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A DC motor with stator inductance , stator resistance , electromotive force (emf) constant , rotor moment of inertia , and damping ratio is modeled using the following differential equations.
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The input variables are the source voltage and the torque load , and the output variables are the rotor angular speed and the stator current .
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In state-space form:
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| (1) |
For control, the controlled input is the voltage and the controlled output is the DC motor speed . The corresponding subsystem is obtained.
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| (2) |
Designing the state feedback controller with gains and () by pole placement with desired poles and .
Obtaining the feedback gain :
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The closed-loop equations of the state feedback control system are obtained next.
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Using outputtype and augment_output, the transfer function of closed-loop system is obtained. The output vector will contain the controller output .
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| (5) |
Assign numerical values for the parameters:
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Next, the numeric values for the desired poles are obtained. For 0.1% overshoot, settling time of about 1 sec, the damping ratio and the natural frequency are defined as follows:
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Then, the numeric values for the feedback gain and the feed-forward gain are:
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Plotting the closed-loop system step response:
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Obtain the properties of the step response such as steady-state value and settling-point.
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| (9) |
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