Hi, my name is Val or Valentine and you can find me at ColourMeVal on all the social media platforms and my job is to entertain you. So please let me know if I'm doing my job correctly, yes? I need to do it. Why do I form Facebook at Why24Channel on Twitter? Hashtag is white in the morning. So allow me, since it's Man Crush Monday, to crash on crash, crush on three, three guys, three, one, two, three. Now their name's Ahad. So please forgive me if I make a mistake. But one is Eric Abumayang. I don't know why you're so handsome. It's a long hard name. I love food. Thank you. And then we have Mane and then we have Mo Salah. So these three guys won the golden boot. Congratulations. Job well done on the Premier League. So we have here the handsome Abumayang. Yes, that one.  And then, yes, Sadio Mane, Mo Salah. I like him. He's so nice. Not that we're the friends or anything, but anything can happen and he could be watching Why254. So let us just appreciate you. Good job guys. Well done. All right, I'm done now. Now we can say hello. Hi guys. Hi. As you can see, I like football. I'm a little obsessed. Yeah, just a bit, just a bit. It pains me to say this. Mane is number six. It's touch here. We had 56 points and then we're number six. So side tonight was 66. Six, six, six. Yeah, of course. Number of the devil. I love what you did to the devil. It's okay. We're going to be all right. But let's now get to focus on you guys. What's your name? Oh, hello. I'm so sorry, but I like to Georgia. Okay, thank you. You're okay. Yeah, I'm a sub-chariot. Yeah, this week. What do you do? I'm a student, law student, African-Azalean university. Yeah. So you're about to drop some torts on us at any time? Oh, actually, yeah. Sure. Yeah, what are your social media handles? Oh, Facebook, cancel, a sub-chariot. Twitter, cancel, a sub-sian, chariot. And also in this account, it surprises him. Okay. I like to finish with the queens because you're special. You're the only one here. Hi. Hi. How are you? I'm good.  I'm going to take it easy today. I'm going to take it easy, very easy. It's not going to be like last time. Oh, okay. Yeah. What do they call you? My name is Arjun Karyuki.  The ones who come from U of N say, the University of Nairobi. All right. What do you study? I'm doing mass communication. Yeah. You enjoy it? Very much. You want to do what we do here? I'm going to come and take your job. Okay. First of all, we can shine together. Yeah. Cool. It's okay. Cool. All right. High five on it. Social media handles? Okay. You look fabulous. Thank you. What is your name? My name is Chilang Adfaith. I am a law student at African-Azarin University. That's why he's scared. I am a feminist. I am a professional mediator, and I am here. Wow. So next time, just before the handshake, we should be calling you. Please do. Okay. So guys, since it was Mother's Day yesterday, we are kind of bringing the party on to Monday and talking about guys and their moms. How much do you love your mom? I love my mom. I love my mom so much. Yesterday, we spent the whole day together. I made a breakfast in bed. There's one thing that I enjoyed. I did. And she's been with me. No, no, no, no, no, no. It was like really special. Like nice toast, toast, toast my eye. And then there was some passion just over there. Where? Where? So, yeah. Sausages. Should we conclude that he's romantic? No. Excuse me, excuse me. That's no. Why? Why? Why do we have to take the standard test of showing your mother love to being a romantic lover? Because it's a psychological test that's been proven. You can tell how you're going to be treated by a guy depending on how he treats the mother. I thought you just said you took half full. That's nothing to do with psychology. It's physical. Surely, it's a thought account. There's no way that I can repair. There's absolutely no way. It's a thought. It's a beautiful gesture.  Is it a choice? Do you practice what you preach? We do practice what we preach, but we don't depend on what we preach or what we preach. Too fast and you cannot always reciprocate what you're not getting. It's tedious. How much do you love your mother? Thank you for the question. Absolutely, like 100% I love my mother so much. Is this the kind of love that you actually go ahead and communicate and call her house, your day, or is that the kind of relationship you have? Okay. To some extent, yes. I do call her. But it's that we're not in the same place. She's not cool here at school. But when I go home and make sure I spend much of the time with her, most of my time just being with her in the kitchen, talking with her. I love being with her. That's all. So it's true what they say that mothers have a bond with their son? Of course. A monumental bond. Wow. And you see, let me take you back to like one of the greatest ballads ever made by Tupac. He sang about his mama. You see, it's not about it's about the mom. So there is no way that you can expect us not to have like that exceptional bond. And you know, and also another point to consider is the roles of our fathers in our lives. And that's why our relationships with our moms are that great. Are they absent, the fathers? Not absent, but obviously, of course. Of course. Of course. Come on come on. The beat of this is something to change. You're doing something else. And mothers are contrary to that kind of, that kind of a pattern of parenting. And that's why the bonds are like this. Yeah. So I don't think this conversation is what you expected it to be because we have a video ready for you and I think it's important we check it out. Woman married her own son yesterday. The woman and her son claimed to be in love with each other and they decided to take their relationship to the next level and get married considering that the mother, Betty Brickle, from Munitsaay in Mass Vingo, is now 6 months pregnant and expecting her son's child, and her grandchild, Brickle, 40, has been a widow for the past 12 years and has been living with her 23 years old son Farin Brickle. She confirmed that she is 6 months pregnant and that she has decided it is better to marry her son because she does not want to marry her late husband's young brothers, whom she says are coveting her. Betty stunned the village court last week when she said the affair with her son had begun 3 years earlier. She said after spending a lot of money sending Farate to school following the death of her husband, she felt she had a right to his money and no other woman was entitled to it. Look, I struggled alone to