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Application of MPC to the power management of a parallel hybrid electric vehicle


Benedikt J. Galliker

Semester/Bachelor Thesis, SS 05

Reducing the fuel consumption of the today cars is one of the biggest challenge for the companies involved. One possibility to save fuel energy are hybrid vehicles. Hybrid means that one combines different power sources to drive the car. Different concepts exists to combine this sources: Most often an inner combustion engine and an electrical motor work in parallel, that means that the two can drive the car separately. In a serial configuration only an electrical motor drives the car and receives the power from the energy storage system (e.g. battery, super capacitors) and an engine-driven generator.
Hybrid cars can save fuel energy because of 1) the possibility of downsizing the engine, 2) regenerative braking and 3) an additional degree of freedom that permits to choose the power sources to satisfy the power demand. The fuel consumption of hybrid cars depends strongly on how this required power is split between the sources. Till now, most often so called ”rule based” control strategies are used to manage this splitting. These are heuristics which try to run the different power sources in their best efficiency region. The battery that feeds the electric motor for example works more efficient if it produces little power, and the engine has it’s best efficiency at higher power. The principle of a rule based control strategy can now be that the electric motor works if little power is required, the engine drives the car if higher power is needed and both are working if the power required exceeds the engine’s maximal power. Further the engine has to recharge the energy storage system if its state of charge is too low.
Better results can be expected from optimal control strategies which try to minimize the fuel consumption. Only a few methods that use optimal control exists [5], [1]. One of these is the equivalent consumption minimization strategy (ECMS), used also in [1]. Periodically a cost function as a sum of fuel consumption and an equivalent fuel consumption related to the state of charge variation is minimized and the resulting power split is applied.
In this work an other form of optimal control, model predictive control (MPC) is applied to a parallel hybrid electric vehicle. An explicit dynamical model of the car is 2 employed to predict the future need of energy throughout a horizon so that the efficiency of the vehicle can be improved. As we will see, we have to apply a non linear model. This requires long calculation times. However, in this work some reasonable and simplifying assumptions will be made to render the problem tractable.

Supervisors: A. Beccuti, Dr. G. Papafotiou, Prof. M. Morari


Type of Publication:

(13)Semester/Bachelor Thesis

M. Morari

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% Autogenerated BibTeX entry
@PhdThesis { Xxx:2005:IFA_2796
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