Wastegate Actuator Modeling and Model-Based Boost Pressure Control
Wastegate Actuator Modeling and Model-Based Boost Pressure Control
Andreas Thomasson, Lars Eriksson, Oskar Leufvén, Per Andersson
The torque response of an engine is important for driver acceptance. For
turbocharged spark ignited (TCSI) engines this is tightly connected to the
boost pressure control, which is usually achieved with a wastegate. A
challenging scenario is when the throttle is fully open and the load is
essentially controlled by the wastegate. First a model for the pneumatic
wastegate actuator and air control solenoid is developed. The wastegate
model consists of three submodels; the actuator pressure, the static
position, and an additional position dynamics. A complete engine model is
constructed by including the actuator model in a Mean Value Engine Model
(MVEM) for a TCSI engine. This model describes the transient boost pressure
response to steps in wastegate control inputs. The subsystems and complete
MVEM are validated on an engine test bench and it explains the overshoot
seen in the step responses.
The model is used to study the system response and give insight into the
dominating phenomena and it points out that the engine speed is important
for the response. Further, for each speed it is sufficient to model the
system as a second order linear system, that captures an overshoot. A
controller consisting of a mapped feedforward loop and a gain scheduled
feedback loop is developed together with a tuning method based on the IMC
framework for the feedback loop. The controller and tuning method is shown
to achieve the desired boost pressure behavior both on the complete MVEM and
on real engines. The experimental validation is carried out both in an
engine test cell and in a vehicle.
Andreas Thomasson, Lars Eriksson, Oskar Leufven and Per Andersson
2009
Informationsansvarig: webmaster
Senast uppdaterad: 2021-11-10
LiU Homepage
