Final Project: Electric Rickshaw modelling

Objective:

• Simulate a Rear wheel driven E-rickshaw.
• For any three standard driving cycles show Energy consumption, Temperature rise of motor and controller.
• For 100 km, constant speed driving at 45 kmph, Calculate Energy consumption and Temeprature rise of motor and controller.
• Battery State of Charge (SOC) for all the cases.

Introduction:

Electric rickshaws 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 to petrol/diesel and CNG auto rickshaws. They are three-wheelers powered by an electric motor ranging from 650 to 1400 Watts. They are mostly manufactured in India and China. Battery-run rickshaws could be a low-emitter complementary transport for the low-income people, who suffer most from a lack of transport facility.

Directly solar-powered e- rickshaw - fitted with solar panels is a type of E-rickshaw. A directly solar-powered rickshaw is an electric auto rickshaw driven solely by one or more electric motors, powered by solar panels mounted on the vehicle and capable of operating while the vehicle is in motion. Theoretically, solar panels could provide power directly to the motors without the need for batteries, but in reality this would be an improbable design choice for a rickshaw, given its intended purpose. In e-rickshaws, however solar panels are not effective and are not frequently used. But solar rickshaw is most commonly used to describe battery electric rickshaws whose batteries are indirectly solar-charged.

Powertrain of an E-Rickshaw

Figure-1

Basic components of Powertrain are,

1. Battery
2. Motor
3. Controller
4. Transmission system
5. Vehicle body

Design in Simulink:

Given:

• Rear wheel driven
• PM brushed type DC motor
• Drive cycles

Procedure:

• Drive Cycle:

Blocks used

Drive cycle

Multiport switch

First choose the Drive cycle which the vehicle will follow. Maximum speed achieved in that drive cycle will decide the design parameters for the motor. Drive cycles taken here are FTP75, Wide open throttle (WOT), Custom data set drive cycle and a contant 45Km/Hr. A multiport switch decides which drive cycle to operate.

Figure-2 FTP75 Drive cycle

Figure-3 Custom data set

Figure-4 Wide open throttle (WOT)

Figure-5 Simulink blockset for input drive cycles

• Vehicle Dynamics

Blocks used

Vehicle body

Simple gear

Tire (Magic)

Rotational Free End

PS Terminator

PS constant

After getting an idea about the maximum speed from the drive cycle, we calculate the Traction force required,

Ft = Traction force = Aerodynamic drag force + Rolling resistance force + Hill climbing force + Acceleration force

Road inclination angle (beta) is considered 0 by using PS constant block and giving value 0. Therefore hill climbing force is 0. Wind velocity (w) is also considered 0

Aerodynamic drag force = Fd = 0.5*(density of air)*(Frontal area)*(Coefficient of drag)*(Velocity^2)

Rolling resistance force = Fr = (Coefficient of rolling resistance)*(weight of vehicle)

Figure-6 Vehicle dynamics blockset

Using Vehicle body block, we can give the mass, drag and C.G values. Pitch is not considered. Connections V, NF, and NR are physical signal output ports for vehicle velocity and front and rear normal wheel forces, respectively. Connection H is the mechanical translational conserving port associated with the horizontal motion of the vehicle body

Figure-7 Mass and C.G values of the body

Figure-8 Drag values

Using Tire (magical), We can give the radiu of the tire, Rolling resistance coefficients and Longitudnal force acting on it. 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. Dynamics is not considered.

Figure-9 Tire peak longitudnal force

Figure-10 Tire radius

Figure-11 Tire coefficient of rolling resistance

Simple gear box is used with a gear ratio of 3. Cnnection B is connected to the motor shaft and Connection F is connected to rear axle because its a rear wheel drive system.

Figure-12 Gear ratio

Figure-13 Forces calculation

• Motor and its Controller

Blocks used

Controlled voltage source

Controlled PWM voltage

H-Bridge with thermal port

DC motor with thermal port

Temperature sensor

Current sensor

Electrical, Mechanical and Thermal referance

Maximum velocity (V) from drive cycle taken is 27.7 m/s

V = (pi*diameter of tire * rpm of tire)/60

N = rpm of tire = 1313

Nm = rated rpm = Gear ratio * N = 3939

if speed regulation is 15%, No load rpm = 4705

Figure-14 Motor and its controller blockset

Dc motor to be considered is PM brushed type motor. After calculating the Traction power of the wheel, slip and efficiencies are considered and finally mechanical power of the DC motor is calculated. Similarly using whel rpm and speed regulation, motor rated speed and no load speed can be calculated.

Figure-15 DC motor electrical parameters

Figure-16 DC motor thermal parameters

Now because we are using a DC motor and the battery supply is also DC, we need a DC/DC converter. In this simulation I have used H-bridge. We need a Pulse width modulation (PWM) signal to operate H-bridge. Also to operate the H- bridge we need to supply the power. Here there are two options External and Internal. We have used Internal power supply. PWM signal amplitude is kept at 5V, which means if the voltage supply is more than 5V, Switch is kept ON.

