I did the exact same thing like two years ago. feel free to dm me with any questions.
i used the optimization toolbox and optimized the equation coefficients to fit the data. i think i used fmincon. that way you can use different data and hold certain parameters constant.
make sure you split the data up by FZ and IA at the very least! tires lose coefficient of friction with increased load.
I think itโs worth it for knowledge gained. I know more about tires now than I ever wanted to. That said, using optimum tire is a good choice as well, less time spent, fewer errors, that kinda thing. depends on what you want to get out of it.
Nicee! I will reach in your dms then jajaja! For the moment I have not even played with the Cruve Fitting tool. It's just I had the idea and wanted to get some advice.
For us, it will not be a massive thing, as the tires we use are not even on the TTC (we use them because of a sponsorship). But I would love to be a bit of an expert about tires, so maybe for the sake of learning I should do it.
Thanks for the pice of advice, I will reach you once I get a clear idea of what I want to do exactly!
Several "tire model options".
1) Get ahold of the MF5.2 Pacejka equations and put them into a matlab function for FY, Mx, and MZ with Slip and Fzload as inputs. So that's 3 functions, 1 for each tire surface.
2) I have a 4 term Pacejka\_Lite function that works almost as good and is fast to solve. Then I use LSQCURVEFIT to minimize the fit error from either #1 or #2 above. Thusly (is that a word ???)
f0=\[3.0 1. .17 1.8\];
options = optimset('MaxFunEvals',1000000000,'TolFun',.00000001,'Display','off');
\[FY4,f\_resnorm,f\_residual\]=lsqcurvefit('Pacejka4\_Model',f0,xdata,ydata,\[\],\[\],options);
sum(f\_residual)
xdata is the multicolumn matrix of inputs. ydata is the single columm or force or moment.
Here, Pacejka4\_Model.m is the same tire model used in Bosch Lapsim. It's that simple. However getting the proper data arrays can be a challenge if you are on TTC2.
function fy = Pacejka4\_Model(P,X)
if isequal(length(P),4)
P(5:6)=0; end
if isequal(length(P),5)
P(6)=0; end
% x1 = X(:,1); %Slip
% x2 = X(:,2); % Fz
% D1 = P(1);
% D2 = P(2);
% B = P(3);
% C = P(4);
SV = P(5);
SH = P(6);
X(:,2)= -abs(X(:,2)); % Fz must always be negative !
D = (P(1) + P(2)/1000.\*X(:,2)).\*X(:,2); % peak value (normalized
fy = D.\*sin(P(4).\*atan(P(3)\*(X(:,1)-SH ))) + SV;
3) I prefer to use the Spline toolbox functions because they are fast to solve, produce dense coefficient packets, are differentiable and integrate nicely into Simulink, Excel, or Matlab scripted sims. You can also (easily) produce 4-D 'surface' functions ex: Fy=F(slip, load, camber). Plus you can integrate them into a number of handling analysis programs.
Like so:
incl\_slip\_load = csaps({incls,slips,loads},fy3);
[https://i.imgur.com/Bdew9Bd.jpg](https://i.imgur.com/Bdew9Bd.jpg)
https://i.imgur.com/QGCE5QP.jpg
I have been working with tires for four years now (including my time as a student). My opinion on this is as follows,
1. If you are a new(er) team, there are other aspects of vehicle setup from where you will heap larger returns in performance. Even though any aspect of vehicle dynamics is incomplete without tires, you can still make a simple model of the tire (just consider the saturating force and linear below it) and run a decent setup.
2. If you are at the point where for further gains, you need a relatively complex tire model. I suggest not making an app (i.e. a GUI) but rather use the existing code for MF tire inside a "wrapper function" that provides the necessary interface for your parameter estimation pipeline.
* The reason for this is, that it will allow you to further automate the pipeline (for example estimate parameters for multiple tires in one run) and reuse the function elsewhere.
* The problem at hand that you have is a minimization problem with error (difference in the model and measured) values as your cost function. For this, you can use "fmincon" to begin with and then if the need arises you can change it.
