P13261 – Electric Vehicle Traction Control System

Team Members from left to right: James Evans (EE), Dan Brownlee

(ME), Joshua Doores (EE), Sean Harriman (ME), Andrew Robison

(ME)

Photo of the actual motorcycle being used on the testbench for

which the traction control system was developed.

Project Description: This project, proposed by the Electric Vehicle team, was intended to research the positive and/or negative effects of

utilizing traction control and transmission system’s on an electric motorcycle. The electric vehicle team intended on competing in the

TTXGP motorcycle race with both, one, or neither of the systems. As the project progressed however, it became apparent that the EV club

might not have enough funding to purchase all of the necessary components (motor, motor controller, high powered batteries) to test both

systems. Therefore, the project description shifted towards developing a testbench for an electric motorcycle that could test a traction

control system. The test bench has been built of a low-carbon structural steel tubing welded into two frames. These frames hold two car

rims that spin on axles inside the frame. These rims will roll at the same speed, acting like a rolling road. This allows the motorcycle to

simulate rolling down a road. Using this, along with a load on the axle given by an alternator powering a hot water heater, we can test a

traction control system by causing a wheelie and rear wheel slip, then allowing the traction control system to keep the front wheel on the

ground, or keep traction on the rear wheel. The traction control system algorithm was developed using the mbed MXP LPC11U24

microcontroller. The controller provided all the necessary inputs/outputs and processing speed required. Two wheel sensors were used to

measure front and rear wheel speed and an accelerometer was used to measure any vertical lift by the motorcycle. A vector board was used

to solder all of the electrical components on one board. These components include: the microcontroller, a mosfet, a dc-dc converter, and

input connections from the wheel sensors and accelerometer. The goal of the whole project was to build a safe way of creating conditions

of front wheel lift and rear wheel slip, so that the traction control system could be tested.

Electrical Specifications/Design: The electrical system design involved

routing power from the 48 V battery system to the motor. In addition, voltage

needed to be dropped down to 5 V in order to power the wheel speed sensors

and the mbed microcontroller, which is running the traction control algorithm.

The accelerometer is powered off the microcontroller at 3.3 V. In addition to

power distribution, safety measures needed to be accounted for, such as fuses,

emergency stop switches, protection diodes, and a pre-charge resistor. Below

is the full electrical schematic diagram. The traction control algorithm,

developed on a mbed MXP LPC11U24 microcontroller, checked for condition

of rear wheel slip and/or front wheel lift. When such conditions were found, a

PWM output was send to the gate of a MOSFET that interfered with the

throttle input to the motor controller, thereby lowering the throttle to the point

where rear wheel slip or front wheel lift has stopped.Testbench set-up with stripped motorcycle on top.

Schematic diagram of the electrical system.

Mechanical Specs:

AutoCAD Drawing of the testbench.

A chain will connect the two rotating

cylinders so that both wheels will spin

at the same time. The purpose of the

A-frame is to hold the rear axle in place

* A special thanks to: Prof. George Slack, Mark Smith, the Electric

Vehicle Club, Dr. Antonio Mondragon, and Dr. Mario Gomes

Preliminary Testing Results: The oscilloscope shows front and

rear pulses and the PWM output

from the microcontroller.