send my son to school and no one helped me. Now you see that my son is working and you accuse me of doing something wrong. Let me enjoy the products of my sweat, she told the village court counsel. Farate said he was more than prepared to marry his mother and would pay off the Lobola balance his father had left unpaid to his grandparents. I know my father died before he finished paying the bride price and I am prepared to pay it off, he said. It is better to publicize what is happening because people should know that I am the one who made my mother pregnant. Otherwise they will accuse her of promiscuity. But local headman Nathan Mopularwa says, we cannot allow this to happen in our village, Mashhoreche, I will ay, ay, ay, this is a bad omen indeed. In the past they would have to be killed but today we cannot do it because we are afraid of the police. He warned them to immediately break off their marriage or leave his village. They chose the latter and have since left the village. I told you it wasn't what you were expecting, I told you, I told you now, put it on Facebook and put it on the hashtag Israel in the morning. So we started with the question how much do you love your mom? Apparently there is somebody out there who really, your thoughts, they are traumatized. Talk to me mom. I was waiting for this opportunity. From the first point he said that it is all about romantic loving but I totally disagree. Now let's see what romantic loving has done to these boys. Why do you have to live with your mom to the age of 26 and above where you can actually get a woman and marry, then end up marrying your own mother? This is a totally forbidden thing in Africa. She's pregnant. She's pregnant, imagine. I just want to imagine how the kid would look like. That's not nice, I'm sorry. At 254 on Facebook, at 254 on Twitter, tell me about it. That's a really painful experience to look at and even to just imagine. You can't understand. My thinking to what it is, maybe the dating scene over there is just too tough. I might never know. It's really difficult. You've got to excuse the behavior but hey, we need some background information as to why this man of Kassatin for two years when he was young, he wants to keep up that behavior which is a full grown adult with 32 teeth. Seriously, I don't think you can justify that act. We just need to say it's outside and public wise and say that it is forbidden. Let's not act like we should listen to the background story of it. He has motivation to marry their own mother. No one. I wouldn't be motivated to be married by my own father. Why? What do you think, sir? Wow. It's down shocking. I've been almost lacking so much to express this. In our society where I come from, we cannot even imagine this and I believe so too.  It's never happened. It has never happened. What I can say from it is even we cannot blame only the man considering the fact that he is the mom. The mom also around.   It should not be the one misleading you. The argument in the video was that she has been working hard to pay off her son to go study all these things, keep him proper fed and everything. So she cannot contemplate another woman. If I can ask, is that like the mom or the step-mom? It's a little bit strange. It's weird. It's like rich and multi kind of stuff. Definitely a cookie. So there's this complex called the Odi Pus complex and we're going to touch on it in a little bit. But before we do that, I want to ask you another question. So we started with how much do you love your mom? Like quantity. So can I ask you how much do you love your dad? I love my dad very much. Yeah? Yeah. Like you're open with him. He's my best friend. Oh, that's so sweet. The opposite of Odi Pus complex is electric complex. Do you think there's a danger of electric complex coming through? I actually think it's how the society raises you. You know, if the society raises you knowing that this is a father whom we should love and respect as a father, then that's it. And this is a mother whom we should love, respect as a mother. So there's no need to get these terms confusing like I love my dad in such a way that I can actually get married to him. No. No.  I like that. Yeah. And there we are together there. We should be. Yeah.   Now, how does your relationship with your mother affect the relationship with your significant other? Well. Like, are there two other women who have children?  And not physical at the end of the day.  Of course, that's always going to be in my mind. I'm used to a certain kind of loving, a certain kind of pattern. And if I don't really see it in you, maybe I might try and throw hints at you. Like, this is what I'd like and this is what I wouldn't like. See the dangers of that. Why can't you be more like my mom? What is the problem? She is like, she has been with her for 20 plus years. And it's difficult when someone else comes with their own total way or different way of reciprocating love. So, yeah. Can I just say something? Say it.   Stop setting standards.  I don't think we have the same kind of love. Why is it supposed to be different yet? While you're marrying each other, it's till death to a spot, through sickness and through health. So what's so different there? What's so different? Because the interpretation that you're having of the mom is the same ones we are going to take at the altar. Are you agreeing with your gentleman? I want to converse with my brother here. For real, I can't talk of us men who don't like our mothers. We like that love, that compassion that they are showing us, even when we do our own. Oh, OK. So wait. You just had an epiphany. So is this why men just randomly treat and expect the woman just like this?  Yeah.  You go up on issues like what? So then when we see our mothers, OK, the way they're acting and the way they love us, and also the values they have, like when they show that love to our daddies, you see these are real love or relationship.  It's like between my mom and my dad. OK, you see those values and how they work it out.  So like, sometimes it cannot favor the lady side, but they have to accept this. This is opening my eyes, yo. So what happens if your dad was absent or if your dad was abusive or if your dad was not the kind of figure that you should be looking up to, to be, you know, to someone else?  Like, hey, it's so deep. So like, ah, for real?   That's what we're saying. No, no, no. That correlation doesn't really stick. But how will you learn how to treat a woman if you don't know how your mother is supposed to be treating you?  