Systematic development of series-hybrid bus
through modelling
Tarun Huria
Giovanni Lutzemberger
Dipartimento di Sistemi Elettrici e Automazione
Università di Pisa
Pisa, Italy
lutzemberger@dsea.unipi.it
Giovanni Sanna
BredaMenarinibus
Bologna, Italy
Giovanni Pede
ENEA
S. Maria di Galeria - Roma, Italy
Abstract—With increasingly stringent regulations on fuel
emissions, vehicle manufacturers have started developing
hybrid and electric versions of their vehicles. This paper
presents a systematic approach to developing series-hybrid
version of an existing bus through power-train modelling.
The approach involves accurate modelling of the
conventional bus, validating it by matching the simulation
results with the tests conducted on the actual bus, and then
developing the hybrid version of the bus.
Keywords—hybrid vehicle, modelling, powertrains
I. NOMENCLATURE
AUX Auxiliary electrical load
BSFC Brake Specific Fuel Consumption
ED Electric Drive
EGS Electrical Generating System
EM Electric machine (either operating as motor or
generator)
EPC Electronic Power Conditioner
EV Electric Vehicle
HEV Hybrid Electric Vehicle
ICE Internal Combustion Engine
PMM Power Management Module
RESS Rechargeable Energy Storage System
SORT Standardised On-Road Test
II. I
NTRODUCTION
With growing concern for environmental problems
amongst governments and international policy formulation
agencies, more stringent standards for fuel consumption
and emissions have been developed. Vehicle manufacturers
have focused their attention on development of hybrid and
electric versions of their vehicles. These vehicles have
advanced power-trains for efficient utilisation of energy.
Electric vehicles (EVs) appear to be the best way out as
they imply reduced oil consumption and zero in situ
emissions. However, factors such as high initial cost, short
driving range, and long charging time are major limitations.
Hybrid electric vehicles (HEVs) were developed to
overcome the limitations of internal combustion engine
(ICE) vehicles and EVs. An HEV combines a conventional
propulsion system with an energy storage system and an
electric drive. When driven in the electric mode, HEVs are
zero emission vehicles (ZEVs). HEVs have an improved
fuel economy, compared to conventional ICE vehicles, and
have a longer driving range than EVs. Hybrid electric
systems are broadly classified as series or parallel hybrid
systems. In the series hybrid system all the torque required
for propulsion is provided by an electric motor, while in the
parallel hybrid system, the torque obtained from the ICE is
mechanically coupled to the torque from the electric motor
[1], [2], [3]. The series HEV solution is commonly chosen
for hybridising buses [4], because of the inherent
characteristics of this power train scheme, and will be
pursued in this paper also.
This paper presents a systematic development of a
complete line of series-hybrid and electric versions of
existing city buses for the Italian bus manufacturer, Breda
Menarini Bus (BMB) [5], through modelling. The models
were made both using a commercial software, LMS
Imagine.Lab AMESim
®
[6] (AMESim), and a custom-built
package using Matlab Simulink™ [7] (Matlab). AMESim
stands for Advanced Modelling Environment for
performing SIMulations of engineering systems.
To inspire confidence in the quality of the models, first
the existing bus was modelled and validated by matching
the simulation results with the results on actual tests
conducted on the existing bus. After confirming the
parameters, models were developed for the series-hybrid
versions of the bus. These were simulated on duty cycles of
the cities where the buses are planned to be deployed. In
Section III, the model for the existing bus and its validation
is presented. Section IV presents the model for the series-
hybrid bus. Finally, in Sections V & VI, the results of the
sizing and conclusion of the study are summarised.
III. M
ODELLING & VALIDATION OF EXISTING BUSES
A. Model of existing buses
Some of the existing BMB buses modelled are shown in
Table I. Figure 2 depicts the model of the existing bus made
using AMESim. Sub-models were made for the ICE, the
automatic gearbox and the auxiliary load. The output from
the ICE is given to the automatic gearbox and the auxiliary
load. The automatic gearbox drives the wheels, and the
feedback from the wheels (i.e. the difference between the
desired speed and the actual speed) guides the response of
the driver based on the required duty cycle. The model was
configurable for different types of buses having different
auxiliary loads and running on different duty cycles.
978-1-4244-8218-4/10/$26.00 ©2010 IEEE