International Journal of Power Electronics and Drive Systems (IJPEDS)

Vol. 12, No. 2, Jun 2021, pp. 650~661

ISSN: 2088-8694, DOI: 10.11591/ijpeds.v12.i2.pp650-661  650

Improved DTC strategy of an electric vehicle with four

in-wheels induction motor drive 4WDEV using fuzzy logic
control

Nair Nouria, Gasbaoui Brahim, Ghazouani Abdelkader, Benoudjafer Cherif

Department of Technology, University of Tahri Mohammed, Smart Grids & Renewable Energies Laboratory,
Bechar, Algeria

Article Info ABSTRACT

Article history: In this paper, we will study a four-wheel drive electric vehicle (4WDEV)
with two control strategies: Conventional Direct Torque Control (CDTC) and
Received Nov 6, 2020 DTC based on fuzzy logic (DTFC). Our overall idea in this work is to show
Revised Dec 31, 2020 that the 4WDEV equipped with four induction motors providing the drive of
Accepted Feb 28, 2021 the driving wheels controlled by the direct fuzzy torque control ensures good
stability of the 4WDEV in the different topologies of the road, bends and
slopes, and increases the range of the electric vehicle. Numerical simulations
Keywords: were performed on an electric vehicle powered by four 15kW induction
motors integrated into the wheels using the MATLAB/Simulink
4W electric vehicle environment, where the reference speeds of each wheel (front and rear) are
Direct torque control obtained using an Electronic Speed Differential (ESD). This can eventually
Direct torque fuzzy control cause it to synchronize the wheel speeds in any curve. The speed of each
Induction motor wheel is controlled by two types of PI and FLC controllers to improve
Lithium-ion battery stability and speed response (in terms of setpoint tracking, disturbance
rejection and climb time). Simulation results show that the proposed FLC
control strategy reduces torque, flux and stator current ripple. While the
4WDEV range was improved throughout the driving cycle and battery power
consumption was reduced.
This is an open access article under the CC BY-SA license.

Corresponding Author:
Nair Nouria
Departement of Technology
Tahri Mohammed University
B. P 417 route Kendsa, University of Tahri Mohammed, Bechar, Algeria
Email: nouria0479@gmail.com

1. INTRODUCTION
Today, in the automotive sector, manufacturers are moving towards improving internal combustion
engines and hybridization with electric motors to minimize CO2 emissions. A more ambitious alternative is
to do without the internal combustion engine, and therefore so-called zero emission propulsion [1], [2].
In general, the most commonly used electric actuators in the majority of industrial applications are built
around the induction motor [3], [4]. The induction motor in particular is characterized by its robustness,
reliability, low cost and does not require regular maintenance. However, its dynamic behaviors are often very
complex, because it's modeling results in a highly coupled nonlinear multivariate system of equations [5],
[6]. Additionally, some of its state variables, including flows, cannot be measured. Different drive techniques
for induction machines have been introduced to provide variable frequency speed control. Most of them are
based on rigorous mathematical formalisms. Among all the control methods, DTC or direct torque control is
considered particularly interesting.

Journal homepage: http://ijpeds.iaescore.com

Int J Pow Elec & Dri Syst ISSN: 2088-8694  651

Takahashi's theory is to specifically evaluate the control pulses used for voltage reversing switches
to maintain electromagnetic torque and stator flow within two predefined depenbrock hysteresis bands [7],
[8]. Such an application of this technique allows decoupling of torque and flow control without the need for
pulse width modulation (PWM) or coordinate transformation. Several studies are still underway to improve
the main classic drawbacks of DTC. Among these drawbacks are torque ripples and stator flux [8], [9].
In this article, we mainly describe the implementation of a robust and efficient control law the
DTFC, which stands for direct fuzzy torque control. Fuzzy logic is a fuzzy linguistic approach used by a type
condition (Si-Then) based on the imitation of approximate qualitative aspects of human reasoning [10]. And
to apply it in our work, we will study a traction system of an electric vehicle (4WDEV). The 4WDEV is
equipped with four asynchronous motors ensuring the drive of the driving wheels controlled by a direct fuzzy
torque control. The proposed control law ensures good stability of the 4WDEV in different road topologies,
curves and slopes and increases the autonomy of the electric vehicle. The second method is introduced to
replace the torque hysteresis controllers, flow rate controllers, and switch table used in the CDTC with fuzzy
logic controllers. The main objective of the DTFC method is to improve the dynamic performance of electric
vehicles and to reduce torque and flow ripples.

