30-07-2012, 12:06 PM
A Matlab-Based Modeling and Simulation Package for Electric and Hybrid Electric Vehicle Design
A Matlab-Based Modeling and Simulation Package.pdf (Size: 219.31 KB / Downloads: 112)
Abstract
This paper discusses a simulation and modeling
package developed at Texas A&M University, V-Elph 2.01. VElph
facilitates in-depth studies of electric vehicle (EV) and
hybrid EV (HEV) configurations or energy management strategies
through visual programming by creating components as
hierarchical subsystems that can be used interchangeably as
embedded systems. V-Elph is composed of detailed models of four
major types of components: electric motors, internal combustion
engines, batteries, and support components that can be integrated
to model and simulate drive trains having all electric, series
hybrid, and parallel hybrid configurations. V-Elph was written
in the Matlab/Simulink graphical simulation language and is
portable to most computer platforms.
This paper also discusses the methodology for designing vehicle
drive trains using the V-Elph package. An EV, a series HEV,
a parallel HEV, and a conventional internal combustion engine
(ICE) driven drive train have been designed using the simulation
package. Simulation results such as fuel consumption, vehicle
emissions, and complexity are compared and discussed for each
vehicle.
Index Terms—Electric vehicle, hybrid electric vehicle, modeling,
simulation.
I. INTRODUCTION
PRESENTLY, only electric and low-emissions hybrid vehicles
can meet the criteria outlined in the California Air
Regulatory Board (CARB) regulations which require a progressively
increasing percentage of automobiles to be ultralow
or zero emissions beginning in the year 1998 [1]. Though
purely electric vehicles (EV’s) are a promising technology
for the long-range goal of energy efficiency and reduced
atmospheric pollution, their limited range and lack of supporting
infrastructure may hinder their public acceptance [2].
Hybrid vehicles offer the promise of higher energy efficiency
and reduced emissions when compared with conventional
automobiles, but they can also be designed to overcome the
range limitations inherent in a purely electric automobile by
utilizing two distinct energy sources for propulsion. With
hybrid vehicles, energy is stored as a petroleum fuel and in an
electrical storage device, such as a battery pack, and is converted
to mechanical energy by an internal combustion engine
(ICE) and electric motor, respectively. The electric motor is
This work was supported by the Texas Higher Education Coordinating
Board Advanced Technology Program (ATP), Texas A&M University Office
of the Vice President for Research, and Associate Provost for Graduate
Studies through the Center for Energy and Mineral Resources and the Texas
Transportation Institute.
K. L. Butler and M. Ehsani are with the Department of Electrical Engineering,
Texas A&M University, College Station, TX 77843-3128 USA.
P. Kamath is with the Motorola, Inc., Schaumburg, IL USA.
Publisher Item Identifier S 0018-9545(99)09279-8.
used to improve energy efficiency and vehicle emissions while
the ICE provides extended range capability. Though many
different arrangements of power sources and converters are
possible in a hybrid power plant, the two generally accepted
classifications are series and parallel [3].
Computer modeling and simulation can be used to reduce
the expense and length of the design cycle of hybrid vehicles
by testing configurations and energy management strategies
before prototype construction begins. Interest in hybrid vehicle
simulation grew in the 1970’s with the development of several
prototypes that were used to collect a considerable amount of
test data on the performance of hybrid drive trains [4]. Studies
were also conducted to analyze hybrid electric vehicle (HEV)
concepts [5]–[11]. Several computer programs have since been
developed to describe the operation of hybrid electric power
trains, including: simple EV simulation (SIMPLEV) from
the DOE’s Idaho National Laboratory [12], MARVEL from
Argonne National Laboratory [13], CarSim from AeroVironment
Inc., JANUS from Durham University [14], ADVISOR
from the DOE’s National Renewable Energy Laboratory [15],
Vehicle Mission Simulator [16], and others [17], [18]. A
previous simulation model (ELPH) developed at Texas A&M
University was used to study the viability of an electrically
peaking control scheme and to determine the applicability of
computer modeling to hybrid vehicle design [19], but was
essentially limited to a single vehicle architecture. Other work
conducted by the hybrid vehicle design team at Texas A&M
University is reported in papers by Ehsani et al. [20]–[24].
V-Elph [25], [26] is a system-level modeling, simulation,
and analysis package developed at Texas A&M University
using Matlab/Simulink [27] to study issues related to EV and
HEV design such as energy efficiency, fuel economy, and
vehicle emissions. V-Elph facilitates in-depth studies of power
plant configurations, component sizing, energy management
strategies, and the optimization of important component parameters
for several types of hybrid or electric configuration
or energy management strategy. It uses visual programming
techniques, allowing the user to quickly change architectures,
parameters, and to view output data graphically. It also includes
detailed models that were developed at Texas A&M
University of electric motors, internal combustion engines,
and batteries.
This paper discusses the methodology for designing systemlevel
vehicles using the V-Elph package. An EV, a series HEV,
a parallel EV, and a conventional ICE driven drive train have
been designed using the simulation package. The simulation
results are compared and discussed for each vehicle.
0018–9545/99$10.00 ã 1999 IEEE
BUTLER et al.: MATLAB-BASED MODELING AND SIMULATION PACKAGE 1771
Fig. 1. System-level representation of a general vehicle drive train in
V-Elph.
II. DRIVE TRAIN DESIGN METHODOLOGY
Several levels of depth are available in V-Elph to allow
users to take advantage of the features that interest them.
At the most basic level, a user can run simulation studies
by selecting an EV, series, or parallel hybrid vehicle, or
conventional vehicle drive train model provided and display
the results using the graphical plotting tools. In addition to
being able to change the drive cycle and the conditions under
which the vehicle operates, the user can switch components in
and out of a vehicle model to try different types of engines,
motors, and battery models. The user can also change vehicle
characteristics such as size and weight, gear ratios, and the
size of the components that make up the drive train.