You are happy. Already you're here complaining. We can't understand. Women's do are from Venus. Dreamers, aha. It comes from inside. Whether you are loving your mom or whether she wasn't treated so well by the dad, it doesn't really change how you're supposed to treat your wife. But what do you have to look to? Like, monkey see, monkey do. Let me answer that. We're talking here of seeing your mommy and like taking what all your dad is doing to her. But seeing the love the mommy has to the daddy, to the husband, you see? So then, you know, okay, to me, I know that woman or mom loves that more, more than the daddy loves her. And so we want to, yeah, we expect that. For the relationship to proceed, yes. Let me just say something. It should be on top. This is just typical and it's a hypothesis that is not working. But it is reality. It is reality, but I want to believe you're living in your own head if that's what you expect, honestly. Because I don't see why I should set a standard of the way my dad treats my mom is the way I expect someone else to treat me. No, that was in 90s when they got married and whatever they decided that's their own. Whatever we are deciding in the 21st century should be just different. Their relationship should actually inspire you, not set a standard of how you should actually act in your own marriage. I don't think so. What I can say about that. Her vulnerability in that situation will make you aware or will make you more compassionate towards your wife. The vulnerability that your mother suffered or any other female in your life, it will inspire you on to ensure that any other person who comes in your life will not face or feel the same way. So that's going to act on your psychology as well. The kind of way he put it is a bit, I feel those are very high expectations. So if you've seen your mom being very, I want to say something that's very soft, like she's never raised her voice or anything. And then you find the Valentine who expresses herself as wish, the way I wish to.   What we feminists say is, a weak man will never know how to handle a very strong woman like you or myself. Whenever, when we try to speak out, they think we're trying to project attitude on them. But that's not the point, we're just picking out our minds. That this is not the way I want things to happen. This is how things should happen. And if you want things to happen this way, then we should have harmony here. It is not like we're projecting attitude or anything. So if acting in submission is supposed to show love, then no. I'm going to go back to the Bible and say, that man is always ahead. And I will still go back to the same Bible that when God made Adam and Eve, He did not say that anyone should be superior over the other and no one should impose authority over the other. How can I miss that? Let me go back to the Bible. Let me go back to that. You see, the system on gender, not gender, but on the lady and my gentleman side, the feminist can say it was corrupted at the end, at the beginning. You see, when God created heaven and earth, He created man. And out of that man, He created a woman. And the man was given the responsibilities more than a woman, like naming the animals in the garden of Eden. Really? To add on that. You're lying. You're lying. Wow. You don't know that. Man wasn't given responsibility. We were both given responsibility. Okay, but naming. Naming. Naming there. No. Let me go to chapter 2 verse 9. It's talking of a lady, a wife submitting to a husband. And for the system to move smoothly, we should accept that. But you see, those who don't accept, you see the breaking families. You see what is happening in the country. A lady would like to compete with a man, like, okay, you're doing this to me, like I will rebut. Then you see, like the man can get hungry, like the lady can kill the man. So if we accept this and move smoothly, the system itself. Can I just pick something that you've said? What you're saying is this. That's your bottom line. Exactly. Imagine you're trying to justify what is illegal. Because we're then not submitting. That is why these guys are doing this. That's so illegal. Okay, let me make that again. You see what's happening is that men was, like, you know what a man can do.  So a lady can just come and compete with, like, you see, when there is some play out, let's say the chick has played a man. You see, the man, like, this is not submitting. Like, the chick playing, the man will just come and it can be upset and provoked and killed. And, like, when the lady do it, we all agree that it's not that offensive. Wow. Considering the fact that polygamy is accepted almost everywhere in the world. Okay, there are so many things I have to say to that. Let's just start with the message. Hi, Val. My name is Mike.  I can't go back single forever. I can't go back home. I can't go back home. Okay, so we did get a couple of news clips ready for you. And I think there's one more video if I'm not too wrong. So I'm hoping my amazing directors up there will play it for me. But we do have to wind up, not already to a conclusion, but what's out of the conclusions? Can I start? Where should I start? Yeah, you're going to start with me. Look at him. I'm going to give you one of the greatest combos ever in the Bible. And this is going to illustrate why, like, the bond between a man and their mother can never be broken. Like, when, in the household of Isaac, when he wanted to bless us all, the mother of her had the conversation. And then he went to Jacob, and then she was like, hey, Dad wants to bless us all. So quick, quick, quick. Well, I thought I'd go and get some goats, and then I'm going to cook the gift people that he likes. And then Jacob was like, Okay, so I'm going to cover that. Let those blessings, those curses that are gonna come, if you're found out, fall on me. If my spaghetti is usually cooked with minced meat in, why would you want to cook it with minced meat and spaghetti? See, it's just like... See, it's just like that. If you're used to... Give me your conclusion, sir. Make it brief, please. Okay, I'll try. I want to conclude by saying that we should all accept the system instead of fighting to do the system. Submitting is not costly. I don't mean like submitting, like nailing down, but just submitting. When you submit, then all things will go through. Like the man will also submit. Yeah, that's all. Thank you, Queen. Thank you. I totally agree with him to some point. The fact that he said