Introduction to Control of Electric Vehicle

Final Project: Electric Rickshaw modelling

Aim:

To Create a detailed MATLAB model of an Electric Rickshaw (three wheel passenger vehicle).

Software used:

MATLAB R2020a (Simulink)

Objectives:

Rear wheels driven by PM brushed type motor

Assume efficiency points of motor controller and motor

Make an excel sheet of all input and assumed data

Results: For any three standard driving cycles show energy consumption, temperature rise of motor and controller.

Introduction :

Battery Electric Vehicles (BEVs), compared to classic internal combustion engine (ICE) vehicles, are fairly simple and easy to operate. The simplest powertrain architecture consists in a high voltage battery, an electric motor with power electronics controller and a single speed gearbox. BEVs are also called pure electric vehicles.

In a BEV the propulsion is based exclusively on the electric energy stored in the high voltage battery.

Battery electric vehicle are increasing their market share because they are the most viable way towards a clean and efficient transport system. Compared with ICE vehicles, the most important advantages of a BEV is the overall high efficiency, reliability and relatively low cost of the electric motor. The main drawback is the low energy density of the high voltage battery.

Electric rickshaws (also known as electric tuk-tuks or e-rickshaws or auto) have been becoming more popular in some cities since 2008 as an alternative to auto rickshaws and pulled rickshaws because of their low fuel cost, and less human effort compared to pulled rickshaws. They are being widely accepted as an alternative petrol/diesel/CNG auto rickshaws. They are wheelers pulled by an electric motor ranging from 650-1400 Watts. They are mostly manufactured in India & China, only a few other countries manufacture these vehicles.

Battery-run rickshaws could be a low-emitter complementary transport for the low-income people, who suffer most from a lack of transport facility, if introduced in a systematic manner according to experts.

Let us consider the Ape E city (Piaggio)

Pure Electric Powertrain:

Archittecture of Electric Vehicle

System Level Configuration:

There are major components which is using in EV

1. Drive Cycle
2. Driver
3. H-Bridge
4. DC Motor
5. Battery Source
6. Controlled PWM Voltage
7. Vehicle and others

Block Diagram

In the designed Electric Rickshaw main blocks are Battery, drive cycle, controller, DC Motor, Vehicle body & Transmission system. Drive cycle is the input data like how a human drive his actual vehicle here FTP75, WOT & Excel (Manually Prepared in Excel sheet) drive cycles are used to make the designed vehicle to give the output how it reacts to the drive cycle. The main objective is to obtain the speed by the driver, to estimate the temperature of Motor and Controller, to

estimate the sates of charge (SOC), distance travelled by the vehicle. There is a SOC block that will estimate the state of charge of a battery, distance is calculated by speed and time parameters for all the three Drive cycles.

MATLAB Model of an Electric Rickshaw:

Initially the current flows to DC Motor from the battery through the DC-DC power converter to drive the motor. The required voltage will be controlled in the controller. The Controller will follow the given drive cycle reference and run the motor in the required rpm. Then the motor power is transmitted to the wheels of a vehicle through the gear box. and the controller will take the vehicle speed and compare and controlled.

Model parameters:

Drive Cycle:

Drive cycle is assumed as the driver's input of a vehicle, it replaced how a driver will drive a vehicle. Here we have used three drive cycles which is used to test the vehicle performances. These drive cycle will have high speed, low speed, braking conditions in it. There are different drive cycles like WOT, FTP75 etc., Here in this model I have used FTP 75, WOT & Manually prepared in Signal Builder excel Drive Cycle source.

FTP 75:

Generates a standard or user-specified longitudinal drive cycle. The block output is the vehicle longitudinal speed. You can import drive cycles from:

- Predefined sources

- Workspace variables, including arrays and time series objects

- mat, xls, xlsx, or txt files

Use the fault tracking parameters to identify drive cycle faults within specified speed and time tolerances.

