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Design and Development of Electric scooter
1.Development history of electric scooter
Europe is the second largest use area of two-wheelers in the world. In the past few years, the European two-wheeler industry has achieved amazing growth. The invention of fuel redefines the face of the automotive industry
Efficient technology will surely witness the arrival of a new era in the two-wheeler industry.
Not gasoline, diesel or any other fuel, but electricity has triggered a revolution in the Indian two-wheeler industry. .
The European two-wheeler industry has accepted the new concept of electric bicycles and scooters, which are very popular personal transportation in North America and other countries. Therefore, electric bicycles or scooters have broad development prospects in the personal field. We studied the design and development and comparison of different parts of the components. This article also introduces electric two-wheeler components, such as batteries, chargers, BLDC motors, controllers, and DC-DC converters.
In recent years, environmental problems caused by fuel vehicles and fuel economy become more and more serious.The vehicles of new energy, which is green, environmentally friendly and economical, is an important goal for economic and social development of many countries, but also the future development direction of the vehicle. EV is a vehicle with zero pollution emissions, mileage and fuel vehicles can be mutually comparable electric vehicles.
Being an e-scooter the electric system plays a promising role in its designing and creation. The electric system consists of battery, motor, motor controller and other electronic equipment. The most important thing that electric system does is that it gives power to the motor which helps in the running of the scooter.
This energy in form of chemical or electric energy is stored in the battery which is used by a hub motor, thus the electric or chemical energy converted to mechanical energy. A proper electric system is important to ensure driver and vehicle safety in case of collision. The brushless DC (BLDC) motor is fixed to hub of rearwheel of escooter. The reason for choosing BLDC motor is its compactness and noiseless operation.
So our main Objectives to design or development an e-scooter are as following:-
- To reduce running cost of vehicle
- To reduce the emissions
- To overcome the draw backs of electric vehicle
- To increase life period and efficiency of existing escooters.
2.System Devlopment
The Key Components in Electric Scooter
Following are the key components in Electric Scooter:-
2.1 Battery Charger
2.2 Battery
2.3 Motor Controller
2.4 Motor
2.5 DC-DC Converter
2.6 Vehicle Computer and Electronics
The electric vehicle is rather simple in structure. The key components are the propulsion parts. Fig.1 shows the configuration.
Fig 1
Fig 1: The key components of Electric Vehicle (Powertrain)
The battery is the main energy storage. The battery charger is to convertthe electricity from mains to charge the battery. The battery voltage is DC and current (I) is inverted into switched-mode signal through power electroniccontroller to drive the motor.
The other electronic components in a vehicle can be supplied to the battery through DC-DC converter that step down the voltage from the battery pack tolower voltage such as 5V-20V.
2.1 Battery Charger
In order to utilize thebattery toitsmaximumcapacity the battery charger plays a crucial role. The remarkable features of a battery charger are efficiency and reliability, weight and cost, charging time and power density. The characteristics of the charger depend on the components, switching strategies,control algorithms.
Fig.2:- Electric circuit diagram of battery charger
This control algorithm can be implemented digitally using microcontroller.The charger consists oftwo stages.
First,one is theAC-DC converter with power factor correction which converts the AC grid voltage intoDC ensuring high power factor. The later stage regulates the charging current and voltage of the battery according to the charging method employed.
The charger can be unidirectional i.e. can only charge the EV battery from the grid or bidirectional i.e. can charge the battery from the grid in charging mode and can pump the surplus amount of power of the battery into the grid.
This is lithium ion battery charger circuit (48v 5A) for 48v 25Ah battery as shown in figure2. The circuit given here is a current limited lithium ion battery charger built around the famous variable voltage regulator IC LM 317. The charging currentdepends onthe valueof resistorR2.Resistor R3 and POTR4determines the charging voltage.
