Control systems with non-minimum phase dynamics

[@mohammedabo-riyash866]

I think if we think of our lives as having varying transfer functions, it would probably sometimes be a non-minimum phase transfer function. Sometimes we think we are going in the wrong direction and our efforts are not doing well and then god just surprises us with this really great output in a very short time.

[@brianblasius]

Another great example of a non-minimum phase system is an inverted pendulum. I designed an LQR controller for it in simulink to control cart position and pendulum angle. When I plotted the outputs, I noticed that it's position never immediately went to the setpoint. It instead went to the opposite direction first, to get the pendulum falling in the other direction so that it can move to the setpoint. I never knew these systems are called non minimum phase systems, but thanks to Brian Douglas and Steve Brunton, I now know what they are.

[@jmadratz]

I am a satellite and ballistic missile guidance, navigation, and control engineer and your explanation is concise and perfectly stated.

[@Eigensteve]

Thanks!

[@isaacharris7534]

I absolutely love your videos! Thank you so much for making these publicly available. The controls community is lucky to have you

[@vemiz]

Just thought of a another example: When turning a ship. At first the rudder pushes the ship in the wrong direction before the rate of the turn catches up =) Great videos Steve. Huge help before my exam

[@virati]

Another (but hyper-simplified) example that I've had good luck with: navigating New York City in a car. When trying to go south to Brooklyn you may need to first go north, then west on the one-way streets you live near to ultimately get into the 'flow' that takes you to your destination.

[@tamasbuzogany3024]

These guys from Washington…just wow. Thanks for making control UNDERSTANDABLE!

[@kmatter11]

No, thank you. This was exactly what I needed to understand.

[@josuemanuelparejacontreras3443]

are you going to make more videos????, these are great I watched all of them!!!

[@k4ll15t1]

Another example is you sitting in front of a fire and you want to make your fire hotter. If you add a new log, the heat you feel will decrease before it increases eventually.

[@Seneca_dengo_dengo]

Fantastic lesson.

[@fjord2141]

What about counter-steering a motorcycle? From Wikipedia: "Countersteering is used by single-track vehicle operators, such as cyclists and motorcyclists, to initiate a turn toward a given direction by momentarily steering counter to the desired direction ("steer left to turn right"). To negotiate a turn successfully, the combined center of mass of the rider and the single-track vehicle must first be leaned in the direction of the turn, and steering briefly in the opposite direction causes that lean."

[@mkschreder]

What is the expression for the magnitude and time delay of the reverse direction response?

[@kubigaming3606]

if u take step response in this situation, the steady state gain will be -0.1 so shouldnt it be under y-axis? 3:22

[@hezi2140]

Why does my step response not look like 3:40? >>G=tf([1 -1],[1 10]); step(G)

[@RoboGenesHimanshuVerma]

Actually there should be a gain of -1 also otherwise system settles to negative of the input. So take tf([-1 1], [1 10])

[@ad2181]

@@RoboGenesHimanshuVerma Agree it -s plus 1 in the numerator.

[@zguan6397]

@@RoboGenesHimanshuVerma Yes, I did what you said here, but the response seems to be good as well. There is no down stage..

[@achsowas100]

parallel forward parking is even harder ;)

[@ididafewthings]

How would you imagine a minimum phase zero? That the negative dip is in negative time?

[@Rene_Christensen]

Minimum phase zeros are the typical ones we have in physical systems. The dips goes positive then, not time.