Patent ID: 7637245

Claim:
A system for controlling an actuator linked to a valve rotatably installed in a passage through which gas flows, the actuator being configured to change, based on a controllable torque parameter and a deviation between a current position of the valve and a target position thereof, torque to be applied to the valve, the torque parameter representing the torque to be applied to the valve, the system comprising: a first storing unit configured to store therein a first threshold, the first threshold being defined in a variation range within which the torque parameter is variable, the first threshold separating the variation range into a first range and a second range, when the torque parameter takes values within the first range, an operational stability of the actuator being ensured, when the torque parameter takes values within the second range, the operational stability of the actuator being difficult to be ensured; and a restricting unit configured to: determine whether the deviation between the target position of the valve and the current position thereof is equal to or lower than a predetermined length in a rotational direction of the valve; and if the torque parameter substantially shifts, from the first range, to and/or through the first threshold in the variation range and it is determined that the deviation is equal to or lower than the predetermined length in the rotational direction of the valve, change the torque parameter such that the torque parameter is within the first range to thereby restrict variation in the torque parameter with a flow of the gas being substantially kept through the passage.