Fully flexible valve actuation (FFVA) is a key enabling technology of internal
engine combustion research and development. Two laboratory electro-hydraulic
FFVA systems have been developed and implemented in R&D test cells. These
FFVA systems were designed using repetitive control (RC), which is based on
internal model principle (IMP), for constant engine speed operation. With the
engine operating in a steady-state condition, the valve profile input is
periodic. This can be accommodated by a repetitive controller, which provides
the function of flexible control to step changes in valve lift, valve opening
duration, and cam phase angle position.
During engine speed transients, as the valve reference trajectory becomes
aperiodic in the time domain, the controllers based on the linear time invariant
(LTI) IMP, such as RC, are no longer applicable. Engine speed transient control
is a desired function to engine research and other similar applications, such as
motor control. Several investigations are reported with limited results because
of the assumption of IMP and periodic input.
This article presents the control design and verification of the iterative
learning control (ILC) algorithm for the laboratory electro-hydraulic FFVA
system. This algorithm tracks valve lift profiles under steady-state and
transient operation. A dynamic model of the plant was obtained from experimental
data to design and verify the effectiveness and robustness of this approach. The
simple structure of the ILC in implementation and low cost in computation are
crucial benefits to recommend the ILC. It is not an IMP-based approach, and its
structure does not depend on the system input. Therefore, it has higher
robustness to perturbation and modeling errors than other control methods for
repetitive valve lift profile tracking tasks.
