Patent ID: 7946162

Claim:
A method for estimating an oxygen concentration in an internal combustion engine comprising an intake manifold, an exhaust manifold, an EGR system, a throttle valve, an air mass sensor for measuring a fresh air flow ({dot over (m)} thr ) entering the intake manifold through the throttle valve, and a plurality of cylinders, the comprising the steps of: estimating a total gas flow ({dot over (m)} o ) entering the plurality of cylinders; calculating an EGR gas flow ({dot over (m)} egr ); calculating an air fraction (f — air — em ) of a gas flowing in the exhaust manifold; calculating a air mass (m im — air ) entering the plurality of cylinders based at least in part on the air fraction (f — air — em ) in the exhaust manifold, the total gas flow ({dot over (m)} o ) entering the plurality of cylinders, the EGR gas flow ({dot over (m)} egr ), and the fresh air flow ({dot over (m)} air ); calculating a total mass (m im ) in the intake manifold based at least in part on the fresh air flow ({dot over (m)} thr ), the EGR gas flow ({dot over (m)} egr ), and the total gas flow ({dot over (m)} o ) entering the plurality of cylinders; calculating the air fraction (f air — im ) in the intake manifold based at least in part on the air mass (m im — air ) entering the plurality of cylinders and the total mass (m im ) in the intake manifold; and calculating a oxygen mass concentration ([O 2 ] m — im ) in the intake manifold based on the air fraction (f air — im ) in the intake manifold.