Final Project: Electric Rickshaw modelling
Aim:
To Create a detailed MATLAB model of an Electric Rickshaw (three wheel passenger vehicle).
Objectives:
- 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
- Results: For any three standard driving cycles show energy consumption, temperature rise of motor and controller.
Block Diagram:
In the designed Electric Rickshaw main blocks are Battery, drive cycle, controller, DC Motor, Vehicle body & Transmission system. Drive cycle is the input data like how a human drive his actual vehicle here FTP75, WOT & 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 sates 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.
Drive train of the Electric Auto Rickshaw
1. Power and motor controlled subsystem ( with temperature sensor ) :
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.
1.2 DC Motor:
• This block represents the electrical and torque characteristics of a DC motor includes Thermal port to series 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
• 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 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 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 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 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 occurs this H-bridge 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.
1.3 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.
The 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 a value equal to the averaged PWM signal. Select Simulation mode as Averaged.
1.4 Temperature Sensor:
• 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.
1.5 Solver Configuration:
Defines solver settings to use for simulation.
(2) Vehicle Body and Tire 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 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 the front tire is free to rotational motion, thus the 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. As 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 get the distance traveled and state of charge
2.1 Vehicle Body Parameters:
• Vehicle body mass, Centre of gravity distance values, and aerodynamic drag variables are modified.
• Pitch dynamics are kept ON with other variable values as default values.
2.1.1 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.
• 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. Here I created a Rear-wheel drive transmission system.
• 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
2.1.2 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 the same direction of the input shaft.
The base is connected to the Motor shaft and the follower is connected to the Rear-wheel derive.
2.1.3 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, 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
(3) Battery And Soc Subsystem Model:
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 the 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 the battery is 330 V
Initial SoC is 100%
The battery as a series internal resistance plus a charge-dependent voltage source
defined by:
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, VI].
• 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.
3.2 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 where 1/inominal 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 were physical to Simulink converter is used to convert the physical signal from simscape block to Simulink signal
3.3 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 the drop-down menu of measurement select current.
• Signal output will connect with scope by adding the current signal to it. (+) the terminal will connect with the battery (-) terminal.
3.4 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 it with different Scope Block.
3.5 PowerGUI:
- The powerful block allows us to choose one of these methods to solve
- Continuous, which uses a variable-step solver from Simulink your circuit:
- Discretization of the electrical system for a solution at fixed time steps. Continuous or discrete phasor solution
- The powerful 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 blocks.
•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 the 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 parts of the Controlled PWM Voltage block
• Here, the selected control type is Pl. Accordingly, the block implements proportional-integral (PI) control with tracking windup and feed-forward gains.
(5)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 are used to test the vehicle performances.
• These drive cycles 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 & Manically prepared in excel Drive Cycle source.
5.1 FTP 75 Drive cycle
Generates a standard or user-specified longitudinal drive cycle.
The block output is the vehicle's longitudinal speed.
we 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 the specified speed and time tolerances
5.2 Wide Open Throttle (WOT):
5.3 Manually prepared Drive Cycle:
• All 3 Drive cycles are controlled by the controller provided above by constant through Multi-part switch
COMPLETE SIMULINK MODEL :
• Initially the current flow 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 gearbox and the controller will take the vehicle speed and compare and control.
OUTPUT RESULTS
1. For FTP75 Drive Cycle:
By running the Vehicle with F1P75 Drive cycle for 2474 see the distance traveled is 12.55 km. The gear ratio in the simple gearbox is kept at 9.
As we can see we got the velocity profile almost completely following the drive cycle data with the maximum speed reaching up to 30km/hr.
The state of charge for the battery drop to 60% of its 100% value for the complete drive cycle. It covered a distance of 12.55 km with a 40% charge still remaining in the battery.
The Temperature of the Motor is increased to 1968°C, the Temperature of the Controller is 627°C with 10000 as the thermal mass given both to the motor and the H - bridge.
2. For WOT Drive Cycle:
By running the Vehicle with WOT Drive cycle for 30 sec. the distance traveled is 0.1584 km. The gear ratio in the simple gearbox is kept at 4, for faster calculations and quick results.
The actual Speed is approximately followed 85% of the reference Drive cycle.
The SOC of the battery reaches 97.5% of the total value till we have the full-throttle working. Later the battery gets charged by the back EMF for the rest of the cycle and charges back to 98.2%.
The Temperature of the Motor is increased to 408°C.
The Temperature of the Controller is = 357°C.
3. For Manually prepared Drive Cycle:
By running the Vehicle with a Manually prepared Drive cycle for 120 sec the distance traveled is 1.038 km. The gear ratio in the simple gearbox is kept at 5, for faster calculations and quick results.
The velocity profile followed the drive cycle data given, it reached the maximum speed of 50km/hr and maintained the speed for most of the part of the travel.
The SOC for the battery is reduced to 91% of the total change. During the end of the drive cycle, it gets charged with the help of the back EMF produced and reaches back to 92.8%
The Temperature of the Motor is increased to 544°C.
The Temperature of the Controller is 408°C.
CONCLUSION
#Created a MATLAB model of an Electric Rickshaw (three-wheel passenger vehicle) by using a 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 (.e: FTP75, WOT, Manually prepared).
# For every respective cycle we saw the velocity profile following the given drive cycle data, and attaining the close value to the actual speed of the drive cycle.
# The SOC of the battery for each cycle depends on various factors. The coefficient of rolling resistance, Thermal mass, Gear ratio, etc. By varying these parameters we can change the SOC of the battery for the particular drive cycle.
# Here I have compromised with the temperature of the 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 these components is not increased to this extent.
# This Battery-powered Rickshaw will be the most popular mode of transport in the future.