Methods and systems are provided for operating an engine to diagnose and compensate for cylinder imbalance in an engine. In one example, a method may include diagnosing a torque imbalance in a multi-cylinder engine by operating the engine at a lean air-fuel ratio (AFR) while an amount of ammonia stored in an selective catalytic reduction (SCR) system is greater than a threshold amount and a temperature of the engine is greater than a threshold temperature; and responsive to the diagnosed torque imbalance, adjusting fueling and spark timing for each cylinder, the adjustments based on an AFR offset of each cylinder determined while adjusting the lean AFR.

A method of operating a fuel injector includes determining a fuel pressure and a total fuel mass M.sub.TF to be injected per combustion cycle, defining first and second pulse widths PW.sub.1 and PW.sub.2 corresponding to first and second commanded fuel masses CM.sub.1 and CM.sub.2 wherein CM.sub.1+CM.sub.2=M.sub.TF, actuating the injector for the first and second pulse widths, detecting an opening delay for the injector, and storing the opening delay. The method may further include increasing PW.sub.1 and decreasing PW.sub.2 by a predetermined amount, repeating selected steps until PW.sub.2 is less than or equal to a predetermined minimum pulse width, changing the fuel pressure by a predetermined pressure amount, cycling through selected steps until the fuel pressure reaches a predetermined target fuel pressure, and commanding the injector to open earlier than a normally commanded opening time by a lead time based on stored opening delay data.

Methods and systems are provided for learning a cylinder-to-cylinder air variation. During conditions when a PFDI engine is operated in a port-injection only mode, prior to port fuel injection, a direct-injection fuel rail pressure may be lowered via direct-injection. Then, prior to a spark event in a port-injected cylinder, the direct-injector may be transiently opened to use the rail pressure sensor for estimating a cylinder compression pressure, and inferring cylinder air charge therefrom.

A method, computer program product and apparatus for the pilot control of a mixture preparation for an internal combustion engine are disclosed, which include determining a configuration of the internal combustion engine. The configuration is determined by a combination of discrete positions of a plurality of actuators which influence at least one operating parameter of the internal combustion engine. The method, computer program product and apparatus additionally determine a constant adaptation component of the mixture preparation which is fed back by an exhaust gas probe of the internal combustion engine, and store the constant adaptation component and the associated configuration in memory. The pilot control of the mixture preparation is performed with the constant adaptation component when the internal combustion engine is operated in the same configuration.

Various embodiments of the present disclosure are directed towards free-piston combustion engines. As described herein, a method and system are provided for displacing a free-piston assembly to achieve a desired engine performance by repeatedly determining position-force trajectories over the course of a propagation path and effecting the displacement of the free-piston assembly based, at least in part, on the position-force trajectory. In a dual-piston assembly free-piston engine, synchronization of the two piston assemblies is provided.

The present invention relates generally to techniques for improving fuel efficiency of a vehicle powered by an internal combustion engine capable of operating at various displacement levels. An autonomous driving unit or cruise controller selects when possible an engine torque output that corresponds to a fuel efficient displacement level. The resultant vehicle speed profile and NVH level is acceptable to vehicle occupants.

A method for controlling a combustion apparatus having a combustion state in which a parameter related to the combustion state reflects a chaotic behavior is provided. The method includes the steps of measuring the parameter and determining a time series of the parameter, shifting the time series by a variable time delay for determining a time-shifted signal, and forming a difference between the time-shifted signal and the time series for determining a time dependent first signal, so that a norm of the difference is lowest. A time dependent second signal is determined, wherein determining the time dependent second signal includes at least one of using a frequency of a desired oscillating combustion state, and shifting the time series by a set time delay. The first signal and the second signal are combined to determine a control signal. The control signal is used to influence the combustion apparatus.

A method for operating an internal combustion engine having a camshaft phase adjuster, including: providing a nonlinear final control element model, which indicates via a functional relationship an angular velocity of a relative adjustment of the camshaft phase adjuster as a function of an actuator correcting variable for the control of the camshaft phase adjuster; carrying out a control based on a deviation between a predefined camshaft angle adjustment setpoint value, and a camshaft angle adjustment actual value, to obtain as a control output a setpoint positioning rate of the camshaft phase adjuster; calculating the actuator correcting variable as a function of the setpoint positioning rate using an inverted final control element model; applying a predefined correction variable to the actuator correcting variable; controlling the camshaft phase adjuster using the actuator correcting variable to which the correction variable has been applied, to operate the internal combustion engine.

Methods and systems are provided for cruise control velocity tracking. In one example, the method or system may generate a torque command output via a velocity controller that allows for an error within bounds to reduce a fuel consumption amount, the torque command output selected from outcomes of a leader and follower game.

A variety of methods and arrangements for reducing noise, vibration and harshness (NVH) in a skip fire engine control system are described. In one aspect, a firing sequence is used to operate the engine in a dynamic firing level modulation manner. A smoothing torque is determined by adaptive control that is applied to a powertrain by an energy storage/release device. The smoothing torque is arranged to at least partially cancel out variation in torque generated by the firing sequence. Various methods, powertrain controllers, arrangements and computer software related to the above operations are also described.