Final Project: Electric Rickshaw modelling

AIM: DESIGN OF AN ELECTRIC RICKSHAW USING MATLAB/SIMULINK

ABSTRACT: In this project, we are creating a simulink model of an electric rickshaw using a PM brushed type DC motor and required lithium ion battery for the motor. Here we have to understand fuctioning and the control of an electric rickshaw , Then we make an actual EV Rickshaw in simulink with using the blocks from the power train block set. we then have to examine how the rickshaw performs for any three standard driving cycles shwoing energy consumption, The temp rise of motor and controller of the vehicle when it travels for 100km with constant speed driving of 45kmph.

OBJECTIVES:

Here we are creating a detailed MATLAB model of an electric rickshaw (three wheel passenger vehicle) as per details below:

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 for 100 km constant speed driving at 45 kmph.

Electric e-rikshaws are going more popular after 2018 , although it is best alternative from petrol/CNG Auto rickshaws because of their low fuel cost zero emissions and less human effort. The electrical version of this system is 48 V vdc can run upto 90 to 100 kms on a single charge. top speed 25 km/hr. and the electric motor power raning from 600 to 1200 watts , it may take 6 to 8 hours to fully charge the battery basic seating capacity is 5 persons.

Here, In the designed electric rickshaw the main blocks are battery ,drive cycle, controller, DC motor, vehicle body and transmission system. The main objective in this project is to obtain speed by the driver, to estimate state of charge, tempreture of the motor and controller, and distance travelled by the motor.

Block diagram:

At the start the current flows from battery to the DC motor Through the DC -DC power converter to drive the motor. The required voltage will be controlled in the controller. The controler is connected to the given drive cycle and rum the motor in required speed, the power is transferred to the wheels of the vehicle through the gear box and the controller will check the vehicle speed and compare according to the given reference speed.

COMPONENTS:

The main components of the EV are:

• Wheels/tires
• Battery
• Motor/generator
• Motor controllers
• Power converters
• Transmission system

Main simulation diagram:

In the below picture , we have done the simulation of an electric vehicle using various drive cycles by using powertrain blockset available in simulink library.First, there is the inputs where we have connected two different drive cycles which provides the reference for the longitudinal driver which compares the two speed and gives accelerator and braking commands to the motor controller block. battery block and vehicle body blocks are further attached and scopes are used for displaying the working status.

System level configuration:

For modelling the whole vehicle in SIMULINK. we need to model the above emntioned components separately and make them work together>.All the main components are available in the library of SIMULINK blocks. so we add components and configure the parameters to fit the the working requirements of the model.

Assumed parameters:

Vehicle body:

Block parameters:

This block contain 6 ports which can be used to model various aspects of the vehicle body. The ports are mentioned below;

• H- This stands for hub and is used to connect the hubs of the wheels to the main body of the vehicle.
• V-Physical signal output port which stands for 'velocity' and is used the output the velocity of the vehicle.
• W- Physical signal input port and allows us to model a wind velocity that acts aginst the vehicle.
• NR- Physical signal output port to connect to connect the rear wheels
• NF- Physical signal output port to connect the front wheels of the vehicle.
• Beta- Physicall signall input port which allows the vehicle to undergo an inclination of hill climbing force.
• Model parameters to set up mass, frontal area amd others.

VEHICLE BODY SUBSYSTEM:

The above blocks are forming a subsystem which serves as a part for the whole vehicle. Four tires are connected, where the right two tires are the rear wheels and the remaining two are the front wheels . they are interconnected to the hub of the vehicle body block. and their respective axles are connected accordingly. We here have connected the rear axle with the gear as we want the model to be a rear wheel drive vehicle. Here the wind velocity port and hill-climbing angle ports are connected to physical constant blocks which is kept as zero.

Tire block parameters:

Here we can also change the geometry , dynamics, rolling resistance other characteristics if we want

Simple gear block parameters:

This block models a gear system with fixed gear ratio with no-inertia effects. However, we can modify the messing of the gear teeth, Here The follower to base teeth ratio has been set to 2 and the output shaft rotates in the same direction as the input shaft.

All these blocks are categorised into a single subsystem which we have names as vehicle body block, which takes the mechanical input from the motor and controller block into the gear and displays the velocity at which the vehicle body moves.

MOTOR AND CONTROLLER SUBSYSTEM:

Components:

• DC Motor
• H-bridge
• Controlled PWM voltage
• Controlled voltage source
• Current sensor

DC-Motor-

For the EV rickshaw model, I have selected to use a DC motor block because DC motors are easy to model and have a very few parameters to run for a particular application. There are two sides of the block , the mechanical side is on the right and the electrical side is on the left. mechanical side has tow ports C and R, C stands for casing and is the stable part and R is the rotor which produces a torque. The electrical side has a positive and negetive side for the voltages to be applied. If positive voltage is applied to the motor block from the positive to the negetive terminal then a positive torque will act from C to R port. The directio of the torque can be cahnged by changing the sign of the back emf or the torque constant. Here i have connected the c port to the mechanical rotational reference because it will be stationary. The R port is connected to the gear in the vehicle body block.

