A Real-time Nonlinear Air Path Observer for Off-Highway Diesel Engines

Air path observation is important for the diagnosis and control of modern diesel engines. Recent air path observers assume the measurement of the mass air flow which is a justified assumption in the automotive domain. However, the mass air flow is usually not measured for series-produced off-highway engines as the pipework is customized. Due to the intense complexity of the air path, a tailored spherical simplex unscented Kalman filter is used to achieve real-time feasibility. In order to consider the dependency of the air path model uncertainty from the engine operating point, a nonlinear residual based adaptation scheme for the measurement noise covariance matrix is proposed. The high accuracy and the computational performance of the observer is demonstrated by GT-POWER simulation runs, testbench measurements, and a running time analysis.