  We propose a delay-dependent sampled-data output-feedback LPV control
technique to address the air-fuel ratio (AFR) regulation problem in spark
ignition (SI) engines. AFR control and advanced fueling strategies are
essential for maximizing fuel economy while minimizing harmful exhaust
emissions. The fuel path of the SI engine, as well as the three-way catalyst
(TWC) simplified dynamics, have been captured by a continuous-time linear
parameter-varying (LPV) system with varying time delay, where the system
dynamics rely on the engine speed, defined as the system's scheduling
parameter. The interconnection of the continuous-time plant and a digital
controller through analog-to-digital and digital-to-analog converter devices
forms a hybrid closed-loop configuration. Therefore, in order to benefit from
continuous-time control synthesis tools, the input-delay method has been
employed to transform the hybrid closed-loop system into the continuous-time
domain with system inherent time delay and an additional delay imposed by the
mapping approach. The designed sampled-data gain scheduled output-feedback
controller seeks to establish the closed-loop asymptotic stability and a
prescribed level of performance for the LPV system with an arbitrarily varying
time delay and varying sampling time, where the synthesis results are provided
in a convex linear matrix inequality (LMI) constraint setting. Finally, several
closed-loop simulation scenarios are conducted, and comparisons are provided to
demonstrate the proposed methodology's performance in achieving precise
reference AFR tracking and disturbance attenuation.
