How can I identify the increasing and decreasing side of half cycle of sine wave using MATLAB code (.m file). For example the flag should set 1 if the amplitude of sine wave is increasing from 0 deg to 90 deg and should set 0 when amplitude is decreasing from 90 deg to 180 deg.
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3\$\begingroup\$ sign and gradient: 0-90 = ++; 90-180 = +-; 180-270 = --; 270-360=-+ \$\endgroup\$– ChuNov 9, 2017 at 18:22
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\$\begingroup\$ From \$ 180^o \$ to \$ 270^o \$ do you want to consider that as increasing (because the absolute value is) or reducing? \$\endgroup\$– Warren HillNov 9, 2017 at 18:45
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\$\begingroup\$ well, talking in terms of logic - In the interval 0-90 , if the absolute value of (current value - previous value >=0) then flag should be 1. Otherwise 0. \$\endgroup\$– Mitu RajNov 9, 2017 at 18:54
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\$\begingroup\$ @WarrenHill i want to divide the entire cycle into 4 segments, absolute value doesn't matter \$\endgroup\$– ruveenaNov 9, 2017 at 19:42
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1\$\begingroup\$ @ruveena This cannot be done as a memoryless system, since there are two possible solutions for any given value. The best you can do by sampling a single point is to determine if you're in the positive or negative half-cycle. \$\endgroup\$– SynchrondyneNov 9, 2017 at 19:55
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1 Answer
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This can be achieved by taking derivative of the sine function either in matlab code or du/dt block in simulink
grad = diff (sin(x));
if (sin(x)>0 && grad>0)
\\0 to 90 deg
if (sin(x)>0 && grad<0)
\\90 to 180 deg
if (sin(x)<0 && grad<0)
\\180 to 270 deg
if (sin(x)>0 && grad>0)
\\270 to 360 deg