Control of engines with fully variable valvetrains

To improve performance, fuel economy, and emissions of automotive engines, automakers have introduced a number of devices intended to vary a previously fixed engine parameter with operating condition. Such devices include variable cam timing and valve lift, variable compression ratio, intake manifold tuning, etc. Combining these devices in an engine promises improved fuel economy, but raises the issue of scheduling and coordination to achieve the benefit and prevent undesirable failure modes. This paper introduces the problem of controlling a fully variable valvetrain configuration, and shows an algorithm for synchronizing variables that have different rates of response with the goal of preventing potential piston-valve interference in mechanically unprotected engines.