Varying weight of a ball with time in a Maglev system

Hello, I'm trying to vary the weight of a magnetically levitated ball with time. Namely, the balls weight is supposed to suddenly chand at time t=20s by 15%. Here is the code I have so far including the initial mass of the ball (0.06 kg):

clc
clear
%% Define knowns

g = 9.81; % gravity [m/s^2]
k = 1.32435*10^-4; % Magnet force constant, [N/amp]
x_0 = 0.015; % steady state position [m]
m_0 = 0.06; % initial ball's weight [kg]
i_0 = 1; % Steady state amps, assumed from NYU experiment [amp]

%% Define variable parameters
i = 1;
R = 10; % From NYU experiment [Ohm]
L = 0.4125; % Inductance from NYU experiment [Henry]

%% Checking Current System Stability

a = (2*k*i_0)/(m_0*x_0^2); % num of TF
b = (2*k*i_0^2)/(m_0*x_0^3); % part of den for TF
num = [a];
den = [1 0 b];
sys = tf(num,den)
% step(sys,t)

%% Simulate Model
maglev_sim = sim('Maglev_Model.slx');

%% Plotting m = 0.06 kg response
figure(1)
plot(maglev_sim.maglev,'LineWidth',2)
title('Position Response for m = 0.06kg')
ylabel('Position (m)')
xlabel('Time (s)')

%% Changing mass with time

The Simulink model is attached. So far I have been able to achieve the desired output of the ball's position being 0.015 m away with the original mass of 0.06 kg but now I need to change the mass with time and have the system still keep the ball at that position.

Any help is appreciated!

[Gebretsadkan Fissha]

Hello, can you help me for solving sliding mode controller nonlinear odes of Maglev system?

[Sam Chak]

Suggest you to post a new question (click on the ASK button) and show the nonlinear ODEs of the Maglev system.

Answer 1

[Kyle Rawding]

Hi -

It sounds like you're interested in updating your transfer function as the simulation runs to account for the changing mass, rather than defining static 'a' and 'b' constants.

I'd recommend taking a look at the accepted answer to this question:

https://www.mathworks.com/matlabcentral/answers/10373-dynamic-transfer-function-in-simulink

Hope that helps!

-Kyle