Final Project: Electric Rickshaw modelling

AIM: Create a detailed MATLAB model of an electric rickshaw (three-wheel passenger vehicle).

INTRODUCTION: Electric rickshaws (also known as electric tuk-tuks or e-rickshaws or toto or e-tricycles) are small 3-wheeled vehicles powered by an electric motor and battery ranging from 650 to 1400 Watts. They save on fuel costs compared to auto rickshaws while offering greater ease of use than pulled rickshaws. This has led to their popularity and widened acceptance in some cities since 2008.

The electrical system used in the Indian version is 48VDC can run 90– 100 km/full charge, top speed of 25 km/hour, and this electric motor power ranges from 650-1400 Watts; the battery takes 8–10 hrs to become fully charged. The basic seating capacity is driver plus 4 passenger total of 5 persons.

Here basically, the e-rickshaw is designed in CREO and MATLAB Simulink. In the designed electric rickshaw main blocks are the battery, drive cycle, controlled, DC Motor, Vehicle body, and transmission system. The Drive cycle is the input of human effort that how he is going to drive his actual cycle. We can use drive cycles like FTP75, WOT, or US06.

The main objective of this project is to obtain the speed of the driver, to estimate the temperature of the motor and controller, and to estimate the state of charge (SOC) and distance traveled by the vehicle. There is a SOC block that will estimate the state of charge of the battery, distance is calculated by speed and time parameters for all three Drive cycles.

METHODOLOGY:

• The electric vehicle consists of a battery, motors, and controller then it generates propulsion power.
• To design any vehicle 1st we have to calculate propulsion power, then the motor is selected.
• Lastly based on the motor rating or operating range and no km/charge we want to depend on everything battery capacity and then battery capacity is selected. So the Design flow of the vehicle engineer has to be like the following :

• Identify what amount of propulsion power is required.
• What is the best suitable motor for that propulsion power?
• Then type of battery and range of battery according to the range.

BLOCK DIAGRAM :

Design and Construction :

• These rickshaws have an M.S. (Mild Steel) tubular chassis, consisting of three wheels with a differential mechanism at 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 aluminum sheets. Vehicles made of fiber are also popular because of their strength and durability, resulting in low maintenance, especially in India.
• The body design is varied from load carriers, and 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.

General detail of E-Rickshaw -

• Battery Type Lithium Ion 330 V 75 Ah
• Vehicle Kerb weight 260 kgs
• Load capacity 340 kgs
• Vehicle speed 7 kmph
• Driving range 140 km (160 Ah)
• No of wheels per axel 2
• Frontal Area 91m
• Drag coefficient 5
• Wheel radius 306m
• Vertical load 3000 N
• Nominal Voltage 330 V
• Rated Capacity 75 Ah
• Initial SOC % 100
• Internal Resistance 5 ohm

SIMULINK MODEL:

1. SUBSYSTEM (VEHICLE BODY)

• The 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 the tires.
• The above diagram represents the vehicle body and three tires.
• Here I created a Rear wheel drive transmission system.
• The gear output is given to the axels of the Rear tires, in the circuit it is shown that the gear is connected to the Rear wheels and the 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's normal force port.
• The vehicle body has an H-Hub, S- Tire slip, N- Normal force, A- axel connection, wind velocity, and inclination angle. The tire 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 get the distance traveled and state of charge.

Tire :

Gear :

• Represents a fixed-ratio gear or gearbox. 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.

Vehicle Body :

• This block basically represents a two-axle vehicle body in longitudinal motion. The block accounts for - body mass, aerodynamic drag, road incline, and weight distribution between axles due to the acceleration road profile.
• Here, connection H is the mechanical translational conserving port hub. NF & NR correspond to the output ports for normal reaction forces on the front axle and rear axle wheels respectively.
• Connection V represents the actual output translational velocity of the vehicle. beta is the road inclination angle & W corresponds to the headwind speed (headwind - direction opposite to that of the vehicle). The gross weight is given to be 600 kg.
• The geometric parameters of the vehicle are given as -
• 

2. DC MOTOR:

• This block represents the electrical and torque characteristics of a DC motor including a Thermal port to sense the temperature of the 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 the 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

Controlled PWM Voltage :

• 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. Select Simulation mode as Averaged.

Temperature Sensor :

• A temperature Sensor is used to measure the temperature of the 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.

Solver Configuration :

Defines solver settings to use for simulation.

