Final Project: Electric Rickshaw modelling

AIM : Design of an Electric Rickshaw using MATLAB Simulink.

ABSTRACT :

In this project, we going to build the MATLAB model of the ELECTRIC RICKHAEW by using a PM brushed type DC motor and a suitable Lithium-Ion battery for the motor. Before that, we will know about what is Electric RICKHAEW, how it's works and the benefits of EV RICKHAE. Then we make an actual EV RICKHAEW model in SIMULINK with suitable blocks from the powertrain block set. My main motto is to check "how my RICKHAEW performs for any three standard driving cycles showing energy consumption, the temperature rise of motor and controller for vehicle cover around 100 km at constant speed driving 45 kmph.

OBJECTIVES :

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.
• 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.

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 vehicle engineer has to be like the following :

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

Introductio:

• E-rickshaw is designed in MATLAB Simulink. In the designed electric rickshaw main blocks are battery, drive cycle, controlled, DC Motor, Vehicle body and transmission system. Drive cycle is the input of human effort that how he is going to drive his actual cycle. We can use drive cycle like FTP75, WOT and manually drive cycle.
• The main objective of this project is to obtain speed by driver, to estimate the temperature of motor and controller, to estimate the state of charge (SOC) and distance travel by the vehicle. There is a SOC block that will estimate the state of charge of battery, distance is calculated by speed and time parameter for all the three Drive cycle.

PROCEDURE :

(1) Vehicle Body Subsystem Model :

• 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 how it inside the vehicle body and transmission system and in the main design, it is referred just only as a transmission system.
• Here I created a Rear wheel drive transmission system.

• The gear output is given to axels of Rear tires, in the circuit it is shown 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, 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 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 the get the distance travelled and state of charge.

Tire :

• Represents the longitudinal behavior of a highway tire characterized by the tire Magic Formula. The 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.
• Connecting A is the mechanical rotational conserving port for the wheel axle. Connecting H is the mechanical translational conserving port for the wheel hub through which the thrust developed by the tire is applied to the vehicle. Connecting N is a physical signal input port that applies the normal force acting on the tire. The force is considered positive if it acts down wards.
• Connecting S is a 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.

Vehicle Body :

• This block basically represents a two-axle vehicle body in longitudinal motion. The block accounts for body mass, aerodynamic drag, road incline, weight distribution between axles due to acceleration road profile.
• Here, the connection H is the mechanical translational conserving port hub. NF & NR correspond to the output ports for nomral reaction forces on 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 vehicle).

(2) Motor & Power Converter Subsystem Model (With Temperature Sensor) :

H-Bridge :

• This block represents an H-bridge motor drive. The block can be driven by the Controlled PWM Voltage block in 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 HBridge blocks.
• If the REV port voltage is greater than the Reverse threshold voltage, then the output voltage polarity is reversed. If the BRK port voltage is greater than the Braking 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.

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 :

• Temperature Sensor is used to mesure the temperature of 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.

(3) Battery And Soc Subsystem Model :

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 stage one is charging and another one is discharging state. The battery is of 75Ah capacity.
  The Nominal voltage of battery is 330 V
  Initial SoC is of 100%
• 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 the giving it to the rate transition and then to gain where 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 percentage of battery.

(4)Motor and control design:

DC 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 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.

• TheMotor 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 we designed had 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 this Hbridge will give an output from the positive and negative terminals of it. These negative & 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.

Simulink Model of Electric Rickshaw :

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.

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.

Output Plots :

• By running the Vehicle with FTP75 Drive cycle for 2474 sec. the distance travelled is 17.79km.

Output drive cycle:

Current response:

Battery SOC response:

Voltage response:

Motor Temperature:

• The actual Speed is approximately followed the 90% of reference Drive cycle.
• The Temperature of Motor is increased to 425C.

For WOT Drive Cycle :

• By running the Vehicle with WOT Drive cycle for 200 sec. the distance travelled is 0.5048km.

WOT cycle response:

SOC and Current:

Voltage response:

Motor Temperature:

• The actual Speed is approximately followed the 85% of reference Drive cycle.
• The SoC% of the battery is reduced to 91% at 100th sec and after that 3 sec., the battery get charged by by back EMF.
• The Temperature of Motor is increased to 322C.

For Manually prepared Drive Cycle :

• To increase the speed of the vehicle, the output voltage amplitude is applied to 400 V.
• By running the Vehicle with Manually prepared Drive cycle for 8000 sec. the distance travelled is 100km.

Manually prepared Drive Cycle response:

Input speed:

SOC and Current:

Voltage response:

Motor Temperature:

• The actual path of the speed is approximately followed the of reference Drive cycle as above.
• The SoC% of the battery is reduced to 85%.
• The Temperature of Motor is increased to 355C.

CONCLUSION :

• Here I have compromised with the temperature of Motor and controller to achieve vehicle speed is near to reference speeds. Since I haven’t used any cooling system in the model. In the real time application, the motor temperature is less than 100 C.
• In the real time application, the motor, battery & controller temperature is controlled by air cooling. Hence, the temperature of this components is not increased to this extent.
• Hence, Created a MATLAB model of an Electric Rickshaw (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, Manually prepared).
• This Battery powered Rickshaw will be the most popular mode of transport in the future.