2. DESCRIPTION OF THE 4-WHEEL DRIVE ELECTRIC VEHICLE

In Figure 1, the 4WDEV drive train shows that the power structure of this drive train consists of
four induction motors built into the wheels driven by four three-phase inverters, the principal power source
for the vehicle being the lithium-ion (li-ion) battery. It is connected to the DC bus via a two-way DC-DC
(Buck-Boost converter) converter. A Ghezouani [8] the four induction motors are driven by the DC bus via a
DC-AC converter. The control method used for each engine is DTFC fuzzy torque control. The goal of this
approach is to enhance the conventional direct torque control DTFC strategy. The rolling engines are
powered by an electronic differential. This system uses the throttle position and the wheel angle, specified as
inputs by the rotation of the wheel.

Figure 1. General structure of the EV4WD four-wheel drive electric vehicle studied

3. LOAD BALANCE OF THE FOUR-WHEEL DRIVE ELECTRIC VEHICLE

As shown in Figure 2, the total force Ftot required to move the electric vehicle forward is the sum of
the different components resulting from the balance of the mechanical forces applied to the vehicle [8], [9].
Table 1 clarifies the concepts used (2) to (8).

Ftot = Froul + Faero + FSlope + Facc = FR + Facc (1)

− Froul is the rolling resistance force related to the rolling coefficient of the wheels (Crr ). The rolling
resistance force is: Froul ≈ gMScooter Crr .
Improved DTC strategy of an electric vehicle with four in-wheels induction motor … (Nair Nouria)
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− Faero is the aerodynamic resistance force, proportional to the air density, to the square of the wind
speed, to the frontal section of the vehicle and to its air penetration coefficient(Cpx ). Its expression
is given by (2).
1
Faero = ρSf Cpx (Vveh − Vwind )2 (2)
2

Frontal section of the vehicle and to its air penetration coefficient(Cpx ). Its expression is given
by (3).
1
Faero = ρSf Cpx (Vveh − Vwind )2 (3)
2

− Fpente is the resistance force of the slope to be climbed. In the case where the electric vehicle would
have to climb a corner slope (αp )as shown in Figure 2, there is an additional force proportional to
the total mass of the vehicle that is applied to its forward motion this force is given by:

Fpente = gMveh . sin(αp ) (4)

Facc is the dynamic term for the acceleration or deceleration of the electric vehicle.

dVveh
Facc = Mveh = Mveh γ (5)
dt

− Finally, the total effort of the vehicle's forward resistance is worth.

1
Ftot = gMveh Crr + ρSf Cpx (Vveh − Vwind )2 + gMveh . sin(αp ) + Mveh γ (6)
2

− The wheel resistance torque Cr is related to the resistance force by (7).

Cr = Ftot . R ω (7)

− The angular velocity ω_(r-i) (rad/s) of each driven wheel is related to the vehicle speed by (8).
Vveh
ωr−i = (8)
2Rω

Table 1. Appearance properties of accepted

manuscripts
𝑀𝑣𝑒ℎ 𝐾𝑔 Total mass of the vehicle
𝐽𝑣𝑒ℎ 𝐾𝑔. 𝑚2 Vehicle inertie
𝑉𝑣𝑒ℎ 𝑚. 𝑠 −1 Vehicle speed
𝑉𝑤𝑖𝑛𝑑 = 0 𝑚. 𝑠 −1 Wind speed
𝑔 = 9.81 𝑚. 𝑠 −2 Acceleration of Gravity
𝐶𝑝𝑥 Air penetration coefficient
𝑆𝑓 𝑚2 Front section of the vehicle
𝜌 𝐾𝑔. 𝑚3 Air volume Density
𝑅𝜔 𝑚 Wheel radius
𝑟𝑟 Right Rear Wheel
𝑙𝑟 Left Rear Wheel
Figure 2. Forces exerted on the four-wheel drive
electric vehicle