BATTERY AND SOC PART:

Battery :

• The battery is required to power the controller and motor. The controller uses the battery power according to produce the input given by the motor to obtain maximum speed. The battery is also used to power every electrical component in the vehicle.
• The Battery block implements a generic dynamic model that represents most popular types of rechargeable batteries.
• 

• The battery has two stages, one is charging and other one is discharging state. The battery is of 75Ah capacity.
  The Nominal voltage of the battery is 330 V
  Initial SoC is 100%
  The battery has a series of internal resistance plus a charge-dependent voltage source defined by :
  V=Vnom⋅SoC1−β⋅(1−SoC)V=Vnom⋅SoC1-β⋅(1-SoC)
• where SoC is the state of charge and Vnom is the nominal voltage. Coefficient beta is calculated to satisfy a user-defined data point [AH1, V1].
• The battery has a positive and negative terminal which is given the voltage-controlled source where the battery consumption is controlled by the motor controller and then it is given to the SOC block.

Battery State of Charge :

• 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 giving it to the rate transition and then to gain 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 a percentage of battery.
• The majority of blocks are simscape blocks where a physical to Simulink converter is used to convert the physical signal from simscape block to Simulink signal.

Controlled Current Source :

The Controlled Current Source block converts the Simulink input signal into an equivalent current source. The generated current is driven by the input signal of the block. The positive current direction is as shown by the arrow in the block icon.

We can initialize the Controlled Current Source block with a specific AC or DC current. If we want to start the simulation in a steady state, the block input must be connected to a signal starting as a sinusoidal or DC waveform corresponding to the initial values.

• Double click controlled current source and from drop down menu of measurement select current.
• Signal output will connect with scope by adding current signal to it.
• (+) the terminal will connect with the battery (-) terminal.

BUS Selector :

The Bus Selector block outputs the signals you select from the input bus. The block can output the selected elements separately or in a new virtual bus.

• Here just we have to manage the output and connected with different Scope Blocks.

PowerGUI :

The powergui block allows us to choose one of these methods to solve your circuit :

• Continuous, which uses a variable-step solver from Simulink
• Discretization of the electrical system for a solution at fixed time steps
• Continuous or discrete phasor solution

The powergui block also opens tools for steady-state and simulation results analysis and for advanced parameter design.

(4) Longitudinal Driver :

• Longitudinal Driver is an inbuilt block provided by the powertrain blockset.

• It is a parametric longitudinal speed tracking controller for generating normalized Acceleration and Braking commands based on reference and feedback velocities.
• The VelFdbk port corresponds to the feedback velocity. The actual velocity output given by the vehicle body is connected here. By comparing the actual (feedback) velocity with the reference velocity, the driver block generates acceleration and braking signals in order to minimize the error between the two concerned velocities.
• Grade corresponds to the grade angle. For this simulation, no inclination is considered and hence, a constant block with value 1 is connected.
• Info gives the output for the bus signal for different block calculations like differences in reference vehicle speed and vehicle speed, etc.
• AccelCmd & DecelCmd correspond to the acceleration and deceleration commands generated respectively and are connected to the corresponding ports of the Controlled PWM Voltage block.
• Here, the selected control type is PI. Accordingly, the block implements proportional-integral (PI) control with tracking windup and feed-forward gains.

REFERENCE VELOCITY DRIVE CYCLE:

• Drive cycle is assumed as the driver's input of a vehicle, it dictates how a driver will drive a vehicle. Here I 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 & US06 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) :

US06

Simulink Explanation :

• 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.

RESULTS :

Output Plots :

1. For FTP75 Drive Cycle :

• By running the Vehicle with FTP75 Drive cycle for 2474 sec. the distance travelled is 10.81KM

Temparature of motor and controller :

SOC:

WOT CYCLE :

• By running the Vehicle with WOT Drive cycle for 600 sec.
• 

TEMPARATURE OF MOTOR AND CONTROLLER:

• 

SOC:

FOR US06 CYCLE:

SOC:

TEMPRATURE OF MOTOR AND CONTROLLER:

COCLUSION:

• Here I created SIMULINK model for E-Rikshaw (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,US06).
• In this model , as we can see that temparature of motor and controller increses very rapidally which is compromised to achieve vehicle speed equal to reference speed ,As no cooling method is used in this model .In real e-rikshaw heat sinks, air cooler , fan is used to reduce the temparature drastically .
• This Battery powered Rickshaw will be the most popular mode of transport in the future.

**SIMULINK model is attached with the project**