Wide Open Throttle (WOT):

Manually prepared Drive Cycle:

All 3 Drive cycles are controlled by the controller provided above by constant through Multi-port switch.

Driver Controller:

A parametric longitudinal speed tracking controller for generating normalized acceleration and braking commands based on reference and feedback velocities.

Use the external actions to input signals that can disable, hold, or override the closed-loop commands determined by the block. The block uses this priority for the input commands: disable, hold, override.

Drive cycle is connected to a longitudinal driver, it has six ports namely velocity reference, velocity feedback, grade, info, Acceleration, Deceleration.

VelRef is given by the drive cycle data and VelFdbk is given by the output of the motor. These two will get compare and the acceleration or deceleration output will be given to the motor controller. Accelcmd is given the PWM generator block and deccelcmd is given to the regenerative port of the h-bridge which uses to generate regenerative braking. Info is used to get any other data from a longitudinal driver block. The grade is to give the input of gradeability to the driver block. This block helps to generate regerate the driver's conditions of the vehicle using the driver cycle block.

I used default parameters and control type PI

Motor & Controller:

1. Motor type: DC Motor (PM brushed type motor)

This block represents the electrical and torque characteristics of a DC motor includes Thermal port to sense the temperature of Motor.

The block assumes that no electromagnetic energy is lost, and hence the back-emf and torque constants have the same numerical value when in SI units. Motor parameters can either be specified directly, or derived from no-load speed and stall torque. If no information is available on armature inductance, this parameter can be set to some small non-zero value.

When a positive current flow from the electrical + to - ports, a positive torque acts from the mechanical C to R ports. Motor torque direction can be changed by altering the sign of the back-emf or torque constants.

Motor Parameters:

Field Type is Permanent Magnet.Model Parameterized by rated Load and speed.The Armature Inductance is as default, We have varied the changes in the No-load Speed @ 9000 RMP, the rated speed @ 5000RPM, the Rated Load (Mechanical Power) at 20 KW, and the Rated DC Supply Voltage @ 60V. All other parameters are as default.

TheMotor controller will get input from the longitudinal driver. Its tasks are to control the speed of the motor and drive according to the input of the driver.

Majorly motor controlled we designed had two main parts named PWM voltage generator and H-Bridge.

Input1 is getting from the accelmd of a longitudinal driver and it is given to a controlled voltage source block where it is input to the controlled PWM voltage.

Controlled PWM voltage will generate a PWM signal in such a way that H-bridge will generate the required voltage to operate the DC motor for the given driver input. PWM voltage block negative reference and REF are grounded and REF of H-bridge respectively. H-bridge is a motor controller that has IGBT components

aligned in the shape of H and will operate only two at a time respectively to the input of the signal from the PWM block. When deceleration occur this H-bridge will give an output from the positive and negative terminals of it. These negative & positive terminals are later connected to the DC motor and battery. All these

components are the simscape electrical components so they need a connection to the solver configuration block which helps to solve the simulation.

2. Controlled PWM Voltage source:

The value of the Output voltage amplitude parameter determines amplitude of the output voltage.

The Controlled PWM Voltage block represents a pulse-width modulated (PWM) voltage source.

Electrical input ports — The block calculates the duty cycle based on the reference voltage across its ref+ and ref- ports. This modeling variant is the default.

PS input — Specify the duty cycle value directly by using an input physical signal port.

where

Vref - is the reference voltage across the ref+ and ref- ports.

Vmin - is the minimum reference voltage.

Vmax - is the maximum reference voltage

Parameters considered:

3. Power Converter:

H-Bridge:

H-Bridge is used as a DC-DC converter.

This block represents an H-bridge motor drive. The block can be driven by the Controlled PWM Voltage block in PWM or Averaged mode. In PWM mode, the motor is powered if the PWM port voltage is above the Enable threshold voltage. In Averaged mode, the PWM port voltage divided by the PWM signal amplitude

parameter defines the ratio of the on-time to the PWM period. Using this ratio and assumptions about the load, the block applies an average voltage to the load that achieves the correct average load current. The Simulation mode parameter value must be the same for the Controlled PWM Voltage and H-Bridge blocks.

