CODEWITHSUNDEEP
drake
Rufus
Rufus

Reputation: 5566

Using >= for constraint throws RuntimeError (please use pydrake.common.containers.EqualToDict)

I am trying to use direct transcription to solve my trajectory optimization problem which involves some trigonometric functions.

I have the following variable types

a[i] = array([<Expression "(state_0(0) + 0.001 * state_0(4))">,
       <Expression "(state_0(1) + 0.001 * state_0(5))">,
       <Expression "(state_0(2) + 0.001 * state_0(6))">,
       <Expression "(state_0(3) + 0.001 * state_0(7))">,
       <Expression "...omitted...">,
       <Expression "...omitted...">,
       <Expression "...omitted...">,
       <Expression "...omitted...">], dtype=object)

b[i] = array([Variable('state_1(0)', Continuous),
       Variable('state_1(1)', Continuous),
       Variable('state_1(2)', Continuous),
       Variable('state_1(3)', Continuous),
       Variable('state_1(4)', Continuous),
       Variable('state_1(5)', Continuous),
       Variable('state_1(6)', Continuous),
       Variable('state_1(7)', Continuous)], dtype=object)

I'm trying to create a constraint as follows

mp.AddConstraint(b[i] <= a[i])

But I get the following error

RuntimeError: You should not call `__bool__` / `__nonzero__` on `Formula`. If you are trying to make a map with `Variable`, `Expression`, or `Polynomial` as keys (and then access the map in Python), please use pydrake.common.containers.EqualToDict`.

Upvotes: 2

Views: 168

Answers (2)

Russ Tedrake
Russ Tedrake

Reputation: 5533

That's correct. Although you can also use the function names like eq(a,b) https://github.com/RobotLocomotion/drake/issues/8315

Upvotes: 1

Rufus
Rufus

Reputation: 5566

It appears that the constraint must be specified per element, i.e.

for j in range(8):
    mp.AddConstraint(b[i][j] <= a[i][j])

Upvotes: 0

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