8000 Add gain scheduling to create_statefbk_iosystem() by murrayrm · Pull Request #827 · python-control/python-control · GitHub
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Add gain scheduling to create_statefbk_iosystem() #827

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Merged
merged 6 commits into from
Dec 30, 2022
Merged

Add gain scheduling to create_statefbk_iosystem() #827

merged 6 commits into from
Dec 30, 2022

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murrayrm
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This PR adds functionality to the create_statefbk_iosystem function, allowing it to be used to set up a simple gain scheduled controller. From the documentation:

Gain scheduling on the desired state, desired input, or system state can be implemented by setting the gain to a 2-tuple consisting of a list of gains and a list of points at which the gains
were computed, as well as a description of the scheduling variables

  ctrl, clsys = ct.create_statefbk_iosystem(
      sys, ([g1, ..., gN], [p1, ..., pN]), gainsched_indices=[s1, ..., sq])

The list of indices can either be integers indicating the offset into the controller input vector or a list of strings matching the names of the input signals.

Example:

    # Create a simple nonlinear system to check (kinematic car)
    def unicycle_update(t, x, u, params):
        return np.array([np.cos(x[2]) * u[0], np.sin(x[2]) * u[0], u[1]])

    def unicycle_output(t, x, u, params):
        return x

    unicycle = ct.NonlinearIOSystem(
        unicycle_update, unicycle_output, inputs = ['v', 'phi'], 
        outputs = ['x', 'y', 'theta'], states = ['x_', 'y_', 'theta_'])

    # Speeds and angles at which to compute the gains
    speeds = [1, 5, 10]
    angles = np.linspace(0, pi/2, 4)
    points = list(itertools.product(speeds, angles))

    # Gains for each speed (using LQR controller)
    Q = np.identity(unicycle.nstates)
    R = np.identity(unicycle.ninputs)
    gains = [np.array(ct.lqr(unicycle.linearize(
        [0, 0, angle], [speed, 0]), Q, R)[0]) for speed, angle in points]

    #
    # Schedule on desired speed and angle
    #

    # Create gain scheduled controller
    ctrl, clsys = ct.create_statefbk_iosystem(
        unicycle, (gains, points), gainsched_indices=['vd', 'theta'])

Includes unit tests and documentation.

@murrayrm murrayrm added this to the 0.9.3 milestone Dec 29, 2022
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coveralls commented Dec 29, 2022 •
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Coverage Status

Coverage: 94.845% (-0.002%) from 94.846% when pulling 51f3b6b on murrayrm:gainsched-23Dec2022 into 49b0077 on python-control:main.

@murrayrm murrayrm merged commit c3488cd into python-control:main Dec 30, 2022
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