PID Controller Implementation in Software - Phil's Lab #6

[@PhilsLab]

New hardware and PCB design course on mixed-signal embedded systems just released! ⏵Course content: www.phils-lab.net/courses ⏵Course sign-up: phils-lab-shop.fedevel.education Something I forgot to mention in the video! Note on 'derivative-on-measurement': Since the 'error signal' effectively going into the differentiator does not depend on the setpoint: e[n] = 0 - measurement, and therefore (e[n] - e[n - 1]) = (0 - measurement) - (0 - prevMeasurement) = -Kd * (measurement - prevMeasurement). Note the minus sign compared to derivative-on-error! I've made the change in the Git repo - before you would have had to use a negative Kd gain to get the same result. Now you can, as normal with derivative-on-error, use a positive Kd gain as usual.

[@abdelhassibdad3413]

Thanks for sharing i have a question how can we get tau and how we chose sampling time ?

[@gerhardwiesinger]

Kd should always be positive, so please change it in git repo (and test code again). To avoid the confusion you could always use error to setpoint.But with a flag set the setpoint always to 0 but only for the derivative component. (hope the intention is clear). So one can choose if "kick in" is wanted or not. BTW: What's the practical impact of the kick in on the output response?

[@PhilsLab]

@@gerhardwiesinger Thanks, I've included the minus sign. Code has been checked and works as expected.

[@gabiold]

@@gerhardwiesinger You might make another derivative term for the setpoint, with a separate Kd(set), and this way you could control how to respond to setpoint change and how to measurement change.

[@EinzigfreierName]

Very good video and one of the best I saw on implementing PID so far. But I don't fully understand how the derivative of the measurement and the derivative of the error can give the same result. This seems to work only if you imply the setpoint is not changing between two measurements, right? I mean, if the setpoint is increasing at the same speed as the measurement, the error is constant and derivative of the error is 0. But the derivative of the measurement would be non-zero in this case. Or am I missing something.

[@patrickhochleitner7754]

This is the first time I find a direct C application from a theoretical control explanation. I've been searching for this for some time on my university's library and no luck at all. Thank you so much for this, you got a fan right here.

[@PhilsLab]

Thank you! Yeah, I had the same problem, as it was quite hard to find complete and documented code online (and in books) that also covers practical issues in implementation - so very glad to hear this has helped.

[@jasonbotzas4528]

I’ve learned this in school only from a theoretical standpoint that glosses over the very important details of “how do we ACTUALLY make this work”. Thank you for increasing my knowledge!

[@TenFeetDown]

Spot on explanation, I swear most people who try and explain this don't understand it themselves. Thanks so much.

[@ObsidianJunkie]

Just finished my ECE undergrad last month. Practical implementations of control systems in digital hardware is something that I never learned and wished was part of my curriculum. Excellent, thanks.

[@PhilsLab]

Very glad to hear you found it helpful. Same for me when I was at university, lots of theory but effectively no mention of how to use it in practice.

[@pkilo2811]

I agree with you perfectly. Most of the lecturers just teach what they read in a book and not implementers. As the author of AoE, Horowitz, said "Most Engineers of this age are rather applied Mathematicians always hiding behind equations"

[@hvinstrumentsandparts1907]

Nice Work, one of the best PID explanations because its not in Matlab or Simulink. You actually see the anti-windup code

[@coorfang426]

I've learned this PID knowledge in the university ~ 6 years ago. But it was definitely not as clear as your illustration and demonstration. Bravo.

[@PhilsLab]

Very happy to hear that, thank you very much!

[@theman3282]

same, i got c+ on control and system..

[@GiancarloAllasia]

I'm a mechatronics engineering student, I've covered a lot of theory about advanced control stategies, but we always skipped PID control and, most of all, its implementation in code. This video is fantastic, you have a very good skill in explaining clearly concepts and this is exactly what I was looking for to have a more practical grasp about such theoretical concepts. Well done!

[@PhilsLab]

Really glad to hear that, thank you!

[@bastianacevedobustos3156]

This channel is slowly becoming one of my favorites, thank you so much!!

[@PhilsLab]

I'm very happy to hear that - thank you!

[@shaungovender7805]

As a fellow lover of microcontrollers and Signal Processing I absolutely love the content on this channel... I have to say that Phil does a great job of getting through the rather advanced mathematics and focuses on only the essentials. Great work.

[@PhilsLab]

Thank you very much, Shaun!

[@Jdozjsnwj783]

By far one of the best KZbinrs at explaining both hardware and software. Clearly very knowledgeable, I am currently consuming your content as fast as possible

[@PhilsLab]

Thank you very much for your kind comment! Definitely more videos to come as well :)

[@kersgames6382]

You saved my day man! I finally understand how to implement basically any continuous time controller onto a arduino or something like that. One can have ALL the understanding of the theory, but if you cannot apply it, you are basically worth nothing for a company. Thank you so much!

