A method for switching a main board and a standby board, the method comprising: determining (S104) a fault grade of the main board; determining (S104') a fault grade of the standby board; and switching (S106) the main board and the standby board according to the fault grade of the standby board and the fault grade of the main board; wherein the main board and the standby board comprise a plurality of microcontroller units, MCUs, and the method further comprising the steps of: determining (S102) one MCU of a plurality of MCUs on the main board as a first main MCU and the remaining MCUs on the main board as auxiliary MCUs; determining (S102') one MCU of a plurality of MCUs on the standby board as a second main MCU and the remaining MCUs on the standby board as auxiliary MCUs; and wherein: the step of determining (S104) a fault grade of the main board comprises determining, by the first main MCU, a fault grade of the main board according to faults in the auxiliary MCUs of the main board and faults in the first main MCU, and the step of determining (S104') a fault grade of the standby board comprises determining, by the first main MCU, a fault grade of the standby board according to faults in the auxiliary MCUs of the standby board and faults in the second main MCU reported by the second main MCU. determining (S104) a fault grade of the main board; determining (S104') a fault grade of the standby board; and switching (S106) the main board and the standby board according to the fault grade of the standby board and the fault grade of the main board; wherein the main board and the standby board comprise a plurality of microcontroller units, MCUs, and the method further comprising the steps of: determining (S102) one MCU of a plurality of MCUs on the main board as a first main MCU and the remaining MCUs on the main board as auxiliary MCUs; determining (S102') one MCU of a plurality of MCUs on the standby board as a second main MCU and the remaining MCUs on the standby board as auxiliary MCUs; and wherein: the step of determining (S104) a fault grade of the main board comprises determining, by the first main MCU, a fault grade of the main board according to faults in the auxiliary MCUs of the main board and faults in the first main MCU, and the step of determining (S104') a fault grade of the standby board comprises determining, by the first main MCU, a fault grade of the standby board according to faults in the auxiliary MCUs of the standby board and faults in the second main MCU reported by the second main MCU. determining (S102) one MCU of a plurality of MCUs on the main board as a first main MCU and the remaining MCUs on the main board as auxiliary MCUs; determining (S102') one MCU of a plurality of MCUs on the standby board as a second main MCU and the remaining MCUs on the standby board as auxiliary MCUs; and wherein: the step of determining (S104) a fault grade of the main board comprises determining, by the first main MCU, a fault grade of the main board according to faults in the auxiliary MCUs of the main board and faults in the first main MCU, and the step of determining (S104') a fault grade of the standby board comprises determining, by the first main MCU, a fault grade of the standby board according to faults in the auxiliary MCUs of the standby board and faults in the second main MCU reported by the second main MCU. the step of determining (S104) a fault grade of the main board comprises determining, by the first main MCU, a fault grade of the main board according to faults in the auxiliary MCUs of the main board and faults in the first main MCU, and the step of determining (S104') a fault grade of the standby board comprises determining, by the first main MCU, a fault grade of the standby board according to faults in the auxiliary MCUs of the standby board and faults in the second main MCU reported by the second main MCU. <EOS>