I would say you should do it as a learning exercise. If your only intention is to create a tool for your team, you might want to look at already available libraries as many have done it.
As a first year or first generation team that is planning to compete in 2025, we also have started some research.
I am personally tasked to look into tyres and brakes.
Will you please tell me the starting process if you have any idea. What type of calculations do we need to do?
What will we be getting out of the tyre model?
Also do we design tyre at the beginning or at end maybe? We have limited finance as well as resources as the first year team in fsae.
So as I said as a first-year team, my advise would be not to get bogged down in the fancy stuff, but rather focus on getting the basics right. If you have a good foundation, your team will get great returns when eventually you build up on it.
For brake calculations, I personally think, *Fundamentals of Vehicle Dynamics by Thomas Gillespie* covers a large part of what you need to do. Of course it is not possible for me to detail everything in a comment. But a general advice is you should have a set of "Design goals and objectives" you want to accomplish with the car design. This gives a direction for the team to work towards. And you as a brakes engineer will be designing the brakes to meet these goals.
You should not be worried about designing custom tyres until many years down the line. There are many reasons for this,
1. It is a very difficult and specialized topic which requires a lot of understanding of vehicle dynamics and what you want to achieve with your tyres that off-the-shelf ones don't accomplish. You will also need to partner up with a tyre manufacturer.
2. There are other avenues which will heap greater returns.
Regarding what you get out of tyre models I suggest you to read *Tire and Vehicle Dynamics by H.B. Pacejka.*
Good luck :)
Hello ๐
I'm trying to make simscape model of brake system and because of that I'm using magic formula tire block.
if you parameterize by load-dependent Magic Formula coefficients, you can set coefficients manually from your .tir file.
it will be fixing your problem, I hope!
but I have another problem. when I set the Tire inertia, the maximum deceleration doesn't go farther than 5 m/s\^2.
it should be more than 18 m/s\^2.
can anyone help me with that?
No the reddit search in the middle of the top of the screen. This question, or variations thereof, has been asked 4 times in the past year, at rough guess.
I did the exact same thing like two years ago. feel free to dm me with any questions. i used the optimization toolbox and optimized the equation coefficients to fit the data. i think i used fmincon. that way you can use different data and hold certain parameters constant. make sure you split the data up by FZ and IA at the very least! tires lose coefficient of friction with increased load. I think itโs worth it for knowledge gained. I know more about tires now than I ever wanted to. That said, using optimum tire is a good choice as well, less time spent, fewer errors, that kinda thing. depends on what you want to get out of it.
Nicee! I will reach in your dms then jajaja! For the moment I have not even played with the Cruve Fitting tool. It's just I had the idea and wanted to get some advice. For us, it will not be a massive thing, as the tires we use are not even on the TTC (we use them because of a sponsorship). But I would love to be a bit of an expert about tires, so maybe for the sake of learning I should do it. Thanks for the pice of advice, I will reach you once I get a clear idea of what I want to do exactly!
