![EMA-CVT simulation block diagram in Matlab The required traction was designed according to the predefined driving dynamics known as EPA Urban Dynamometer Driving Schedule (UDDS) and EPA Highway Fuel Economy Test Cycle (HWFET) [19]. The UDDS cycle simulates an urban route of 12.07 km with frequent stops. The maximum speed is 91.25 km/h and the average speed is 31.5 km/h. The cycle consists of two phases: the first phase begins with a cold start and run for 505 s (about 5.78 km at 41.2 km/h average speed) and the second phase run for 867 s as shown in Figure 4. Furthermore, the HWFET cycles as shown in Figure 5 is a chassis dynamometer driving schedule developed by the US EPA for the determination of fuel economy of light duty vehicles. It simulates a highway route of 16.45 km with average speed of 77.7 km/h at 765 seconds.](https://www.researchgate.net/profile/Abdul-Hassan-Jaafar/publication/343124044/figure/fig2/AS:915915227033600@1595382615071/EMA-CVT-simulation-block-diagram-in-Matlab-The-required-traction-was-designed-according_Q320.jpg)
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March - April 2020
ISSN: 0193-4120 Page No. 13775 - 13781
13775
Published by: The Mattingley Publishing Co., Inc.
EMA-CVT Performance for UDDS and HWFET
Cycles with Fuzzy Logic Approach
Abdul Hassan Jaafar1, Ataur Rahman 2
1,2 Department of Mechanical Engineering, Faculty of Engineering, International Islamic University Malaysia
Article Info
Volume 83
Page Number: 13775 - 13781
Publication Issue:
March - April 2020
Article History
Article Received: 24 July 2019
Revised: 12 September 2019
Accepted: 15 February 2020
Publication: 20 April 2020
Abstract
Continuously variable transmission (CVT) is moreeffective in transferring power from the
engine to the wheels than gear-based transmission as it able to provide an unlimited number
of gear ratios to suit different drivingenvironments. Conventional CVT system that
operatesbased on hydraulic actuation mechanism experienced slow acceleration when move
from stop, less torque while climbing the mountain and continuously create unpleasant
noise. The hydraulic fluid viscosity falls below the optimum value when its temperature is
too high due to long run and result in losses of the input power transmitting. An alternative
to conventional actuation system, the electromagnetic actuation (EMA) mechanism,is
discussed in this paper. The EMA forcewas controlled byvarying the supply current with a
fuzzy logic controller (FLC) based on sensor input. A simulation that mimic a Toyota Wish
car moves along the UDDS and HWFET driving cycles has been introduced here. The FLC
was successfully producing the required current to operate the EMA for the mention driving
cycles.For UDDS cycle, the system generated about 2.2-2.6 kN electromagnetic force with
about 5.6-6.06 A current supply. On the other hand, for HWFET cycle with current supply
of 5.75-6.05 A, the required electromagnetic force of 2.4-2.6 kN was produced. Fuzzy Logic
Controller enable the system to fast response in generating the required current. For both
driving cycles, the controller took about 2.1-2.2 seconds to regulate the current level from
zero value to the targeted current level.
Keywords; Green Transportation; Electromagnetic Actuator; CVT
INTRODUCTION
A transmission system is used to adjust the
proportion of torque and speed, i.e. the power,
which is delivered from the engine to the drive shaft
of a car. In a manual transmission, the gearbox
provides different ratios between the engine and the
wheel by a system of gears. The gearbox requires a
friction clutch to disengage the engine crankshaft
from the gearbox while changing the gear ratios. An
automatic gearbox provides various gear ratios
automatically by a special gearing mechanism and
the torque converter is the component that make the
automatic gear changes possible.
Continuous variable transmission (CVT) is a new
type of automatic transmission that uses a pair of
cone-shaped pulleys connected by a metal belt in
providing the ratio of rotations, or the gear ratio,
between the engine and the drive shaft. Different
gear ratios are achieved through the change in the
diameter of the pulleys with accordance to the car
speed and road condition. Thus, cars equipped with
the CVT system utilized the fuel more efficiently
[1]. The CVT will continue to replace traditional
gearing system in the coming years as more car
manufacturers turn to CVT such as in the new Saga
[2], the new City [3], Teana [4], and Audi A5 2.0
TDI [5] to increase their fuel economy.
A study had been conducted by [6] to compare the
performance of the manual transmission, automatic
transmission and continuously variable transmission.
Simulation result on cars with 1500 kg weight and
engine capacity of 3000 cc showed that the time
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taken to accelerate to 100 km/h is 10.20 sec for
manual transmission, 10.76 sec for automatic
transmission, and 7.85 sec for CVT. Besides, The
Torotrak Group [7], a green automotive technology
company, claimed about 19% less fuel consumption
for their CVT transmission compared to a vehicle
with conventional gearbox along with a reduction in
harmful emissions.