if you submit, he will submit too. That's okay. But the fact that you're trying to set a standard for relationships high, so high, that you're comparing me with your mother, that's not working. So let's try and scrap that out and live in the 21st century. Yeah, because for the longest time, men have been telling us with the eyes of high expectations. The expectations are out of this world. They carry so high in the moon. Okay, I'll laugh. Women have been told to respect our husbands. And husbands have been told to love their wives. It's a difference. So, where does it come from? Which is hard already because I have a mouth. Yeah. Wow. I revenge my man loving his mom too much by loving my father in love too much. It worked miracles and he came back to love me. Okay. To be continued. That's why 254 on Facebook and 254 on Twitter. Thank you so very much for taking this ride with us from 7 until 10 in the morning. Tomorrow is money making Tuesday. You really don't want to miss it. Thank you again. Have an amazing day and have an amazing week. We'll see you on Wednesday.


This talk will be modeling and simulation of physical systems for hobbyists. Manuel Eipel wanted to lower the entry thresholds for the subject and so explaining modeling and simulation techniques that help even small projects for makers and hobbyists. So please welcome Manuel for the talk about modeling simulation and physical systems for hobbyists. Thank you for the kind introduction and welcome everybody. Actually I forgot to say that all examples that I will show in this talk can be downloaded on the website of the talk so if you want to try it out already right now while I'm actually going to show the examples you can do so. So let's get started by taking about this title a little bit to see what is meant by the individual words and by this have a rough outline of what we're going to talk about. So first modeling in this context means to create a mathematical description of the system so we look at the physics of for example a robot that we want to build or a mechanism then we extract the different physical effects look at the equations that are represented in these effects put it all together and then we obtain a mathematical description. And simulation that means that once we have this system, this model we are going to use the computer to perform calculations from one time step to the next so to basically extrapolate from an initial state of the system to how the behavior is going to be in time. In this talk I want to talk about physical systems so hardware that we can create and not some sort of fictional physics for computer games or something but release something like a mobile robot with a small drone or similar that as a maker you want to create. And I'm addressing this talk to hobbyists. I don't want to reduce the knowledge and competences of hobbyists but only say by this that the resources that we're going to use in this talk are commonly available tools and not simulation software that you have to buy for tens of thousands of euros and I'm not exaggerating about it. So maybe a quick round like who did math courses at university level? Okay, it's quite a lot. So actually I prepared the talk to address it to everybody who had 10th grade school math so it might be a bit familiar to you already but then you can help your neighbors who have difficulties. So let's get started. What's the motivation behind doing simulation? Why do we want to simulate something? So imagine with your friend you want to build a small self-balancing robot like this so it's a very easy design. Two wheels left and right which have one motor, each wheel has one motor and then there's a rod going up with a camera fixed on top so that you actually have a higher point of view so that you see something and this is actually an inverted pendulum so if you build it like this without a controller it will just fall over but it's quite easy to implement at least hardware-wise. So you want to build this with your friend and you say okay I'm good at programming but I am not so good with the mechanical aspects so your friend says okay no problem I will build the hardware but then you're stuck okay you don't have the hardware yet so how do you want to develop the software if you don't have the hardware? And this is where simulation can help for example. So in the time that your friend is building the hardware you can already start the software you just have your simulator, you recreate the hardware while it's absent and then you can program your controller everything that you want and once the hardware is ready you keep the controller you throw away the simulator and ideally then the system is complete so I build a small simulator for this example and Python you can also download the code so you see here the simulation is already running but it's perfectly balanced so it's not dropping yet but if I push it a little bit from the side it will tip over I didn't activate the controller yet so it's like if you have your robot without power if you push it a little bit it will tip over so now I can activate the controller and then push it a little bit and then you see that the controller will actually bring it back so the controller is the part that you will implement in software and the hardware is basically this part the tipping over part the hardware that your friend will build and let's see I cannot even make it drive around just as one example of what you can simulate with the methods that we're going to see okay the problem is I don't have that much time so we're not going to go all the way start with very basic models and then we see how far we go so to summarize the motivation simulation can be used as a placeholder so while the hardware is built you have the simulator and then you exchange it or it can be used as a virtual test bench for example for scenarios where you don't necessarily want the real hardware because it's risky behavior and it can be damaged okay now one step back modeling what is it and what are the basic foundations so imagine our friend Newton here under his apple tree and now we cut the apple loose and we ask ourselves okay what's going to happen we can look at that at different levels of detail from a very simple level to a very detailed level at the simple level you could say okay the apple moves down so you see on the plot the line just goes down constant velocity then well this is an observation that you can make very easily just by looking at it you don't need to measure anything then