A Flexible Low-Cost Time Synchronizer For Gnss/Ins Integration

For the design of a hybrid GNSS/INS or other multi-sensors navigation system, a very challenging topic is the timing issue. Unknown time synchronization errors among IMU, GNSS receiver and other sensors lead to significant data source errors and degrade alignment or navigation performance. Traditional methods to resolve this problem is based on hardware, software or the combination of both, each of which is unable to achieve the simultaneous optimization of cost and performance. In this paper, a flexible, low-cost time synchronization system (FLTS) is proposed to eliminate time synchronization errors and supply satisfied precision with much lower complexity and cost. Some key issues on Field Programmable Gate Array (FPGA) hardware design and programming of FLTS are detailed discussed. To achieve millisecond synchronization precision, the 1PPS (Pulse Per Second) signal from GPS receiver is used as time reference to add timestamps for the output data of INS and other auxiliary navigation sensors. With low cost hardware and flexible configuration, our FLTS wins features of grand usage and expansibility, and can meet the time synchronization needs not only of GNSS/INS integration, but also other multi-sensors navigation systems.