Final Project: Electric Rickshaw modelling

Matlab Model for Electric rickshaw

Aim:

To design the electric rickshaw using Matlab Simulink as per given details and to create a detailed report.

Given:

• Rear wheel driven by Pm brushed motor.
• To make excel sheet with all input and assumed data.
• To simulate for three driving cycles
• To find energy consumption, temperature rise of motor and motor controller for 100kms with 45kmph.

Purpose:

Because of the depletion of fossil fuels and pollutions caused by burning the fossil fuels affects the environment by producing the greenhouse and poisonous gas. And additionally day by the cost of the fuel also increases. This paves the way to the entry of electrical vehicles which uses the electrical energy, the cleanest energy. It does not produce any pollution.

Software used:

• Matlab/ Simulink

Main Components:

• Drive cycle
• Battery
• Power Controller
• Motor
• Vehicle Body

Model:

Blocks Used:

• Drive cycle source
• Longitudinal driver
• Controlled Voltage Source
• Controlled PWM Voltage
• H- Bridge
• Current sensor
• Voltage Sensor
• Brushed DC motor
• Mechanical rotational sensor
• PS terminator
• Battery
• Controlled current source
• Electrical reference
• Mechanical rotational reference
• Heat flow rate sensor
• Convective heat transfer
• Thermal mass
• Controlled temperature source
• Thermal reference
• Solver Configuration
• Discrete time integrator
• Gain
• Constant
• Rate transition
• Simple Gear
• Tire (Magic formula)
• Vehicle Body
• PS constant
• PS-Simulink converter
• Simulink-PS converter
• Sum
• Integrator
• Divide
• Display
• Powergui

Explanation and Configuration of Components used:

For better understanding let us go from backward.

Vehicle Body:

Vehicle Body block:

This block 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 acceleration and road profile. We can also include pitch and suspension dynamics or additional variable mass and inertia. The vehicle does not move vertically relative to the ground.

Connection H is the mechanical translational conserving port associated with the horizontal motion of the vehicle body. Connections V, NF, and NR are physical signal output ports for vehicle velocity and front and rear normal wheel forces, respectively. Connections W and beta are physical signal input ports corresponding to headwind speed and road inclination angle, respectively. M represents the additional mass.

Configuration:

The mass is set to 400kg.

Tire (Magic formula):

This block represents the longitudinal behaviour of a highway tire characterized by the tire Magic formula. The effects of tire inertia, stiffness, and damping can be included.

Connection A is the mechanical rotational conserving port for the wheel axle. The rotational output from the Simple gear is given to this port. 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. The H port from the vehicle body is connected to this port. Connection N is a physical signal input port that applies the normal force acting on the tire. The NR and NF from the vehicle body is given to this port accordingly. Connection S is a physical signal output port that reports the tire slip.

The parameters are kept default and rolling resistance is neglected.

Simple Gear:

This block represents a fixed-ratio gear or gear box. The gear meshing and viscous bearing losses can be included if needed.

Connections B and F are base and follower which are mechanical rotational conserving ports. It specifies the relation between base and follower rotation directions with the Output shaft rotates parameter.

Configuration:

The value of gear ratio is changed to 17 and direction of rotation of output shaft set as same as input shaft.

Motor Drive:

Controlled voltage source:

The block represents an ideal voltage source that is powerful enough to maintain the specified voltage at its output regardless of the current passing through it. The output voltage is V = Vs, where Vs is the numerical value presented at the physical signal port.

The input to the physical signal port is given from the Accelerator command of the Longitudinal driver.

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. The voltage from the controlled voltage source is given to the ref+ port. The ref- port is connected to the ground.

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.

Configuration:

The simulation mode is set to averaged for the faster simulation. The output voltage at 100% duty cycle is set to 0.2V. Other parameter are set to default.

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 H-Bridge 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. The PWM port and REF port is connected to the PWM output port and REF output port of controlled PWM voltage. The REF and REV ports are connected to the ground. The BRK port is connected to the controlled Voltage source which is controlled by the Deceleration command from the Longitudinal Driver. The thermal port is enabled by right clicking the block and select simscape and select block choices and select show thermal port.

Configuration:

The simulation mode is set to averaged. The regenerative braking is set to always enabled. Output voltage amplitude is set to 600V which is given to brushed DC motor. Other parameters of the blocks are set to default.

Heat flow rate sensor:

The block is used to measure heat flow rate in a thermal network. There is no change in temperature across the sensor. The physical signal port H reports the heat flow rate through the sensor. The positive flow direction is from port A to port B.

