Electric Rickshaw modelling

Aim: To model and simulate Electric Rickshaw.

Objective:

• Rear-wheel drive-by PM brushed type motor.
• Simulation for three drive cycles.
• Energy consumption, temperature rise and controller parameters to be display as a result.

Theory:

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/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, only a few other countries manufacture these vehicles. Battery-run rickshaws could be a low-emitter complimentary transport for the low-income people, who suffer most from a lack of transport facility if introduced in a systematic manner according to experts.

Design and construction:

These rickshaws have an M.S(Mild Steel) tubular Chassis, consisting of three wheels with a differential mechanism the rear wheels. The motor is a brushless DC motor manufactured mostly in India and China. The electrical system used in the Indian version is 48V and in Bangladesh is 60V. The body design from the most popular Chinese version is of very thin iron or aluminium sheets. Vehicles made in fibre are also popular because of their strength and durability, resulting in low maintenance, especially in India. The body design is varied from load carriers, passenger vehicles with no roof, to full body with windshield for drivers comfort. It consists of a controller unit. They are sold on the basis of voltage supplied and current output, also the number of MOSFET (metal oxide field-effect transistors) used. The battery used is mostly a lead-acid battery with a life of 6–12 months. Deep cycle batteries designed for electric vehicles are rarely used. The weight of the electric car has also been a recurring design difficulty in them.

Chasis of Electric Rickshaw:

Specifications:

• MAX. SPEED<25Kmph
• MILEAGE 100 Km
• SEATING/LOAD CAPACITYD+4 Passenger/40 Kg
• BATTERY CAPACITY100 Ah
• BATTERY TYPELead Acid Battery
• TYRE (F+R)3x17”, 6PR
• MTOR TYPEBLDC Direct Drive Motor
• MOTOR INPUT VOLTAGE48V DC
• BRAKE (F+R) 130 mm Dia (Drum Type)
• CHARGERCompact & Easy to use 48V-12A/15,3-Stages SMPS Charger
• SPEEDOMETERAnalog
• STARTING SYSTEMElectric Start
• FRONT SHOCK ABSORBERHydraulic (Telescopic Type)
• REAR SHOCK ABSORBERLeaf Spring + Hydraulic (Telescopic Type) With Spring
• CHASSIS TYPESheet Metal, Spoke Type
• GROSS VEHICLE WEIGHTComfort 735 Kg

Dimensions:

• L X W X H2790 X 1000 X 1800 mm
• WHEEL BASE 1780 mm
• TURNING RADIUS 2755 mm
• GROUND CLEARANCE235 mm

Matlab model of Electric Rickshaw:

Blocks used in this model:

1. Tire(magic formula)
2. Vehicle body
3. Dc motor
4. H-Bridge converter
5. Controlled PMW voltage
6. PID controller
7. Battery
8. Controlled current source
9. Current, Voltage sensors
10. Drive cycle( FTP75,WOT), Signal builder

Blocks explanation:

1.Tire(magic formula)

The Tire (Magic Formula) block models a tire with longitudinal behaviour given by the Magic Formula, an empirical equation based on four fitting coefficients. The block can model tire dynamics under constant or variable pavement conditions. The longitudinal direction of the tire is the same as its direction of motion as it rolls on the pavement. This block is a structural component based on the Tire-Road Interaction (Magic Formula) block. To increase the fidelity of the tire model, you can specify properties such as tire compliance, inertia, and rolling resistance. However, these properties increase the complexity of the tire model and can slow down the simulation. Consider ignoring tire compliance and inertia if simulating the model in real-time or if preparing the model for hardware-in-the-loop (HIL) simulation.

Ports: N - Normal force on the wheels.

S - Slip angle between tire and road

H - Wheel hub

A - Axle on which tires sits on

2.Vehicle body

The Vehicle Body block represents a two-axle vehicle body in longitudinal motion. The vehicle can have the same or a different number of wheels on each axle. For example, two wheels on the front axle and one wheel on the rear axle. The vehicle wheels are assumed identical in size. The vehicle can also have a centre of gravity (CG) that is at or below the plane of travel. The block accounts for body mass, aerodynamic drag, road incline, and weight distribution between axles due to acceleration and road profile. Optionally include pitch and suspension dynamics. The vehicle does not move vertically relative to the ground. The block has an option to include an externally defined mass and an externally defined inertia. The mass, inertia, and centre of gravity of the vehicle body can vary over the course of simulation in response to system changes.

Input ports:

• W - Headwind speed (m/s)
• beta - Road incline angle(rad)
• CG - Centre of gravity(m)
• M - Mass(kg)
• J - External moment of inertia(kg*m^2)

Output ports:

• V - Longitudinal velocity(m/s)
• NF - Front axle normal force(N)
• NR - Rear axle normal force(N)

Conserving port:

• H - Horizontal motion

3.DC motor

The DC Motor block represents the electrical and torque characteristics of a DC motor using the following equivalent circuit model:

The resistor R corresponds to the resistance you specify in the Armature resistance parameter. The inductor L corresponds to the inductance you specify in the Armature inductance parameter. DC motor block is used to supply propulsion power to the wheel through the gearbox. There are various types of DC motor block such as BLDC, PMDC, etc based on the propulsion requirement proper motor is used as per the voltage supply conditions.

