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shiling2007 opened this issue Apr 24, 2022 · 3 comments
Closed

Need helps to figure out the Error and how to fix it #727

shiling2007 opened this issue Apr 24, 2022 · 3 comments

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@shiling2007
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I am running the example from https://github.com/python-control/python-control/blob/master/examples/kincar-flatsys.py. And I am getting an error message as below,

ValueError Traceback (most recent call last)
in ()
130 # Simulation the open system dynamics with the full input
131 t, y, x = ct.input_output_response(
--> 132 vehicle_flat, T, ud, x0, return_x=True)
133
134 # Plot the open loop system dynamics

2 frames
/usr/local/lib/python3.7/dist-packages/control/timeresp.py in _process_labels(labels, signal, length)
681 # Make sure the signal list is the right length and type
682 if len(labels) != length:
--> 683 raise ValueError("List of %s labels is the wrong length" % signal)
684 elif not all([isinstance(label, str) for label in labels]):
685 raise ValueError("List of %s labels must all be strings" % signal)

ValueError: List of output labels is the wrong length**

The program is running in google Colab environment with python version 3.7.
Your help would be much appreciated.
@roryyorke
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That example was updated recently. Assuming you're running python-control version 0.9.1 (check with import control as ct; print(ct.__version__), you need the example file from 0.9.1.

@murrayrm
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Alternatively, you can edit the latest version of the example to be compatible with the earlier version of the code. Here's the diff to implement:

--- a/examples/kincar-flatsys.py
+++ b/examples/kincar-flatsys.py
@@ -109,7 +109,7 @@ def plot_results(t, x, ud):
 # Create differentially flat input/output system
 vehicle_flat = fs.FlatSystem(
     vehicle_flat_forward, vehicle_flat_reverse, vehicle_update,
-    inputs=('v', 'delta'), outputs=('x', 'y', 'theta'),
+    inputs=('v', 'delta'), outputs=('x', 'y'),
     states=('x', 'y', 'theta'))

The change is that in the latest master the default for a flat system is that the default outputs are the flat outputs (in v0.9.1, the default outputs were the entire state, which didn't really make sense). This was changed in PR #709.

@shiling2007
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I am good now. Thanks a lot.

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@roryyorke @murrayrm @shiling2007