control.connect(sys, Q, inputv, outputv)[source]

Index-based interconnection of an LTI system.

Deprecated since version 0.10.0: connect will be removed in a future version of python-control in favor of interconnect, which works with named signals.

The system sys is a system typically constructed with append, with multiple inputs and outputs. The inputs and outputs are connected according to the interconnection matrix Q, and then the final inputs and outputs are trimmed according to the inputs and outputs listed in inputv and outputv.

NOTE: Inputs and outputs are indexed starting at 1 and negative values correspond to a negative feedback interconnection.

  • sys (InputOutputSystem) – System to be connected.

  • Q (2D array) – Interconnection matrix. First column gives the input to be connected. The second column gives the index of an output that is to be fed into that input. Each additional column gives the index of an additional input that may be optionally added to that input. Negative values mean the feedback is negative. A zero value is ignored. Inputs and outputs are indexed starting at 1 to communicate sign information.

  • inputv (1D array) – list of final external inputs, indexed starting at 1

  • outputv (1D array) – list of final external outputs, indexed starting at 1


out – Connected and trimmed I/O system.

Return type



>>> G = ct.rss(7, inputs=2, outputs=2)
>>> K = [[1, 2], [2, -1]]  # negative feedback interconnection
>>> T = ct.connect(G, K, [2], [1, 2])
>>> T.ninputs, T.noutputs, T.nstates
(1, 2, 7)


The interconnect() function in the input/output systems module allows the use of named signals and provides an alternative method for interconnecting multiple systems.