at the more detailed level you see that if you make a more precise measurement actually your apple is accelerating so you have this parabolic curve because of the gravitation the apple becomes faster and faster and then if you go at an even more detailed level you notice that there's actually aerodynamic drag so it won't accelerate infinitely but it will eventually reach a saturation velocity this is for example when a skydiver is falling from the sky then you clearly notice this effect of a longer period so the take home message that I want to show with this slide is that actually depending on the question that you want to look at with your modeling and your simulation you should choose an appropriate level of detail so as simple as possible and as detailed as necessary and this might actually change for the same system so at one point in time you might be interested in this starting behavior so you need the acceleration and at another point in your project you might be interested only at what happens here at saturation velocity okay now we go even one step further back in the mathematical methods so differentiation and integration because this is very essential that many physical measures are linked to each other through differentiation or integration for example if you take the position x velocity v and acceleration a then if you differentiate x you get velocity v and if you differentiate that again then you get the acceleration a and the other way around by integration then you obtain velocity again and the position so you might remember this equation from school for calculating the derivative so basically the derivative is defined as the ratio of the function you want to differentiate at two points in time, point t plus h and t so the difference of this divided by the distance in time so the h and if you then have this corner case where h goes towards zero you actually obtain the derivative at the point t so in this case the velocity at the point t now if you take this equation and you modify it a little bit so you multiply by h and you add the x of t then you obtain this equation which is one way of calculating the integration so x in this case at the point t plus h in time so you see that it depends on the x of t so a little bit earlier in time and it also depends on the velocity so the derivative of x a little bit earlier in time multiplied by h and again if you take this corner case where h goes towards zero then you obtain x of t plus h so this means actually by integrating we can look a tiny little bit into the future because the derivatives are always running ahead in time of the function that was differentiated if you integrate it backwards you can look a bit into the future and that's exactly what we want to do in simulation we want to say we have an initial state at point t and then we're interested to know what happens at point t plus a little bit so in the following we're always going to integrate for the simulation and not differentiate the only problem is now this corner case definition that's nice for mathematicians but it's not really useful for computations we cannot write this in software so what we're going to do is we're going to use the so-called Euler method and this simply means that we replace this corner case limit of h going towards zero of h by a finite value ts which is often called the sampling period so finite means we just take a small but defined value and not this limit thingy and then with ts we're actually only going to calculate the points in time at integer multiples of ts so we call k the index and then we calculate the points in time at t equals k times ts so this is discretization and yeah so we transform this equation into this one we do invite by ts and we obtain this nice equation which is x of k plus 1 equals x of k plus v of k times ts so this is something that we can easily implement in software we just have a for loop and every time we do that so I'm going to show you a simple example in spreadsheet just to show that well it's pretty independent of what software you use so let's define some constants here on the left side we take a sampling period of 1 millisecond let's put the unit here so we have it in seconds then we have the index here we call it k, we have the time here we call it t and we're interested in the position we call it x and in the velocity we call it v we call it one point in time so we begin at time zero and everything is zero like this let's get a bit more space here so now we have this formula so we need a k plus 1 that's not a problem, we just say ok the next k is equal to previous k plus 1 the time we say is equal to this index k times the sampling period so we use these dollar signs so it doesn't change if we can't be pasted and then we have the integration formula so the x is the previous x times the previous v times the previous velocity and then we apply it by the sampling period like this again with the dollar signs and now we would be boring if the velocity is zero all the time so let's put a velocity of 0.5 meters per second for example and now we want the next moment in time so we just do the same operation over again so I just copy paste the lines and this is now the time evolution for example I can now plot position over time I just add this plot I tell it to take the time on the x axis and take the position on the y axis ok, insert it here alright so yeah it's not very exciting but it's exactly what we expect if we integrate a constant over time so we just obtain a straight curve so let's add the acceleration now we call it A ok we start the acceleration from the beginning like this and now what we do is we actually use the same formula that we used for the position so this one we also use it for the velocity we copy paste it and then we can copy this line and now if we want we can repeat this like a bit longer ok so you see now we have a constant acceleration we integrate two times so we get the position as a parabola shape like this actually I could have added a negative acceleration just to have the drop from before so this is already quite useful if we now say that the acceleration input is not a constant but for example we have the acceleration input from an acceleration sensor then just by using this method which doesn't rely on any knowledge of the shape of the acceleration right so we can just give it random input and it will always integrate it so if we have the sensor input from the accelerometer and we integrate it twice then we can keep track of our position