[@leecaraway706]

Very well done! You are an excellent teacher. Concise and to the point, good flow with no fumbles. That is hard to do. I have been doing this for over 45 years and you are in the top five for good teachers.

[@PhilsLab]

Thank you, Lee. That's very kind of you to say, very happy to hear that!

[@bouipozz]

Great video thanks! Helped enormously with my 3rd year project. Nice to see the theory and practical being connected as this is often neglected and causes much difficulty

[@georgetroulis]

About time a video like this exists. I'm taking control systems right now as an undergrad and I've been waiting to use that theory in practice. Your videos have been perfect for that transition. Perfectly timed :)

[@PhilsLab]

Awesome, very glad to hear that - hope you can put the code here to use! :)

[@bluehornet6752]

Brilliant video! I've forgotten some (most?) of my differential equations concepts, but you gave a very nice review--and I love your PID algorithm. The flight sim was most impressive as well. Thanks for making this video!

[@PhilsLab]

Thank you, Tom! Very glad to hear that - hope you can use the algorithm in one of your projects! :)

[@felipegutierrez7856]

Very good explanation. I would add that the tracking error states the direction that the gain of the PID control will take. If the error is positive the gain will be positive, and vice versa.

[@vencibushy]

This is a very nice information. I believe that the design can be further improved with a better anti-windup mechanism. Integrator clamping is a rather crude way to prevent the saturation of the control signal. A much better and elegant solution is the back-calculation algorithm which dynamically modifies the integrator. It's a simple yet very efficient solution. You need to impose a software saturation borders of your controller's output. Then you calculate the difference across this saturation. The resulting signal is now a second error in the system which is fed back via a negative feedback loop to the integrator's input. The signal can be further amplified(or attenuated) with it's own coefficient. For example - a microcontroller can be an effective linear controller when the output is PWM. If we assume a control signal implemented over 10-bit PWM the software saturation is 0 to 1023.

[@BrianTCarcich]

[update: whoops, this may already be implemented in the updated anti-wind-up] /* or, more simply: */ p = ...; i = ...; d = ...; /* P, I, D terms */ out = p + i + d; /* sum to output */ out = (out>limMax) ? limMax : ((out

[@benjaminpaik]

It might be worth considering adding a separate variable to integrate the errors before multiplying the integral gain. The float (essentially being scientific notation in base 2) will stop integrating if the value you are adding (0.5 * Ki * (error + prevError)) drops below the LSB of the fractional portion of the float for a given exponent of the integrator. In other words, you can introduce a steady-state error that won't be resolved for sufficiently small errors. The effect is exacerbated for low values of Ki and T.

[@nanajerry824]

DR RORPOPOR HERBAL on KZbin changed my entire life with his herbal medicine. I appreciate you sir, for taken away my PID 🌿🌿🌿🌿

[@sergeyzolotykh9872]

It is by far the best video about PID, specially about practical implementation of the controller.

[@akaHarvesteR]

Immediately subbed. This is probably one of the best videos on PID control out there, and AFAIK, the only one that does a good job of explaining how to implement one in real life, where computation is discrete and numerical noise is inescapable. Loved the idea of dt-on-measurement. Had never seen that before, and now I wish I had thought of that.... time to update my PID code!

[@PhilsLab]

Thank you man, really glad to hear that. Yeah, I wish more people would actually show how to implement things in real-life, far too much time spent on theoretical learnings that don't translate 1-to-1.

[@akaHarvesteR]

@@PhilsLab Very true. Oh, and I implemented a new PID controller based on yours just now, and it's a significant improvement over my old one! Many thanks! One thing I was still curious about, if I could ask for an elaboration, was on how you worked out the resulting expressions, especially for D. You mentioned using a bilinear transformation to transform values to discrete space, but your expressions have the transformation already folded in with the integration and diff. That was the one part where I had to just take your word for it, because algebra is really not my thing. In any case, most excellent video! Thanks again!

[@kylemilner]

Fantastic video Phil! Suggestion: Increase font size so we can see your code a bit easier. Keep the great content coming!

[@PhilsLab]

Thank you, Kyle! That's a very good suggestion, I'll keep that in mind for future videos.

[@darkstar2111]

14:48 - As the guy who reviews the other people code for living I do really appreciate making the code easier to read rather than super fancy, short and 'sophisticated'. Especially in C# or JavaScript where you have at least 40 ways to achieve same thing and new syntactic sugars every two years.

