Too many input arguments in ode45 using anonymous function

I am trying to solve a forced vibration problem using state spac representation. Please tell me what is wrong with my code.

mass = 750; % Mass of the body [kg]

stiffness = 50000; % Stiffness Coefficient of spring [N/m]

damping = 0; % Damping coefficient of damper [Ns/m]

time = 0:0.01:1; % Time [s]

x_0 = 0.01; % Initial Condition displacement

x_dot_0 = 0; % Initial Condition velocity

mass_extruded = 0.03; % Mass of the excitation [kg]

omega = 6.28; % Angular frequency of the excitation [1/s]

radius = 0.24; % Radius of the excitation [m]

force = omega^2*radius*mass_extruded; % Calculate the force with given parameters

w0 = [x_0, x_dot_0]; % Create a vector with initial conditions

A = [0 1; -stiffness/mass -damping/mass]; % Create system Matrix

B = [0; force/mass]; % Create excitation vector

dw = @(w) A*w - B*cos(omega*time); % Define derivative

[tsim,wsim] = ode45(@(w) dw, time, w0);

[madhan ravi]

@(t,w) ...

We can’t run picture , upload your code as text.

[DAKSH GANATRA 17BME0726]

gives the same error

[DAKSH GANATRA 17BME0726]

I have edited the question and added the text. Please kindly take a look

Answer 1

[Steven Lord]

The ODE solvers will generally (with the exception of ode15i) call your ODE function with two input arguments. [ode15i will call your ODE function with three input arguments.] Even if your ODE function doesn't use both of those input arguments, it must accept them.

Your dw function probably wants to accept the time input t and use it instead of the vector time that it currently uses.

[DAKSH GANATRA 17BME0726]

So what changes do I need to make?

[Steven Lord]

As madhan ravi said, "dw = @(t, w) ...". My suspicion is that you want to use t instead of time in the body of the dw function.

Answer 2

[Ameer Hamza]

There are some mistakes in the way you wrote the ODE and called ode45. Following code run fine

mass                       = 750;                 % Mass of the body [kg]
stiffness                  = 50000;               % Stiffness Coefficient of spring [N/m]
damping                    = 0;                   % Damping coefficient of damper [Ns/m]
time                       = 0:0.01:1;            % Time [s]
x_0                        = 0.01;                % Initial Condition displacement
x_dot_0                    = 0;                   % Initial Condition velocity
mass_extruded              = 0.03;                % Mass of the excitation [kg]
omega                      = 6.28;                % Angular frequency of the excitation [1/s]
radius                     = 0.24;                % Radius of the excitation [m]
force = omega^2*radius*mass_extruded;             % Calculate the force with given parameters
    
w0 = [x_0; x_dot_0];                             % Create a vector with initial conditions
A = [0 1; -stiffness/mass -damping/mass];                              % Create system Matrix
B = [0; force/mass];                              % Create excitation vector
dw = @(t, w) A*w - B*cos(omega*t);                             % Define derivative    
[tsim,wsim] = ode45(dw, time, w0); % equivalent: [tsim,wsim] = ode45(@(t, w) dw(t, w), time, w0);
plot(tsim, wsim)
legend({'x', 'x\_dot'})