How can I turn s/s to 1?

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sadel
sadel 2011-6-8
I run this code and if I click yes without change anything in the inputdlg, I receive 's/s'. How can I return this to '1' in this situation?
prompt={'Proportional Coefficient Input','Integral Coefficient Input','Derivative Coefficient Input'};
defans={'1','0','0'};
answer=inputdlg(prompt,'PID Coefficient Input',1,defans,'on');
if (~isempty(answer))
if (~isempty(answer{1}))&(~isempty(answer{2}))&(~isempty(answer{3}))&(answer{1}~='0')
syms s
x1=str2num(answer{1});
x2=str2num(answer{2});
x3=str2num(answer{3});
handles.pid(1)=x1(1);
handles.pid(2)=x2(1);
handles.pid(3)=x3(1);
handles.PID_num=[handles.pid(3),handles.pid(1),handles.pid(2)];
handles.PID_den=[1,0];
handles.PID_sys=tf(handles.PID_num,handles.PID_den);
evalc('handles.PID_sys')
end
end

采纳的回答

Paulo Silva
Paulo Silva 2011-6-8
prompt={'Proportional Coefficient Input','Integral Coefficient Input','Derivative Coefficient Input'};
defans={'1','0','0'};
answer=inputdlg(prompt,'PID Coefficient Input',1,defans,'on');
if (~isempty(answer))
if (~isempty(answer{1}))&(~isempty(answer{2}))&(~isempty(answer{3}))&(answer{1}~='0')
syms s
x1=str2num(answer{1});
x2=str2num(answer{2});
x3=str2num(answer{3});
handles.pid(1)=x1(1);
handles.pid(2)=x2(1);
handles.pid(3)=x3(1);
handles.PID_num=[handles.pid(3),handles.pid(1),handles.pid(2)];
handles.PID_den=[1,0];
handles.PID_sys=tf(handles.PID_num,handles.PID_den);
[num,den] = tfdata(handles.PID_sys);
if(num{:}==den{:})
handles.PID_sys=1;
end
evalc('handles.PID_sys')
end
end
  7 个评论
sadel
sadel 2011-6-8
with this handles.PID_sys=tf([1],[1]); instead of this handles.PID_sys=1 is better!!! :)
Paulo Silva
Paulo Silva 2011-6-8
even better -> handles.PID_sys=tf(1);

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更多回答(1 个)

Walter Roberson
Walter Roberson 2011-6-8
s/s is not generally 1. In particular, that fails for 0, infinity, -infinity, and NaN.
  1 个评论
Paulo Silva
Paulo Silva 2011-6-8
that's why the tf leaves the results the way it does, I never seen the s/s situation before, always had transfer functions with more poles than zeros, sometimes it's good to be here trying to help others, we always learn new things.

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