Symbolic Toolbox Exponential Equations
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Hi Everyone
Getting started with symbolic tool box and live editor.
Trying to enter the below Wiebe Function equation using symbolic toolbox so i can find the derivative and build up the governing equations for the system.
However, getting stuck on simply entering the equation with the syms function, doh, as the e term has (t/td) to the power m+1, can you help with how i actually code this in the live editor so i can use and later solve for dx
Thanks everyone.;-)
My attempt at creating x
syms x exp t t_d m
t_d = sym('t_d')
x = 1 - exp(-6.908*(t/t_d))^(m+1)
回答（1 个）
Ameer Hamza
2020-4-2
编辑：Ameer Hamza
2020-4-2
exp is a built-in function. Don't define it as a variable.
syms x t t_d m
x = 1 - exp(-6.908*(t/t_d)^(m+1));
dxdt = diff(x,t)
Result
dxdt =
(1727*exp(-(1727*(t/t_d)^(m + 1))/250)*(t/t_d)^m*(m + 1))/(250*t_d)
If you use live script, it will also render the equation to be displayed properly
6 个评论
PB75
2020-4-2
Thanks Ameer,
Great response.
When i enter the value of C which is -6.908 it does not fully simplify the equation in live editor, hence you have to divide through by 250 on num and dem, is this due to the decimal places on that constant? can this be simplified within syms?
Thanks again
Patrick
t_d =
x =
dxdt =
Ameer Hamza
2020-4-2
编辑：Ameer Hamza
2020-4-2
Is there a specific reason for simplifying it to that value?
PB75
2020-4-2
Ameer Hamza
2020-4-2
Try this to get fractional values
syms x t t_d m
x = 1 - exp(-6.908*(t/t_d)^(m+1));
dxdt = vpa(diff(x,t))
PB75
2020-4-6
Ameer Hamza
2020-4-6
Glad to be of help.
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2020-4-6
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