Electrical ports:

• -: Negative terminal
• +: Positive terminal

Mechanical ports:

• R - Motor rotor
• C - Motor case

As DC motor block contains two parts one is electrical and another is mechanical. The electrical part is connected to the controller port and the machine is connected to the gearbox and electrical reference. The parameters of the DC motor can be changed as per the required conditions. Here we have chosen as rated power and no-load speed. As the rated power in an electric vehicle is in kW so we change W to kW and it is a range of 50-100 we have kept here as 50kW of rated power. According to vehicle speed and gear ratio rated speed can be changed here we have taken as 3000rpm as the rated speed of the motor and no-load speed as 5000 rpm. The battery pack contains various cells of 3.6kW of power each and are connected in series and parallel combination for supplying the power supply voltage as per the rated power. Here we have taken the rated DC supply voltage as 80 V.

4.H-Bridge converter

The H-Bridge block represents an H-bridge motor driver. The block has the following two Simulation mode options:

Ports:

• -: Negative load connection port
• +:Positive load connection port
• V-:Negative voltage connection
• V+:Positive voltage connection
• PWM: pulse width modulated signal
• ref: Reference
• REV: Reverse
• BRK: Brake
• H: Thermal

5.Controlled PMW voltage

The Controlled PWM Voltage block represents a pulse-width modulated (PWM) voltage source. The block has two modelling variants, accessible by right-clicking the block in your block diagram and then selecting the appropriate option from the context menu, under Simscape >Block choices:

For the Electrical input ports variant of the block, the demanded duty cycle is

where:

Explanation:

• As we know transmission is the main part of the vehicle which is used to supply the propulsion powers from the motor and the battery to the wheels.
• Under transmission, the number of components comes which are wheels, gearbox, throttle, power input etc.
• In this transmission subsystem blocks used are Tire and vehicle body.
• There are 3 tire blocks used as 3 wheels of the rickshaw and here we have connected the gearbox with the rear wheel to make it a rear-wheel drive.
• The vehicle body block is been connected to these wheels by all the input and output ports.
• In-vehicle body block we have connected as ps constant block to beta and wind velocity as we have assumed both as zero and hub motor port is also connected with the wheels H port.

2. DC Motor system.

Explanation:

• Here we used a DC motor as a power source to the gearbox.
• Here also we have enabled the thermal port to get the temperature output while the motor is running to give power supply to the gearbox.
• Here we have used inertia block to give the initial start in a positive direction to the shaft which is connected between motor and gearbox.

3. Motor controller.

Explanation:

• This motor controller subsystem contains H-Bridge and a Controlled PWM Voltage block.
• H-Bridge block is used to supply the power from the battery to the DC motor.
• H-Bridge has 4 switches that give the controlled DC voltage supply to the DC motor and we can also control the supply of voltages.
• Here we have enabled the thermal output of the H-bridge controller to get the temperature output of the controller while the vehicle is in motion.
• In H-Bridge we have control on PWM voltage, Reverse and braking effect also.
• As below we can see block parameters, for simulation mode we have two options internal and external as we choose internally we have a choice of PWM mode and averaged mode.
• In PWM mode the simulation time increases drastically as if the simulation time is of 5 secs then PWM mode is effective but as now our simulation time is in mins or hours so here averaged mode is been chosen as it is faster compared to PWM mode.
• Also, we have kept regenerative mode enable and load current characteristics as smoothed.
• Also, we have to change the output voltage amplitude to the voltage we have supplied to the DC motor.
• As from the Controlled PWM voltage block which is connected to the input PWM Pin in the H-Bridge block.
• This block will apply pulses and based on these pulses from the fixed battery voltage variable output voltage will be available to the motor and the motor speed and motor torque are changed.
• So basically this subsystem will control the power supply to the DC motor using the following blocks.

Steps for enabling thermal output of H-Bridge:

First, select the block and right-click on the block we will get multiple options from which we have to select simscape>> block choices>> show thermal port.

3.SOC calculation.

Explanation:

• Here in this subsystem, there is the number of blocks used are rate transition, gain, constant, add, etc.
• Rate transition block takes input from the controlled current source block as soc input signals and do a sampling of the signals and gives to gain block.
• Gain block multiplies the sampling signal with the rated voltage and gives it to the discrete-time integrator block.
• Discrete-time integrator block integrates the signal and adds it to the constant given and supply is to the gain block again.
• Gain block multiplies it with the 100 and gives it to the SOC output.

4. Battery pack system.

Explanation:

• Here we have used a lithium-ion battery block to give the current and voltage supply to the rickshaw.
• A controlled current source block is used so that there is no excessive load on the battery if there is a change in speed or torque value.
• We have a bus selector block that takes the battery performance and gives us its SOC state, Current discharge and voltage supplied by the battery.

