[GSoC] Added methods to StateSpace class to calculate state and output vectors. #26685

abhiphile · 2024-06-07T17:24:35Z

Added methods to StateSpace class to calculate state and output vectors by using the ODE module.

State vector can be found by solving the equation $\dot x= Ax + Bu$ by using the ODE module. linodesolve() function type2 has been used to find the solution.
Output vector is calculated by using the state_vector function and by using the equation $y = Cx + Du$.

References to other Issues or PRs

Brief description of what is fixed or changed

Other comments

Release Notes

physics.control
- Added methods to find state and output vectors for StateSpace.

sympy-bot · 2024-06-07T17:24:42Z

✅

Hi, I am the SymPy bot. I'm here to help you write a release notes entry. Please read the guide on how to write release notes.

Your release notes are in good order.

Here is what the release notes will look like:

physics.control
- Added methods to find state and output vectors for StateSpace. (#26685 by @abhiphile)

This will be added to https://github.com/sympy/sympy/wiki/Release-Notes-for-1.14.

Click here to see the pull request description that was parsed.

<!-- Your title above should be a short description of what
was changed. Do not include the issue number in the title. -->
Added methods to `StateSpace` class to calculate state and output vectors by using the ODE module.
1. State vector can be found by solving the equation $\dot x= Ax + Bu$ by using the ODE module. `linodesolve()` function `type2` has been used to find the solution.
2. Output vector is calculated by using the `state_vector` function and by using the equation $y = Cx + Du$.

#### References to other Issues or PRs
<!-- If this pull request fixes an issue, write "Fixes #NNNN" in that exact
format, e.g. "Fixes #1234" (see
https://tinyurl.com/auto-closing for more information). Also, please
write a comment on that issue linking back to this pull request once it is
open. -->


#### Brief description of what is fixed or changed


#### Other comments


#### Release Notes

<!-- Write the release notes for this release below between the BEGIN and END
statements. The basic format is a bulleted list with the name of the subpackage
and the release note for this PR. For example:

* solvers
  * Added a new solver for logarithmic equations.

* functions
  * Fixed a bug with log of integers. Formerly, `log(-x)` incorrectly gave `-log(x)`.

* physics.units
  * Corrected a semantical error in the conversion between volt and statvolt which
    reported the volt as being larger than the statvolt.

or if no release note(s) should be included use:

NO ENTRY

See https://github.com/sympy/sympy/wiki/Writing-Release-Notes for more
information on how to write release notes. The bot will check your release
notes automatically to see if they are formatted correctly. -->

<!-- BEGIN RELEASE NOTES -->
* physics.control
  * Added methods to find state and output vectors for StateSpace.
<!-- END RELEASE NOTES -->

Update

The release notes on the wiki have been updated.

abhiphile · 2024-06-07T17:40:24Z

Doctest

For doctest I've used this resource https://web.mit.edu/2.14/www/Handouts/StateSpaceResponse.pdf.
Example 1 for state_vector
Example 2 for output_vector

Unit Test

For unit test the following resources are used

Test 1 : https://lpsa.swarthmore.edu/Transient/TransMethSS.html
Test 2 : https://web.mit.edu/2.14/www/Handouts/StateSpaceResponse.pdf (Example 11)

github-actions · 2024-06-07T19:07:32Z

Benchmark results from GitHub Actions

Lower numbers are good, higher numbers are bad. A ratio less than 1
means a speed up and greater than 1 means a slowdown. Green lines
beginning with + are slowdowns (the PR is slower then master or
master is slower than the previous release). Red lines beginning
with - are speedups.

Significantly changed benchmark results (PR vs master)

Significantly changed benchmark results (master vs previous release)

Full benchmark results can be found as artifacts in GitHub Actions
(click on checks at the top of the PR).

abhiphile · 2024-06-08T15:38:28Z

@Sc0rpi0n101 @faze-geek Please take a look at this PR.

sympy/physics/control/lti.py

moorepants · 2024-06-19T18:47:19Z

sympy/physics/control/tests/test_lti.py

+    t = symbols('t')
+    ss1 = StateSpace(A1, B1, C1, D1)
+    assert ss1.state_vector(initial_conditions=i1, var=t) == Matrix([[ 4*exp(-t) - 3*exp(-2*t)],
+                                                              [-4*exp(-t) + 6*exp(-2*t)]])


There are no tests with symbolic matrices. Will this work with such matrices?

I don't think the StateSpace model supports symbolic matrices as of now. Kindly raise an issue and we can discuss it there.

It may be possible that some functions in StateSpace model doesn't support symbolic matrices but I've tested that most of the methods in StateSpace support symbolic.

>>> a11, a12, a21, a22 = symbols('a11 a12 a21 a22') >>> b1, b2 = symbols('b1 b2') >>> c1, c2 = symbols('c1 c2') >>> d1 = symbols('d1') >>> A = Matrix([[a11, a12], [a21, a22]]) >>> B = Matrix([[b1], [b2]]) >>> C = Matrix([[c1, c2]]) >>> D = Matrix([d1]) >>> ss = StateSpace(A, B, C, D) >>> ss StateSpace( Matrix([ [a11, a12], [a21, a22]]), Matrix([ [b1], [b2]]), Matrix([[c1, c2]]), Matrix([[d1]])) >>> ss.rewrite(TransferFunction) [[TransferFunction(-c1*(a12*b2 - a22*b1 + b1*s) - c2*(-a11*b2 + a21*b1 + b2*s) + d1*(-a11*a22 + a11*s + a12*a21 + a22*s - s**2), -a11*a22 + a11*s + a12*a21 + a22*s - s**2, s)]]

Ohh yes, I recall this. Thanks for letting me know.