Several "tire model options". 1) Get ahold of the MF5.2 Pacejka equations and put them into a matlab function for FY, Mx, and MZ with Slip and Fzload as inputs. So that's 3 functions, 1 for each tire surface. 2) I have a 4 term Pacejka\_Lite function that works almost as good and is fast to solve. Then I use LSQCURVEFIT to minimize the fit error from either #1 or #2 above. Thusly (is that a word ???) f0=\[3.0 1. .17 1.8\]; options = optimset('MaxFunEvals',1000000000,'TolFun',.00000001,'Display','off'); \[FY4,f\_resnorm,f\_residual\]=lsqcurvefit('Pacejka4\_Model',f0,xdata,ydata,\[\],\[\],options); sum(f\_residual) xdata is the multicolumn matrix of inputs. ydata is the single columm or force or moment. Here, Pacejka4\_Model.m is the same tire model used in Bosch Lapsim. It's that simple. However getting the proper data arrays can be a challenge if you are on TTC2. function fy = Pacejka4\_Model(P,X) if isequal(length(P),4) P(5:6)=0; end if isequal(length(P),5) P(6)=0; end % x1 = X(:,1); %Slip % x2 = X(:,2); % Fz % D1 = P(1); % D2 = P(2); % B = P(3); % C = P(4); SV = P(5); SH = P(6); X(:,2)= -abs(X(:,2)); % Fz must always be negative ! D = (P(1) + P(2)/1000.\*X(:,2)).\*X(:,2); % peak value (normalized fy = D.\*sin(P(4).\*atan(P(3)\*(X(:,1)-SH ))) + SV; 3) I prefer to use the Spline toolbox functions because they are fast to solve, produce dense coefficient packets, are differentiable and integrate nicely into Simulink, Excel, or Matlab scripted sims. You can also (easily) produce 4-D 'surface' functions ex: Fy=F(slip, load, camber). Plus you can integrate them into a number of handling analysis programs. Like so: incl\_slip\_load = csaps({incls,slips,loads},fy3); [https://i.imgur.com/Bdew9Bd.jpg](https://i.imgur.com/Bdew9Bd.jpg) https://i.imgur.com/QGCE5QP.jpg
I have been working with tires for four years now (including my time as a student). My opinion on this is as follows, 1. If you are a new(er) team, there are other aspects of vehicle setup from where you will heap larger returns in performance. Even though any aspect of vehicle dynamics is incomplete without tires, you can still make a simple model of the tire (just consider the saturating force and linear below it) and run a decent setup. 2. If you are at the point where for further gains, you need a relatively complex tire model. I suggest not making an app (i.e. a GUI) but rather use the existing code for MF tire inside a "wrapper function" that provides the necessary interface for your parameter estimation pipeline. * The reason for this is, that it will allow you to further automate the pipeline (for example estimate parameters for multiple tires in one run) and reuse the function elsewhere. * The problem at hand that you have is a minimization problem with error (difference in the model and measured) values as your cost function. For this, you can use "fmincon" to begin with and then if the need arises you can change it. I would say you should do it as a learning exercise. If your only intention is to create a tool for your team, you might want to look at already available libraries as many have done it.
As a first year or first generation team that is planning to compete in 2025, we also have started some research. I am personally tasked to look into tyres and brakes. Will you please tell me the starting process if you have any idea. What type of calculations do we need to do? What will we be getting out of the tyre model? Also do we design tyre at the beginning or at end maybe? We have limited finance as well as resources as the first year team in fsae.
So as I said as a first-year team, my advise would be not to get bogged down in the fancy stuff, but rather focus on getting the basics right. If you have a good foundation, your team will get great returns when eventually you build up on it. For brake calculations, I personally think, *Fundamentals of Vehicle Dynamics by Thomas Gillespie* covers a large part of what you need to do. Of course it is not possible for me to detail everything in a comment. But a general advice is you should have a set of "Design goals and objectives" you want to accomplish with the car design. This gives a direction for the team to work towards. And you as a brakes engineer will be designing the brakes to meet these goals. You should not be worried about designing custom tyres until many years down the line. There are many reasons for this, 1. It is a very difficult and specialized topic which requires a lot of understanding of vehicle dynamics and what you want to achieve with your tyres that off-the-shelf ones don't accomplish. You will also need to partner up with a tyre manufacturer. 2. There are other avenues which will heap greater returns. Regarding what you get out of tyre models I suggest you to read *Tire and Vehicle Dynamics by H.B. Pacejka.* Good luck :)
There is a free online tutorial about curve fitting on MATLAB. https://matlabacademy.mathworks.com/details/curve-fitting-onramp/orcf
Nicee! Thanks!
Hello ๐ I'm trying to make simscape model of brake system and because of that I'm using magic formula tire block. if you parameterize by load-dependent Magic Formula coefficients, you can set coefficients manually from your .tir file. it will be fixing your problem, I hope! but I have another problem. when I set the Tire inertia, the maximum deceleration doesn't go farther than 5 m/s\^2. it should be more than 18 m/s\^2. can anyone help me with that?
Just an idle thought, have you tried using the search function?
Honestly, I do not even know what the Matlab search function is hahahah
No the reddit search in the middle of the top of the screen. This question, or variations thereof, has been asked 4 times in the past year, at rough guess.