Transformer T1 steps down the mains voltage and bridge D1 does the job of rectification. C1 is the filter capacitor. Diode D1 prevents the reverse flow of current from the battery when charger is switched OFF or when mains power is not available
2.2 BATTERY
Batteries are the components that store electrical energy,allowing for the motor ofthe vehicle inquestiontorun.There is already an analysis between different kinds of batteries as seen in the table.1 below, The main materials that allow recharging are nickel cadmium, nickel zinc, nickel metal hydride, and lithium-ion/lithium-polymer, these are respectively listed as NiCd, NiZn, NiMH, and Li-ion/Li-Po on the battery analysis table. Specific energy is energyperunitof mass denotes a lighter battery as the value increases if the energy were to be kept constant
From this table lithium ion battery was the most efficient choice for an electric bike because it offers high energy density while remaining relatively light-weight and compact in size. Lithium ion batteries can be very dangerous;therefore it is essential to research the quality of the lithium ion cells and the protective implementations used.
➢ Battery management systems
It is also referred as BMS. The battery system is formed by a number of battery cells. They are connected in parallel or series that is according to the design. Each of the cell should be monitoring and regulated. The conditioning monitoring includes the voltage, current andtemperature.Themeasured parameters are used to provide the decision parameter for the system control and protection.
2.3 Motor Controller
A motor controller is a device or group of devices that serves to govern in some predetermined manner of performance of an electric motor. A motor controller mightinclude a manual or automatic means for starting and stopping the motor, selecting forward or reverse rotation, selecting and regulating the speed, limiting or regulating the torque, and protecting against overloads and fault.
In this project we are using “sine wave vector controller”. The battery block is interfaced with the motor controller block. The motor controller controls all the functional capabilities and is the central component of the system. The basic requirement for the control is to regulate the amount of power applied to the motor, especially forDC motors. The motor controller can be adjusted to synchronize with other brushless motors.
To drive and controlthe BLDC motor,theuseofmotor controller was implemented. The motor controller is anessentialdevice for any motor driven device. The motor controller is analogous to the human brain,processing information and feeding it back to the end user.
Of course,the applications of a motor controller vary based on the task that it will be performing.One ofthe simplest applications is a basic switch to supply power to the motor, thus making the motor run. As one utilizes more features in the motor,the complexity ofthe motor controller increases. Field-Oriented Control (FOC) or sine wave vector controller is an important technology for motor systems, particularly those using permanent magnets(PM).
In general, FOC provides an efficient way to control BLDC motor in adjustable speed drive applications that have quickly changing loads and can improve the power efficiency of an BLDC motor.
2.4 Bldc Hub Motor
The use of the permanent magnets(PM) in electrical machines in place of electromagnetic excitation results in many advantages such as no excitation losses, simplified construction, improved efficiency, fastdynamicperformance and high torque or power per unit volume.A brushless dc (BLDC) motor is a synchronous electricmotor which is powered bydirect current electricity (DC) andwhich has as electronically controlled commutationsystem,instead of a mechanical commutation system based on brushes.
In such motors, current andtorque, voltage andrpmare linearly related. In BLDC motor the electromagnets do not move,instead the permanent magnets rotate and the armature remains static. The construction of modern brushless dc motor is very similar to the ac motor, known as permanent magnet synchronous motor.
Fig.3
Figure3 illustrates the structure of a typical three phase brushless dc motor. The stator windings are similar to those in a poly phase ac motor, and the rotor is composed of one or more permanent magnets.
Brushless dc motors are different from ac synchronous motors in thatthe former incorporates somemeans todetect the rotor position or (magnetic poles) to produce signals to control the electronic switches. The most common position/pole sensor is thehall element,but somemotorsuse optical sensors.
Fig.4:- Two phase brushless dc motor
2.5 Dc-Dc Controller
A DC-to-DC converter is an electronic circuit or electromechanical device that converts a source of direct current (DC) from one voltage level to another. It is a type of electric power converter. The different configurations of EV power supply show that at least one DC/DC converter is necessary to interface the FC (frequency controller), the
Battery or the Supercapacitors module to the DC-link.
In electric engineering, a DC to DC converter is a category of power converters and itis an electric circuitwhichconverts a source of direct current (DC) from one voltage level to another, by storing the input energy temporarily and then releasing that energy to the output at a different voltage.
