Final Project: Electric Rickshaw modelling

1) Create 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.
• For any three standard driving cycles show energy consumption, temperature rise of motor and controller for 100 km constant speed driving at 45 kmph.

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-tuk or e-rickshaws or auto) have been becoming more popular in some cities since 2008 as an alternate 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 and 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.

SYSTEM LEVEL CONFIGURATION :

There are major components which is using in EV

• Drive cycle.
• Driver.
• H-bridge.
• DC motor.
• Battery source.
• Controlled PWM voltage.
• Vehicle and others.

BLOCK DIAGRAM :

• In the designed electric rickshaw main blocks are battery, drive cycle, controller, DC motor, vehicle body and transmission system. Drive cycle is the input data like how a human drive his actual vehicle here FTP75, WOT and 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 states 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 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 drivers input of a vehicle, it replaced 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, FTP&% etc.

FTP75 :

• Generates a standard or user specified longitudinal drive cycle. The block output is the vehicle longitudinal speed. It can import cycles from
• Predefined sources.
• Workspace variables, including arrays and time series objects.
• mat,xls,xlsx or txt files.

Using the default tracking parameters to identify drive cycles faults within specified speed and time tolerances.

WIDE OPEN THROTTLE (WOT) :

MANUALLY PREPARED DRIVE CYCLE :

LINK : https://docs.google.com/spreadsheets/d/1r06IOw-kpok5foj_Av5ouuoKap3tz3bv/edit?usp=sharing&ouid=117055300290228577873&rtpof=true&sd=true

DRIVER CONTROLLER :

• A parametric longitudinal speed tracking controller for generating normalised 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 the priority for the input commands that are disable, hold and override. Drive cycle is connected to a longitudinal driver, it has six ports namely velocity reference, velocity feedback,grade,info, Acceleration and deceleration.

• Velref is given by the drive cycle data and velfdbk is given by the output of the motor. These two will get cmpared 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 gradability to the driver block. This blocks helps to generate the drivers conditions of the vehicle using the driver cycle block. I have used default parameters and control type PI.

MOTOR AND CONTROLLER :

MOTOR TYPE DC MOTOR (BRUSHED TYPE MOTOR) :

• This block represents the electrical and torque characteristics of a DC motor includes thermal port to sence 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 shall 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 positive and negative 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.
• The motor 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 has two main parts named PWM voltage generator and H-bridge.
• Input 1 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 his H-bridge will give an output from the positive and negative terminals of it. These negative and 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.

CONTROLLED PWM VOLTAGE SOURCE :

• 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 positive and negative reference ports and PS input to specify the input value.

• At time zero the pulse is initiated 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.

POWER CONVERTER :

H-BRIDGE :

H-bridge is used as a DC-DC converter ;

• This block represents an H-bridge motor drive. This block can be driven by the controlled PWM voltage block is 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 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.

SOLVER CONFIGURATION :

Defines solver settings to use for simulation.

REFERENCE :

• Electrical reference is used to ground all the electrical connections.
• Mechanical rotational reference is used to ground all the mechanical rotational parts.
• Thermal reference is used to ground the thermal sensor.

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 has two stage one is charging and another one is discharging state. The battery is of 75ah capacity. The nominal voltage of battery is 330V. Initial SOC is of 100%.

The battery as a series internal resistance plus a charge dependent voltage source defined by,

V = `V_(nom.SOC)/(1 - beta.(1-SOC)`

Where,

SOC is the state of charge,

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.

VEHICLE BODY AND 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 inside the vehicle body and transmission system and in the main design it is referred just only as a transmission system.
• The gear output is given to axles of rear tires in the circuit 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 and 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 were we can assign wind velocity and inclination angle as per requirement. Velocity is the output port were we can get at which speed the vehicle is moving. The velocity is taken out to get the distance travelled and state of charge.

VEHICLE BODY :

WHEELS :

• Represents the longitudinal behaviour of a high way tire characterized by the tire magic formula. This 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 the normal force acting on the tire.
• The force is considered positive if it acts downwards. Connection S is 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.

INERTIA :

• This block represents an ideal mechanical rotational inertia. This 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 accecelerated in the positive direction.

SIMPLE GEAR :

• Gear ratio represents a fixed ratio gear or gear box. No inertia or compliance is modeled in this block. You can optionally include gear m,eshing 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 varients.
• Output shaft rotates in same direction of the input shaft. Base is connected to the motor shaft and the follower is connected to the rear wheel drive.

RESULTS :

1) For FTP75 Drive cycle :

By running the vehicle with FTP75 Drive cycle for 2474 sec, the total distance travelled is 5.698km.

• The actual speed is approximately followed the 90% of the reference drive cycle.

2) For WOT drive cycle :

By running the vehicle with WOT drive cycle for 200sec, the distance travelled is 0.002567 km.

• The actual speed is approximately followed the 85% of reference drive cycle.
• Energy consumed by the battery is increased linearly till 100 second to approx 1050Wh and then reduced gradually due to back emf and finally at the end of the cycle, energy consumption is reached to 900Wh.

3) For manually prepared drive cycle :

To increase the speed of the vehicle, the input voltage amplitude is applied to 400V. By running the vehicle with manually prepared drive cycle for 200 sec the distannce travelled is 1.478km.

Conclusion :

• Matlab model of an electric rickshaw is created. It is simulated for three driving cycles and its results are analysed.
• In real time application the motor, battery and controller temperature is controlled by air cooling. Hence the temperature of this components is not increased to this extent.
• Since we have'nt used any cooling system in the model. In the real time application the motor temperature is less than 100C.