ok but now we want to model something so we don't have an accelerometer yet so where do we get the acceleration from ok one warning always keep the sampling period small we're going to discuss later on what small means ok so some building blocks I can obviously not summarize all physical equations that exist but in mechanics I will show some of electromechanics that are useful like for mobile robots if you have a motor turning something with gears maybe and then a sort of lever mechanism for example so we start from the simplest version so a moving mass just imagine a billiard ball for example which has a mass m and a velocity v and now if we want to change this movement we need a force F again this is our friend Newton telling us that and this is the second law of motion so the force that we need is proportional to the mass times the acceleration ok I need to accelerate a little bit because time is running out so the same equation that you have for linear motions you also have for rotational motions which is the right side and then you can also have the weight so this is in the apple example so the force from the weight is just a mass times the gravitational constant and other effects that you can have are for example spring force and viscous damping these two are actually not only useful if you truly have spring damper mechanism like you would have in a suspension for example but it is also useful if you for example want to model a hard contact like I had in the beginning in the simulation example the robot tipping over and falling on the ground so you just put the stiffness quite high and the damping as well and you will obtain this effect of an input of a contact so let's see if we now combine this for example we want to have just for the sake of the example a small mass spring damper so we put the gravitation here we put the spring here and the damper here damper so what I didn't say here is that this F is not necessarily one force but it is the resultant force so this is actually a vector addition so you take all forces together and then this is the F which drives your acceleration so this is what I am going to do here some from here to there I need some constant so for the gravitation I need the mass so let's say 2 kilo it's a bit heavy but ok let's make it half a kilo then let's say the spring stiffness we just put 100 Newton per meter and the damper let's put 10 so of course this setting of the parameters now I do a bit random but ideally you would look at your system when you design it and then calculate these values so that they correspond to what you are actually building now I just make a simple example so I pick them at random ok so then we have the gravitation if we look here m times g ok so I also need the g so that's the well known 9.81 meter per second square so that's the mass the mass times this we again add the dollar signs and then we have the spring so the spring I set the x0 at zero so the x0 is the equilibrium position and so we had minus ok times position and now what you see here what I didn't say but if you know a little bit about physics and math you see that this is actually a differential equation that we are going to solve here but yeah you don't need to worry too much right now because the Euler method is taking care of that so we also need the damping here times velocity ok and now I'm just going to copy it all the way down so that I have like 60 seconds it takes a bit longer because yeah it's a lot ok and actually what you see here is that what I said before about the sampling period was a problem right now because we're actually doing an error in the Euler method in the integration and if the normally because we have this feedback loop in the differential equation it's not a problem because if there is an error then it will be compensated in the feedback loop but if the sampling period is too big then this error is actually multiplied and then you get this instability behavior so I can also show it with a bit bigger effect like if I take only 100th of a second then you see here if you look at the values it's actually going to infinity so my simulation is not robust and this means that the sampling period is just too big and the simulation is becoming unstable so now I picked a smaller value which of course is a problem because now I'm only simulating 6 seconds instead of 60 but you see that here is a trade-off to make between model complexity and precision which means more computation resources are needed and the robustness of the simulation sorry? so the question was whether this was a resonation yeah right but in theory this maybe I made an error in my calculations let me show you the one that I prepared okay I'm just going to take the one where I prepared it properly because obviously I made an error in the calculations so this is the effect that you are expecting right? so you start at a certain position then you have an oscillation through the spring which is bringing back the mass to the center and then you have a damping so it slowly fades out okay actually I'm also running out of time I wanted to also treat some electric principles and electromechanics to show an electric motor I can quickly show it to you in the slides so the nice thing of the electric motor is that it shows how to solve problems where you actually have two equations which are entangled with each other and you can also see in this example the effect of taking into account one physical principle or ignoring it in this case the effect of the coil so as I said you can download it from the website and then have a look at it if you're interested right so this brings me already to the end of the talk just some tips and tricks to summarize so as I said the sampling period needs to be small as a rough estimate I usually take around 100 times faster than the system time constant so for a mechanical system usually 1 millisecond is okay I don't know why I had an error before but 1 millisecond usually works fine if you have the electric motor with the coil then you need to reuse the sampling period maybe to 10 microseconds that depends on the system time constant as I said then as a second point use block diagrams so this is what I mean by block diagrams it helps you to keep track of which physical measures influence which other physical measures well it's a bit difficult to read maybe in the beginning but you get used to it and then it's really useful and then if you want to be sure about what you're doing or you're having more complex models maybe