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Case-1: For FTP75 drive cycle:

Input model:

Input parameters:

1- PID block parameters

2- DC Motor:

3- H-Bridge block:

4- Controlled PWM voltage block:

Output:

1- Distance travelled:

Result:

• Distance travelled by the vehicle is 17.76km for the applied voltage of 60V.
• This distance is calculated using velocity feedback given.

2- Velocity:

Result:

• Here the input given to the vehicle velocity was the FTP75 drive cycle.
• Here we can observe that velocity by the vehicle is approximately the same as of standard drive cycle given as input.
• As here we can observe while steep braking of the vehicle, our vehicle takes more time for the braking as the standard drive cycle.
• While acceleration also vehicle takes comparatively more time to get at that peak velocity.
• As per the standard drive cycle peak velocity attained by the vehicle is 25m/s but the velocity traced by the vehicle is about 23-24m/s which is almost similar.

3- Temperature output of Motor controller(H-Bridge):

Result:

• Here as per the drive cycle as speed increase the temperature also increases and as hen vehicle deaccelerates temperature all decreases.
• From 1400sec to 2100 sec we can observe there is a constant path which means there is no change in temperature.
• The initial temperature of the controller was 298.15 and the final temperature after completing the drive cycle was 298.17.

4- DC motor temperature output:

Result:

• Here as per the drive cycle as speed increase the temperature also increases and as hen vehicle deaccelerates temperature all decreases.
• From 1400sec to 2100 sec we can observe there is a constant path which means there is no change in temperature.
• The initial temperature of the controller was 298 and the final temperature after completing the drive cycle was 385.
• The temperature rise is more as compared to the controller temperature.

5- SOC:

Result:

• Here we gave the input as FTP75 drive cycle and run the model for 2474 sec.
• So here we can observe the SOC of the battery is been discharged by 1.5% of the total 100% battery charge.
• SOC of the battery is 99.2% after the drive cycle is completed.
• As we observe the graph there is no steady-state in the signal sometimes it is going up and sometimes it's going down, while the curve is going down means the battery is getting discharged and while the curve is going up it means the battery is getting charged again.
• The battery is getting charged due to regenerative braking.
• The maximum discharge SOC of the battery is 98.5.
• From 1200sec to 2000 sec the battery is discharging continuously.

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Case-2: For WOT drive cycle:

Input parameters:

1-Drive cycle(WOT)

Output:

1- Distance travelled:

Result:

• Distance travelled by the vehicle is 0.4243km for the applied voltage of 60V.
• This distance is calculated using velocity feedback given.

2- Velocity:

Result:

• Here for WOT, the output which we are getting is almost similar to the value which we gave to the block parameters.
• While acceleration signal is getting exponentially increased and it is taking almost 18 sec to achieve 45kmph or 16.66m/s of speed which we gave as the WOT input condition.
• Also while deacceleration the vehicle takes more time to come at rest. It almost takes 12sec to deaccelerate the vehicle to 0.

3- Temperature output of Motor controller(H-Bridge):

Result:

• Here as we can observe temperature rise when the vehicles accelerated and it is constant when the vehicle speed is constant.
• If we compare it with WOT drive cycle we can observe that while deceleration also there is a rise in temp this is due to regenerative braking effect as the motor act as a generator at that time and it charges the battery and the controller are controlling the generator parameters.
• The maximum temperature attend by the controller here is 298.152.

4- DC motor temperature output:

Result:

• Here as we can observe temperature rise when the vehicles accelerated and it is constant when the vehicle speed is constant.
• If we compare it with WOT drive cycle we can observe that while deceleration also there is a rise in temp this is due to regenerative braking effect as the motor act as a generator at that time and it charges the battery and the controller are controlling the generator parameters.
• The maximum temperature attends by the motor is 305.5.

5-SOC:

Result:

• Here for the WOT drive cycle, the output for SOC we are getting is the battery is discharged by 0.2% out of 100% of the total charge.

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Case-3: For 45kmph constant speed up to 100 km using signal builder block:

Input model:

Input parameter:

Output:

1-Distance travelled:

Result:

• Distance travelled by the vehicle is 99.96km for the applied voltage of 60V.
• This distance is calculated using velocity feedback given.

2- Velocity:

Result:

• Here we can observe that as per the input value output is 100% accurate and we are achieving the 45kmph of constant speed for 100km of range.

3- Temperature output of Motor controller(H-Bridge):

Result:

• We can observe here is that as for the constant speed the temperature of the controller increases linearly.
• The maximum temperature of the controller attained is 298.151.
• As the distance travelled increases temperature of the controller increases.

4- DC motor temperature output:

Result:

• We can observe here is that as for the constant speed the temperature of the DC motor increases linearly.
• The maximum temperature of the DC motor attained is 301.8.
• As the distance travelled increases temperature of the DC motor increases.

5- SOC:

Result:

• Here we can observe the SOC of the battery is constant throughout the 100 km range.
• This is because there was no change in the velocity of the vehicle.
• SOC is 100% after the 100km of range.

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Conclusion:

• We successfully modelled and simulated the Electric Rickshaw.
• Results are been plotted for the temperature of controller, energy consumption, the temperature of DC motor and also 100km range at a constant speed of 45 kmph.