update default params computation in interconnect()

Author: murrayrm

control/nlsys.py

@@ -710,6 +710,11 @@ def __init__(self, syslist, connections=None, inplist=None, outlist=None,
         if outputs is None and outlist is not None:
             outputs = len(outlist)
 
+        if params is None:
+            params = {}
+            for sys in self.syslist:
+                params = params | sys.params
+
         # Create updfcn and outfcn
         def updfcn(t, x, u, params):
             self._update_params(params)
@@ -2268,7 +2273,8 @@ def interconnect(
 
     params : dict, optional
         Parameter values for the systems.  Passed to the evaluation functions
-        for the system as default values, overriding internal defaults.
+        for the system as default values, overriding internal defaults.  If
+        not specified, defaults to parameters from subsystems.
 
     dt : timebase, optional
         The timebase for the system, used to specify whether the system is

control/tests/interconnect_test.py

@@ -666,15 +666,29 @@ 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})
+        states=1, inputs='u', outputs='y', params={'a': 2, 'c':2})
 
     # Simple system for serial interconnection
     sys2 = ct.nlsys(
         None, lambda t, x, u, params: u[0],
-        inputs='r', outputs='u')
+        inputs='r', outputs='u', params={'a': 4, 'b': 3})
 
-    # Create a series interconnection
+    # Make sure default parameters get set as expected
     sys = ct.interconnect([sys1, sys2], inputs='r', outputs='y')
+    assert sys.params == {'a': 4, 'c': 2, 'b': 3}
+    assert sys.dynamics(0, [1], [0]).item() == 4
+
+    # Make sure we can override the parameters
+    sys = ct.interconnect(
+        [sys1, sys2], inputs='r', outputs='y', params={'b': 1})
+    assert sys.params == {'b': 1}
+    assert sys.dynamics(0, [1], [0]).item() == 2
+    assert sys.dynamics(0, [1], [0], params={'a': 5}).item() == 5
+
+    # Create final series interconnection, with proper parameter values
+    sys = ct.interconnect(
+        [sys1, sys2], inputs='r', outputs='y', params={'a': 1})
+    assert sys.params == {'a': 1}
 
     # Make sure we can call the update function
     sys.updfcn(0, [0], [0], {})