Study of power line communication modems for automotive communication networks

Abstract

Power line communication (PLC) technology has become very attractive in the automotive sector. As vehicle manufacturers aim to produce vehicles with improved fuel economy, comfort and technology, they are limited by current vehicle communication networks due to increased bulk and complexity. PLC technology has been suggested as a solution for this issue by utilizing existing power wires as a communication channel. However reliability is a big challenge with PLC technology, especially with critical systems such as braking, steering and engine control. This thesis studies the feasibility, reliability and possible improvements of PLC for controlling vehicle subsystems such as heating, ventilation and air conditioning (HVAC) system. In order to determine feasibility, several modems were examined for cost and ease of implementation. After selecting a modem solution, the PLC prototype modem was tested on an HVAC system test bed to control various fans, blowers and pumps over a DC power line. The PLC solution was then tested using a 2003 Ford Focus ZTS and a 2011 Ford Edge SE. The tests consisted of repeatedly sending a code from a transmitter connected to the vehicle battery while a receiver was connected to a power port inside the vehicle. The tests were run in several vehicle states e.g. Off, electronics on engine off and engine idle. The results from the tests showed that communication can be established over a vehicle power line with reasonable cost and ease. However reliability of the proposed solution needs to be improved before it can be implemented in vehicles. To improve performance of the proposed PLC solution, an impedance matching network for PLC was proposed. From current research an adaptive matching network utilizing active inductors and capacitor banks was designed and simulated. The designed matching network was simulated with several different automotive loads such as a vehicle battery and various lights. Simulations results showed the proposed matching network was capable of matching impedances with all the simulated automotive loads. When the circuit was built up and tested, there were issues with stability and cost of construction. The results show that more work needs to be done before PLC can become a suitable solution in vehicle communication network. With improvements such as impedance matching, line drive ability and robust modulation schemes, it won't be long before PLC will be a viable vehicle network solution.