If the REV port voltage is greater than the Reverse threshold voltage, then the output voltage polarity is reversed. If the BRK port voltage is greater than the Braking threshold voltage, then the output terminals are short circuited via one bridge arm in series with the parallel combination of a second bridge arm and a freewheeling diode. Voltages at ports PWM, REV and BRK are defined relative to the REF port.

If exposing the power supply connections, the block only supports PWM mode.

Motor controller Parameters:

Threshold Voltage =2.5 V

PWM Amplitude =5V

Reverse Threshold =2.5 V

Braking Voltage =2.5 V

Output Voltage =60 V

4. Temperature Sensor:

Temperature Sensor is used to mesure the temperature of H-Bridge and Motor.

This block measures temperature in a thermal network. There is no heat flow through the sensor. The physical signal port T reports the temperature difference

across the sensor. The measurement is positive when the temperature at port A is greater than the temperature at port B.

5. Solver Configuration:

Defines solver settings to use for simulation.

6. References

Electrical Reference: Used to ground the all the electrical connections.

Mechanical Rotational Reference: Used to ground all the mechanical rotational parts.

Thermal Reference: Used to ground the thermal sensor.

Battery:

Battery Parameters:

State of charge (SoC):

SoC is the percentage or level of battery presents after certain travel or consumption of battery charge by the vehicle. In the designed vehicle battery charge or

SOC is calculated by the giving it to the rate transition and then to gain where 1/(nominal battery capacity) then to a discrete-time integrator and it will get minus

from the 1 as it is considered a 100% of battery and it is multiplied with 100 to get percentage of battery.

The majority of blocks are simscape blocks where physical to simulink converter is used to convert the physical signal from simscape block to simulink signal.

Vehicle Body & Transmission:

Motor will produce the rotational output which will give to the vehicle body and transmission system. The rotational output is taken by the gear system here to

maintain the constant speed throughout the transmission without any loss in speed from the motor to tires. Below is a diagram that is how it is how it inside the vehicle body and transmission system and in the main design, it is referred just only as a transmission system.

Here I created a Rear wheel drive transmission system.

The gear output is given to axels of Rear tires, in the circuit it is shown that gear is connected to Rear wheels and front tire is free to rotational motion, thus

vehicle moves forward. N is the normal force caused by the tires and it is given to the vehicle body normal force port. The vehicle body has an H-Hub, S- Tire slip,

N- Normal force, A- axel connection, wind velocity, inclination angle. The tires hub is connected as a common node to the vehicle body. The vehicle body wind

velocity is connected to a constant block and the beta-inclination angle is connected to another constant block where we can assign wind velocity and

inclination angle as per requirement. Velocity is the output port where we can get at which speed the vehicle is moving. The velocity is taken out to the get the

distance travelled and state of charge.

1. Vehicle Body:

This block creates a Pulse-Width Modulated (PWM) voltage across the PWM and REF ports. The output voltage is zero when the pulse is low, and is equal to the

Output voltage amplitude parameter when high. Duty cycle is set by the input value. Right-click the block and select Simscape->Block choices to switch between

electrical +ref/-ref ports and PS input u to specify the input value.

At time zero, the pulse is initialized as high unless the duty cycle is set to zero or the Pulse delay time is greater than zero.

The Simulation mode can be set to PWM or Averaged. In PWM mode, the output is a PWM signal. In Averaged mode, the output is constant with value equal to

the averaged PWM signal.

No.of Wheel per axle are 2 (Rear Wheels), where as front wheel is free to rotate.