Here i have choosen to parameterize the block by rated power, rates speed and no-load speed. This lets us modify the parameters suchas DC supply voltage, rated load. I have kept all values default except for the no-load speed, rated speed and rated load.

H-bridge:

This is a power converter which is needed to provide power of the correct form and magnitude from one component to other. In case of EV,s a power converter is needed to provide a DC voltage from the battery of the EV to the DC motor, so that it can fuction properly at the required parameters.Here i have used an H-bridge motor drive as my power converter. The left side is for controlling the voltage signalsand the right side terminals to provide the controlled voltage to the DC motor the left side ports are:

• PWM- Pulse width modulation
• REF- Reference
• REV- Reverse
• BRL- Brake

The output coltage magnitude is set to 220 volts and the simulation is kept in average mode beacuse PWM mode will take longer durations of simulation. In the section of bridge parameters the output voltage amplitude was modified to 400 volts according to the DC motor.

Controlled Pwm voltage :

Next, i have used a 'controlled PWM voltage' to provide a controlled pulse width modulated voltage to the H-bridge block. The pulses of voltage created by this block are dependent on the duty cycle which is in that ratio of the time that the switch is ON to the time taken for one cycle. The duty cycle formula is given by:- Duty cycle= Ton/Ton +Toff= Ton /Tcyc. where Ton = On time,Tcyc=Time taken for one cycle.

Here all the parameters are set to their default values. I have chosen the averaged simulation mode so that it will feed voltage pulses within quicker simulation times to the H-bridge. The remaining parameters of input scaling and output scaling are unchanged.

Controlled voltage source:

This block provides the necessary voltage that is powerfull enough to maintaion thr voltage at the output regardless of the current that passes through it.In this subsystem @ control voltage blocks ahve been used . One block is used for acceleration and other to provide the voltage for deacceleration.

Electrical reference block is used to create grounding effect for electrical circuits. In my model, we have used it in 2 parts . First to create an electrical ground between Controlled voltage source, controlled PWM voltage, H-bridge blocks. The second is for the battery system which will be modelled afterwards.

Solver configuration block is used to solve any necessary equations in a model. I Have used them in the connection to the REV port of the H-Bridge block.

Battery Subsystem:

Components:

• Li ion battery
• Controlled current source
• Bus selector

Li ion Battery:

The battery will be the energy store of the EV and will contain the electrical energy in DC form and provide this energy to operate.

Nominal voltage has been set to 60.8 volts,Rated capacity has been set to 630 Ah ohms and an infinite charging capacity

Nominal voltage is sufficient for supplying the voltage to DC-motor and H-bridge blocks.

Controlled current source:

This block is a part in the battery sub-system. Similar to voltage source, this block produces an ideal current that is powerfull enough to maintain the specified current regardless of the voltage across it.

Bus selector:

This selector block accepts a bus as input which can be created from a Bus Creator, Bus Selector or a block that defines its output using a bus object. The left listbox shows the signals in the input bus. Use the Select button to select the output signals. The right listbox shows the selections. Use the Up, Down, or Remove button to reorder the selections. Check 'Output as bus' to output a single bus signal. he parameters are shown below.

Current sensor:

This current sensor block represents an ideal current sensor and is used to convert the current measured in an electrical circuit to a physical signal that is proportional to the current. It measures the current in the battery circuit and the DC motor. The positive and negetive terminals across which thecurrent sensor is inserted in to the circuit. The third port outputs the physical signal , In my model it sends the signal to te controlled current source.

SOC (state of charge) :

To measure the state of charge of the battery, a system was created of various blocks. The first block is Bus selector block used to handle data transfer and integrate the value of the current signal with respect to time and next is the Product block is used in order to multiply the signal coming from Bus selector block. This block will The integrate the multiplied valu of current and voltage . Assuming the battery is always fully charged I have added the constant block with a value of 1 representing 100%.Next a Divide block is used to perform product and Division operations athese blocks are made into a subsystem called SOC estimate. A scope block is used at the junction of the PS-simulink converter block to plot the output signall of the current from the battery.

Speed measurement :

In order to measure the speed. I have modified the scope block to have two input ports where one port takes the output velocity signal from the vehicle sub-system block and other port takes the output signall from the drive cycle to the reference velocity port on the longitudinal driver block. This has been done to compare the two speeds and check weather they overlap and achieve the same speed.

