I'm trying to use the DirectTranscription / DirectCollocation methods with a user declared Vector or LeafSystem, but run into a problem with casting to AutoDiffXd. For instance, the following code snippet:
from pydrake.all import VectorSystem, DirectTranscription
class CustomVectorSystem(VectorSystem):
def __init__(self):
VectorSystem.__init__(self, 1, 1)
self.DeclarePeriodicDiscreteUpdate(0.01)
self.DeclareDiscreteState(1)
def DoCalcVectorOutput(self, context, u, x, y):
y.SetFromVector(x + u)
def DoCalcVectorTimeDerivatives(self, context, u, x, x_dot):
x_dot.SetFromVector(x + u)
def DoCalcVectorDiscreteVariableUpdates(self, context, u, x, x_n):
x_n.SetFromVector(x + u)
sys = CustomVectorSystem()
DirectTranscription(sys, sys.CreateDefaultContext(), 10)
Leads to this error:
Traceback (most recent call last):
File "debugging.py", line 24, in <module>
DirectTranscription(sys, sys.CreateDefaultContext(), 10)
RuntimeError: The object named [] of type drake::pydrake::(anonymous)::Impl<double>::PyVectorSystem does not support ToAutoDiffXd.
Similarly for a LeafSystem. I've tried building the system with type AutoDiffXd by doing VectorSystem_[AutoDiffXd], but DirectTranscription seems to only accept float types and tries to do the conversion itself.
All the working DirectTranscription examples I found use either LinearSystem or a Plant whose dynamics are defined in C++ code---how should I declare a System such that I can run DirectTranscription on it?
