Final Project: Electric Rickshaw modelling

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

Theory:

E-rickshaws are now fairly popular amongst Indian rickshaw drivers and have created new opportunities for people, as they require a minimum investment to earn a living. They offer huge returns in less time, are easy to operate, and have low maintenance and running costs. A lot of variants are available these days, most of them started as low-quality products and were imported from China. These days Indian e-rickshaws have been developed offering higher quality and better services at an equivalent cost. E rickshaws can provide a decent income since the battery charging cost is far lower than any other fuel, new material such as fiberglass has been introduced in them since the material provides high strength, and durability, and is lighter than metals.

E Rickshaws in India are built over tubular chassis, a body is kept light in weight to increase the life of the battery, the main electronic components that make the drive are the motor, controller, harness, batteries, and throttle. The mismatch between any of these components is undesirable and may reduce performance.

DESIGN and CONSTRUCTION:

Mahindra Treo comes in a distinctive shade of blue. It offers enhanced comfort levels for passengers with better ingress and egress. The Treo measures 2,746mm in length, 1,350mm in width, and 1,750mm in height, while the wheelbase measures 2,050mm. It gets a turning radius of  2.9m and a curbs weight of 340 kg. Its space frame architecture with corrosion-free SMC panels presents a dent-free body and easy repair or replacement. Mahindra Treo gets its battery pack positioned above the rear axle and gets fatter 12” tires as compared to those seen on the e-Alfa Mini. Tires present better maneuverability on Indian road conditions while clutchless drive technology allows for a quieter vibration-free ride. It is seen with a hydraulic brake set up allowing for a top speed of 45 kmph. Charging time is 3 hours and 50 minutes to offer a range of 110 km on a single charge. The Mahindra Treo also comes in with a feature to swap batteries once they are fully discharged.

PROCEDURE:

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 the tires.
• Below is a diagram that is how it is how 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 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.

Tier:

• 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.

                

• 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. 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.

Gear

    

• Represents a fixed-ratio gear or gear box. 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, weight distribution between axles due to the 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 a vehicle). The gross weight is given to be 600 kg.
• The geometric parameters of the vehicle are given as:

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.

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.

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.

Solver Configuration

           

Defines solver settings to use for simulation.

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%

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.
• The majority of blocks are simscape blocks where 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 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.
• (+) terminal will connect with 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 mange the output and connect with different Scope Block.

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.

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 a difference 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 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, FTP75 etc., Here in this model I have used FTP 75, WOT & Manually prepared in excel Drive Cycle 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)

                              

Manually prepared Drive Cycle

Simulink Model of Electric Rickshaw

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 at the required rpm.
• Then the motor power is transmitted to the wheels of a vehicle through the gearbox. and the controller will take the vehicle's speed and compare and controlled.

 OUTPUT PLOTS

For FTP75 Drive Cycle

• By running the Vehicle with FTP75 Drive cycle for 2474 sec. the distance traveled is 5.004 Km

Scope:

 

• The actual Speed is approximately followed the 90% of reference Drive cycle.
• The Temperature of Motor is increased to 340^0 C..
• The Temperature of Controller is approx 300^0 C.

For WOT Drive Cycle

• By running the Vehicle with WOT Drive cycle for 200 sec. the distance travelled is 0.1189 Km

• The actual Speed is approximately followed 85% of the reference Drive cycle.
• The SoC% of the battery is reduced to at the 100th sec and after that 100 to 200 sec., the battery gets charged by back EMF.
• The Temperature of Motor is increased to 308^0 C.
• The Temperature of Controller is approx 298.15^0 C.

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 a Manually prepared Drive cycle for 120 sec. the distance traveled is 0.7716 Km

Scope

 

• The actual path of the speed is approximately followed the of reference Drive cycle as above.
• The SoC% of the battery is reduced to 
• The Temperature of Motor is increased to 325^0 C
• The Temperature of Controller is 298.15^0 C

CONCLUSION

• Here we have compromised with the temperature of the Motor and controller to achieve vehicle speed near reference speeds.
• In the real time application, the motor, battery & controller temperature is controlled by air cooling. Hence, the temperature of these components is not increased to this extent.
• Hence, Created a MATLAB model of an Electric Rickshaw (three-wheel passenger vehicle) by using a Li-ion battery, and PM Brushed DC Motor.
• Detremined the variations of Temperature of the Motor and controller, SoC% and Energy consumed by the vehicle for all three Reference Drive cycles (i.e.; FTP75, WOT, Manually prepared).