DEVELOPING AND BUILDING A PROTOTYPE REAR WHEEL DRIVE ELECTRIC CAR. PRJ.021 PRESENTER: MURIITHI JOSEPH NYAGA F17/0294/2004. SUPERVISOR: EXAMINER: DR. J.M MBUTHIA MR. N.S WALKADE
An electric car is an alternative fuel car that utilizes electric motor and motor controllers instead of an internal combustion engine. WHY ELECTRIC CAR? Decreasing supply of fossil fuels. Raising cost of petrol/ fossil fuels. Negative effects emissions from petrol powered vehicles are having on environment.
OBJECTIVE: To develop and build a prototype rear wheel drive electric car.
Advantages of Electric vehicles. Have fewer moving parts. Require minimal maintenance. Are more energy sufficient compared to gasoline engines. They are quiet in operation. They are zero emission.
Vehicle options. There are 4 main options for alternative transportation VEHICLE OPTION Hydrogen Fuel Cell vehicles Hybrid vehicles Bio Fuels Battery Electric vehicles. Series Hybrids Parallel hybrids
Hydrogen Fuel Cell vehicles. A hydrogen fuel cell consists of a chemical reaction of hydrogen and air, giving electrical energy and water as by products. Then this electrical energy is used to power the electric motor.
Hybrid vehicles. They use electric motors and other types of engine. There are two types of hybrid vehicles: i) Series Hybrid- have internal combustion engine which runs a generator to charge or maintain the battery pack. ii) Parallel Hybrid- both the electric motor and engine drives the vehicle.
Bio- fuels A bio-fuel is any liquid fuel produced from sources other than mineral reserves. These fuels are as substitute for, or additive to petrol and diesel. The most commonly used Bio-fuels are biodiesel and bio-ethanol.
Battery Electric vehicles The electric power to drive the motor is usually derived from rechargeable battery packs in the vehicle.
MAIN COMPONENTS OF AN ELECTRIC VEHICLE
(I) MOTORS Are the main components of an E V that converts electrical energy into mechanical energy. The commonly used motors in EVs are: series wound brushed motors, a.c motors, brushless d.c motors and permanent magnet motors.
(II) SPEED CONTROLLER Speed controller is crucial to the efficiency and smooth operation of the electric car. It is rated according to the voltage and amperage ranges. For d.c motors PWM controllers or resistive speed controllers can be used.
(III) DC/DC CONVERTER This taps the full battery pack voltage and cuts it down to a regulated13.5 volts. By tapping the full pack, it ensures even discharge of batteries.
(IV) SAFETY COMPONENTS Circuit Breakers: Provides a fail-safe manual interruption of the battery power in an event of a drive system malfunction or during routine servicing. Ignition Key Main Contactor: Used to switch high currents remotely by means of lowlevel control voltage. Pot Box: is an interface between the throttle pedal and the speed controller. Fusible Link: Is inserted in the traction battery circuit in each pack and it breaks the circuit in case of a short circuit.
(V) INSTRUMENTATION/GAUGES They allow monitoring of an EV s performance. The primary requirements of gauges are reliability, accuracy and readability. Types of gauges used include: Ammeter State-of-charge gauge High Voltage meter Low Voltage meter
PROTOTYPE DESIGN AND IMPLEMENTATION
BLOCK DIAGRAM OF DESIGN Divided into 3 main blocks
POWER SUPPLY SYSTEM Consists of dry cells, voltage regulator, capacitors, protection diode and an indicator diode
DRIVER CIRCUIT. Consists of power BJTs, silicon diodes, resistors and test motor (permanent magnet dc motor) connected to form a H- bridge circuit.
CONTROL CIRCUIT Consists of set-speed switches, direction change switches, indicator LED and Attiny26L microcontroller
FINAL DESIGN CIRCUIT It s a combination of the three blocks.
A PHOTOGRAPH OF FINAL DESIGN SETUP.
RESULTS: Sample PWM output wave form at 70% duty cycle.
Relationship between armature voltage and current to motor at 70%duty cycle and supply voltage. Supply voltage (V) V(s) Armature voltage (V) V(a) Armature current (A) I(a) 11.1 13.9 15.9 19.8 9.2 10.0 10.2 10.3 0.03 0.16 0.21 0.24
A plot of armature voltage versus armature current
CONCLUSION Objective was achieved where by it was possible to control speed, brake, run forward and reverse the prototype electric car designed.
RECOMMENDATION Use of microcontroller as the main control unit in an electric car can greatly reduce the discrete electronic components in design. Thus results in a more efficient and light electric car.
THANK YOU