The storage may be in either magnetic field storage components (inductors, transformers) or electric field storage components (capacitors).DC/DC converters canbedesigned to transfer power in only one direction, from the input to the output.However, almost all DC/DC converter topologies can be made bi-directional. A bi-directional converter can move power in either direction, which is useful in applications requiring regenerative braking.
The amount of power flow between the input and the output can be controlled by adjusting the duty cycle (ratio of on/off time of the switch).Usually, this is done to control the output voltage, the input
current, the output current, or to maintain a constant power. Transformer-based converters may provide isolation between the input and the output. The main drawbacks of switching converters include complexity, electronicnoise and high cost for some topologies
3. Performance Analysis
➢ Hub Motor Calculation
3.1 Motor Specification
Volt (V) = 48 v, Power (P) = 1000 w
3.2 Power Equation
Power (P) = Current (I) × Voltage (V)
Hence, I = P ÷ V = 1000 ÷ 48 = 20.83 Amp.
3.3 Speed of Motor In RPM
N=K÷ ( d × 0.001885 ) =35÷(25.4×0.001885)=731RPM
Where, N = Speed In RPM, K = Speed In kmph
d = Wheel Diameter in cm
• Wheel Diameter (d) is 10 inch (Given)
1 inch = 2.54 cm, So, d = 10 inch = 25.4 cm
• Speed In kmph (K) is 35 kmph (Given)
3.4 Torque of the motor (T)
T = (P×60)÷(2×𝜋×N)=(1000×60)÷(2×3.14×731) =13.06Nm
Torque of the wheel hub motor, T = 13.06 Nm
3.5 Selection of Motor
For deciding the power rating of vehicle, the vehicle dynamics like rolling resistance, gradient resistance, aerodynamic drag, etc. has to be considered. For illustration procedure for selecting motor rating for anelectric scooterof gross weight 170 kg is considered. The force required for driving a vehicle is calculated as:
Ftotal = Frolling + Fgradient + Faerodynamic drag
Where, Ftotal = Total force
Frolling = Force due to Rolling Resistance
Fgradient=Force due to Gradient Resistance
Faerodynamic drag=Force due to Aerodynamic Drag
Ftotal is the total tractive force that the output of the motor must overcome, in order to movie vehicle.
ROLLING RESISTANCE
Rolling resistance is the resistance offered to the vehicle due to the contact of tire with road. The formula for calculating force due to rolling resistance is given by equation:
Frolling = Crr × M × g
Where, Crr = Coefficient of Rolling Resistance,
M = mass in kg, g = acceleration due to gravity = 9.81 m/s2
For application consider, Crr = 0.004 as per below table And
weight of our scooter = 170 kg
4. System Operation
Basically, electric motor drive circuit has DC brushless controller of 48Vwhich is powered by the battery of capacity 48V through MCB (miniature circuitbreaker).The functionof MCB is protect the circuit under over current/over voltage condition. The controller supply in a specified sequence is given to motor by controller.
The hall effect sensor connected at the shaft of BLDC motor which gives signal to the controller and thus respective windings get energized as per position of motor shaft. The throttle or speed changerhandle bar is connected electrically to the controller.Hence, variable speed can be obtained by accelerating the bar.
Also, the braking systemis connectedelectrically tocontroller.As soon as brakes are applied, it will open the circuit andthenbattery is disconnected from motor causes motor speed reduction and in a specified time, motor will stop.
5. Conclusion
Now a days, utilization of fuel vehicles are increased rapidly which result into more air pollution. To control this,utilization of EV is must because it’s several advantages like electric scooter is an eco-friendly product,Itis more suitable for city as it can avoid the emission of harmful gases and thereby it can reduce the atmospheric pollution.
Due to frequent increase in fuel prices, the electrically charged vehicle seen to be the cheapest one compared to the traditional vehicle. E-scooters are more suitable for rural areas where the numbers of petrol bunks are not adequate,so that the rural people can charge the vehicle with the help of electricity. To understanding theEVtechnology,this study helps to provide outline of EV (Scooter) and there various components.
