State-variable Simulation in MATLAB在MATLAB仿真状态变量.docx

ME 344 Fall 2012State-variable Simulation in MATLAB(Linear Time-Invariant System Simulation – Part II)This handout briefly describes commands related to finding the response of a system represented in standard state space form to various inputs or initial conditions. Additional information, including examples, can be found in Section 5.2 of the textbook (System Dynamics, 2nd Edition, W. Palm). A previous handout, Transfer Function Simulation in MATLAB (Linear Time-Invariant System Simulation – Part I) covered finding the response of a system represented by a transfer function (or transfer matrix).Creating a modelThe ss command creates a state-space model:sys=ss(A,B,C,D)where the matrices A,B,C, and D are the various matrices in the standard state-variable format, and sys is the name of the variable you’re creating to hold your model. Converting a modelIf you know the matrices A, B, C, and D corresponding to state-space form, but wish to create a transfer function object, you can find the necessary numerator and denominator coefficients using the ss2tf command:[num,den]=ss2tf(A,B,C,D);Likewise, if you knew the transfer function representation and wanted to find the equivalent state-space form, you can use the tf2ss command:[A,B,C,D]=tf2ss(num,den);If you have a model already created in memory, you can obtain the transfer function or state-space information using the tfdata and ssdata commands, regardless of the form in which the model was originally created. For example, if you have a variable sys holding a model created using either the ss or the tf command, you can find a representation of the system in standard state-space form using[A,B,C,D]=ssdata(sys) which returns four numerical matrices, and the transfer function representation using[num,den]=tfdata(sys,’v’) as described in the previous handout.Note that the state-variable model corresponding to a given transfer function is not necessarily unique. If you create a state-variable model, your choice of A,B,C