Figure-17 H-bridge Simulation mode

Figure-18 PWM signal amplitude

Figure-19 H-bridge output voltage

Figure-20 H-bridge thermal mass

These PWM signal are created using PWM controlled voltage. For more time samples, frequency is kept high. Duty cycle input voltage is specified and output voltage is specified as 120V.

Figure-21 PWM frequency

Figure-22 Input voltage for 100% duty cycle

Figure-23 PWM output voltage

Signal to the PWM controlled voltage is coming from the error signal from controller as brake and acceleration command. These command are feeded to PWM controlled voltage through controlled voltage source.

• Battery

Figure-24 Battery blockset

Blocks used

Controlled current source

Li-ion battery

Bus selector

Integrator

Display and Scope

Divide

Because we are using an internal power supply system in the motor and its controller circuit, we extract the current using a current sensor and give it to the battery using controlled current source. Now the voltage of the battery is decided to be 120V and rated capacity is 120Ah. Battery response time is kept as 5 sec. Sate of charge (SOC), Voltage and Current are extracted using a Bus selector and Energy consumed and Battery state of charge are plotted.

Power = V*I = Energy consumed per unit time

Figure-25 Battery parameters

• Controller or Longitudnal Driver

Referance velocity is the velocity coming from drive cycle. Velocity feedback is taken from the vehicle dynamics. Using a PI controller the error is configured and the value is given to either acceleration or deacceleration command. Grade is not considered here. PI values are taken as default and are shown below,

Figure-26 PI values

Results:

• Case-1: For FTP75 drive cycle

Figure-27 Drive cycle and Actual velocity

Figure-28 Motor temperature

Figure-29 Motor controller temperature

Figure-30 Battery State of charge (SOC)

• Case-2 Custom data Drive cycle

Figure-31 Drive cycle and Actual velocity

Figure-32 Motor temperature

Figure-33 Motor controller temperature

Figure-34 Battery State of charge (SOC)

• Case-3 Constant velocity of 45 Km/hr or 12.5 m/s for 100 Km

Figure-35 Drive cycle and Actual velocity

Figure-36 Motor temperature

Figure-37 Motor controller temperature

Figure-38 Battery State of charge (SOC)

Figure-39 Final E-rickshaw blockset

Table-1

Parameters	FTP75	Custom cycle	Constant 12.5 m/s or 45Km/hr
Motor temperature (K)	329.5	307.3	339.6
Motor controller temperature (K)	305	300.2	307
Distance covered (Km)	17.73	2.068	124.8
Energy consumed (KWh)	1.975	0.201	10.48
Battery SOC at the end	84.5	98.4	18
Simulation time (s)	2500	200	10000

Conclusion:

• For FTP75 drive cycle, If we run the simulation for 2500 sec, distance covered by the vehicle will be 17.73 Km. After covering 17.73 Km, battery will be discharged by 15.5 % which means still 84.5% of the the battery SOC will be present. Motor temperature will be raised to 56.35 deg C (or 329.5K) and the controller temperature will be 31.85 deg C (or 305 K). Energy consumed will be 1.975 KWh.
• For Custom drive cycle, If we run the simulation for 200 sec, distance covered by the vehicle will be 2.068 Km. After covering 2.068 Km, battery will be discharged by 1.6 % which means still 98.4% of the the battery SOC will be present. Motor temperature will be raised to 34.15 deg C (or 307.3K) and the controller temperature will be 27.05 deg C (or 300.2 K). Energy consumed will be 0.201 KWh.
• For constant velocity (12.5 m/s or 45 Km/hr) drive cycle, If we run the simulation for 10000 sec, distance covered by the vehicle will be 124.8 Km. After covering 124.8 Km, battery will be discharged by 82 % which means still 18% of the the battery SOC will be present. Motor temperature will be raised to 66.45 deg C (or 339.6K) and the controller temperature will be 33.85 deg C (or 307 K). Energy consumed will be 10.48 KWh.
• Now if the motor and its controller thermal mass is increased, there temperature will come down. If the rated capacity of the battery will be decreased, battery will be discharged faster and energy consumed will be lower.
• Simulink file- https://drive.google.com/file/d/1E8cMltZlaEREivsqwWXxq23Z8wMIQJgx/view?usp=sharing
• Custom drive cycle - https://docs.google.com/spreadsheets/d/1Y1CWtXQPx0cEh2Wnmw5DyKv3M-WPp4mx/edit?usp=sharing&ouid=101631644608920724054&rtpof=true&sd=true
• Traction fore calculation - https://docs.google.com/spreadsheets/d/1AbrgnuL-jFnEb71jD0-ZR-8jMqwJ-4Bv/edit?usp=sharing&ouid=101631644608920724054&rtpof=true&sd=true