Distance measurement:

Mathematical blocks and scope block is used to measure the distance travelled by the vehicle. First we had to implement the integrator block to integrate the velocity siganal that is output from the velocity sub-system. Dividen block along with constant block having a value of 1000 is used to divide the integrated speed . This will give us the distance travelled in kilometers.

Longitudional driver and drive cycle:

The longitudinal driver block is used for giving normalized acceleration and deacceleration commants to a controller based on two sets of data. The first data is the reference velocity and second data is the feedback velocity.The reference velocity data coming from drive cycle source and is compared to the feedback velocity data coming from the vehicle body. If the reference velocity is greater than the feedback velocity, an acceleration comand will be given as an output to the controlled voltage source. If the reference velocity is lesser than the feedback velocity, a deacceleration command is given as output to anpother controll voltage source. For the output acceleration and deacceleration commands i have used simulink-PS converter block. In this case the input signal; is velocity data and this is logic data which have to be converted to a voltage signal The ports in this block are:

• Velref- This stands for the reference velocity and it is the velocity data provided from a drive cycle source.
• Velfdbl- This stands for feedback velocity and it is coming from the vehicle's body velocity port
• Grade- This port provides a grade or inclination angle on which the vehicle is travelling in degrees.
• Info- This port is for the bus signals which consists of block calculations
• Accelcmd- This port provides the acceleration command to a controlled voltage source
• Deacclcmd- This port provides the deacceleration command to another voltage source.

Drive cycle:

A drive cycle is a data set that contains velocity and time data for the purpose of modelling the motion of a vehicle. It is a plot of the vehicle velocity against the time and it is made to resembl typicall driving conditions that a consumer may experience themselves in. For example here i have used Three types of drive cycle data one is the 'Urban dynamometer driving schedule' and other two are 'artemis motorway of 130 kmph' and Wide open throttle condition where we have to run the vehicle for 100secs at a speed of 45km/h . Drive cycles are used by various testing procedures such as mileage, pollution tests, and acceleration and top speed tests.There are three ways of implementing a drive cycle. One method is to create your own drive cycle with spreedsheet or excelsheet. Another method isuse a signal builder and create siganls according to the user and the method that we used is to implement industry standard drive cycles which are previosly used to test parameters of the vehicle.

Case 1:

Artemis motorway 130km/hr

Results case 1:

Artemis motorway 130km/hr

I ran the above drive cycle for my EV model and took the outputs given from speed, energy, tempreture and SOC scopes. The distance travelled by the vehicle in the drive cycle is also measured using the display block. Before simulation the run time was updated according to the drive cycle time 1068secs.

Speed scope:

From this scope we can see two signals. The blue signal represents the vehicles body speed and the yellow signal is the Artemis drive cycle data . As we can see that the longitudinal driver successfully maintains the drive cycle data , process it and controls the vehicle's speed according to the reference speed. the graph overlaps eachother effectively during acceleration and deacceleration.

From the energy scope we can see that for the first drive cycle :

Energy consumed is= 2789Wh

Remaining SOC is= 93.35%

Distance travelled is= 29.03kms

Motor tempreture= 899.9K

Controller tempreture= 635.4K

Results case 2:

Urban dynamometer driving schedule:

Speed scope:

Energy consumed is= 595.3Wh

Remining State of charge is= 98.32%

Distance travelled is= 13.82km

Motor tempreture is= 662.8K

Controller tempreture is= 409.6K

Results case 3:

WOT(Wide open throttle) 45km/hr

Speed scope:

Energy consumed is =924.7Wh

Distance travelled is= 6.5kms

Remaining state of charge is= 97.84%

Motor tempreture= 772.3K

Controller tempreture is=523K

Google drive link for model: https://drive.google.com/file/d/1MooCbMlsO6Fuouu_1ajl6iZn4WZhucOb/view?usp=sharing

Google drive link for assumed parameters: https://docs.google.com/spreadsheets/d/1Dxc3as8Zo_l_sl8tXrggD3rqvW51UlzN/edit?usp=sharing&ouid=104314629743700747481&rtpof=true&sd=true

CONCLUSION:

• Created a matlab model of an Electric rickshaw(three wheed passenger vehicle) using Li-ion battery. PM brushd DC motor
• Determined the variations of tempreture rise of motor and controller ,SOC% and energy consumed by the vehicle for all three refernce drive cycles
• For every respective cycle we saw the velocity profile following the givn drive cycle data and attaining close value to the actual speed of the drive cycle.
• The SOC of the battery depends on various factors , the coefficient of thermal mass, rolling resistance, gear ratio, By varying these parameters we can change the SOC of the battery'
• The tempreture of the system depends on the thermal mass mentioned in the motor block and the H-bridge varying the thermal mass we can change the tempreture.
• In real time application, The motor, battery and controller tempreture is controlled by air cooling . Hence the tempreture of components is not increased .
• The battery powered rickshaw will be the most popular mode of transport in the future.