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I. Concepts and Tools Mathematics for Dynamic Systems Time Response

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1 I. Concepts and Tools Mathematics for Dynamic Systems Time Response
Differential Equation Transfer Function State Space Time Response Transient Steady State Frequency Response Bode and Nyquist Plots Stability and Stability Margins Extensions to Digital Control

2 A Differential Equation of Motion
Newton’s Law: A Linear Approximation:

3 Laplace Transform and Transfer Function

4 State Space Description

5 From State Space to Transfer Function

6 Linear System Concepts
States form a linear vector space Controllable Subspace and Controllability Observable Subspace and Observability The Linear Time Invariance (LTI) Assumptions Stability Lyapunov Stability (for linear or nonlinear systems) LTI System Stability: poles/eigenvalues in RHP

7 A Motion Control Problem

8 From Differential Eq. To Transfer Function

9 Transfer Function model of the motion plant

10 Unity Feedback Control System

11 Common Nonlinearities

12 Linearization

13 Time Response

14 Open Loop Transient Response
How parameters of transfer functions affect output Terminologies for 1st and 2nd order systems

15 Basis of Analysis

16 First Order Transfer Function

17 Pure 2nd Order Transfer Functions

18 Pure 2nd Order Transfer Functions

19 Pure 2nd Order Transfer Functions

20 Terminologies

21 Calculations

22 Pure 2nd Order Transfer Functions

23 Pure 2nd Order Transfer Functions

24 Pure 2nd Order Transfer Functions

25 Steady State Response Steady state response is determined by the dc gain: G(0)

26 Steady State Error

27 Frequency Response: The MOST useful concept in control theory
Performance Measures Bandwidth Disturbance Rejection Noise Sensitivity Stability Yes or No? Stability Margins (closeness to instability) Robustness (generalized stability margins)

28 Frequency Response

29 Bode Plot (Magnitude and Phase vs. Frequency) G(s) =1/(s +2)

30 Polar Plot: imaginary part vs. real part of G(jw) G(s) =1/(s +2)

31 Bandwidth of Feedback Control
-3dB Frequency of CLTF 0 dB Crossing Frequency (wc) of Gc(jw)Gp(jw) Defines how fast y follows r

32 Disturbance Rejection

33 Noise Sensitivity

34 Nyquist Plot Using G (jw) to determine the stability of

35 The Idea of Mapping

36 Nyquist Contour RHP

37 Nyquist Stability Criteria
Determine stability by inspection Assume G(s)H(s) is stable, let s complete the N-countour The closed-loop system is stable if G(s)H(s) does not encircle the (-1,0) point Basis of Stability Robustness Further Reading: unstable G(s)H(s), # of unstable poles

38 Nyquist Stability Criteria
Stable Unstable

39 Stability Robustness The (-1,0) point on the GH-plane becomes the focus Distance to instability: G(s)H(s)-(-1)=1+G(s)H(s) Robust Stability Condition Distance to instability > Dynamic Variations of G(s)H(s) This is basis of modern robust control theory

40 Gain and Phase Margins (-1,0) is equivalent of 0dbÐ(-180)° point on Bode plot |G(jw)H(jw)| ÐG(jw)H(jw)

41 Stability Margins: Nyquist Plot Bode Plot

42 Digital Control

43 Discrete Signals

44 Digital Control Concepts
Sampling Rate Delay ADC and DAC Resolution (quantization levels) Speed Aliasing Digital Control Algorithm Difference equation

45 Discrete System Description
h[n]: impulse response Difference equation u[n] h[n] y[n]

46 Discrete Fourier Transform and z-Transform

47 Discrete Transfer Function and Frequency Response

48 Application of Basic Concepts to Previously Designed Controllers


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