4. THE IN-WHEEL ELECTRIC DRIVE IM MODEL

For the elaboration of control strategies, it is necessary to find a compromise between
the complexity and the accuracy of the modeling and since the objective of the present work is the direct
torque control based on fuzzy logic (DTFC) based on the knowledge of the amplitude and position of
the stator flux [11], [12] the complete model of the machine in the Park reference frame linked to the stator
reference frame (α-β) (9) to (12).

𝑥̇ = 𝐴𝑥 + 𝐵𝑢 (9)

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such as:
𝑇 𝑇
𝑥 = [𝑖𝑠𝛼 𝑖𝑠𝛽 𝜑𝑠𝛼 𝜑𝑠𝛽 ] , 𝑢 = [𝑢𝑠𝛼 𝑢𝑠𝛽 ] (10)
𝜔𝑟 1
−𝜂 𝜔𝑟 𝐾 0
𝜎𝐿𝑠 𝜎𝐿𝑠
𝜔𝑟 1
𝜔𝑟 −𝜂 − 𝐾 ;𝐵= 0 (11)
𝜎𝐿𝑠 𝜎𝐿𝑠
𝑅𝑠 0 0 0 1 0
[0 𝑅𝑠 0 0 ] [0 1]

with:

𝑀2 𝐿𝑠 𝐿𝑟 1 1 1 1
𝜎 =1− , 𝑇𝑠 = , 𝑇𝑟 = , 𝜔𝑟 = 𝑝Ω𝑟 , 𝐾 = ,𝜂= − ( + ) (12)
𝐿𝑠 𝐿𝑟 𝑅𝑠 𝑅𝑟 𝜎𝐿𝑠 𝑇𝑟 𝜎 𝑇 𝑇 𝑟 𝑠

5. CONVENTIONAL DTC FOR ONE IN-WHEEL INDUCTION MOTOR DRIVE

In the mid-eighties, I suggested a Method for the Direct Torque Control of Induction Motors (DTC)
in the literature of Takahashi T [13], [14], Noguchi and Deerbrook. The DTC theory is based on a direct
determination of the pulses used for the voltage inverter switches. This is done to maintain
the electromagnetic torque and the stator flow in two hysteresis bands. Such application ensures that torque
and flux control are disconnected.
The voltage inverter allows for 7 locations in the phase plane, which corresponds to the 8 sequences
of the voltage vector at the inverter output [15], [16]. The block diagram in Figure 3 shows a synoptic DTC
diagram used in a three-wheeled electric scooter inductive motor. The flux calculation can be estimated from
the stator current and voltage measurements of the induction machine [17]. Table 2 shows the DTC control
truth table.
t
φsα = ∫0 (vsα − R s isα ) dt (13)

t
φsβ = ∫0 (vsβ − R s isβ ) dt (14)

The stator flux module is.

φs = √φsα 2 + φsβ 2 (15)

The 𝑁𝑖 field in which the vector 𝜑𝑠 is located is determined from the components 𝜑𝑠𝛼 and 𝜑𝑠𝛽 the angle 𝜃𝑠
between the repository (α-β) and the vector𝜑𝑠 [18].
φsβ
θs = arctg ( ) (16)
φsα

When the two flux components are reached, the electromagnetic torque can be calculated by [19].
3
Tem = p[φsα isβ − φsβ isα ] (17)
2

Table 2. DTC control truth table

Sector 𝑁𝑖 𝑆1 𝑆2 𝑆3 𝑆4 𝑆5 𝑆6
∆𝑇𝑒𝑚 = 1 V2 V3 V4 V5 V6 V1
∆𝜑𝑠 = 1 ∆𝑇𝑒𝑚 = 0 V7 V0 V7 V0 V7 V0
∆𝑇𝑒𝑚 = −1 V6 V1 V2 V3 V4 V5
∆𝑇𝑒𝑚 = 1 V3 V4 V5 V6 V2 V1
∆𝜑𝑠 = 0 ∆𝑇𝑒𝑚 = 0 V0 V7 V0 V7 V0 V
∆𝑇𝑒𝑚 = −1 V5 V6 V1 V2 V3 V4

