Abstract

In a dual dependent variable cam timing system, the desired intake global phase is reached by directly controlling the global phase of exhaust VCT phaser and controlling the local phase of intake VCT phaser. The global intake set point specified by an engine controller is converted into a local intake set point first, then passed through a set point filter, and compared with the measured local intake phase. The difference (error signal) is passed through a PI controller and a phase compensator, which have the same control structures as those of exhaust VCT phaser control, to form a control signal.