Bendesarts

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These are replies submitted by Bendesarts

Thank you for your help.

Here the text file of the function of modulation

variables

  real hidden rise_time;
equations
               rise_time = (stop_time - start_time);
               if time < start_time then
                              x = 0;
               else
                              if time < stop_time then
                                              if time < rise_time/2 then
                                              x = 4*(1/rise_time^2)*(time^2)/2;  

                                               else
                                              x = -2*(1/rise_time^2)*(time-rise_time/2)^2+(2/rise_time)*(time-rise_time/2)+1/2;          

                                               end;

                               else
                              x = 1;
                              end;
               end; 

with
start_time=0s
stop_time=3s

 

Here the text file of the modified chirp signal defined with 3 parts : a progressive step from 0 to 3 s (it is this function which is modulated by the m signal programmed with the code above), a periodic signal from 3s to 5s and the chirp signal from 5s.

 

parameters

                real F=5000;
               real t0 = 3.0 {s};
               real start_time = 5.0 {s};
               real stop_time = 25.0 {s};
               real f_start = 5.0 {frequency, Hz};
               real f_stop = 25.0 {frequency, Hz};
               real omega_start;
               real omega_stop;

variables

                real omega {frequency, rad/s};     // current frequency {rad/s}
               real freq {frequency, Hz};                    

                real hidden t;
               real hidden dw;
               real hidden dt;
               real hidden dwdt;
               real hidden dwdt2;
               boolean hidden change;

initialequations

                omega_start = (2*pi)*f_start;

                omega_stop = (2*pi)*f_stop;

                dw = omega_stop - omega_start;

                dt = stop_time - start_time;

                dwdt = dw/dt;

                dwdt2 = dwdt/2;

equations

                "calculate at least at the start and stop time"

                "change = timeevent (start_time) or timeevent (stop_time);"

                              

                FF = if time < t0 then

                               F*m*sin( time * omega_start ) 

                else

                               if time > stop_time then

                                               F*sin( time * omega_stop )

                               else

                                               if time > start_time then

                                                               F*sin( (time - start_time)*( omega_start + (time - start_time) * dwdt2  )  )

                                  else

                                     F*sin( time * omega_start )

                                  end

                               end       

                end;

 

I hope it is enough clear and don’t hesitate if you need more.

Thanks a lot for your help.

Perfect. Thank you

Hello,

You help me a lot.

In fact, I add with this picture more precision about my code.

 

One of the function in my chirp signal is modulated by a function which is a motion profile called m.

I hope that with this precision it is clearer.

If you don't mind, it would be create if you can precise me how I can modify the modelica code inside the chirp signal block. 

Thanks a lot for your help

 

I precise my question.

I know the function that I need to implement to obtain this kind of excitation since I have already program it in a another software (20-sim). My question is more how can I implement a function like that to modify the amplitude of the chirp signal block in MapleSim.

Here the picture of the program :

 

Thanks a lot for your help.

@bjdehart 

Very clear.

Thanks a lot for your help.

@bjdehart 

OK Thank you.

Indeed, when i delete the '1' values shown in the Inspector, then the default values will appear.

However, if i don't do this process, is the default value is used or not ?

In other word, must I do this process for all my parameters if i want to use the default values i have set ?

Thanks a lot for your help

 

 

with the bad values of the parameters in diagram area

 

@bjdehart 

Sorry you are right. I made a mistake. MapleSim made the calculations of all these relations before starting the simulation.

 

 

 

 

I wiould like to define relations here to define some parameters.

Thank you for your ideas ?

@Axel Vogt 

The context is the determination of explicit function in the constraints equations of a multibody system.

I detemine 3 expressions of the parameters i want to calculate which depend of 3 others parameters.

gamma1(t):=f(x(t),alpha(t),beta(t))

phi1(t):=f(x(t),alpha(t),beta(t),gamma1(t))

psi1(t):=f(x(t),alpha(t),beta(t))

Questions :

1) I would like to determine phi1(t) without evaluate gamma1(t) in its expression

I believe i have to determine my expression with using ' ' a bit like that phi1(t):=f(x(t),alpha(t),beta(t),'gamma1(t)')

I didn't manage in my code. May you have idea so as to determine phi1(t):=f(x(t),alpha(t),beta(t),gamma1(t)) without evaluating gamma1(t)

(SEE Equation 4.5 in my code)

2) I would like to determine

gamma1(t)

phi1(t)

psi1(t)

knowing that x(t):=0.12
alpha(t):=0
beta(t):=0

gamma1(t) is not evaluated.

Did you see in my code the issue ?

(SEE Equation 6.1 in my code)

constraintes_7.mw

Thank you for your help

@Mac Dude 

Great.

The solution based on the use of latex function works!!!

Thanks a lot for your help

@Bendesarts 

I detail a bit more my issue.

When i use solve function solve(%=0,gamma1);

I find \arctan \left( b,a \right) +\pi -\arccos \left( {\frac {c}{\sqrt {{a}^ {2}+{b}^{2}}}} \right)

arctan(b, a)+Pi-arccos(c/sqrt(a^2+b^2))

So i find only one solution and i would have linked to find 2 solutions :

gamma=-arctan(b, a) + arccos(c/sqrt(a²+b²))

and gamma=-arctan(b, a) - arccos(c/sqrt(a²+b²))

Have you some ideas why i don't find 2 solutions ?

Thanks a lot for your help

@Alejandro Jakubi 

I tried with MathML package and it is the same.

It is very annoying because i need to make a nice document with equations well presented.

Thank you for your help.

Thank for other ideas?

@Bendesarts 

No sorry the error message is not exactly this one.

The message is :

The paperweight doesn't contain equations data.

However, i have the impression to copy equations ...

OK indeed it looks good.

And after i want the 2 solutions given automatically by a solve function

gamma=-psi + arccos(c/sqrt(a²+b²))

and gamma=-psi - arccos(c/sqrt(a²+b²))

how can i program it ?

Thanks a lot for your help

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