Current pulley-based CVT utilized the electro-
hydro-mechanical (EHM) actuation system to
provide sufficient clamping force for the desired
CVT ratio [8]. The EHM moves and maintain the
pulley sheave at the desired position by hydraulic
means. Hydraulics, often called fluid power, is a
method of transmitting motion and/or force [9]. The
amount and direction of the oil flow are controlled
electronically by solenoid valves. In this system, the
hydraulic pump draws off the engine power
continuously to provide the pressurized oil to the
system and thus increase the car fuel consumption.
According to Tawi et al. [10] CVT that use the EHM
actuation system possesses some major issues that
make it less efficient such as high power
consumption, power loss and belt misalignment.
Besides, the hydraulic fluid viscosity falls below the
optimum value when its temperature is too high due
to long run and result in losses of the input power
transmitting. Thus, the holding force of pulley
sheave is not stable and affect the response and the
performance of the car.Therefore, for further
improvement of CVT performance, this study
emphasizes on the development of a fast actuation
system, “electromagnetic actuated mechanism for
CVT system,” which is the core discussion of this
study. The study will use Toyota Wish as an object
of study including calculation, simulation and
experimental.
METHODOLOGY
An analytical model of the EMA-CVT is formulated
based on the vehicle traction force for various road
conditions, power requirement to generate the
electromagnetic force (Fem) and the simplified CVT
mathematical models found in literature.
Development of new electromagnetic actuator
mechanism is presented in this section. A fuzzy
logic based control system is presented in this
chapter as a mean to intelligently regulate the power
required by the EMA-CVT for various driving
scenario.
EMA-CVT Analytical Model
A vehicle needs to generate an enough tractive force
to overcome the opposing force due to the
combination of gravitational force, rolling resistance
at the tire, and aerodynamic drag force. The
acceleration of a vehicle is defined by all the forces
acted on it and follows the Newton’s second law
could be represent as,
(1)
wherem_c is the total mass of the vehicle, F_TR is
the traction force of the vehicle, and F_RL is the
total road load. The road load resistive forces are
normally the rolling resistance between tires and
road surfaceR_roll, aerodynamic dragR_AD, and
uphill grading resistanceR_g.The traction torque of
the car is computed by using the following
equation[11]:
(2)
where is the mass of the vehicle in kg,
g
is the
gravitational acceleration constant equal to 9.81
m/s2, the wheel radius, the adhesion
coefficient of the road, distance from the front
wheel to CG in m, the coefficient of rolling
motion resistance, is the height of CG in m,
the wheel base in m, the slope angle with respect
to the horizon in degree.
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Figure 1: Force analysis on the pulley surface
Normally, the pushing force is higher than the
pulling one since it has to move against the rotating
belt. Figure 1 shows the basic force acting on the
surface of the pulley. The clamping force that need
to be supplied to maintain the gear ratio can be
calculated using equations below (Mohamed &
Albatlan, 2014; Nishizawa et al., 2005; Rahman et
al., 2014; Yamaguchi et al., 2005):
(3)
Where, are transmission torque forsecondary
pulley in Nm, is the belt angle, is belt frictional
coefficient of secondary pulley, is radius
forsecondary pulley in m.In this study, the
electromagnetic actuator (EMA) function is to
generate an electromagnetic force to push and hold
the CVT pulley sheave at desired gear ratio. The
electromagnetic force is designed to be equal or
higher than the required clamping force. The design
is emphasized more on the pushing electromagnetic
force since it is crucial to maintain the belt at its
exact position to produce the desired gear ratio
(GR). The force generated from electromagnetic
actuator could be simplified by following equation
(Boldea & Nasar, 1997; Clarke, 2017; Leander et
al., 1987)
μ
2
BA
=F o
2
gg
em
(1)
By substituting the magnetic field strength
l
F
He
m
=
into magnetic flux density equation
HB
0
=
, the equation becomed[16]
g
IN
g
F
Bm
00 ==
(02)
Substituting into equation (1), yield the following
equation.
( )
g
A
IN
Fog
em 2
2
2
=
(3)
Where
N
is number of turns,
I
is the supplied
current,
μ0
is the permeability of free space (has a
fixed value of
10
47−
),
g
is the airgap or in this
case it is the actuator stroke length (Lstroke)
separating between the two ferromagnetic bodies,
and
Ag
is the airgap face area. From the above
equation, the electromagnetic force depends on the
number of coil turns, supplied current, effective area
of the core, and the gap between the electromagnet
and the pulling object. The only controlled
parameter is the supplied current. The
electromagnetic force produced is directly
proportional to the supplied current, which means
that the force shall be increased greatly by
increasing the current supply. However, over flow of
the current may create over heating which will
damage the solenoid. In practical, for better
performance and safety, a cooling system is needed
to cool the solenoid.A new-version of
electromagnetic actuator is presented in this paper.
