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1. (40 points). From the shown system response to a 5 volts step, find the transfer function: 2. (40 points). Use the signal flow graph method for finding the transfer function Y(S)/R(S) 3. (20 points). Determine the validity of the second-order approximation for the function. Justify your answer. G(S) = \frac{1}{(s + 4)(S^2 + 4S + 8)}
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Step 1:
I'll solve this problem step by step, carefully following the LaTeX formatting guidelines:

Problem 1: Transfer Function from System Response

Step 2:
: Analyze the Step Response

- Settling time ≈ $$1 \text{ second}
From the given system response graph:

Step 3:
: Determine System Characteristics

- Steady-state gain = $$\frac{4}{5} = 0.8
- Percent overshoot = \frac{5 - 4}{4} \times 100\% = 25\%

Step 4:
: Estimate Transfer Function

G(s) = \frac{\omega_{n}^{2}}{s^{2} + 2\zeta\omega_{n}s + \omega_{n}^{2}}
Typical second-order transfer function form:

Final Answer

G(s) = \frac{4}{s^{2} + 2(0.5)(2)s + 4} Problem 2: Signal Flow Graph Transfer Function Step 1: Identify Signal Flow Graph Elements - Forward paths - Feedback paths - Node relationships Step 2: Apply Mason's Gain Rule \frac{Y(s)}{R(s)} = \frac{\text{Sum of forward path gains}}{\text{1 - Total loop gain}} Problem 3: Second-Order Approximation Validity Step 1: Analyze Transfer Function G(s) = \frac{1}{(s + 4)(s^{2} + 4s + 8)} Step 2: Check Denominator Characteristics - First factor: s + 4 - Second factor: s^{2} + 4s + 8 Step 3: Evaluate Approximation - The function contains a first-order and second-order term - Poles: - 4, - 2 \pm j^2 It's a mixed first and second-order system, so a second-order approximation would be inappropriate. Note: A complete solution would require more detailed mathematical analysis of the system's poles and zeros.