Modeling and Optimal Control of Heavy-Duty Powertrains
Heavy duty powertrains are complex systems with components from
various domains, different response times during transient operations
and different efficient operating ranges. To ensure efficient
transient operation of a powertrain, e.g. with low fuel consumption or
short transient duration, it is important to come up with proper
control strategies. In this dissertation, optimal control theory is
used to calculate and analyze efficient heavy duty powertrain controls
during transient operations in different applications. This is enabled
by first developing control ready models, usable for multi-phase
optimal control problem formulations, and then using numerical optimal
control methods to calculate the optimal transients.
Optimal control analysis of a wheel loader operating in a repetitive
loading cycle is the first studied application. Increasing fuel
efficiency or reducing the operation time in such repetitive loading
cycles sums up to large savings over longer periods of time. Load
lifting and vehicle traction consume almost all of the power produced
by a diesel engine during wheel loader operation. Physical models are
developed for these subsystems where the dynamics are described by
differential equations. The model parameters are tuned and fuel
consumption estimation is validated against measured values from real
wheel loader operation. The sensitivity of wheel loader trajectory
with respect to constrains such as the angle at which the wheel loader
reaches the unloading position is also analyzed. A time and fuel
optimal trajectory map is calculated for various unloading
positions. Moreover, the importance of simultaneous optimization of
wheel loader trajectory and the component transients is shown via a
side to side comparison between measured fuel consumption and
trajectories versus optimal control results.
In another application, optimal control is used to calculate efficient
gear shift controls for a heavy duty Automatic Transmission system. A
modeling and optimal control framework is developed for a nine speed
automatic transmission. Solving optimal control problems using the
developed model, time and jerk efficient transient for simultaneous
disengagement of off-going and engagement of in-coming shift actuators
are obtained and the results are analyzed.
Optimal controls of a diesel-electric powertrain during a gear shift
in an Automated Manual Transmission system are calculated and analyzed
in another application of optimal control. The powertrain model is
extended by including driveline backlash angle as an extra state in
the system. This is enabled by implementation of smoothing techniques
in order to describe backlash dynamics as a single continuous function
during all gear shift phases.
Optimal controls are also calculated for a diesel-electric powertrain
corre- sponding to a hybrid bus during a tip-in maneuver. It is shown
that for optimal control analysis of complex powertrain systems,
minimizing only one property such as time pushes the system transients
into extreme operating conditions far from what is achievable in real
applications. Multi-objective optimal control problem formulations are
suggested in order to obtain a compromise between various objectives
when analyzing such complex powertrain systems.
Vaheed Nezhadali
2016
Informationsansvarig: webmaster
Senast uppdaterad: 2021-11-10
LiU Homepage
