From 6b00fd42cca247f5109e10ad2fae6f7dfef5e885 Mon Sep 17 00:00:00 2001
From: Richard Murray <murray@cds.caltech.edu>
Date: Sun, 7 Apr 2024 10:54:35 -0700
Subject: [PATCH] fix typo in ICSystem updfcn, outfcn: update_params ->
 _update_params

---
 control/nlsys.py                   |  4 ++--
 control/tests/interconnect_test.py | 30 ++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/control/nlsys.py b/control/nlsys.py
index c154c0818..38efea355 100644
--- a/control/nlsys.py
+++ b/control/nlsys.py
@@ -706,10 +706,10 @@ def __init__(self, syslist, connections=None, inplist=None, outlist=None,
 
         # Create updfcn and outfcn
         def updfcn(t, x, u, params):
-            self.update_params(params)
+            self._update_params(params)
             return self._rhs(t, x, u)
         def outfcn(t, x, u, params):
-            self.update_params(params)
+            self._update_params(params)
             return self._out(t, x, u)
 
         # Initialize NonlinearIOSystem object
diff --git a/control/tests/interconnect_test.py b/control/tests/interconnect_test.py
index 285e9d096..f4b0c59a8 100644
--- a/control/tests/interconnect_test.py
+++ b/control/tests/interconnect_test.py
@@ -16,6 +16,7 @@
 
 import numpy as np
 import scipy as sp
+import math
 
 import control as ct
 
@@ -659,3 +660,32 @@ def test_interconnect_rewrite():
         outputs=['y', 'z'])
 
     assert icsys.input_labels == ['u[0]', 'u[1]', 'w[0]', 'w[1]']
+
+
+def test_interconnect_params():
+    # Create a nominally unstable system
+    sys1 = ct.nlsys(
+        lambda t, x, u, params: params['a'] * x[0] + u[0],
+        states=1, inputs='u', outputs='y', params={'a': 1})
+
+    # Simple system for serial interconnection
+    sys2 = ct.nlsys(
+        None, lambda t, x, u, params: u[0],
+        inputs='r', outputs='u')
+
+    # Create a series interconnection
+    sys = ct.interconnect([sys1, sys2], inputs='r', outputs='y')
+
+    # Make sure we can call the update function
+    sys.updfcn(0, [0], [0], {})
+
+    # Make sure the serial interconnection is unstable to start
+    assert sys.linearize([0], [0]).poles()[0].real == 1
+
+    # Change the parameter and make sure it takes
+    assert sys.linearize([0], [0], params={'a': -1}).poles()[0].real == -1
+
+    # Now try running a simulation
+    timepts = np.linspace(0, 10)
+    resp = ct.input_output_response(sys, timepts, 0, params={'a': -1})
+    assert resp.states[0, -1].item() < 2 * math.exp(-10)