use some specialized tools for example SciPy which has a good ordinary differential equation solver or open modellica or an edit where you can basically just compose a system as you find it you just add a block for the spring you add another block for the damper and then it takes care of that or a SciLab with XCOS where basically you use this block diagram method to define your equations instead of writing them down and so as I said they have better differential equation solving they're also more efficient because often they use variable time steps so they see when it's critical to reduce the sampling period and when it's less critical and also very helpful other data logging and visualization tools that come with the software otherwise it's sometimes really cumbersome to keep track of all your variables and then plot them nicely okay so actually I think I accelerated that much that I still have some time so I can maybe show you how this works in OMEdit which is also free software and it's basically a graphical tool to use open modellica and open modellica itself as a modelling, programming well let's say definition language okay something is not working because it's not starting as it should okay then I can show you the python code of the simulator that I showed in the beginning so this one so what I did here was to define two classes just to have them run in different threads one thread for the simulation and another one for the visualization and actually the simulation part is pretty simple and then the visualization part takes more lines of code so you see here that there's a reset function where you just define the initial state and then if you look at the simulation part itself you find again what we had before so there's a simulation loop here I do a busy idle well here's the busy idle just to have a sort of fake realtime and then here you see the Euler method integration so in this case it's just a bit contracted with the plus equal notation but basically it means theta equals theta plus omega times the sampling period and then once more for the yeah omega the rotational speed then the different torque effects so in this case that's the rotational version and not the linear version and then at some point the controller I didn't separate it nicely in this example but usually you should and the same again for the linear motions so I got the sign that time is up and yeah I would be happy to take some questions yeah time is up but we're not letting you go yet because we do have time for questions out in the room there are microphones please if you have any questions stand behind one of the microphones and I will call out the microphone number and you can ask a question please don't be shy seems like there are a lot of you that are quite knowledgeable about the subject stand up behind the microphones we have a question from microphone number four hello and thanks for the talk I would like to ask if you have the code somewhere available all the examples that I showed are on the side of the talk itself so if you go in the far plan then there are links to where you can download these files are there examples online somewhere not from me probably millions of examples but for this talk I just created these ones I just have one more for the drag with the drop of drag which you also find but yeah so this is drop after so this is your chance if you want to ask any questions and share the answer to your question with the rest of us please get up to one of the microphones and are there any questions from the internet there is no signal from the signal so is there a question from the internet no let's give Manuel a big round of applause thank you for his talk


Hey guys, welcome to the 30 paintings in 30 days project. If you choose to join me on the 30 paintings in 30 days journey, I hope that you do share and tag me and post like on social media and stuff, maybe film some videos, tag me in the description, something like that. I am kind of excited about the project. I do do daily drawing. I don't necessarily do daily painting, but making a daily practice out of something like this encourages you to get better at it, encourages you to work it into your daily routine or weekly routine. It also is a way to use up supplies. So if that's your goal, maybe you don't want to do 30 paintings in 30 days, but you want to do 30 collages in 30 days. That works too. So let me know. Let's get to painting and I'll see you then. Hey guys, we are here for painting number 24 of our little 30 and 30 painting series where we're doing all these little watercolor sort of studies. We did have to switch journals because I filled up the last one that we were working in, and I will be honest with you. I am not a huge fan of the paper in this journal, which I'm not sure. I'm not sure what the brand is. I do think it's from Hobby Lobby. The other journal we were working in was a Moleskine watercolor journal. I also like Strathmore. I'm a fan of Arches and Fabriano paper. I don't remember what the brand is on this one, but I'm not a huge fan. It tends to really bleed through the back really badly. I've done some other work in here. You can see on this page. So we're going to just be working on single sides. I learned that with this journal right away pretty quickly. And I'm probably not going to tape off any edges because I really just want to use up the paper in this journal because, again, not a fan. So there we go. All my disclaimers are said and done. I've got all my brushes out. I've got some clean water. I switched paint palettes. So this is one of my bigger palettes, and this is my Shmiki palette. I have this year been doing a project inspired by the beauty YouTubers that do project pan trying to use up some of their makeup and try things that are just sitting that they haven't tried yet to see if they even like them. And I figure, you know, artists and people who have tons of art supplies, we kind of need to do the same thing. So I have this Shmiki palette. I do love it. I just don't use it very much because I have lots of other watercolor paint. And I'm a huge Daniel Smith fan, although this palette is great and they're fabulous colors. I really, really love my Daniel Smith colors, but I have it. I should use it. It was expensive. So yeah. All right. I also have a inspiration photo page turned in my book over there. I think the images are from either a magazine page or wrapping paper or something. And they're sort of illustratorly versions of poppies, which just inspired me to