the ball I use is magnetic in nature and I would have electromagnet as actuators that would either attract or repel that ball
How about building electrostatic charge so that ball will always be attractive towards top of curve, and be repelled by any deviation caused when getiing closer to instability, making the system as a capacitor..
Brain, Stability is when the controlled item is always within the desired maxium and minium. The minimum may not be zero and the maximum is not infinity.