[@PhilsLab]

I'm glad to hear that! Although not primarily a software guy myself, I try my best to make my code as easy-to-read as possible. I've been meaning to read 'Clean Code' for a while but still hasn't happened yet - one day...

[@martinestorninhoblocher1010]

Hey Phil, Great video. Information is not to extent but the fundamental concepts are there, plus you actually give an example of a real world application, which at the end of the day is what really matters. Thank you.

[@Giblet535]

Friday evening, and an implementation of PID controllers. Perfect! I wish mathematicians wrote out their formulas in C. Translating from meat puppet is tedious.

[@PhilsLab]

Thank you! Yeah, I wish more control theory books would have more snippets of actual code..

[@steefant]

@@PhilsLab when looking at actual code written by control theorists i am not so sure that would be a good thing... ;)

[@bonafontciel]

that's cool. I made one 2 years ago in C for a coolling system(control Fan via PWM) sold by a famous PC part vendor.

[@SuburbanDon]

This is great Thanks ! You've made life a bit easier for many of us semi-boneheads.

[@PhilsLab]

Thanks, Don!

[@baskarv7975]

Dear Friend , I have no words to Thank You ,, I watched lot of Videos to Understand the PID but its really very hard to understand ,, Your video really makes me to understand the PID Very Clean and Nice Explanation Thanks a lottt ..... Very Very Helpful .. God bless you my dear friend. all other your videos are very very nice :) :)

[@PhilsLab]

Thank you, Baskar!

[@ecarvalho17]

A video about tunning those parameters would be cool either. Nice content!

[@PhilsLab]

Thank you! Yes, will be doing an extensive video on that in an upcoming video series on controller design!

[@diggleboy]

This lecture takes me back to classical control systems and their design. Great presentation with the math and examples. Very important when it comes to controls systems in vehicles of all kinds, especially high speed, high performance and high agility systems: Fighter aircraft, Formula 1 race cars, guided rocket systems and so much more.

[@PhilsLab]

Thank you! Yeah, control systems are absolutely everywhere. Incredibly important in almost all areas of engineering.

[@NilsKullberg]

What a nice video! - Informative and straight to the point. No frills. Just results. Big thanks!

[@PhilsLab]

Thank you, very glad you liked it!

[@thorntontarr2894]

Phil, an amazing morning watch and followup; excellent use of references to read. I am invested in Arduino IDE now on VSC & PlatformIO so making your code compile directly may be a task but not impossible. So, just what hill am I climbing to get VSC & PlatformIO to be happy. However steep and tall that hill is, what you have theoretically discussed and digitally implemented is understood quite well thanks to your presentation style and knowledge. I will checkout the 6 part video series to learn more.

[@nanajerry824]

DR RORPOPOR HERBAL on KZbin changed my entire life with his herbal medicine. I appreciate you sir, for taken away my PID 🌿🌿🌿🌿

[@HelmutTschemernjak]

Interesting topic, I did’t know about a PID controller until now. From a programming topic, I would create this PID controller in C++ which encapsulates it more like a re-useable PID block. For the float data types I would may use a template type to be flexible for different use cases with uint8_t, uint16_t, etc. as some MCU’s don’t offer float support and the software float simulation eats a lot flash memory. Great video, thanks.

[@PhilsLab]

Thank you, Helmut. I like your ideas! Yes, C++ would offer a nicer way to make a class out of the PID controller. I tend to go with C these days, as I'm mainly programming for STM32s and C - to me - is just much better integrated than C++. And yeah, MCUs without a floating point unit will have a bit more work to do running this code. Then again, most PID scenarios will commonly only run at a few hundred Hz or kHz, and the update routine is not particularly math-heavy so I've been able to run this on things like Arduino Nanos. Even though these days all I work on is STM32s with floating point units haha. Thanks again for your comment!

[@HelmutTschemernjak]

​@@PhilsLab today MCUs have sufficient flash and memory resources that C++ works great with them. I work with STM32L0, L4, D21 and ESP32, the entire code written in C++. At present for embedded projects with Mbed-os and Arduino OS. Simple data structures like a dynamic list of objects, a hash map etc. all this is available in C++ with good documentation without re-inventing algorithm in C where basic little support is given by the C library, with C++ all this is included. I started some time ago with Silicon Labs MCUs doing basic low level stuff like an async serial. When I moved to STM, all this was different and it was needed to start over again for basic stuff like a async serial or a simple timers. Basically wasting my engineering efforts without being able to bring my work to a new platform like Atmet D21. With Mbed-os all this is much better because Mbed OS has identical C++ APIs for all major ARM based MCUs, there are about 150 development boards available from different vendors all Mbed-os compatible. For ArduinoI wrote on top of Arduino Mbed-OS compatible IO and timer libraries. This means for larger projects my C++ code is 98% identically for different MCUs even across OS’s like Mbed and Arduino. For a software engineer re-purposing code boosts productivity brings more stable and maintainable code. Focusing on the solution and being flexible to support entirely new MCU vendors is something where clean C++ Code blocks can help. Regards from Hannover, Germany. Helmut

[@klave8511]

One important attribute for controlling mechanical actuators is to avoid constant tiny adjustments. If the measurement is noisy and that translates to continuously changing an actuator, the increased wear from the jitter type adjustments leads to premature failure. This can be mitigated right at the controlled device by, for example, using a slotted coupling so that there is a bit of hysteresis. It should really be part of the control system, be it PID or any other.