Parameters of the Vehicle Body:

2. Wheels:

Represents the longitudinal behavior of a highway tire characterized by the tire Magic Formula. The block is built from Tire-Road Interaction (Magic Formula) and Simscape Foundation Library Wheel and Axle blocks. Optionally, the effects of tire inertia, stiffness, and damping can be included.

Connection A is the mechanical rotational conserving port for the wheel axle. Connection H is the mechanical translational conserving port for the wheel hub through which the thrust developed by the tire is applied to the vehicle. Connection N is a physical signal input port that applies the normal force acting on the tire. The force is considered positive if it acts downwards. Connection S is a physical signal output port that reports the tire slip. Optionally expose physical signal port M by setting Parameterize by to Physical signal Magic Formula coefficients. Physical signal port M accepts a four element vector corresponding to the B, C, D, and E Magic Formula coefficients.

Parameters of Wheels:

3.Inertia:

The block represents an ideal mechanical rotational inertia.

The block has one mechanical rotational conserving port. The block positive direction is from its port to the reference point. This means that the inertia torque is positive if the inertia is accelerated in the positive direction.

4. Simple Gear box:

Gear Ratio

Represents a fixed-ratio gear or gear box. No inertia or compliance is modeled in this block. You can optionally include gear meshing and viscous bearing losses.

Connections B (base) and F (follower) are mechanical rotational conserving ports. Specify the relation between base and follower rotation directions with the Output shaft rotates parameter. Optionally include thermal effects and expose thermal conserving port H by right-clicking on the block and selecting Simscape

block choices to switch between variants.

Output shaft rotates in in same direction of input shaft.

Base is connected to the Motor shaft and the follower is connected to the Rear wheel derive.

Results:

1. For FTP75 Drive Cycle:

By running the Vehicle with FTP75 Drive cycle for 2474 sec. the distance travelled is = 21km

-The actual Speed is approximately followed the 90% of reference Drive cycle.

-Energy consumed by the battery is ≈ 9⋅ 727 kWh` at the end of the cycle.

The SoC% of the battery is reduced to ≈ 80 % .

The Temperature of Motor is increased to 420 C.

The Temperature of Controller is ≈ 2*10^5 C

2. For WOT Drive cycle:

By running the Vehicle with WOT Drive cycle for 11000 sec. the distance travelled @ 45kmph is = 137 km.

-The actual Speed is approximately followed the 95% of reference Drive cycle.

-Energy consumed by the battery is increased linearly till 11000 sec. to approx. 40 KWh i . e almost total battery capacity of vehicle.

-The SoC% of the battery is reduced to ≈ 0 % by 11000 sec

-Distance travelled by EV Rickshaw = 137 km in single charge which is range of vehicle.

-The Temperature of Motor is increased to 1000C.

-The Temperature of Controller is ≈ 8*10^5C.

3. For Manually prepared Drive cycle:

By running the Vehicle with Manually prepared Drive cycle for 120 sec. the distance travelled is = 11 km

-The actual path of the speed is approximately followed the of reference Drive cycle as above.

-Energy consumed by the battery is varied with respect to time= 1500 wh

-The SoC% of the battery is reduced to 96%

-The Temperature of Motor is increased to 310C .

-The Temperature of Controller is 25000C

Conclusion:

-Here We have compromised with the temperature of Motor and controller to achieve vehicle speed is near to reference speeds. Since we haven’t used any cooling system in the model. In the real time application, the motor temperature is less than 100 C.

-In the real time application, the motor, battery & controller temperature is controlled by air cooling. Hence, the temperature of this components is not increased to this extent.

-Hence, Created a MATLAB model of an Electric Rickshaw (three wheel passenger vehicle) by using Li-ion battery, PM Brushed DC Motor.

-Detremined the variations of Temperature of Motor and controller, SoC% and Energy consumed by the by vehicle for all the three Reference Drive cycles (i.e.; FTP75, WOT, Manually prepared).

This Battery powered Rickshaw will be the most popular mode of transport in the comming days.