Reputation: 836
I am doing control engineering and I often face problems of the type below and I want to know if there is a way to deal with this in sympy.
question:
tl:dr: I want to make a MatrixSymbol
dependent on a scalar Symbol
representing time, to allow differentiation w.r.t. time.
Actual problem: v(t)=[v1(t),v2(t),v3(t)]
is a vector function of the time t
and I want to calculate the Projection into the direction of v and it's time derivative. In the end I would love to get an expression of v
, v.diff(t)
and v.T
(the transpose).
attempts:
I've tried different things and show the closest one:
This does the algebra I need, but I cannot take derivatives w.r.t. time
v = MatrixSymbol('v',3,1)
# here i'm building the terms I want
projection_v = v*sqrt(v.T*v).inverse()*v.T
orthogonal_v = Identity(3)-projection_v
orthogonal_v.as_explicit()
orthogonal_v
shows the abstract equation form that I need. In the end - to check and see the result again, I'd also like to make it explicit and see the expression as a function of v[0,0]
, v[1,0]
, and v[2,0]
for MatrixSymbol the function .as_explicit()
does exactly that beginning with sympy version 1.10. (Thanks Francesco Bonazzi for pointing this out.)
The problem however is, that I cannot make these a function of t
and take the derivative of projection_v
w.r.t. the time t
.
I also tried
t = Symbol('t',real=True,positive=True)
v1 = Function('v1',real=True)(t)
v2 = Function('v2',real=True)(t)
v3 = Function('v3',real=True)(t)
v_mat = FunctionMatrix(3,1,[v1,v2,v3]);
but it seems FunctionMatrix
is meant to evaluate the functions directly instead of being an analog to the scalar Function
.
Effectively I want to be able to calculate orthogonal_v.diff(t)
and then see the component wise operations with something like orthogonal_v.diff(t).as_explicit()
. Is this possible?
Upvotes: 0
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