GPS enabled speed control embedded system speed limiting device with display and engine control interface

Abstract

In the past decade, there have been close to 350,000 fatal crashes in the United States [1]. With various improvements in traffic and vehicle safety, the number of such crashes is decreasing every year. One of the ways to reduce vehicle crashes is to prevent excessive speeding in the roads and highways. The paper aims to outline the design of an embedded system that will automatically control the speed of a motor vehicle based on its location determined by a GPS device. The embedded system will make use of an AVR ATMega128 microcontroller connected to an EM-406A GPS receiver. The large amount of location input data justifies the use of an ATMega128 microcontroller which has 128KB of programmable flash memory as well as 4KB SRAM, and a 4KB EEPROM Memory [2]. The output of the ATMega128 will be a DOGMI63W-A LCD module which will display information of the current and the set-point speed of the vehicle at the current position. A discrete indicator LED will flash at a pre-determined frequency when the speed of the vehicle has exceeded the recommended speed limit. Finally, the system will have outputs that will communicate with the Engine Control Unit (ECU) of the vehicle. For the limited scope of this project, the ECU is simulated as an external device with two inputs that will acknowledge pulse-trains of particular frequencies to limit the speed of a vehicle. The speed control system will be programmed using mixed language C and Assembly with the latter in use for some pre-written subroutines to drive the LCD module. The GPS module will transmit National Marine Electronics Association (NMEA) data strings to the microcontroller (MCU) using Serial Peripheral Interface (SPI). The MCU will use the location coordinates (latitude and longitude) and the speed from the NMEA RMC output string. The current speed is then compared against the recommended speed for the vehicle's location. The memory locations in the ATMega128 can be used to store set-point speed values against a particular set of location co-ordinates. Apart from its implementation in human operated vehicles, the project can be used to control speed of autonomous cars and to implement the idea of a variable speed limit on roads introduced by the Department of Transportation [3].