[@PhilsLab]

Yes, that's a great point and something I only broadly hinted at with the 'derivative amplifies HF noise' part, but should have explicitly mentioned that this over-actuation due to noise in a control system will cause actuator wear.

[@10e999]

Great video. I'd like to see a software-focused follow up from your "Flight Control System Design: Hardware" video.

[@PhilsLab]

Thank you! Yes, I'll be doing a video series on control system design, which includes software implementation, and also hope to make a video on the extended Kalman filter which runs on the FCS.

[@KJ7NLL]

Thank you, I am going to use this for my antenna rotor controller that has phi and theta to track satellites. Me and my dad are currently trying to contact the International Space Station using the rotor controller!

[@PhilsLab]

Awesome, hope your antenna tracker works out!

[@KJ7NLL]

@@PhilsLab The antenna tracker works, here it is! kzbin.info/www/bejne/rKPPqGeHhbCAiLs

[@eduardoc1252]

Great video Phil! What is the alpha in TestSystem_Update function used to calculate the output?

[@kenwallace6493]

Well done and very applicable to digital power conversion. Modeling PID systems in a simulator like LTspice would be very useful.

[@PhilsLab]

Thank you, Ken! I'll see if I can make a video on (PID) control in circuit simulators.

[@StMartin81]

Great video! What I would be interested in is how to derive the derivative part of the controller with the integrated low-pass filter. It looks like this is a very common problem but I haven't found a good video which describes the transformation of the transfer funtion from the laplace domain to the actual implementation in the discrete time domain.

[@alexbenitic]

You are the best Philip, this is by far the best PID video I've ever seen. Please make more such videos. Thanks a lot .!

[@PhilsLab]

Thank you very much! Yes, got a larger control theory one lined up - going from theory through to practical implementation.

[@nightrook5732]

Our college is all about theory and no shit given about practical side. I always wanted to know the implementation. Thanks for sharing this!!!!

[@PhilsLab]

Was the same for me at uni.. :( Glad you found the video helpful!

[@chenhaoting235]

thanks for your detailed tutal. Two question, in your github code: pid->differentiator = -(2.0f * pid->Kd * (measurement - pid->prevMeasurement) /* Note: derivative on measurement, therefore minus sign in front of equation! */ + (2.0f * pid->tau - pid->T) * pid->differentiator) / (2.0f * pid->tau + pid->T); 1.Kd use positive value? 2. why not caculate differentiator part int the way below? pid->differentiator = -(2.0f * pid->Kd * (measurement - pid->prevMeasurement) /* Note: derivative on measurement, therefore minus sign in front of equation! */ - (2.0f * pid->tau - pid->T) * pid->differentiator) / (2.0f * pid->tau + pid->T); thanks very much.

[@romualdyap4708]

Thank you for the really well explained tutorial especially the implementation in the code. I was searching for something like this. This is exactly what I was looking for! Many thanks on your really awesome video!

[@avejst]

Great walkthrough of the problems with PID's Great walkthrough of the implementation in C Thanks for sharing :-)

[@nanajerry824]

DR RORPOPOR HERBAL on KZbin changed my entire life with his herbal medicine. I appreciate you sir, for taken away my PID 🌿🌿🌿🌿

[@TheEmbeddedHobbyist]

Hi Phil, maybe a follow up on tuning the PID, how to get to the set point in the quickest time but limiting over and undershoot. tuning and stability are often just off as I think they are harder than getting the loop running. great video and I will be looking at this for my next soldering iron software update.

[@PhilsLab]

Thank you! I've actually got a video planned going from mathematical modelling, to controller design, to simulation, and finally through to real-world implementation. As you say, showing how to actually tune a control system and how theory compares with practice.

