MATLAB: Continuous to discrete and plotting

hagai

[EDIT: 20110527 15:15 CDT – reformat – WDR]

hey and thanks in advance.

i have a continuous system(A,B,C,D matrices) and what i'm trying to do is:

1. plot on one graph the continuous and equivalent discrete systems response to a sequence of steps moved in time

2. the same only for a run entry

thanks again,

hagai

Best Answer

thanks, ended up using c2d

Related Solutions

MATLAB: Is the discrete approximation of a continuous system less accurate using the C2D function with a smaller sample time step

The corresponding discrete poles for Ts=0.001 are:

>> exp(.001*pole(Hc))

9.9998e-001

9.9999e-001

1.0000e+000

which is very close to a triple pole at z=1. Using the transfer function representation for discrete systems with multiple poles near z=1 will typically result in significant loss of accuracy at low frequencies.

The Control System Toolbox documentation includes the following examples that explain this in detail:

- Control System Toolbox, Using the Right Model Representation

- Control System Toolbox, Sensitivity of Multiple Roots

Such problems go away when using the state-space representation. Try the following code:

Hz = c2d(ss(Hc),.001,'t');
figure, step(Hc,Hz,1000)
figure, bode(Hc,Hz)

Note that there is a limit to how small Ts can get before all useful information about the dynamics gets vanished by the round off noise. Given the time constant of the continuous system, a sampling time of Ts = 1 or Ts = 0.1 is enough to get an accurate discretization.

MATLAB: Discrete Continuous Simulink Question

There is no problem using continuous and discrete blocks in simulink. If for example the output y(t) of a continuous system is the input u[n] of discrete system:

u[n] is the the signal y(t) taken at each sample time ts.

Best Answer

Related Solutions

MATLAB: Is the discrete approximation of a continuous system less accurate using the C2D function with a smaller sample time step

MATLAB: Discrete Continuous Simulink Question

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