The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art.
Solenoid actuators can be used to control fluids (liquids and gases), or for positioning or for control functions. A typical example of a solenoid actuator is the fuel injector. Fuel injectors are used to inject pressurized fuel into a manifold, an intake port, or directly into a combustion chamber of internal combustion engines. Known fuel injectors include electromagnetically-activated solenoid devices that overcome mechanical springs to open a valve located at a tip of the injector to permit fuel flow therethrough. Injector driver circuits control flow of electric current to the electromagnetically-activated solenoid devices to open and close the injectors. Injector driver circuits may operate in a peak-and-hold control configuration or a saturated switch configuration.
Armatures of fuel injectors move in response to magnetic flux and magnetic force generated when the solenoid devices are electromagnetically activated. Movement of the armature overcomes biasing forces of spring activated pintles to effect opening of the fuel injectors. While the generated magnetic fluxes and magnetic forces are theoretically proportional to electrical current applied to the solenoid devices, residual magnetic flux within the fuel injectors can result in deviations from desired values. The magnetic residual flux is attributed to persistent eddy currents and magnetic hysteresis within the fuel injector as a result of shifting injected fuel mass rates that require different initial magnetic flux values. As a result, relying only upon applied current flow to the solenoid devices will result in inaccurate estimations of armature motion and position during a fuel injection event.