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Reference guides are available for functions and commands supported by OML, Tcl, and Python.
Reference Guide for OpenMatrix Language Functions
The Reference Guide contains documentation for all functions supported in the OpenMatrix language.
Control System Commands
isstable
Checks if an LTI model is stable or unstable

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Reference guides are available for functions and commands supported by OML, Tcl, and Python.
- Scripting Guide for OpenMatrix Language
  OpenMatrix is a mathematical scripting language.
- Reference Guide for OpenMatrix Language Functions
  The Reference Guide contains documentation for all functions supported in the OpenMatrix language.
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    - acker
      Ackermann's formula (pole placement gain selection for single-input systems).
    - append
      Appends the inputs and outputs of the two models.
    - augstate
      Add states to the outputs of a state-space model.
    - balreal
      Computes a Gramian balanced realization of an LTI model.
    - bdschur
      Block diagonalization with the Schur factorization.
    - blkdiag
      Builds a block diagonal matrix with the input parameters.
    - bode
      Bode diagram.
    - c2d
      Computes a discrete-time state-space model from a continuous-time state-space model.
    - care
      Solves the continuous-time Algebraic Riccati Equation.
    - covar
      Steady-state co-variance.
    - ctrb
      Controllability matrix.
    - ctrbf
      Calculates the controllability staircase form.
    - d2c
      Converts a discrete model to continuous time model.
    - damp
      Compute natural frequencies, damping ratios, and poles.
    - dare
      Solves the Discrete-time Algebraic Riccati Equations.
    - db2mag
      Transforms decibels (dB) to magnitude.
    - dcgain
      Low-frequency (DC) gain of a state-space or transfer function model
    - dlqr
      Linear-quadratic regulator for a discrete-time model.
    - dlyap
      Solve discrete-time Lyapunov or Sylvester equations.
    - dlyapchol
      Solves discrete-time Lyapunov equations with a square-root solver.
    - dss
      Constructs a descriptor state-space model.
    - dss2ss
      Converts a descriptor state-space system into regular state-space form.
    - dssdata
      Extracts data from a descriptor state-space model.
    - esort
      Sorts continuous-time poles in descending order by the real component.
    - estim
      Returns the state estimator for a given estimator gain.
    - expm
      Compute the matrix exponential.
    - filt
      Constructs a transfer function model in DSP format.
    - gensig
      Generates an input signal for the lsim function.
    - gram
      Computes the observability and controllability Gramians.
    - hsvd
      Hankel singular values of a state-space or transfer function model.
    - impulse
      Compute the impulse response of a control system.
    - isct
      Returns true if the LTI model is in continuous time.
    - isctrb
      Returns true if the state-space model is controllable.
    - isdt
      Returns true if an LTI model is in discrete time.
    - isobsv
      Returns true if the state-space is observable.
    - issiso
      Checks if an LTI model is single-input/single-output (SISO)
    - isstable
      Checks if an LTI model is stable or unstable
    - kalman
      Kalman filter or estimator.
    - logm
      Matrix logarithm.
    - lqe
      Linear quadratic estimator (Kalman Filter)
    - lqr
      Linear-quadratic regulator for a continuous-time model.
    - lqry
      Calculates the optimal steady-state feedback gain matrix K.
    - lsim
      Simulates LTI model response to arbitrary inputs.
    - lyap
      Solves continuous Lyapunov or Sylvester equations.
    - lyapchol
      Solves continuous-time Lyapunov equation using a square-root solver.
    - mag2db
      Computes magnitude from decibels (dB).
    - margin
      Margin stability.
    - minreal
      Minimal realization.
    - nyquist
      Nyquist diagram.
    - obsv
      Returns the observability matrix of a state-space model.
    - obsvf
      Calculates the observability staircase form.
    - padecoef
      Computes the Pade approximation of time delays.
    - parallel
      Connects two state-space or transfer functions in parallel.
    - pid
      Constructs a continuous-time PID controller transfer function.
    - place
      Pole assignment.
    - pole
      Compute poles for a state-space or transfer function model.
    - prescale
      Scale a state-space model.
    - reg
      Creates a state regulator with specified state-feedback and estimator gains.
    - rlocfind
      Find gain and poles for specific points of a root locus diagram.
    - rlocus
      rlocus diagram.
    - rsf2csf
      Transforms a real Schur form to a complex Schur form.
    - series
      Connects two state-space or transfer function in a series.
    - sqrtm
      Matrix square root.
    - ss
      Constructs a state-space model.
    - ss2ss
      Transforms a state-space model to another state-space model.
    - ss2tf
      Converts state-space model parameters to transfer function model parameters.
    - ss2tfc
      Convert state-space model parameters to transfer function model parameters.
    - ssdata
      Extracts data from a state-space model.
    - step
      Compute the step response of a control system.
    - tf
      Constructs a transfer function model
    - tf2ss
      Transforms transfer function parameters to state-space parameters.
    - tf2ssc
      Transforms transfer function parameters to state-space parameters.
    - tf2zp
      Transforms (continuous) transfer function parameters to zero-pole-gain parameters.
    - tf2zpk
      Transforms (discrete) transfer function parameters to zero-pole-gain parameters.
    - tfdata
      Extracts data from a transfer function model.
    - zp2ss
      Zero-pole to state-space conversion.
    - zp2tf
      Zero-pole to transfer function conversion.
    - zpk
      Constructs a zero, pole, gain model.
    - zpkdata
      Extracts data from a zero-pole-gain model.
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- Python in Compose Reference Guide
Appendix
Get help for the optional libraries that are available in the Extension Manager.
Frequently Asked Questions
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isstable

Checks if an LTI model is stable or unstable

Syntax

BRES = isstable(SYSLTI)

Inputs

SYSLTI: An LTI model.

Outputs

BRES: A Boolean true if it is stable.

Examples

State-space model input:

sys_tf=tf([1],[1 3 2]);
sys=ss(sys_tf);
R1=isstable(sys)

R1 = 1

Transfer function model input:

sys_tf=tf([1],[1 5 6 0 0]);
R2=isstable(sys_tf)

R2 = 0

Comments

Returns true if the LTI model is stable.