Please help on my error code here.

Hi everyone

I been working on my code function [varargout] = ZieglerNichols(varargin)

But I had encountered an error here while working on it.

Please somebody help me to tell me how to fix it.

function [varargout] = ZieglerNichols(varargin)

%ZIEGLERNICHOLS Computes PID gains using Ziegler-Nichols

%

% [KP, KI, KD] = ZIEGLERNICHOLS(KU, TU) Computes the KP, KI, and KD gains

% for a PID controller using the Ziegler-Nichols method.

%

% [...] = ZIEGLERNICHOLS(KU, TU, TYPE) does as above but for the

% specified control TYPE. Valid values are

%

% 'ClassicPID'

% 'P'

% 'PI'

% 'PD'

% 'PessenIntegrationRule'

% 'SomeOvershoot'

% 'NoOvershoot'

%

% [KP, KI, KD, TI, TD] = ZIEGLERNICHOLS(KU, TU, TYPE) does as above but

% also returns the parameters TI and TD.

%

% For more information, see

% https://en.wikipedia.org/wiki/Ziegler%E2%80%93Nichols_method.

%

% For example usage see https://youtu.be/n829SwSUZ_c?t=1434.

%

%INPUT: -KU: Ultimate gain that leads to steady oscillations

% -TU: Oscillation period (seconds)

% -TYPE: char array denoting the type of desired control

%

%OUTPUT: -KP: Proporational gain

% -KI: Integral gain

% -KD: Derivative gain

%

%----------------------OBTAIN USER PREFERENCES-----------------------------

switch nargin

case 3

%User supplies all inputs

KU = varargin{1};

TU = varargin{2};

TYPE = varargin{3};

case 2

%Assume ClassicPID

KU = varargin{1};

TU = varargin{2};

TYPE = 'ClassicPID';

otherwise

error('Invalid number of inputs');

end

%-----------------------CHECKING DATA FORMAT-------------------------------

% KU

% TU

assert(TU > 0, 'TU should be a positive value')

%-------------------------BEGIN CALCULATIONS-------------------------------

if(strcmp(TYPE,'ClassicPID')==1)

KP = 0.6*KU;

Ti = TU/2;

Td = TU/8;

elseif(strcmp(TYPE,'P')==1)

KP = 0.5*KU;

Ti = NaN;

Td = NaN;

elseif(strcmp(TYPE,'PI')==1)

KP = 0.45*KU;

Ti = TU/1.2;

Td = NaN;

elseif(strcmp(TYPE,'PD')==1)

KP = 0.8*KU;

Ti = NaN;

Td = TU/8;

elseif(strcmp(TYPE,'PessenIntegrationRule')==1)

KP = 0.7*KU;

Ti = 2*TU/5;

Td = 3*TU/20;

elseif(strcmp(TYPE,'SomeOvershoot')==1)

KP = KU/3;

Ti = TU/2;

Td = TU/3;

elseif(strcmp(TYPE,'NoOvershoot')==1)

KP = 0.2*KU;

Ti = TU/2;

Td = TU/3;

else

error('Unsupported TYPE')

end

%Compute KI and KD based on KP, TI, and TD

KI = KP/Ti;

KD = Td*KP;

%If KI or KD are NaN, change to 0 so it is compatible with simulations

if(isnan(KI))

KI = 0;

end

if(isnan(KD))

KD = 0;

end

%Package outputs

varargout{1} = KP;

varargout{2} = KI;

varargout{3} = KD;

varargout{4} = Ti;

varargout{5} = Td;

%In the command window it said "Error in ZieglerNicholsMethod (line 54)

if(strcmp(TYPE,'ClassicPID')==1) "

please help ASAP!