Convective Heat transfer for H bridge:

The block models heat transfer in a thermal network by convection due to fluid motion. The rate of heat transfer is proportional to the temperature difference, heat transfer coefficient, and surface area in contact with the fluid.

Configuration:

The area is set to 100cm^2 and the heat transfer coefficient is set to 60 W/(m^2*K).

Controlled temperature source:

This block represents an ideal energy source in a thermal network that can maintain a controlled temperature difference regardless of the heat flow rate. The temperature difference is set by the physical signal port S. A positive temperature difference causes the temperature at port B to be greater than the temperature at port A.

DC motor:

This block represents the electrical and torque characteristics of a DC motor. It assumes that no electromagnetic energy is lost, and hence the back-emf and torque constants have the same numerical value when in SI units.

When a positive current flows 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. The input to the motor is given by the H-Bridge. The port C is connected to ground and the port R is the mechanical rotational port connected to the simple gear.

Configuration:

The model parameterization is set to by rated load and speed. The no load speed and rated speed is set to 12000 rpm and 11500 rpm. The rated load is set to 150kW. And Rated Dc supply voltage is set to 600V. All other values are set to default.

Convective Heat transfer for DC Motor:

Configuration:

The area is set to 10cm^2 and the heat transfer coefficient is set to 5 W/(m^2*K).

Current Sensor and Voltage Sensor:

The ideal current sensor is a device that converts current measured in any electrical branch into a physical signal proportional to the current. It is used to measure the current to motor.

Connections + and - are conserving electrical ports through which the sensor is inserted into the circuit. Connection I is a physical signal port that outputs current value.

The ideal voltage sensor is a device that converts voltage measured between any electrical connections into a physical signal proportional to the voltage. It is used to measure the voltage applied to motor.

Connections + and - are conserving electrical ports through which the sensor is connected to the circuit. Connection V is a physical signal port that outputs voltage value.

Battery:

Controlled Current Source and Battery:

An ideal current source is powerful enough to maintain the specified current through it regardless of the voltage across it. The output current is I = Is, where Is is the numerical value presented at the physical signal port. This physical signal port is connected to the physical signal port of the current sensor. The positive this block is connected to the negative of battery and negative port to positive of the battery for the charging of battery.

The battery is used to deliver and store the energy. The thermal port of Battery is enable by right clicking the block and select the simscape and select block options and select show uninstrumented thermal port.

Configuration:

The nominal voltage is set to 600V and current directionality is enabled. Battery charge capacity is set to finite and the Ampere hour rating is set to 500hr*A. All other parameters are set to default.

Convective Heat transfer for battery:

Configuration:

The area is set to 20cm^2 and the heat transfer coefficient is set to 20 W/(m^2*K).

SOC (State of Charge):

Rate transition handles data transfer between different rates and tasks. It is used to convert to continuous to discrete. Discrete time integrator is used to accumulate the input signal.

Gain of SOC:

Configuration:

The value of gain is set to 1/(AH*3600). Where AH is set to 500.

Longitudinal Driver:

A parametric longitudinal speed tracking controller for generating normalized 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 this priority for the input commands: disable, hold, override. The VelRef is connected to the output of the Drive cycle source. The VelFdbk is connected to output port V of the vehicle body.

Drive Cycle Source:

Drive cycle source 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 such as FTP75, WOT, US06, etc
• Workspace variables, including arrays and time series objects
• mat, xls, xlsx, or txt files

It is set to FTP75 and the simulation time is updated.

Finally the velocity from the vehicle body is converted from m/s to kmph by adding the gain of 3.5. It is then integrated and divided by 3600 to get the distance in kmph. This is displayed in the display.

The efficiency curve of the vehicle is calculated by calculating the values of reference speed and output speed through rate transition and discrete time integrator. Then the output speed is divided with input speed to get the efficiency of vehicle. i.e) (Output speed)/ (Input speed).

The output speed and the reference speed is given to the speed comparison scope. The battery temperature, converter temperature and motor temperature is given to the thermal scope. The voltage across motor, current and speed of motor and Soc is given to another scope.

By modelling and configuring with above values the model is simulated.

Analysis:

1) FTP75:

When the model is run with above configuration for FTP75 drivecycle the results are,

Model with distance travelled in display:

Distance travelled by the vehicle during the FTP75 drive cycle is 17.59kms.