Improved DTC strategy of an electric vehicle with four in-wheels induction motor … (Nair Nouria)
654  ISSN: 2088-8694

Figure 3. Conventional DTC for induction motor drive in the wheels used in the 4WDEV

6. DIRECT TORQUE FUZZY CONTROL OF THE ASYNCHRONOUS MACHINE

The traditional DTC control provides rapid and precise response to electromagnetic torque and
stator flux. The greatest drawback of this power, however is the large torque, stator flux and current ripple
due to the use of hysteresis comparators [20]. This section proposes to boost the efficiency of the traditional
CDTC Control, Direct Torque Fuzzy Control (DTFC). This method proposes to replace the hysteresis
comparators and the selection table with a controller based on a fuzzy inference system [21], [22]. Figure 4
shows the schematic diagram of the DTFC control of an induction motor integrated in the wheels of the four-
wheel drive electric vehicle. The obtained torque (eTem) and flux (𝑒𝜑𝑠 ) errors as well as the angle 𝜃𝑠 are
required by the fuzzy inference system to evaluate the reference voltage vector to drive the torque and flux to
their desired values.

Figure 4. Schematic diagram of the direct fuzzy control (DTFC) of the MI integrated in the wheels of the EV

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Int J Pow Elec & Dri Syst ISSN: 2088-8694  655

Figure 5 displays the membership functions for the fuzzy inference method input and output
variables. Trapezoidal and triangular association functions have been selected. The input of the torque error
consists of 3 fuzzy sets N (negative), Z (zero) and P (positive). Two fuzzy sets were considered for the flow
error membership functions, N (negative) and P (positive) [23]. The stator flux angle can be defined by six
linguistic variables(𝜃1 ⟶ 𝜃6 ), to have a fine adjustment. The inferential device output variable is divided
into eight individualtons, two null voltages (V0 and V7) and six null voltages. The output variable
membership functions are shown in Figure 5. The different possible combinations of 3 fuzzy sets for torque
error, 2 fuzzy sets for flux error and six sectors for stator flux angle form 36 rules in the basis of the inference
system.

Figure 5. The membership functions for the input and output variables of the fuzzy inference system

The rule base is based on a stator flux diagram (α-β) in the plane. For example, if the angle θs of
the stator flux lies in the value of θ2if one wants to slowly decrease the torque and quickly increase the flow
then the vector V1 is the most suitable alternative. The same rationale is used to construct the rule base for
the fluid direct torque control in Table 3. The laws are the fluid control inferior engine. They express in
a relation between elementary fluffy proposals or conjunctions of fundamental proposals [21], [23].

𝑅𝑖 : 𝑖𝑓 𝑒𝜑𝑠 𝑖𝑠 𝐴𝑖 𝑎𝑛𝑑 𝑒𝑇𝑒𝑚 𝑖𝑠 𝐵𝑖 𝑎𝑛𝑑 𝜃𝑠 𝑖𝑠 𝐶𝑖 𝑡ℎ𝑒𝑛 𝑣 𝑖𝑠 𝑉𝑖 (18)

With 𝐴𝑖 , 𝐵𝑖 and deare the linguistic variables of the flux error, the torque error and the stator flux angle,
respectively. 𝑉𝑖 is the output linguistic variable and 𝑅𝑖 is rule number i.

Table 3. Fuzzy logic switching rules

eφs eTem θ1 θ2 θ3 θ4 θ5 θ6
N N V5 V6 V1 V2 V2 V4
P V0 V7 V0 V7 V0 V7
Z V6 V4 V5 V6 V1 V2
P N V3 V1 V3 V3 V4 V5
P V7 V0 V7 V0 V7 V0

αi = min (μAi (eφs ), μBi (eTem ), μCi (θs )) (19)

By fuzzy reasoning, Mamdani's minimum process (20).

