Ultra low power embedded system with sensing and data logging for efficient operation of energy harvesting from road traffic
The thesis research is aimed at designing and developing a low power sensing and data logging system capable of successfully operate with piezoelectric materials and the power source for the system, but is equally capable to operate with other alternative energy sources. The sensing and data logging system is utilized to extract road traffic data such as number of vehicle axles, speed of the vehicles, type of vehicles and pavement temperature. The system consists of microcontroller based hardware and the functionality of the system is fully programmable. Very intelligent program codes are implanted into the microcontroller to manipulate the entire operation of the system in order to cope with the energy constraint from utilizing alternative energy source like piezoelectric material as the power source for the system. In this regard, the algorithm for the program codes is developed in a way to significantly reduce power consumption by the system to operate. Modifications in the hardware of the system are made with the objective to reduce power consumption, while ensuring no degradation of functionality of the system.
The design and implementation of the system on the hardware and software levels necessitated adroit applications of cutting-edge technologies based on microcontroller and energy converters. The system operates at 3mW, senses the speed and temperature with high accuracy from road traffic and is powered entirely by piezoelectric devices imbedded in the pavement of the road. The system, though currently equipped to sense axle count, speed and temperature, also has provisions to incorporate other sensing capabilities such as electric field, magnetic field, light etc. The system being fully programmable, adds huge flexibility in operation and yields incredible user-friendliness. Any important change or incorporating additional sensing features can be achieved by just altering the program codes in order to make the hardware adaptable with the newly added sensing capability. A Storage Device (SD) card is the data storage device demonstrated in this research which logs all the data be used for analysis or archiving.
Considering the manual collection and the associated limitations of logged data from the SD card, Bluetooth communication is examined to transfer the data logged into the SD card to an android device. Mechanical modules carrying the piezoelectric devices and the system will be buried underneath a paved road and hence, wireless communication of data transfer is an imperative and a challenging feature of the system. This feature is achieved successfully suing Bluetooth communication. The full functionality of the system is tested using various electromechanical testing systems such as UTM-25 and MTS Acumen machine. The sensing and data logging capability of the system is also tested with signal generator to verify the limits and range of operation of the system. Testing was conducted with 6"X6" and 12"X12" mechanical enclosure modules referred as HiSEC (Highway Sensing and Energy Conversion) modules and all the results obtained are very satisfactory. Upgraded data storage in the Electrically Erasable Programmable Read Only Memory (EEPROM) is also successfully completed in order to allow retrieving of the latest logged data in case of failures.