An intermediate user can create his/her own vehicle configurations
using a blank vehicle drive train template as shown
in Fig. 1. This drive train was constructed graphically by
connecting the main component blocks (drive cycle, controller,
power plant, and vehicle dynamics) using the Simulink visual
programming methodology through the connection of
the appropriate input and output ports. The power plant is
blank and is designed using component models selected from
a component library. Components can be isolated to run
parameter sweeps that create performance maps which assist in
component sizing and selection. A controller block is designed
with logic statements which create the signals required to
control the individual system-level components. A vehicle
dynamics block is designed with input parameters such as
road angle, mass, and drag coefficient necessary to compute
vehicle output dynamic parameters such as engine speed and
road speed. The drive cycle block is designed by selecting a
drive cycle from those supplied by the package or creating a
new drive cycle.
Finally, advanced users can pursue sophisticated design
objectives such as the creation of entirely new component
models and the optimization of a power plant by creating
add-on features that are compatible with the modeling system
interface. V-Elph allows the interconnection of many types of
electrical or mechanical component utilized in a vehicle drive
train, even experimental technologies such as ultracapacitors.
Component models can be created from lookup tables, empirical
equations, and both steady-state and dynamic equations.
Each component model is created using the general model and
interface shown in Fig. 2. The component models are stored
in a library, called the library of components as shown in
Fig. 3. The speed at which the simulation executes is highly
Fig. 2. Component input/output interface.
Fig. 3. Library of components.
dependent on the complexity of the component models used
in a vehicle design. Various detailed component models are
currently utilized in the V-Elph package. They were developed
by members of the ELPH research team at Texas A&M
University and designed based on steady-state and dynamic
equations.
III. DESIGN OF VEHICLE DRIVE TRAINS
In this section, the design and analysis of an EV drive train,
two parallel HEV drive trains with different control strategies,
a series HEV drive train, and a conventional ICE-driven
vehicle drive train using the V-Elph package are discussed.
A description is given of the performance specifications and
the control strategy and power plant developed for each
vehicle design. A typical mid-sized family sedan was used
as the basis for each vehicle. The vehicles’ components
were sized to provide enough power to maintain a cruising
speed of 120 km/h on a level road and an acceleration
performance of 0–100 km/h in 16 s for short time intervals.
The vehicles were also designed to maintain highway speeds
for several hundred seconds. The ICE, motor, battery, and
vehicle dynamics models were appropriately customized to
meet the specific vehicle performance requirements for each
vehicle design.
1772 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 48, NO. 6, NOVEMBER 1999
Fig. 4. Power plant representation of conventional vehicle drive train designed
using V-Elph.
TABLE I
SPECIFICATIONS OF ICE DRIVE TRAIN
Simulation studies were performed for each vehicle using a
simple acceleration and deceleration drive cycle, an FTP-75 urban
drive cycle, a federal highway drive cycle, and a commuter
drive cycle. Various performance parameters generated during
the simulation studies are graphically presented in the paper.
A table is included which compares performance parameters
such as fuel consumption and emissions for each simulation
study.
A. ICE Conventional Drive Train Design
The conventional ICE-driven drive train was designed based
on the specifications of a Buick LeSabre (1991 model) [28].
The vehicles four-speed automatic transmission was modeled
as a manual transmission with a clutch, retaining the same
overall gear ratios. It is a four-door sedan six-passenger vehicle
with a desired 0–60 mph in the 10-s range characteristic and a
curb weight of 3483 lbs (1580 kgs). The power plant is shown
in Fig. 4. Table I shows the engine and vehicle specifications
utilized to design the conventional drive train.
B. Parallel Hybrid Electric Drive Train Design
In a typical parallel design, consisting of an ICE and an
electric motor in a torque-combining configuration, either the
ICE or the electric motor can be considered the primary
energy source depending on the vehicle design and energy
management strategy. The drive train can also be designed
so that the ICE and electric motor are both responsible for
propulsion or each is the prime mover at a certain time in
the drive cycle. A component’s functional role could change
within the course of a drive cycle due to battery depletion
or other vehicle requirements. Vehicle architecture decisions,
control strategies, component selection and sizing, gearing, and
Fig. 5. Parallel HEV drive train configuration.
other design parameters become considerably more complex in
a parallel hybrid due to the sheer number of choices and their
effect on a vehicles performance given a particular mission.
The vehicle drive train configuration in Fig. 5 was designed
in V-Elph for a parallel HEV. It is based on a typical midsized
family sedan with a gross mass of 1838 Kg that includes
the additional batteries used in the hybrid power plant. The
drive train includes a controller which manipulates the torque
contributions of the electric motor and ICE. The battery
provides power for the induction motor. The ICE model was
sized to provide enough power to maintain a cruising speed of
120 km/h on a level road and the electric machine was sized
to provide acceptable acceleration performance of 0–100 km/h
in 16 s for short time intervals.
The ICE model was designed based on Powells engine
analysis [29]. The induction machine model [20] performs two
functions in the drive train: as a motor it provides torque at the
wheels to accelerate the vehicle, and as a generator it recharges
the battery during deceleration (regenerative braking) or whenever
the torque produced by the power plant exceeds the
demand from the driver. Vector control was utilized to extend
the constant power region of the motor, making it possible to
run the motor over a wide speed range. The motor can provide
the requested torque up to the constant power threshold at
speeds above the base speed of the motor; operation beyond
this point is restricted to avoid exceeding the motor’s power
rating. The HEV design utilizes the wide speed range of
the vector-controlled induction motor to improve the overall
system efficiency.