achapt 8 - REGULATING THE REFERENCE PATH(DISCRETELY-ACTING...

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REGULATING THE REFERENCE PATH (DISCRETELY-ACTING ACTUATORS) 8 REGULATING THE REFERENCE PATH (DISCRETELY-ACTING ACTUATORS) This chapter considers the regulation problem restricted to the case in which the control force is produced by discretely-acting actuators. The feedback is therefore nonlinear. The class of nonlinear forcing functions is very broad – really any force that is not a linear function of the state variables. This class of forcing functions is too broad to treat in a comprehensive manner. Instead, this section treats a few popular types of nonlinear feedback methods the ones commonly implemented by discretely-acting actuators. Examples of actuators that, by design, are discretely-acting are solenoids, pneumatic and hydraulic devices, and braking systems. The most common type of discretely-acting actuator operates in a bang-off-bang manner. The bangs refer to constant levels of force in one direction or another. One can distinguish between bang-off-bang actuators by the proportion of bang time. At one MAE 461: DYNAMICS AND CONTROLS
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REGULATING THE REFERENCE PATH (DISCRETELY-ACTING ACTUATORS) extreme, the actuator is always on – banging in one direction or another. This is called bang-bang control . At the other extreme, the actuator on-time is very small – banging over short bursts of time. This is called impulse control . It turns out that time-optimal control is of the bang-bang type, and that fuel-optimal control is of the impulse type. Therefore, in practice, bang-off-bang control can be thought of as a compromise between fuel- optimality and time-optimality.
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This note was uploaded on 09/17/2009 for the course MAE 469 taught by Professor Silverberg during the Fall '08 term at N.C. State.

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achapt 8 - REGULATING THE REFERENCE PATH(DISCRETELY-ACTING...

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