An Observer-Based Controller Design Method for Improving Air/Fuel Characteristics of
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14-02-2011, 10:12 AM
Seibum B. Choi and J. Karl Hedrick
In the urban traffic mode, the engine is known to beoperated mostly in a transient state. However, the wide operatingrange, the inherent nonlinearities of the induction process andthe large modeling uncertainties make the design of the fuelinjectioncontroller very difficult. Even though a sliding modefuel-injection control method is in good agreement with thecharacteristics of the system, the unavoidable large time-delaybetween control action and measurement causes the problem ofchattering. In this paper, an observer-based fuel-injection controlalgorithm is suggested for fast response and small amplitudechattering of the air-to-fuel ratio. The characteristics of theproposed controller are compared with those of other controllers.The proposed controller is simple enough for on-line computationand is implemented on an automotive engine using a PC-386.The simulation and the experimental results show that thisalgorithm reduces the chattering magnitude considerably whilespeeding up the transient response and is robust to modelingerrors.Index Terms—Chatter free, delay effects, engines, fuel injection,observers.
THE method selected to meet the new exhaust emissionsstandards has been to use a catalytic converterthat simultaneously oxidizes and reduces engine emissions.Unfortunately, the efficiency of the catalyst is very sensitiveto the variation of the air-to-fuel (A/F) ratio. Therefore, it isapparent that the main issue of the control of the S.I. engineis to control the fuel-injector(s) to keep the A/F ratio close tostoichiometry (14.7) both in steady-state operation and duringtransients. The steady-state operation is trivial compared tothe transient control, since all the air-induction dynamics andthe fueling dynamics disappear at steady state. However, inthe urban traffic mode, the engine is operated mostly in atransient condition, and this makes the design of a controllervery difficult
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