Speed Comparison Plot:

Actual speed of vehicle in Kmph:

According to the given drive cycle the vehicle moves. There will be some minor difference between the reference speed and actual speed of the vehicle. By changing the gear ratio, this error can be reduced. The actual speed nearly follows the reference speed. The efficiency of the vehicle can be visualized in the scope. The maximum velocity of the vehicle is around 79 kmph.

Thermal scope:

When the vehicle is accelerating the average increase in temperature of battery above ambient of 298.15K is around 7 K and the average increase in temperature of motor and controller above ambient of 298.15K is reduced by using the heat sink for the better operation and is around 50K and 12K. The maximum increase in temperature of battery, converter and motor is 10K, 16K and 80K.

Scope for voltage, current and speed of motor and SOC:

According to the accelerating and decelerating command from the longitudinal driver the voltage and speed of the speed is increased and reduced. During acceleration the current direction is positive and the battery is discharging. During deceleration or braking the current direction is reversed and the battery is charging. This is called the regenerative braking. The state of charge of the battery at the end of drivecycle is 94.6% due to ideal high efficiency considered.

Efficiency curve:

The efficiency of the vehicle is around 93 to 99.5%. The average efficiency is around 98.5% due to ideal conditions considered. The actual environmental factors affects the efficiency.

2) WOT (Wide Open Throttle):

For WOT the no load speed of the motor is set to 8000 rpm and the rated speed is set to 5000 rpm. The rated load is set to 70kW and the thermal mass is increased to 1300 J/K. Then mass of thermal mass is increased to 500kg and the specific heat is 400 J/kg/K. then the gear ratio is reduced to 2. The drivecycle WOT parameters are reference speed at 45, the start time is 30sec, end time is 1000sec and the deceleration time is 900sec.

Model with distance covered in display:

Total distance covered during WOT is 33.95kms.

Speed comparison plot:

As from the plot the output speed follows nearly the reference speed with some error.

Thermal scope:

The increase in temperature of the battery during WOT is 10K and is maintained constant throughout the cycle. The maximum increase in temperature of converter(H bridge) and motor is 150K and 1.4K.

Other scope:

The state of charge at the end of WOT is around 86%. The during the reversal of current the battery gets charged.

Efficiency:

The efficiency of the vehicle for the WOT drivecycle is plotted and is around 87 to 94%

3) Pulse generator input:

The Pulse generator parameters are amplitude to 45 and time period is 500 and the duty cycle is 70%. The phase delay is set to 30sec.

Model with distance covered in display:

The distance covered during this cycle is 28.75 kms.

Speed comparison plot:

The difference between the reference speed and actual speed is plotted and is comparatively low.

Thermal plot:

Whenever the motor is in acceleration the temperature is increased in the battery, converter and the motor. Due to less speed of motor the increase in temperature is very less. But the converter temperature is increased to maximum of 140K.

SoC plot:

The state of charge at the end of this cycle is 87.5%. The vehicle covers the distance of 28.75kms within 7.5% of charge.

Efficiency:

The efficiency of the vehicle is roughly above 90%.

4) Constant speed at 45 for 100kms:

The constant of 45 is given as input and it is simulated for 3000sec for the vehicle to cover 100kms. When the model is simulated without compensating the heat sink values the plots are like below.

Plot without compensating the heat:

The temperature of the converter is goes on increasing and attains the maximum of 1300K. This may affect the converter and motor and produces the serious problem hence it must be reduced by using the proper heat sink.

By making the above values, the model is simulated.

By compensating with the above value of heat sink the temperature increase is greatly reduced and is around 250K. Since motor is running with less rpm the temperature of the motor is very less and is also compensated with heat sink for the efficient operation.

Model with distance covered in display:

The distance is 99.39km around 100km as per given condition.

Speed comparison and efficiency:

The actual speed is slightly lagging behind the reference speed. This can be increased by further reducing the gear ratio. The efficiency is around 73% to 90%.

SOC plot:

The state of charge of battery at the end of cycle with the vehicle covered over the distance of 100km is 73% i.e) with 22% of battery the vehicle covers the 100kms.

Result:

The electric rickshaw model is simulated for various driving cycles and the output plots are visualized and discussed above. The model is tested as per given conditions. So according to the different driving the model specifications has to be changed slightly. The temperature compensation and the efficiency of the vehicle is clearly visualized.

Drive Link:

https://drive.google.com/drive/folders/1poM8qJUQkaThlnWXLe252ldlc9jIMgZz?usp=sharing