 # Math Review with Matlab:

## Presentation on theme: "Math Review with Matlab:"— Presentation transcript:

Math Review with Matlab:
4/1/2017 Math Review with Matlab: Complex Numbers Sinusoidal Addition S. Awad, Ph.D. M. Corless, M.S.E.E. E.C.E. Department University of Michigan-Dearborn

Sinusoidal Addition General Sinusoid Euler’s Identity
A useful application of complex numbers is the addition of sinusoidal signals having the same frequency General Sinusoid Euler’s Identity Sinusoidal Addition Proof Phasor Representation of Sinusoids Phasor Addition Example Addition of 4 Sinusoids Example

General Sinusoid A general cosine wave, v(t), has the form:
M = Magnitude, amplitude, maximum value w = Angular Frequency in radians/sec (w=2pF) F = Frequency in Hz T = Period in seconds (T=1/F) t = Time in seconds q = Phase Shift, angular offset in radians or degrees

Euler’s Identity A general complex number can be written in exponential polar form as: Euler’s Identity describes a relationship between polar form complex numbers and sinusoidal signals:

Useful Relationship Euler’s Identity can be rewritten as a function of general sinusoids: Resulting in the useful relationship:

Show that the sum of two generic cosine waves, of the same frequency, results in another cosine wave of the same frequency but having a different Magnitude and Phase Shift (angular offset) Given: Prove:

Complex Representation
Each cosine function can be written as the sum of the real portion of two complex numbers

Complex Addition ejwt is common and can be distributed out
The addition of the complex numbers M1ejq1 and M2ejq2 results in a new complex number M3ejq3

Return to Time Domain The steps can be repeated in reverse order to convert back to a sinusoidal function of time We see v3(t) is also a cosine wave of the same frequency as v1(t) and v2(t), but having a different Magnitude and Phase

Phasors Time Domain Voltage: v(t) Complex Domain Phasor: V(jw)
In electrical engineering, it is often convenient to represent a time domain sinusoidal voltages as complex number called a Phasor Standard Phasor Notation of a sinusoidal voltage is: Time Domain Voltage: v(t) Complex Domain Phasor: V(jw)

Phasor Addition Time Domain Complex Domain Time Domain
As shown previously, two sinusoidal voltages of the same frequency can easily be added using their phasors Time Domain Complex Domain Time Domain

Example: Use the Phasor Technique to add the following two 1k Hz sinusoidal signals. Graphically verify the results using Matlab. Given: Determine:

Phasor Transformation
Since Standard Phasors are written in terms of cosine waves, the sine wave must be rewritten as: The signals can now be converted into Phasor form

Rectangular Addition To perform addition by hand, the Phasors must be written in rectangular (conventional) form Now the Phasors can be added

Transform Back to Time Domain
Before converting the signal to the time domain, the result must be converted back to polar form: The result can be transformed back to the time domain:

Matlab can be used to verify the complex addition: » V1=2*exp(j*0); » V2=3*exp(-j*pi/2); » V3=V1+V2 V3 = i » M3=abs(V3) M3 = 3.6056 » theta3= angle(V3)*180/pi theta3 =

Time Domain Addition The original cosine waves can be added in the time domain using Matlab: f =1000; % Frequency T = 1/f; % Find the period TT=2*T; % Two periods t =[0:TT/256:TT]; % Time Vector v1=2*cos(2*pi*f*t); v2=3*sin(2*pi*f*t); v3=v1+v2;

Code to Plot Results Plot all signals in Matlab using three subplots
subplot(3,1,1); plot(t,v1); grid on; axis([ 0 TT -4 4]); ylabel('v_1=2cos(2000\pit)'); title('Sinusoidal Addition'); subplot(3,1,2); plot(t,v2); ylabel('v_2=3sin(2000\pit)'); subplot(3,1,3); plot(t,v3); ylabel('v_3 = v_1 + v_2'); xlabel('Time'); v_1 prints v1 \pi prints p

Plot Results Plots show addition of time domain signals

Verification Code Plot the added signal, v3, and the hand derived signal to verify that they are the same v_hand=3.6056*cos(2*pi*f*t *pi/180); subplot(2,1,1);plot(t,v3); grid on; ylabel('v_3 = v_1 + v_2'); xlabel('Time'); title('Graphical Verification'); subplot(2,1,2);plot(t,v_hand); grid on; ylabel('3.6cos(2000\pit \circ)');

Graphical Verification
The results are the same Thus Phasor addition is verified

Four Cosines Example Given: Determine:
Example: Use Matlab to add the following four sinusoidal signals and extract the Magnitude, M5 and Phase, q5 of the resulting signal. Also plot all of the signals to verify the solution. Given: Determine:

Enter in Phasor Form Transform signals into phasor form
Create phasors as Matlab variables in polar form » V1 = 1*exp(j*0); » V2 = 2*exp(-j*pi/6); » V3 = 3*exp(-j*pi/3); » V4 = 4*exp(-j*pi/2);

» V5 = V1 + V2 + V3 + V4; » M5 = abs(V5) M5 = 8.6972 » theta5_rad = angle(V5); » theta5_deg = theta5_rad*180/pi theta5_deg = Add phasors then extract Magnitude and Phase Convert back into Time Domain

Code to Plot Voltages Plot all 4 input voltages on same plot with different colors f =1000; % Frequency T = 1/f; % Find the period t =[0:T/256:T]; % Time Vector v1=1*cos(2*pi*f*t); v2=2*cos(2*pi*f*t-pi/6); v3=3*cos(2*pi*f*t-pi/3); v4=4*cos(2*pi*f*t-pi/2); plot(t,v1,'k'); hold on; plot(t,v2,'b'); plot(t,v3,'m'); plot(t,v4,'r'); grid on; title('Waveforms to be added'); xlabel('Time');ylabel('Amplitude');

Code to Plot Results Add the original Time Domain signals
v5_time = v1 + v2 + v3 + v4; subplot(2,1,1);plot(t,v5_time); grid on; ylabel('From Time Addition'); xlabel('Time'); title('Results of Addition of 4 Sinusoids'); Transform Phasor result into time domain v5_phasor = M5*cos(2*pi*f*t+theta5_rad); subplot(2,1,2);plot(t,v5_phasor); grid on; ylabel('From Phasor Addition'); xlabel('Time');

Compare Results The results are the same