The bobbin where the copper wire is wound on it, as
shown in Error! Reference source not found., is
made from iron to increase the stored magnetic
energy to produce stronger electromagnetic force. A
stopper or mover, made of iron, is attached on the
non-magnetic (aluminium) plunger to act as an
object of the actuator force.
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Figure 2: Cut view of new electromagnetic
actuator
2.2 EMA-CVT Performance based on UDDS and
HWFET Cycles
Simulation Performance of electromagnetic force
and electrical current requirement for operation of
EMA-CVT of a Toyota Wish passenger car with the
EPA Urban Dynamometer Driving Schedule
(UDDS) and the EPA Highway Fuel Economy Test
Cycle (HWFET) cycles is presented in this section.
The car with the mass of 1700 kg, maximum speed
of 120 km/h or 33 m/s, the road friction coefficient
equal to 0.5, the wheel radius of 0.295 m, the drag
area of 0.633, and rolling motion resistance
coefficient of 0.02 was considered. The traction
torque associated with the clamping force that
required to operate the EMA-CVT system are
modeled in Matlab simulation as described in Figure
3 where the input parameters of the system are
vehicle speed and road grades. The traction force of
the car model block was built based on the equation
(2) where the car weight, air density, rolling
coefficient and drag coefficient was considered.
From the traction force, the traction torque at
propeller shaft (or the output shaft of the CVT) was
found by multiplying with the wheel radius size and
the gear ratio of the final gear. The required current
estimator model block was built based on equation
(3) and (6) where it calculate the corresponding
current based on the traction torque at the propeller
shaft, CVT pulley’s size, and the size of EMA.
Figure 3: EMA-CVT simulation block diagram
in Matlab
The required traction was designed according to the
predefined driving dynamics known as EPA Urban
Dynamometer Driving Schedule (UDDS) and EPA
Highway Fuel Economy Test Cycle (HWFET) [19].
The UDDS cycle simulates an urban route of 12.07
km with frequent stops. The maximum speed is
91.25 km/h and the average speed is 31.5 km/h. The
cycle consists of two phases: the first phase begins
with a cold start and run for 505 s (about 5.78 km at
41.2 km/h average speed) and the second phase run
for 867 s as shown in Figure 4. Furthermore, the
HWFET cycles as shown in Figure 5 is a chassis
dynamometer driving schedule developed by the US
EPA for the determination of fuel economy of light
duty vehicles. It simulates a highway route of 16.45
km with average speed of 77.7 km/h at 765 seconds.
Figure 4: Urban dynamometer driving schedule
(UDDS)
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Figure5: Highway Fuel Economy Test Cycle
(HWFET)
RESULT AND DISCUSSION
The Fuzzy logic controller simulation block in
Figure 3 has two inputs: current error and rate of
current error, respectively, and one output: current
flow.Figure 6 and Figure 9 compared the required
clamping force and generated electromagnetic force
for the UDDS and HWFET driving cycle
respectively. The generated electromagnetic forces
are equal or higher than the required clamping force
and this ensure the CVT pulley sheave can maintain
its position. Based on the electromagnetic force
above, the system regulate the current supply
accordingly as shown in Figure 7 and Figure 10
respectively for UDDS and HWFET cycles. In order
to generate the electromagnetic force of 2.6 kN, the
electromagnetic actuator draw about 2.6 ampere
current from the power supply. The current
requirement is directly proportional to the
electromagnetic force and agreed with the equation
(6). Figure 8 and Figure 11 shows the current level
error, i.e. the different between the targeted current
and the produced current level. If it is zoomed, the
controller took about 2.1 and 2.2 seconds to regulate
the current level from zero value to the targeted
current level.
Figure 6: Simulation result for required
clamping force and generated electromagnetic
force for UDDS cycle
Figure 7: Simulation result for the required and
actual current for UDDS cycle
Figure 8: Simulation result for controller error
for UDDS cycle
Figure 9: Simulation result for required
clamping force and generated electromagnetic
force for HWFET cycle
Figure 10: Simulation result for the required and
actual current for HWFET cycle
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Figure 11: Simulation result for controller error
for HWFET cycle
CONCLUSION
This paper present analytical model of the
electromagnetic actuated CVT based on Toyota
wish size car. Simulation by Matlab Simulink on
relation between clamping force, electromagnetic
force and current supply was done based on the
standard UDDS and HWFET driving cycles. The
following conclusions are achieved based on the
contents of this paper:
The intelligent system can develop the
electromagnetic for as according to the required
clamping force. The current was regulated to meet
the traction force due to the vehicle speed pattern of
UDDS and HWFET.
For UDDS cycle, the system generated about 2.2-2.6
kN electromagnetic force with about 5.6-6.06 A
current supply. On the other hand, for HWFET cycle
with current supply of 5.75-6.05 A, the required
electromagnetic force of 2.4-2.6 kN was produced.
Fuzzy Logic Controller enable the system to fast
response in generating the required current. For both
driving cycles, the controller took about 2.1-2.2
seconds to regulate the current level from zero value
to the targeted current level.
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