[@JeremyDWilliamsOfficial]

What does PID stand for? This: A proportional-integral-derivative controller (PID controller or three-term controller) is a control loop mechanism employing feedback that is widely used in industrial control systems and a variety of other applications requiring continuously modulated control. A PID controller continuously calculates an error value e(t) as the difference between a desired setpoint (SP) and a measured process variable (PV) and applies a correction based on proportional, integral, and derivative terms (denoted P, I, and D respectively), hence the name. -wiki

[@ravimannanikkad884]

First Time I am commenting on a video because you blew away me with your explanation/implementation skills. Thank you so much for the explanation

[@PhilsLab]

Thank you very much, Ravi!

[@Adrixcorp]

really useful man, you took me back in time to review system control concepts

[@PhilsLab]

Very glad to hear that, thank you!

[@chuxu1647]

Very impressed! The best I ever saw, clearly explained it in less than 20 minutes!

[@PhilsLab]

That's very kind of you to say - thank you!

[@osahonojo1897]

Thank you for this video! The explanation and example code were exactly what I was looking for.

[@owenplanchart]

thanks very much for this tutorial. Could you please explain the difference between T and tau. Sampling time vs Time constant for the filter? Where do we get its value from? How do we use this: (-3dB frequency in Hz, fc = 1 / (2*pi*tau))?

[@iamAK47]

Good question

[@TonySingh7]

Absolutely brilliant video! Many thanks for making this and showing the unity simulation as well, that was a new thing to see.

[@PhilsLab]

Thank you very much! My pleasure, I'm glad you liked it!

[@michaelwirtzfeld7847]

Clear and concise. Love the use of engineering paper!

[@PhilsLab]

Thank you, Michael!

[@alextolosa6891]

Thank you for everything, all the videos and information... every thing is increadible and very helpful. Nonehtless, i have a question, but why your PID has limits of -5 and 5 and for the integration part of -10 tup to 10, it is controlling the motors isn't it? For example if you control an AC motor with a trigger to a DIAC circuit, meaning the trigger should be between 0 up to 10 ms, if it is taken half the sin of the mains at 50 Hz, the PI output never can be negative, meaning that the clamping should be between this 0 ms up to max max max 10 ms, isn t it? Thank you very much

[@zyntist]

Thank you very much for your videos, you are a beast!! Please DO NOT STOP (EVER) and excuse my stupidity but i have to ask. I tested your code and of course it works perfectly, but I would like to understand why (when you simulate the first order system update) the output of the plant is: output = (SAMPLE_TIME_S * inp + output) / (1.0f + alpha * SAMPLE_TIME_S); I'm not grasping that and it's haunting me. Much love from Spain ^^

[@PhilsLab]

Thank you very much for your kind words! No worries, basically I start from the continuous time, first-order system: x' = -alpha * x + u. Then we can approximate the derivative to be: x' = (x[n] - x[n-1]) / T - where T is the sample time in seconds, such that: (x[n]-x[n-1])/T = -alpha * x[n] + u[n]. Then, rearranging: x[n] * (1 + alpha * T) = u[n] * T + x[n-1]. And rearranging again: x[n] = (T * u[n] + x[n-1]) / (1 + alpha * T). Which is the expression you see in the code. Let me know if that helps!

[@zyntist]

​@@PhilsLab It absolutely does, thank you master ^^ As you are so kind I'm gonna bother you with a last question. Could you recommend me the best (complete and to the point) book/tutorial in your opinion to review/master control systems theory from a practical point of view? I'm working in a new job with stm32, just testing and validating hw/sw at the moment, but I will need to dive into motion control design problems soon. My background was a very wide industrial engineering and ended working programming PLCs in the automotive industry (no analog control). I finally got out of that hell and found a cool job but I have some gaps and need to refresh this as I never got the chance to implement the things I really loved to study. Sorry for the long post

[@kimollivier]

How ignorant I was to write a sludge pump controller in assembler for a 6800 chip (not the Motorola one) that emulated a PDP8 mini computer. I tested it on a model and it worked. I was lucky in 1979. I wasn't aware of PID but it's obvious now. At the time there were no digital controllers, they were all analog and there wasn't anything for a pneumatic pump. I managed to increase the percent solids from 1% to 8% which was thought to be impossible. It still flowed and saved a lot of heat energy. I only had a few hundred 12 bit words. How large is the compiled code? I started programming by hand in octal, but found a cross assembler written in Fortran IV that ran on a mainframe. I could print out the code and enter it by hand. Burning a ROM was a major undertaking. The original language assumed magnetic core memory where the return address of a subroutine was written into the first word of the subroutine and the return was a relative jump using the value. Can't do that in a ROM.

[@PhilsLab]

Thanks for your comment, Kim! To be honest, what you did with the 'limited' technology at the time seems far more impressive to me than writing this little PID C program I did here! Would have loved to have been around as an engineer back in the 70s/80s. The code here takes up about 4kB of memory (and a couple tens of bytes of RAM).

