Steering control device

A steering control device that controls a steering device that assists steering of a vehicle and that includes a synchronous motor that generates assist torque and a power conversion circuit that applies a voltage to the synchronous motor, the steering control device comprising:

• a current control processing circuit that manipulates the voltage, which is applied to the synchronous motor by the power conversion circuit, in order to control a current that flows through the synchronous motor to a command value;
• a control angle manipulation processing circuit that manipulates a control angle that determines a phase of the command value in order to control a detected value of steering torque, which is torque input to a steering member, to target torque through feedback control;
• and
• a torque-based guarding processing circuit that performs a guarding process such that an update amount for the control angle determined by the control angle manipulation processing circuit is equal to or less than a torque-based upper-limit guard value, which is an upper-limit guard value for a magnitude of the update amount in a rotational direction of the synchronous motor that matches the detected value, and equal to or more than a torque-based lower-limit guard value, which is a lower-limit guard value for the magnitude of the update amount in the rotational direction of the synchronous motor that matches the detected value, wherein
• the torque-based guarding processing circuit includes a contraction processing circuit that gradually contracts an allowable range of the update amount determined by the torque-based upper-limit guard value and the torque-based lower-limit guard value using, as a condition, at least one of a state in which the magnitude of the update amount is more than the torque-based upper-limit guard value and a state in which the magnitude of the update amount is less than the torque-based lower-limit guard value.