Improved DTC strategy of an electric vehicle with four in-wheels induction motor … (Nair Nouria)
656  ISSN: 2088-8694

μVi (v) = min (αi , μVi (v)) (20)

𝜇𝐴𝑖 (𝑒𝜑𝑠 ), 𝜇𝐵𝑖 (𝑒𝑇𝑒𝑚 ), 𝜇𝐶𝑖 (𝜃𝑠 ) and (v) 𝜇𝑉𝑖 (𝑣) designating respectively the degrees of membership of 𝑒𝜑𝑠 ,
𝑒𝑇𝑒𝑚 , 𝜃𝑠 andt 𝑣 to the fuzzy sets 𝐴𝑖 , 𝐵𝑖 , 𝐶𝑖 and 𝑉𝑖 .
In our case, the output is constituted by a set of singletons, we will apply the MAX method (21). The
value corresponding to 𝜇𝑉𝑜𝑢𝑡 (𝑣) should then be converted to a voltage vector. In the proposed fuzzy
controller for defuzzification the method of the center of gravity was used. Figure 6 shows the characteristic
surface of the proposed fuzzy controller, it expresses the variations of the actual value of the controller output
as a function of the inputs when the latter are traversing the speech universe.

36
μVout (v) = maxi=1 (μVi (v)) (21)

Figure 6. Characteristic surface of the fuzzy selection table

− Design of fuzzy logic speed controller

The classic PI controller has been used in speed control for the majority of different induction motor
control strategies. However, the PI controller has not provided satisfactory performance in case of sudden
speed changes, load torque disturbances, low speed control due to continuous variations in machine
parameters and operating conditions. The refore, in order to overcome these drawbacks, controllers based on
fuzzy logic are highly desirable. In this work the classical PI controller is replaced by artificial intelligence
techniques, such as Fuzzy Logic Control (FLC) to improve drive performance [23, 24].
The deviation between the reference speed and the actual speed of the induction machine,
𝑒(𝑘) = 𝜔𝑟∗ (𝑘) − 𝜔𝑟 (𝑘), and the variation of this deviation ∆𝑒(𝑘) = 𝑒(𝑘) − 𝑒(𝑘 − 1), are used as fuzzy
controller input fuzzy variables of the speed and the controller output is the reference electromagnetic torque
∗
𝑇𝑒𝑚 , the block diagram of which is shown in Figure 7 the fuzzification of the fuzzy controller input and
output variables is shown in Figure 7. Each of the three linguistic variables is represented by five fuzzy
subsets (GN=Large Negative, PN=Small Negative, Z=Zero, PP=Small Positive, GP=Large Positive).
Moreover, the defuzzification has been performed by the center of gravity method associated with the sum-
product interference method [8], [25].
Degree of membership
Degree of membership

Degree of membership

n p PP
1 N Z P
1 GN PN Z PP GP 1 GN PN Z GP

0.8 0.8 0.8

0.6 0.6 0.6
0.4 0.4 0.4
0.2 0.2 0.2
0 0 0
-4 -2 0 2 4 -4 -2 0 2 4 -4 -2 0 2 4
Referenc e Torque Tem* Change in error s peed Speed Error
(a) (b) (c)
∗
Figure 7. Functions of the FLC speed controller members for (a) the reference torque 𝑇𝑒𝑚 , (b) the variation
of the speed error ∆e(k) and (c) the speed error e(k)

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Such that, for the 𝑖 𝑡ℎ rule: 𝜇𝑐𝑖 is its degree, 𝑋𝐺𝑖 is the abscissa of its center of gravity and 𝑆𝑖 is the
surface of the output fuzzy subset. The rule base for deciding the output of the inference system consists of
25 If-Then rules in this case because there are 5 fuzzy sets in each of the inputs. Table 4 shows representing
the inference rule base.

