UWE Bristol Engineering showcase 2015

Ross Sanders
Electrical and Electronic Engineering
Project Supervisor
Rohitha Weerasinghe
Electric power train for Formula Student electric car
What is formula student?
Formula Student (FS) is Europe's most established educational motorsport
competition, run by the Institution of Mechanical Engineers. Universities
from across the globe are challenged to design and build a single-seat racing
car in order to compete in static and dynamic events, which demonstrate
their understanding and test the performance of the vehicle.
Electric car entry class
This is the first year that UWE have had an electric car design team. Formula
student teams can be entered in one of two classes, class one and class two.
Class one teams enter with a fully built car that can compete in the dynamic
events such as acceleration and endurance test. Class two teams do not have
a full car but compete in the static events which judge the design of the car
based on the engineering undertaken and the business decisions made by
the team. A class two entry is considered to be capable of being entered as a
full class one entry in 12 months’ time. This is the time considered necessary
to build the car from the designs produced for class two entry. Formula
student rules allow only one class one entry per university so the petrol team
will enter a class one car this year and the electric team will enter a class one
team next year.
Car design
The 2015 UWE formula student electric car is designed to use four hub
mounted motors that drive the wheels through a single ratio planetary gear
box.
The motors chosen are Bosch MS102D0800 which can provide up to 45Nm of
torque and has a rated power of 16kW. The motor is powered by three by a
phase AC supply.
Battery selection
The car uses 324 Manganese Cobalt Oxide (LiNiMnCoO2) batteries that have
a total weight of 40Kg to provide the motors with up to 133A (the maximum
permitted by formula student rules) at 600V. The batteries have a total
capacity of 6KWh, which is enough power to complete the 22Km endurance
event at Silverstone.
Motor controller
The motor controller is a variable frequency power inverter that converts the
DC power from the batteries into three phase AC with a variable frequency
to control the speed of the motors. The controller a Cypress pSOC to
generate PWM signals that represent sine waves to control a high power
IGBT module. The IGBT chops the DC power supply to produce an AC supply.
The resistance and inductance of the motor filters the PWM signal into a
pure sine wave that powers the motors most efficiently.
As one motor is uses to drive each wheel of the car the speed of all the
motors must be adjusted during cornering to provide maximum traction. To
achieve this the steering angle is measured and used as input to an algorithm
that calculates the speed required by each wheel. Each of the four motor
controllers can communicate over a CAN bus connection to transmit
information about motor temperature and motor position. The CAN bus is
also used to send torque and speed demands to each motor controller .
Project summary
Design a motor controller system for the 2015
UWE Formula Student electric race car.
Project Objectives
Develop a motor controller system for a four
wheel drive hub motor based electric car. The
controller must supply three phase AC power
at a variable frequency from a battery source.
Project Conclusion
A motor controller system was developed
that provided Pulse Width Modulation
encoded three phase power to the motor. The
controller used a Cypress Programmable
System on Chip to control a Hex packaged
Insulated Gate Bipolar Transistor to provide
up to 150A at 600V (peak to peak) to the
motor.