[@nafisahmed6247]

a brief explanation of the choice of tau and T would be very much appreciated.

[@David_94]

Nice video, the next one could be something like "PID Controller Implementation on microcontroller" explaining the interruptions

[@PhilsLab]

Thanks, David - yes, in the latest video series (Control System Design) I show an actual implementation on a microcontroller.

[@nikolatotev]

I have a question regarding the use of the PID controller. For example, you have to balance a bar at a set angle with two motors on the ends (something like half of a quadcopter). The measurement is the current angle or the angular rate of the system. The input into the plant is some sort of number for example from 125-250 (min to max throttle). My question is - what kind of unit does the PID controller work in and how is the unit selected? On one hand, it's good for it to work with the input from the gyro since that's how the system determines the error between the desired angle and the current angle, but on the other hand, its good for it to work with the throttle value, because that's what the PID is supposed to output.

[@davebenemerito310]

Probably my new favorite channel! Thanks for this videos man!

[@PhilsLab]

Awesome - thank you!

[@alexeyveseliev106]

Especial thanks for the filter in derivative channel!

[@PhilsLab]

My pleasure, thank you!

[@miladchalipa2002]

Thanks for the useful Video, I decided to implement your PID algorithm to Temperature control of 1000 degrees furnace and wondering how to determine TAU and sample time. Note that my microcontroller will generate 2 seconds PWM (slow PWM) and I will control the temperature through Duty Cycle. regards

[@tornadoflore]

Excellent video. Exactly what I was searching for.

[@PhilsLab]

Thank you!

[@lucasbertolossi1598]

Hey Phil. Thank you for the video! I just have a question, isn't the term 1/(2tau +T) missing on the first derivative term? I know the minus sign has been fixed, but i think this is another mistake, or am I missing something? I implemented a PID controller without that term, and it worked after I tweaked the parameters, but just in case...

[@csobrinho]

I think the content is very good but you need some sort of presentation mode like the one intelij has or else you are using 25% of the whole video real estate. Always consider the users that see this video on the tv or a small screen. Thanks and keep them coming!!

[@PhilsLab]

Thank you! Yeah, I wasn't thinking about users with small screens at the time of making the video unfortunately. In new videos I'll make sure to make things like the code more legible.

[@erikev]

Great video. Could you please include what tools you use? What IDE are you using?

[@PhilsLab]

Thank you! My IDE is CodeBlocks. Tool-wise I'm using Matlab and Unity for simulations and to do the slides I'm using Notability on an iPad.

[@smith1401]

Very detailed and clear explanation! Great video 👍 One thing though. Maybe you can increase the font size or the zoom level in you IDE for other videos for those of us watching on mobile phone screens :)

[@PhilsLab]

Thank you! Yes, I unfortunately forgot about people watching this on phone screens - will definitely make the font size larger in upcoming videos. Sorry about that!

[@smith1401]

Phil S no worries! You have really great content (I would also watch it if the font stays tiny) :D

[@RaoulRacingRC]

Nice video! Could you also explain how a PID controller works for positioning a DC-motor with an encoder for example? Would love to see how to implement such a PID controller in C

[@PhilsLab]

Thanks! In an upcoming series I'll go more into detail on how to tune/design a control system. Not quite a DC-motor example, but definitely very applicable to that as well. Hope that will help!

[@icnmamun]

Hi Phil it is a very helpful tutorial. Wondering how would you select the tau. thanks

[@lamse_barmajiyye]

In fact, the video is very useful and useful I have a question please: How can I use this library to drive a washing machine's AC brushed motor I wrote a simple code to do that (C code) But the motor does not start smoothly, it is jumping The reason is that I did not use PID thank you Mr. Philips

[@jamescullins2709]

Wow, you overshot my runway. I have no idea what you are talking about. Not your fault but my lack of knowledge of the C language math. Still very interesting. Thanks

[@PhilsLab]

Sorry about that, James! I'm glad that you still found it interesting though. I can recommend Brian Douglas' KZbin channel if you're interested in getting an intro on control theory.

[@jamescullins2709]

@@PhilsLab Not your fault, my friend. Yes I do have an interest in control theory. I will look up Brian. Thanks

[@ayoublasbate]

You did an amazing Job...Thank you sooo much...it really helped me out with my project about underwater drone!! Hope we'll see more content from you...peaaace!!!

[@PhilsLab]

Awesome, thank you - very glad to hear that!

[@usmanhaider4653]

Great work thanks. Question. What is difference between tau and sampling Time?

[@thinkingthing4851]

Thank you!!!!!🎉 Needed this

[@timowolff1105]

Thank you for this greatful video explanation. One question which values did you choose for the kp, ki and kd gains and how did you choose them? Thank You very much!

