why am I getting the error "Incorrect number or types of inputs or outputs for function 'step."

my code is

clear all, close all

m1 = 10;

m2 = 350;

kw = 500000;

ks = 10000;

B = [ 1000 2000 3000 4000 ];

t = 0:0.01:2;

for i = 1:4

b = B(i);

F = [ 0 1 0 0; -( ks/m1 + kw/m1 ) -b/m1 ks/m1 b/m1; 0 0 0 1; ks/m2 b/m2 -ks/m2 -b/m2 ];

G = [ 0; kw/m1; 0; 0 ];

H = [ 1 0 0 0; 0 0 1 0 ];

J = 0;

y = step( F, G, H, J, 1, t );

subplot(2,2,i);

plot(t, y(:,1), ':', t, y(:,2), '-' );

legend('Wheel','Car');

ttl= sprintf('Response with b = %4.1f',b);

title(ttl);

end

and i got

"Incorrect number or types of inputs or outputs for function 'step'."

this message

[Dyuman Joshi]

Which step function are you trying to use?

Look through the documentation of that function and see what the expected number of inputs are and the type of input.

[Mathieu NOE]

this is ok for older matlab releases

if you use a recent matlab version, please create first the system sys and them call step(sys) as described in the doc :

Step response of dynamic system - MATLAB step - MathWorks France

FYI , in ttachment the "old" step function if you need it

[Jon]

This is also detailed in my answer below

Answer 1

[Jon]

This runs for me in R2023b, what version are you running? If I look at the actual step.m file in my directory, which comes up as C:\Program Files\MATLAB\R2023a\toolbox\control\ctrlobsolete\step.m

I see that the calling arguments that you use will no longer be supported. Instead you must make a linear system and pass this to test. Perhaps on your version the call using A,B,C,D matrices is already no longer supported.

% Old help

%warning(['This calling syntax for ' mfilename ' will not be supported in the future.'])

%STEP Step response of continuous-time linear systems.

% STEP(A,B,C,D,IU) plots the time response of the linear system:

% .

% x = Ax + Bu

% y = Cx + Du

m1 = 10; 
m2 = 350;
kw = 500000;
ks = 10000;
B = [ 1000 2000 3000 4000 ];
t = 0:0.01:2;
for i = 1:4
	b = B(i);
	F = [ 0 1 0 0; -( ks/m1 + kw/m1 ) -b/m1 ks/m1 b/m1; 0 0 0 1; ks/m2 b/m2 -ks/m2 -b/m2 ];
	G = [ 0; kw/m1; 0; 0 ];
	H = [ 1 0 0 0; 0 0 1 0 ];	
	J = 0;
	y = step( F, G, H, J, 1, t );
	subplot(2,2,i);
	plot(t, y(:,1), ':', t, y(:,2), '-' ); 
	legend('Wheel','Car');
	ttl= sprintf('Response with b = %4.1f',b);
	title(ttl);
end

In any case I would recommend calling using the current version of step, which is

figure % make new figure
m1 = 10; 
m2 = 350;
kw = 500000;
ks = 10000;
B = [ 1000 2000 3000 4000 ];
t = 0:0.01:2;
for i = 1:4
	b = B(i);
	F = [ 0 1 0 0; -( ks/m1 + kw/m1 ) -b/m1 ks/m1 b/m1; 0 0 0 1; ks/m2 b/m2 -ks/m2 -b/m2 ];
	G = [ 0; kw/m1; 0; 0 ];
	H = [ 1 0 0 0; 0 0 1 0 ];	
	J = 0;
    sys = ss(F,G,H,J);
	y = step( sys,t );
	subplot(2,2,i);
	plot(t, y(:,1), ':', t, y(:,2), '-' ); 
	legend('Wheel','Car');
	ttl= sprintf('Response with b = %4.1f',b);
	title(ttl);
end