∑25
i=1 μci XGi Si
∆T∗em = (22)
∑25
i=1 μci Si

Table 4. Fuzzy rule

𝑒⁄ GN PN Z PP GP
∆𝑒
GN N Z N N Z
PN N N N Z P
Z n N Z P P
PP n Z P P P
GP Z P P P P

7. PROPOSED SPEED CYCLE FOR THE 4WD ELECTRIC VEHICLE

We have proposed a relatively short 10s speed loop to test the efficiency of the DTFC direct fuszy
torque control strategy of the 4WDEV traction system, and Figure 8 presents the speed profile of the cycle.
This route is characterized by seven successive phases. In the first stage, the vehicle is pushed straight at a
speed of 50Km/h in the second stage. a right turn is imposed on the vehicle by a steering angle command
(𝛿 = 25°) as shown in Figure 9, in the third phase, the 4WDEV runs on a straight road at the same speed, in
the fourth phase a left turn is imposed on the vehicle with a steering angle command (𝛿 = −15°). The fifth
phase, the vehicle runs on a straight road with a speed of 50Km/h. In the sixth phase, the VE4WD climbs an
inclined road with an angle of 10° (slope) with a speed of 70Km/h. Finally, the last one (7) presents the
deceleration phase where the speed of the vehicle is 30Km/h. The constraints of the road are presented in
Table 5.

Table 5. Topologies of specified driving routes

Phase Time (Sec) Event information Véhicule speed Km/h
01 0s < t < 1,5s Straight road 50 km/h
02 1,5s < t < 2,5s Curved road SIDE right 50 km/h
03 2,5s < t < 4s Straight road 50 km/h
04 4s < t < 5s Curved road SIDE left 50 km/h
05 5s < t < 6s Straight road 50 km/h
06 6s < t < 8s Climbing slope 10% 70 km/h
07 8s < t < 10s Straight road 30 km/h

Figure 9. Steering angle variation

Figure 8. Specify driving road topology

8. RESULTS AND DISCUSSION

The numerical simulations in this section were done with the MATLAB/Simulink environment on
an electric vehicle drive system driven by four 15kW induction motors, which were integrated in the wheels

Improved DTC strategy of an electric vehicle with four in-wheels induction motor … (Nair Nouria)
658  ISSN: 2088-8694

as shown in Figure 1. The objectives of the simulation carried out evaluated the effectiveness of the different
control strategies proposed (conventional DTC and DTFC) on the dynamics of the electric vehicle, and a
comparison was made between the two. This system was simulated using a reference wheel speed given by
the topology shown in Figure 8. The dynamic and aerodynamic characteristics of the vehicle and Table 6
includes induction motor parameters. The aerodynamic torque is reduced with DTFC control relative to
CDTC. 56.6Nm with DTFC and 57.1Nm per CDTC (phase 6, see Figure 10). This value can be explained by
the large frontal zone in the case of CDTC versus DTFC. It can be seen that the overall resistive torque is
improved in DTFC compared to CDTC (see Figure 11).

Table 6. Proposed 4WD electric vehicle and IM parameters

Parameters Name Symbol Value Parameters Name Symbol Value
Wheel radius Rw (m) 0.32 Rotor Inductance 𝐿𝑟(𝐻) 0.149
Vehicle mass M (kg) 1300 Rotor Inductance 𝐿𝑠(𝐻) 0.149
Aerodynamics drag coefficient Cd 0.3 Mutual Inductance 𝑀(𝐻) 0.141
Vehicle frontal area Af (m2) 2.60 Stator Resistance 𝑅𝑠(Ω) 1.37
Tirerolling resistance
Cr 0.01 Rotor Resistance 𝑅𝑟(Ω) 1.1
coefficient
Air density Ρair (kg/ m2) 1.2 Number of pole pairs 𝑝 2
Gear coefficient kgear 5 Motor- load inertia 𝐽(𝑘𝑔. 𝑚2 ) 0.1
Width of vehicle dω(m) 1.5 Rated power 𝑃𝑛(𝐾𝑤) 10
Length of vehicle Lω(m) 2.5 Viscous friction coefficient 𝑓𝑐(𝑁. 𝑚. 𝑠) 0.00014

Figure 10. Vehicle Aerodynamics torque variation with Figure 11. Globally vehicle resistive torque
CDTC and DTFC