moorepants · 2024-06-19T18:48:40Z

sympy/physics/control/lti.py

+            input_vector = zeros(self._B.shape[1], 1)
+        sv = self.state_vector(initial_conditions, input_vector, var)
+        res = self._C*sv + self._D*input_vector
+        return res.simplify()


In general, simplify should not be called in library code due to large potential performance costs.

moorepants · 2024-06-19T18:54:28Z

sympy/physics/control/lti.py

@@ -3838,6 +3840,108 @@ def num_outputs(self):
        """
        return self._D.rows

+    def state_vector(self, initial_conditions=None, input_vector=None, var=None):


Given these are all kwargs, what happens if you call .state_vector(). I don't see a test case for that.

moorepants · 2024-06-19T18:57:50Z

sympy/physics/control/lti.py

+
+        initial_conditions : Matrix
+            The initial conditions of `x` state vector.
+        input_vector : Matrix


I don't see any test cases for when you pass something like u = Matrix([Heaviside(t)]). Does something like this work? It is super common to use a step function. What about u = Matrix([sin(t)])? Or any other common input function to test?

@abhiphile It is your responsibility to make such tests. If you stick to MATLAB examples then only numerical tests will be supported and not symbolic ones. Let's make a separate PR only for such tests (it would cover all the StateSpace methods not just this one).

Yes @faze-geek I'm working on a new PR which resolves the issues of this PR.

moorepants · 2024-06-19T19:02:26Z

sympy/physics/control/lti.py

+        """
+
+        if not var:
+            var = Symbol('t')


Would this not be better in the function signature? def state_vector(var=Symbol('t')) then the user will know what symbol is used if they don't pass one.

moorepants · 2024-06-19T19:05:02Z

sympy/physics/control/lti.py

+            mat1 = mat1.replace(dummy_symbols[ind], v)
+        return mat1
+
+    def output_vector(self, initial_conditions=None, input_vector=None, var=None):


I'm not a huge fan of the names of these new methods. You are solving the linear ordinary differential equations initial value problem. initial_value_problem_solution or ivp_sol or solve_ivp (which is same as scipy's numerical method) seem more aligned with what the methods actually do.

We also already have dsolve() terminology in SymPy, so copying what we already have for these names is also probably a good idea.

Do you mean that the output_vector() should be renamed as dsolve() or ivp_sol() ?

Yes, both state_vector and output_vector coudl have better names. You also do not need a state_vector method because you can always pass C = eye(len(A)) to make y = x. I would only expose the single method to the users and name it something that aligns with the naming already in sympy or the name in scipy.

abhiphile changed the title ~~Added methods to StateSpace class to calculate state and output vectors.~~ [GSoC] Added methods to StateSpace class to calculate state and output vectors. Jun 7, 2024

Sc0rpi0n101 approved these changes Jun 10, 2024

View reviewed changes

faze-geek reviewed Jun 11, 2024

View reviewed changes

sympy/physics/control/lti.py Outdated Show resolved Hide resolved

faze-geek requested a review from sylee957 June 11, 2024 02:18

faze-geek added GSoC physics.control labels Jun 11, 2024

sylee957 reviewed Jun 14, 2024

View reviewed changes

sympy/physics/control/lti.py Outdated Show resolved Hide resolved

abhiphile requested a review from Sc0rpi0n101 June 17, 2024 03:38

faze-geek approved these changes Jun 18, 2024

View reviewed changes

Added methods to StateSpace class to calculate state and output vectors.

54b676e

abhiphile force-pushed the gsoc2.1 branch from 358f04b to 54b676e Compare June 18, 2024 18:43

Sc0rpi0n101 merged commit 84b9fc7 into sympy:master Jun 19, 2024
48 checks passed

moorepants reviewed Jun 19, 2024

View reviewed changes

abhiphile mentioned this pull request Jun 24, 2024

[GSoC] Changed the output_vector to dsolve and added support of symbolic matrices. #26736

Merged

abhiphile mentioned this pull request Jul 2, 2024

Added tests using symbolic matrices in StateSpace. #26758

Merged

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

[GSoC] Added methods to StateSpace class to calculate state and output vectors. #26685

[GSoC] Added methods to StateSpace class to calculate state and output vectors. #26685

abhiphile commented Jun 7, 2024

sympy-bot commented Jun 7, 2024 •

edited

Loading

abhiphile commented Jun 7, 2024

github-actions bot commented Jun 7, 2024 •

edited

Loading

abhiphile commented Jun 8, 2024

moorepants Jun 19, 2024

faze-geek Jun 20, 2024

abhiphile Jun 20, 2024

faze-geek Jun 21, 2024

moorepants Jun 19, 2024

moorepants Jun 19, 2024

moorepants Jun 19, 2024

faze-geek Jun 20, 2024

abhiphile Jun 21, 2024

moorepants Jun 19, 2024

moorepants Jun 19, 2024 •

edited

Loading

faze-geek Jun 20, 2024

moorepants Jun 20, 2024

abhiphile Jun 20, 2024

moorepants Jun 21, 2024

[GSoC] Added methods to StateSpace class to calculate state and output vectors. #26685

[GSoC] Added methods to StateSpace class to calculate state and output vectors. #26685

Conversation

abhiphile commented Jun 7, 2024

References to other Issues or PRs

Brief description of what is fixed or changed

Other comments

Release Notes

sympy-bot commented Jun 7, 2024 • edited Loading

abhiphile commented Jun 7, 2024

Doctest

Unit Test

github-actions bot commented Jun 7, 2024 • edited Loading

abhiphile commented Jun 8, 2024

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

moorepants Jun 19, 2024 • edited Loading

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

sympy-bot commented Jun 7, 2024 •

edited

Loading

github-actions bot commented Jun 7, 2024 •

edited

Loading

moorepants Jun 19, 2024 •

edited

Loading