US Patent 9740178 Primary controller designation in fault tolerant systems

A fault tolerant controller system includes a first controller and a second controller. One of the first and second controllers designated as a primary controller for generating control signals intended to control actuation devices on a vehicle under non-fault operating conditions, and the other of the first and second controllers designated as a secondary controller generating control signals intended to control actuation devices on the vehicle. The actuation devices are responsive only to the designated primary controller. An error is detected in the primary controller and a message is transmitted from the faulty controller to the non-faulty controller identifying the error. The non-faulty controller is subsequently designated as the primary controller. The control signals including an identifier that identifies the non-faulty controller as the designated primary controller. In response to detecting the error, the faulty controller is reset to operate in a safe operating mode as the secondary controller.