Implementation of Optimal Energy Management of High Capacity Vehicles with Electrically Propelled Dolly Under Lateral Constraints using CasADi
Typ
Examensarbete för masterexamen
Program
Systems, control and mechatronics (MPSYS), MSc
Publicerad
2022
Författare
Johannesson, Wilhelm
Li, Ying
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
To lower the environmental impact of road freight transport, high-capacity transport
vehicles with electrically propelled dolly trailers (e-dollys) are proposed as a more efficient way of transportation. This distributed propulsion hybrid vehicle introduces
challenges regarding lateral stability and new possibilities for energy management.
In this thesis, these properties are addressed by a model predictive control (MPC)
strategy. The thesis includes design of an optimal energy management MPC for a
A-double truck with an e-dolly, using the optimization toolbox CasADi. The MPC
controller finds the optimal speed, soc, internal combustion engine (ICE) gears, ICE
propulsion, electric motor (EM) propulsion and retardation and braking.
The MPC is designed using CasADis symbolic framework and sequential linear and
quadratic programs (SLP) and (SQP), and IPOPT as optimization algorithms. The
two dynamic models are: an explicit ordinary differential equation (ODE) describing the longitudinal dynamics and an implicit differential algebraic equation (DAE)
describing both lateral and longitudinal dynamics. Discretization of explicit and
implicit model dynamics is done with Runge-Kutta and IDAS numerical integration
methods. A method for decoupling ICE gears from the mixed integer nonlinear program (MINLP) is designed and gear optimization is done with a one-step algorithm.
A method for implementing online shrinking horizon as the truck is getting close to
its destination is developed for the sequential programs. Two types of lateral stability constraints are tested, one rule based calculated speed limit, and one directly
constraining states in the lateral dynamics model.
The MPCs are evaluated with simulations and the fuel consumption is compared to
a diesel truck. The MPC computation time is evaluated in respect to real time implementation. The two lateral stability constraints are evaluated. The MPC using
SLP, and the rule based lateral stability constraint is determined to be fast enough
to be implemented in real time but, the rule-based stability constraint is lacking
and cannot guarantee lateral stability unless very conservative constraints are considered. The MPC including the nonlinear lateral dynamics is too computationally
expensive to implement in real time for long horizons, but its optimal trajectories
can serve as a benchmark for further simplifications of the lateral dynamics.
Beskrivning
Ämne/nyckelord
Model predictive control , optimal energy management , motion control , optimization , lateral stability , electrified propulsion , high capacity transport vehicles , distributed propulsion and simulations