METHOD AND SYSTEMS FOR EGR CONTROL

Various methods and systems are provided for estimating fresh intake air flow. In one example, a system comprises an engine (104) having an intake manifold (115) to receive fresh intake air and an exhaust gas recirculation (EGR) system (160) to supply EGR to the intake manifold (115), where flow of EGR through the EGR system (160) is controlled by one or more exhaust valves (170). The system further includes a controller (180) configured to adjust a position of the one or more exhaust valves (170) based on an estimated fresh intake air flow rate, where during a first set of operating conditions, the fresh intake air flow rate is estimated based on a total gas flow rate into the engine (104) and further based on a current position of the one or more exhaust valves (170), intake manifold pressure, air-fuel ratio, and fuel flow to one or more cylinders of the engine (104). 提供了用于估计新鲜进气空气流的各种方法和系统。在一个示例中，一种系统包括具有进气歧管(115)以接收新鲜进气空气的发动机(104)和排气再循环(EGR)系统(160)以供应EGR至进气歧管(115)，其中穿过EGR系统(160)的EGR的流由一个或更多个排气阀(170)控制。系统进