GeezerVison

^{Originally posted by zhengzl18 October 17, 2022}
Hi,
I'm running the example code of the optimal module: https://python-control.readthedocs.io/en/0.9.2/optimal.html#example
When calling the solve_ocp method, a parameter called "horizon" is required:

horizon = np.linspace(0, Tf, 3, endpoint=True)
result = opt.solve_ocp(
    vehicle, horizon, x0, traj_cost, constraints,
    terminal_cost=term_cost, initial_guess=u0)

In this setting, it works just fine.

But when I tried to change the horizon into something like (changing nothing but the number of points in the linspace):

horizon = np.linspace(0, Tf, 4, endpoint=True)

the result seemed to be extremely strange, with the inputs u always remaining the same:

Summary statistics:
* Cost function calls: 9
* Constraint calls: 20
* System simulations: 27
* Final cost: 16000.0
    cost: 16000.0
     fun: 16000.0
  inputs: array([[10., 10., 10., 10.],
       [ 0.,  0.,  0.,  0.]])
     jac: array([ 0.00000000e+00,  2.44140625e-04,  1.22070312e-04,  0.00000000e+00,
       -3.62099047e+06, -6.84054738e+06, -2.12256850e+06, -7.49211857e+05])
 message: 'Optimization terminated successfully'
    nfev: 9
     nit: 5
    njev: 1
 problem: <control.optimal.OptimalControlProblem object at 0x7ff0cb281df0>
  states: array([[  0.        ,  33.33333333,  66.66666667, 100.        ],
       [ -2.        ,  -2.        ,  -2.        ,  -2.        ],
       [  0.        ,   0.        ,   0.        ,   0.        ]])
  status: 0
 success: True
    time: array([ 0.        ,  3.33333333,  6.66666667, 10.        ])
       x: array([10., 10., 10., 10.,  0.,  0.,  0.,  0.])

It's the case for all num except 3 in the np.linspace(0, Tf, num).

I'm confused by this results and wonder what's the actual use of 'horizon'? (I do notice from the comments that it's a "List of times at which the optimal input should be computed", but I still can't understand)

Hope for any help.

Thanks!

Activity

murrayrm
self-assigned this
on Nov 19, 2022
murrayrm
added
bug
on Nov 19, 2022
murrayrm
added this to the 0.9.3 milestone on Nov 19, 2022
murrayrm
linked a pull request that will close this issueAdd collocation method for optimal control problems #799 on Nov 26, 2022
murrayrm
closed this as completedin #799 on Dec 2, 2022

Metadata

Assignees

murrayrm

Labels

bug

Type

No type

Projects

No projects

Milestone

0.9.3

Relationships

None yet

Development

No branches or pull requests

Issue actions

You are visitor 01402503 — GeezerVison does not store the pages you look up.
Best viewed with Netscape Navigator 4.7 or Internet Explorer 6 at 800×600. No cookies required.