Minimizing GPS Clock Synchronization Error for PX4-Based Unmanned Aircraft

In order to build an Time Sensitive Network(TSN) based on unmanned aircraft such as drones, clock synchronization between nodes must be very precise. To do this, it is necessary to minimize the error that occurs when each unmanned aircraft synchronizes the clock of the flight controller using the time information received from the GPS module. This paper proposes a method to synchronize the clock of the flight controller directly connected to the GPS module without changing the general hardware configuration of the unmanned aircraft. The flight controller receives a message containing time information from the GPS module more than 5 times per second and updates the clock of the RTOS, but the clock synchronization error between controllers is very large, with an average of 21.64ms. To minimize the synchronization error and S/W delay, we match various parameters of the GPS module and flight controller, improve the firmware source code running on the controller, and change the default settings of the RTOS. This can reduce the clock synchronization error between flight controllers by up to 84.1%.