PERFORMANCE EVALUATION OF THREE-PHASE INDUCTION MOTOR DRIVING AN ELECTRIC VEHICLE UNDER DIFFERENT ROAD CONDITIONS

: Electric vehicles (EV) has been introduced as an alternative to the conventional vehicle as a mid-range vehicle to the world due to environmental considerations and technology development. Many electric motors can be used as the main driver of electric vehicles. Induction Motor (IM) is one of these types. This search uses MatLab/Simulink program for modeling and simulating MITSUBISHI I-MIEV type vehicle as a model of city vehicle based on an IM as the main engine. Four cases were studied by simulating a complete (EV + IM) model with different slopes of road, wind speeds, different road types, and different speeds of vehicle. Simulation tests indicate the IM's ability to drive the electric vehicle in high stability. Thus the specifications of EV depend upon the specifications of IM used as the main driv e for EV and mechanical components for EV


Introduction
The rapid development in electric power, control technology, and micro electricity led to rapid development in the electric vehicle. Hence, the interest in electric vehicles increases as an alternative to the traditional vehicle. Undoubtedly, these vehicles will be part of the main means of transport in the future. The mini electric vehicle has a compact size, no pollution, strength, comfort, and noise. The promotion of small EVs is still difficult because of their high price compared with a conventional vehicles. EV performance can not be compared with conventional vehicles due to its technical restrictions in the industry for comparison longdistance trips and an instance [1]. Many types of research cover the performance of IM as the main drive for the electrical vehicle as in [2-3-4-5]. This work aims to study the performance of IM used as the main drive for electrical vehicles of MITSUBISHI I-MIEV under the influence loads represented like different slopes of road, different vehicle speeds, wind speeds, and different types of roads that upon. Vehicle specifications like dimensions of the vehicle, tire dimensions, gearbox ratio are considered in the model (IM+EV). This work contributed to EV loads calculating based on motion equations applied in EV and effected on IM as the main motor in EV to determine the vehicle's specifications and safe driving in the city.

Mathematical Background
The dynamic of the vehicle is necessary to identify the tractive force as the required load on the EV in different road conditions . To determine the vehicle's performance, vehicle dynamics must be considered because the speed of EV depends upon the balance between the motive forces generated by the electric motor and running resistive forces [5]. Figure(1) shows the dynamic equation of a vehicle moving along the longitudinal direction on the road, which is used for modeling the motion of the vehicle ' s body as all forces on the vehicle are considered [6].

Dynamic Equation of Load on EV
There are several forces of resistance during the driving of vehicles. These forces are described in the equations below. The equations consider the characteristics of the vehicle. This paper uses MITSUBISHI I-MIEV as a model to calculate the forces acting on the vehicle. The model is shown in Table (1). [6].
At steady state (reach to required speed )for EV. is zero thus will be F tra = + + Faerogravity force which depends on the angle of the road at uphill driving Frollrolling force, which depends on a rolling resistance between wheels and type of roads.as shown in table (2) [ 7] Faeroaerodynamic force which depends on an air resistance of the car acceleration force The relation between gear ratio (G), wheel angular speed ( w) and angular motor seed ( m) is given as: m=G× [8] (8) And the torque (Tm) at the motor shaft is given as:

Mathematical Formals for IM and FOC
The use of the IM as the main mover in the electric vehicle should give high speeds at low torque while giving high torque only at low speeds. The vector field can obtain this requirement using the IM, as the main mover in the electric vehicle by applying an effective fieldoriented control (FOC) algorithm to control the  (3)and Park and Clark transformation [10].
L r = L lr + L m (8) Where is space vector filed

Modeling of Gearbox
We select a single-stage transmission with a fixed gear ratio to fulfill all requests with low cost, low speed, and simplicity for the entire driving system in EV, as shown in figure (3). It is an adequate solution for this kind of city electric car [11].

Modeling DC/AC Inverter and FOC
EV uses the battery as the input voltage to the inverter, and the output AC voltage of the inverter is given to IM. The FOC technique generates the signals to lead the inverter switches using the Space Vector Pulse Width Modulation (SVPWM) technique, as shown in figure (4) [12]. In the FOC motor drive system, the rotor flux and torque are separated to get the high dynamic performance of the torque and speed for both transient and steady-state conditions in driving IM.

The Case Studies:
Four cases were adopted in the complete EV model with the gearbox to assess the performance of IM used as the main drive in EV as blow:

Case (1)
In this case, the induction motor operating in the EV for 15 seconds with different loads represented by changing the slope of the road from 5 degrees to 30 degrees with(1)passenger, wind speed=0, vehicle speed =80 km/h, and type of road is concrete.

Case (2)
In this case, the IM operated in the EV for 15 seconds with different loads represented by changing vehicle speed with one passenger that's mean we change the speed for EV from 10 km/h to 110 km/h, wind speed =0, the slope of road =0 and type of road is concrete.

Case (3)
In this case, the IM operates in EV for 15 seconds at different loads represented by changing wind speed from 0 to 25 m/s, road slope=0, vehicle speed =80 km/h for one passenger, and road type is concrete.

Case (4)
In this case, the IM operates in an electric vehicle for 15 seconds with different loads represented by changing the type of road with one passenger, vehicle speed = 80 km/hr, wind speed = 0, and slope of road=0.

Results and discussion:
Depending on the  The IM draws a current that depends on the change of road slope until EV reaches the maximum slope for road represented by the highest current value of the rated current or rated torque of the IM. We can determine the maximum slope of the road which EV can climb is(15degree).

Case (2)
Table (5) shows the simulation results for the second Case. We saw the induction motor draws different currents according to the change in the vehicle speed until EV reaches the maximum speed represented by the highest value of the rated current of the IM.   (3), in which the results of simulation showed that the induction motor used in the EV draws a current that depending on the change in wind speed until IM reaches the rated value of the current or rated value of torque that's refer to the highest value of wind speed can EV afford it thus we can determine the maximum speed of wind for driving which EV can afford is (15-20) m/sec.

Case (4)
Table (7) shows the simulation results for case (4) in which the IM draws different current values depending on the type of road users; thus, we can drive EV on any type of road without any problem.

Conclusion
The simulation results and the studied cases show that road conditions (road inclination), wind speed, and vehicle speed specified by the driver are loads that the vehicle's propulsion engine (IM) must overcome until the vehicle moves as it generates forces and torque greater than the maximum torque of the propulsion engine without the gearbox. The gearbox in the electric vehicle is necessary to overcome these loads with the size of the propulsion engine to be suitable for placing inside the vehicle. The type of roads have no effect on the performance of the induction motor as shown in the fourth case for driving EV in city.