Patent ID: 8358578

Claim:
A redundant communication system comprising: a first control device which calculates a control command value of an electric power device equipped in a vehicle, and outputs a first command signal and a second command signal respectively corresponding to the control command value; a second control device which controls the electric power device on the basis of one of a first control command value and a second control command value respectively corresponding to the first command signal and the second command signal received from the first control device; a primary communication line which connects the first control device and the second control device, and transmits the first command signal from the first control device to the second control device; and a secondary communication line which connects the first control device and the second control device, and transmits the second command signal from the first control device to the second control device, wherein communications through the primary communication line and the secondary communication line are carried out in different communication protocols, and wherein the second control device comprises: a primary communication line abnormality determining unit which determines that the primary communication line is abnormal, when a non-reception state of the first command signal or an abnormality state of the first command signal continues during a predetermined period; and a control command value switching unit which selects one of the first control command value and the second control command value in a switching manner, and wherein the control command value switching unit switches the selection from the first control command value to the second control command value within the predetermined period from a start time at which the non-reception state of the first command signal or the abnormality state of the first command signal starts until a time at which the primary communication line abnormality determining unit determines that the primary communication line is abnormal.