Transcription of Second Order Systems
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1 Second Order SystemsSecond Order Equations()1222++=ssKsG Standard Form 2d2ydt2+2 dydt+y=Kf(t)Corresponding Differential EquationK = Gain = Natural Period of Oscillation = Damping Factor (zeta)Note: this has to be !!!2 Origins of Second Order Equations1. Multiple Capacity Systems in SeriesK1 1s+1K2 2s+1becomeorK1K2 1s+1() 2s+1()K 2s2+2 s+12. Controlled Systems (to be discussed later)3. Inherently Second Order Systems Mechanical Systems and some sensors Not that common in chemical process controlExamination of the Characteristic Equation 2s2+2 s+1=0 Two complex conjugate rootsUnderdamped0 < < 1 Two equal real rootsCritically Damped = 1 Two distinct real rootsOverdamped > 13 Response of 2ndOrder system to StepInputsFast, oscillations occurUnderdampedEq. 5-51 Faster than overdamped, no oscillationCritically dampedEq. 5-50 Sluggish, no oscillationsOverdampedEq. 5-48 or 5-49 Ways to describe underdamped responses: Rise time Time to first peak Settling time Overshoot Decay ratio Period of oscillationResponse of 2ndOrder Systemsto StepInput ( 0 < < 1)1.
Response of 2nd Order Systems to Step Input ( 0 < ζ< 1) 1. Rise Time: tr is the time the process output takes to first reach the new steady-state value. 2. Time to First Peak: tp is the time required for the output to reach its first maximum value. 3. Settling Time: …
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