Abstract: A steer-by-wire steering system including a steering device including a steering motor and a controller configured to supply a steering current to the steering motor based on a steering request. The controller includes a plurality of microcomputers, a plurality of drive circuits, and a plurality of temperature sensors. When a detection temperature difference that is a difference between detection temperatures of any two of the plurality of temperature sensors is greater than a predetermined threshold, each of the plurality of microcomputers executes an independent calculation control to independently calculate and set a current limit value, which is an upper limit value of the steering current, based on a detection temperature of one of the plurality of temperature sensors corresponding to itself, irrespective of detection temperatures of one or more of the plurality of temperature sensors other than the one of the plurality of temperature sensors corresponding to itself.

Abstract: A steer-by-wire rudder system includes a first system having a first motor unit that drives a rudder mechanism and a first control unit that controls the first motor unit, and a second system having a second motor unit that drives the rudder mechanism and a second control unit that controls the second motor unit. The first control unit and the second control unit perform cooperative control for controlling the first motor unit and the second control unit to cooperate with each other. When the cooperative control is not performed, one of the control of the first motor unit by the first control unit and the control of the second motor unit by the second control unit continues, and the other thereof stops.