The driver provides the steering angle of the front wheels; the electronic differential is centered on
the speeds of the driving wheels. The speeds of the two right-hand drive wheels located on the outside of the
bend (right turn phase 2) Switch at speeds greater than the two inside left drive wheels of the bend. At the
moment t=4s the vehicle is in the second left turn 9 (phase 4); the same thing for the electronic differential
calculates the references of the new speeds to turn the wheels to stabilize the vehicle inside the left turn.
Table 7 shows the speed values for each wheel for both turns (phases 2 and 4).
A Fuzzy Logic Controller (FLC) was used in place of another traditional PI type to help improve the
speed response of the vehicle. The advantage of this controller lies in its robustness against speed variations
and follows the setpoint without overshooting and with good accuracy. Figure 12 shows the simulation
results of the linear velocity of the 4WD vehicle using the two control strategies (DTC with a PI type velocity
controller and DTFC with FLC). From the results we can notice that the effect of the disturbances is clearly
visible in the linear velocity response of the vehicle by using the DTC strategy (where the vehicle is driven
on a 10% slope phase 6 road) with an overtaking of 0.15%. The result of the two control laws can be
summarized in Table 8. On the other hand, the DTFC strategy gives us a good dynamic in terms of following
the instruction (setpoint) without over speeding in the stationary case with a low-rise time and zero static
error.
The evolution of the four electromagnetic torque propulsion engines (IM) of the 4WD electric
vehicle is given in Figure 13 (a) and Figure 13 (b), using both conventional DTC and DTFC control
strategies. The results obtained illustrate quite clearly good torque response dynamic output of the proposed

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DTFC control. In addition, a significant reduction in torque ripple can be seen, compared to conventional
direct torque control (DTC).

Table 7. Values of the four-wheels speed in phases 2 to 4 Table 8. Performances of the DTC and DTFC
Wheel speed Phase 02 Phase 04 in the speed response
(Km/h) CDTC DTFC CDTC DTFC Control Rising Time Over shoot Speed Error
Front left wheel 61,12 61,10 53,54 53,49 Type [Sec] [%] [%]
Front right wheel 55,31 55,25 51,85 51,80
Rear left wheel 45,35 45,15 48,35 48,33 DTC 0.16 0.15 0.01
Rear right wheel 39,52 39,43 47,21 47,19 DTFC 0.11 0 0

(a) (b)

Figure 12. Vehicle Variance of linear speed (a) and error rate (b) at various points

(a)

(b)

Figure 13. Electromagnetic torque response developed by the four motors using (a) conventional DTC,
(b) DTFC

Figure 14 (a) and Figure 14 (b) shows the trajectory of the stator flux vector in the plane (α-β)
related to the stator for the right front (LF) motor. It can be seen that the trajectory of the end of the stator
flux in the case of DTFC control (Figure 14 (b)) takes a uniform circular shape with a radius equal to 0.97Wb
centered at the origin which presents a good decoupling of the flux from the torque.

Improved DTC strategy of an electric vehicle with four in-wheels induction motor … (Nair Nouria)
660  ISSN: 2088-8694

(a) (b)

Figure 14. (a) Trajectory of stator flow in the plane (α-β) of the front left engine using classic DTC and
(b) DTFC

9. CONCLUSION
In this paper, we have focused on the application of one of the methods of artificial intelligence
which is fuzzy logic in a four-wheel drive electric vehicle. after having been able to determine the
performance of DTFC compared to DTC, the law of the proposed new control, i.e. DTFC, ensures a good
stability of the 4WDEV in different road topologies, curves and slopes and increases the autonomy by
reducing consumption of the electric vehicle energy, this was quite clear from the simulation results
(MATLAB/Simulink), from which we noticed the reduction of ripples and the rapidity in the torque and flow
dynamics during the starting phase of the machine.

ACKNOWLEDGEMENTS
This work was financially supported by, Smart Grids & Renewable Energies Laboratory Laboratory,
TAHRI Mohammed University of Bechar Algeria and DGRSDT Algeria.

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Improved DTC strategy of an electric vehicle with four in-wheels induction motor … (Nair Nouria)