[@PhilsLab]

Thank you very much! Tuning the controller is actually quite an involved process and unfortunately it'd be a rather lengthy reponse. I am making a new video series on control system design, where I'll be going into detail on how to choose those parameters.

[@lucasbertilho2055]

​@@PhilsLab This would still be really appreciated.

[@samibahlous979]

Nice work ! I just want to ask you how can we determine the value of Tau that we will use it in the filter part . Thank you .

[@diocorissosa4448]

Thank you for sharing. I do have a question. In the code, I see that actually coded the tick time "Tau". I've read in a microcontroller forum that Tau is not needed to be coded because it is taken care of every time the new sensor value is obtained in a tick fashion. It is confusing, since I see some code include the time variable and some code don't. Can you please explain?

[@jesusreignonhigh6732]

Would love to also see a PID auto-tune code.

[@rjgonzalez8108]

Great content! What textbooks have you found helpful in understanding control theory? Preferably, optimal control and it's practical considerations?

[@PhilsLab]

Thank you! In general, I personally really like 'Modern Control Systems' by Dorf and Bishop. Covers everything from basic to intermediate control theory with many examples along the way. If you're only after something on digital control systems, I'd recommend 'Digital Control of Dynamic Systems' by Franklin. Regarding optimal control, I must say I haven't come across particularly 'practical' textbooks. If you've heard of H-Infinity control, that is something I used for my final year project at university (self-balancing bicycle): philsal.co.uk/wp-content/uploads/2019/08/FinalReport.pdf

[@rjgonzalez8108]

@@PhilsLab thanks!

[@tttuberc]

Great video and easy to understand. Also I'm so glad to have found your channel which has lots of great contents.

[@connectme2karthik]

Hi Phil, could you also make a video on how to tune a PID either for this application or for another specific application like the gyroscope you example you already have?

[@PhilsLab]

Hi Karthik, I'm planning on making a video on PID motor control in the near future. Just waiting on the PCBs to arrive..

[@doco6186]

Very informative and well presented

[@PhilsLab]

Thank you!

[@interestingengineering291]

Thanks for making this nightmare to become interesting for me

[@PhilsLab]

Haha glad it got better!

[@zero2spearo]

Wow, I do a fair amount of embedded control systems, and this video was a huge help - it never occurred to me to LPF my derivative terms. Often times doing servo systems I want a larger derivative but can't due to instability. Maybe this is in the video and I missed it, but what are the considerations for determining the corner frequency of the filter? Should it just be slightly beyond the maximum output speed of the entire system?

[@zero2spearo]

Also, what do you think about having a zero-crossing detector on the integral term so that if the controller overshoots it zeros the integral term?

[@PhilsLab]

Hi Brett, Sorry for the late reply! Very glad to hear that you found this video to be helpful. Effectively, if you could get away with not filtering the derivative term at all, that's what you would want to do. The more you filter the D term, the further it gets into actually being a simple proportional controller. It's hard to say in general, but needs to be determined on a case-by-case basis. I typically choose it via root-locus to maintain stability even with a heavily filtered D term. Essentially, you want to filter the D term to reduce actuator wear and prevent noise being amplified too heavily. This usually has to be done in practice on the real-world system! Regarding zero-crossing detector, yeah you can pretty much do that with dynamic integrator clamping - which is pretty much what you described. I generally find that simple integrator clamping is sufficient for most tasks and makes the implementation easier!

[@iamAK47]

Very nice explaination, could you perhaps show it in an embedded system perhaps flash it on a pic and show the real time effects of it.

[@TobiasvN]

Hi Phil. Great Videos over all. Just the right mixture of being not too specific or too general. I have a question: How do you get good Kp, Ki and Kd values for your System without trial and error? I had to build some PID control loops running on STM32 and did that almost like you did. The real struggle was finding those values!

[@PhilsLab]

Hi Tobias, Thank you very much! That's a very good question and something that would probably take quite a few paragraphs to answer. I am planning on making another video on how to design/tune a PID controller for a real-world system, going through theory to arrive at the gains, and including the final implementation and demonstration using an STM32. This will most likely be on a propeller-based pendulum (aeropendulum, I believe it's usually called). I am happy to try and write up a couple paragraphs on how I'll be calculating the gains before the video is released if that would help? Have you had any experience with control theory? I hope to have the video up in the next two weeks, just waiting on the parts to arrive. The 'trial and error' method, most straightforward, and least theoretical way is to tune the controller gains in real-time while the system is running, which I assume is what you have been doing - this may of course not always be possible. But if it is, start off with all gains zero. Then increase the P gain until you get a fast enough response with minimal overshoot. If you have some steady-state offset/error, you need to add I gain. If this causes the system to start oscillating, try adjusting (decreasing) the P gain or add a touch of D gain. As you see, this is still very much trial and error, but maybe a bit more guided. There's also a method called 'Ziegler-Nichols', which is often mentioned in textbooks.