maybe do some poppy flowers. So I'm going to get my brush. I usually start with the half inch flat Princeton Neptune brush, which I love. And I'm going to just get it wet here and we're going to start with the chrome orange here in the Shmiki palette, which is this color here. And I'm going to just kind of map out some poppy petals. I'm suggesting a poppy. I'm not trying to be realistic about it. And the page that I have turned to, it has these illustratorly flowers that remind me of a poppy, but they are not poppies. So we are just being expressive and we're taking inspiration from and we are trying new things, which is what this is all about. And I'm just using my brush. I'm putting it flat on the paper and then I'm just kind of turning it to do sort of a petally shape, seeing what I get. Of course, I'm starting light. We'll work our way darker. Although I live in Oregon now, I am a California native for those that don't know. And I'm just inspired to do some sort of California poppy or orange poppy. I don't know that it will come out looking like California poppy, because I don't think California poppies have black centers and I kind of want to give it a black center. So anyway, but I want that kind of orangey apricotty color. Okay, then I'm going to go into transparent orange. I'm going to add a little bit of that to the petals and use it as my shadow color, really getting the edges getting the center where the center of the flower is and the petals would be curling in so it would be a little bit darker to the viewer. And, you know, the paint is still wet or semi wet, so it's going to blend a little bit. I am using just the tips of my flat brush and occasionally touching it flat down to the paper to get a different kind of mark. And it's just really all about playing with the mark making getting used to working with your brush, whichever one you're choosing to do this with something like that. I like that. There is a paint gray in here, one, two, three, four, which is a dark blue gray, one of my favorite colors. There we go. So we're going to put that here, and then we're going to give it a dry. I'll be right back. Okay, now we can go on. I want to admit to you something. So when you're doing a painting and even though you kind of know in the back of your mind it's not really done yet, but you really like where it is at. Stop and take a picture. I just did that with this. I could really, really, although despite the fact that I don't like the paper and you can tell it's just doing funky things already on the back. I could see me using this as inspiration or taking this having my daughter help me take this exact image and put making stickers out of it or background paper or fabric or something else. Just as it is without adding anything else. So I did stop and take a photo. So there's a hint of kit for you. All right, let's get keep going. I'm going to for now stick with my flat brush but we'll see how long that lasts. I am going to pick up some neutral tint and mix it with the Pains gray. I have some dark something over here on the palette too. So let's just mix them all together. I'm going to just tap the edges of the brush to the center of the flowers to add some darkness and depth to what's going on. Okay, while that dries, we're going to grab a green and I'm going to grab. Okay, sorry, there was suddenly noise in the background. It's children outside playing. I'm going to grab the olive green, olive green yellow that's in this palette. And we are going to just suggest some some greenery. Again, I'm so I'm just I push, touch the brush to the paper, push it down and then just twist it around. Then I'm going to rinse it off. I'm going to get some water. And again, this paper this paper must have a lot of cotton or something in it. It just really really absorbs the paint super super quickly. And I kind of don't always have time to move things around the way I want because of what it's doing with the paint. It's a challenge to work with, but you know, this is a good illustration of why you should do some of these little studies. You don't have to do 30 of them in 30 days, but these kind of studies are a great idea when you're trying new paint, new paper or new brushes just to get used to the supplies that you have. Okay, I am going to now go in with we're going to let those greenery suggestions dry. And I'm going to go in with what color do I want to go with? Maybe ultra violet, which is a purple. I've got one of my smaller round brushes. This is around number one. And I'm going to go into these flower centers into a little more water.  So, so rather than drying things all the time, you can of course, you know, a proper watercolor is what they do is they do the like the leaves and then they'll work on another part of the painting while those dries and then those dry and then they'll go back to work on the leaves. So I usually have no patience, so I usually don't do it that way. Okay, that's pretty good. Then I'm going to take the same brush and I'm going to go in with cadmium red light, which is an orangey red. We're going to just add a little bit of that into a little bit of more. There we go. And again, we're just defining some shapes, not all of them work. I like to be more of a suggestive painter, so it's not about doing detail, not for me. It may be for you. There's nothing wrong with that. So I'm just, again, as I've stated in other videos, I'm barely touching the brush to the paper just using the very tip of it to just do a partial outline on some of these petal-y shapes. There we go. So there you go. There's our poppies. I'm going to give it a dry and on to the next. How is that for today's painting? I hope you enjoyed the process. And if you want instruction on the painting, you need to be over on Patreon. They are going to get the talking version here on YouTube. You're just going to get the speed food through version. Sorry. If you'd like to support the free content here on Facebook or in the, here on Facebook, Holy Cow. If you'd like to support the free content here on YouTube or over in the Facebook art groups, I certainly would appreciate that. You can of course join Patreon. We do have YouTube membership here for a small fee. And also I have an Etsy shop and I have PayPal tip jar and all that stuff. So check out the video description. Relevant links will also be down there. And yeah, don't forget the most important things.  Do share your work with me. I would love to see what you're doing. That's it for now. See you later. Bye guys.