how to make input to the system time variable?

2023 10 31
2 个回答
回答已采纳
更新时间：2023 11 3
9 次查看（30 天）

0 个投票

I would like to make an input that is time varying.
I have attached a photo that describe the time varying input I want.
Im a beginner. I hope someone can help me with this. Thank you
Im open to all suggestions or references that can help me learn.

1 个评论
显示 -1更早的评论 隐藏 -1更早的评论

Rik
Rik 2023-10-31
I have some difficulty understanding what you actually want to achieve in terms of Matlab code. It seems like there are a few steps missing.
Have a read here and here. It will greatly improve your chances of getting an answer.

请先登录，再进行评论。

请先登录，再回答此问题。

 采纳的回答

Sam Chak
Sam Chak 2023-10-31
编辑：Sam Chak 2023-10-31
Ran in:

1 个投票

Ran in:
Okay @Min Khant, the problem is incomplete. However, you can learn by yourself using this example for tracking the desired trajectory . Change the tau number as you wish to observe the time response of .
tspan = linspace(0, 20, 3001); % can set tspan from 0 to π
y0 = [0; 0]; % initial values
[t, y] = ode45(@odefcn, tspan, y0);
yd = pi/2 - pi/4*cos(t); % desired trajectory
% Plots
plot(t, yd), hold on
plot(t, y(:,1)), grid on
title('Time response of \theta(t) in tracking \theta_{d}', 'fontsize', 10)
xlabel('t', 'fontsize', 10), ylabel('\theta', 'fontsize', 10)
legend('\theta_{d}', '\theta(t)', 'location', 'best', 'fontsize', 10)
% Simplified Robt dynamics
function dydt = odefcn(t, y)
dydt = zeros(2, 1);
% parameters
M = 1;
b = 1;
m = 1;
g = 1;
r = 0.16; % true value
rmeas = 0.08; % measured
kp = 1;
kd = 2;
% desired trajectory
yd = pi/2 - pi/4*cos(t);
dyd = 1/4*pi*sin(t);
ddyd = 1/4*pi*cos(t);
% tau input (3 variants)
tau1 = M*ddyd + b*dyd + m*g*rmeas*cos(yd); % so-called feedforward control
tau2 = M*ddyd + M*kd*dyd + M*kp*yd - M*kd*y(2) - M*kp*y(1) + b*y(2) + m*g*r*cos(y(1)); % perfect r
tau3 = M*ddyd + M*kd*dyd + M*kp*yd - M*kd*y(2) - M*kp*y(1) + b*y(2) + m*g*rmeas*cos(y(1)); % imperfect r
dydt(1) = y(2);
dydt(2) = (- b*y(2) - m*g*r*cos(y(1)) + tau3)/M; % <-- change the tau number
end

4 个评论
显示 2更早的评论 隐藏 2更早的评论

Min Khant
Min Khant 2023-10-31
编辑：Min Khant 2023-10-31
thank you for generously answering my question even though I was bad at making a question. sir
as I am a beginner, I found simulink easier than coding in Matlab and thus I tried to finish my midterm project building blocks in simulink. i have alrdy finished problem 2(in attached file) by building blocks for feedback control. Now in problem 3 I have to create blocks for feedforward control which including a time-varying desired theta value. I wanted to ask how I can create a simulink block that can defines the desired time varying input.
Min Khant
Min Khant 2023-10-31
I was willing to create an input that defines time-varying desired theta and differentiate it twice and build other necessary blocks to complete the feedforward tau which will lated be fed into the plant.
if there are better ideas than mine , I am willing to hear it sir
Sam Chak
Sam Chak 2023-10-31
Hi @Min Khant
Good to hear that you like Simulink. This following approach is generally more accurate than applying the differentiation block twice to get . If you find the solution helpful, please consider clicking 'Accept' ✔ on the answer and voting 👍 for it.
Min Khant
Min Khant 2023-11-3
May I know how to use derivative block consecutively? sir
as i tried , it does not function properly

请先登录，再进行评论。

更多回答（1 个）

Aquatris
Aquatris 2023-10-31

0 个投票

You can create your own numeric integration to solve the equation and provide the desired input in each time step.
Here is an example (the accepted answer) which you can modify for your need.

类别

在 帮助中心 和 File Exchange 中查找有关 Simulink Functions 的更多信息

产品

版本

R2023b

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by