[@huseyinyurdakul4190]

​@@PhilsLab Hi from Turkey, Phil . Firstly thanks for this video and we look forward to STM32 presentation.

[@MrMbilde]

In the video you say that the material from which the tustin discretization is done should be linked. I cannot find it, so could you link it either in the desciption or as a comment to this comment? Otherwise, really nice video :)

[@CarlosDelcristo]

Great video, thank you very much for sharing... looking forward to the next one

[@PhilsLab]

Thank you, Carlos - more videos to come soon!

[@Gengh13]

Thanks for the video, it's well organized and really easy to follow, you are a great teacher. Subscribed.

[@PhilsLab]

That's great to hear - thank you!

[@mikegenco9646]

Equations in PIDController_Update reduce to output or measurement =.98 pid.out. other factors must be artifacts from past alternatives. I am somewhat familiar with Laplace and Z transform but would appreciate a detailed documentation of each and every step starting with basic differential equations for PID through Z transform. I have started with your code and I am converting it to run in real time on an Arduino mega and will incorporate changes to gains, setpoint, unwinding limits and hopefully also graph in real time but Arduino IDE 2.o3 is new to me having used 1.86 for years. Thanks much for your help.

[@SrikanthChilivery]

Thank you very much. I am planning to use your algorithm for industrial control (add few features). Being control engineer I really don't understand Control Modelling. Can u share reference study material you suggest for understanding and design of PID controller?

[@AbdullahKahramanPhD]

This is great! Thank you :) Could you do a practical implementation on a heater with a response time of about 5 seconds?

[@PhilsLab]

Thank you! I'm currently thinking about what practical (real-world) system I can make a video on to show how to design a control system from theory through to implementation. Is there any specific heating system you're looking at currently?

[@AbdullahKahramanPhD]

@@PhilsLab Perhaps a heated system that stitches a thin layer of plastic film going inside two conveyor belts that are pushed toward themselves.. Conveyor belts are teflon, and the heater is heating one of them by touching at the stitch point. It is a technique used in MiniPakr air cushion machines

[@theman3282]

probably take a look at 3D printer code, there's PID controller involved, reading the gear teeth/revolution of stepper motor to prevent position overshoot, thermal management etc.

[@denisvounckx]

Thanks for this nice explanation. Although I still wonder how the time is handled in the TestSystem_Update function. I was expecting there a kind of sleep.

[@PhilsLab]

The test function is not in real-time, so I didn't need a form of sleep function. Essentially it's just there to 'offline-test' the functionality.

[@quahntasy]

*Thanks for such a great explanation and that too on my birthday*

[@PhilsLab]

Thank you - happy birthday!

[@BinderTronics]

Thx for the code. If you are using OBS to record. Try adding the Noise Suppression filter. Should help with the static when you talk. Sounds like you are already using a Noise Gate. If you got something on Kalman filters please share If you are willing. Been spending way to much time trying to deciphering the mathematicians hieroglyphs.

[@PhilsLab]

Thanks! Yeah, I’ve upgraded my mic so the noise should be much better. Will be doing a video on Extended Kalman Filters in the near future, so hope that can help!

[@BinderTronics]

@@PhilsLab The static I was hearing, was static on my headset. New one, got it the day I made the comment. Audio driver seems to not handle low frequency voice data very well. Anyways. Thank you for considering the Kalman Filters. Got a somewhat working one but it just has awful response time to a change in input. Single axis input from a gyroscope or temperature.

[@MrFiskur1]

Great video pal! I can't find the link for the dynamic integrator clamping method that you mentioned in the video anywhere in the description :/ Could you maybe upload it here in the comments section? Cheers

[@PhilsLab]

Thank you! Here's the link to the anti-windup scheme: e2e.ti.com/blogs_/b/industrial_strength/archive/2013/04/13/teaching-your-pi-controller-to-behave-part-vii

[@mrechbreger]

Thank you for explaining that topic!

[@darth_dan8886]

What is the reason to NOT want the derivative kick? The output is clamped anyway, and I, personally, find it very handy to be able to kick the system into overdrive when it suddenly finds itself too far from the set point.

[@thuctranminh2170]

I'm really grateful for this video Phil!. It help me a lot. Thank you!!

[@PhilsLab]

Really glad to hear that, thank you!

[@kissingfrogs]

very much enjoyed the video and so looking forward to the code walk thru but could not follow easily as the text was so small.

[@PhilsLab]

Thanks! Yeah, sorry about the code size - will keep it much larger for future videos.