From 578b17713974c594c8092863e2c02c7899384e46 Mon Sep 17 00:00:00 2001 From: Stefan Kletzenbauer Date: Thu, 27 Apr 2023 18:08:12 +0200 Subject: [PATCH 1/2] added discrete2cont()-funciton to convert discrete LTI-systems back to continuous systems --- control/statesp.py | 40 +++++++++++++++++++++++++++++++++++++++- 1 file changed, 39 insertions(+), 1 deletion(-) diff --git a/control/statesp.py b/control/statesp.py index 41f92ae21..9966469ae 100644 --- a/control/statesp.py +++ b/control/statesp.py @@ -164,7 +164,7 @@ def _f2s(f): class StateSpace(LTI): - r"""StateSpace(A, B, C, D[, dt]) + """StateSpace(A, B, C, D[, dt]) A class for representing state-space models. @@ -1988,3 +1988,41 @@ def linfnorm(sys, tol=1e-10): fpeak /= sys.dt return gpeak, fpeak + +def discrete2cont(sys, method='zoh'): + """ Transform a discrete state-space system to a continuous state-space system. + Parameters + ------ + sys : Discrete LTI (StateSpace or TransferFunction) system to transform + method: The method that was used for discretization + + Returns + ------ + sysc : Continuous LIT (StateSpace or TransferFunction) system depending on the input form. + """ + # check if system is of type state space and convert if not + #if sys. + + if not(isinstance(sys, StateSpace)): + sys = convert_to_statespace(sys) + was_tf = true + if method == 'zoh': + Ac = scipy.linalg.logm(sys.A)/sys.dt + Bc = np.linalg.inv(np.linalg.inv(Ac)@(sys.A-np.eye(np.shape(sys.A)[0])))@sys.B + + # remove small numbers + Ac = np.around(Ac/1e-6)*1e-6 + Bc = np.around(Bc/1e-6)*1e-6 + + # turn -0 to 0 + Ac[np.abs(Ac)<1e-6] = 0 + Bc[np.abs(Bc)<1e-6] = 0 + + sysc = StateSpace(Ac,Bc,sys.C,sys.D,0) + else: + raise NotImplementedError("Method: " + method + " is not implemented in this function!") + + if was_tf: + sysc = ss2tf(sysc) + + return sysc From ee22b8ab772b74c4506c516fb07a215001e2826a Mon Sep 17 00:00:00 2001 From: Stefan Kletzenbauer Date: Thu, 27 Apr 2023 18:36:01 +0200 Subject: [PATCH 2/2] Added function discrete2cont() to convert discrete LTI systems to continuous --- control/statesp.py | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/control/statesp.py b/control/statesp.py index 9966469ae..ca6f99d86 100644 --- a/control/statesp.py +++ b/control/statesp.py @@ -164,7 +164,7 @@ def _f2s(f): class StateSpace(LTI): - """StateSpace(A, B, C, D[, dt]) + r"""StateSpace(A, B, C, D[, dt]) A class for representing state-space models. pFad - Phonifier reborn

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