Feedforward current control method of DC servomotor using table for software servo system

A feedforward current control method is presented. This method is based on the software compensator to select the proper PWM ratio and driving mode at a certain reference current and motor speed for the PWM switching method to control the motor current. Therefore, the motor current was controlled by completely digitalized circuits. The main feature of the suggested method is the use of a 2-dimensional table prepared beforehand and includes the value of a suitable PWM ratio and driving mode. This method does not require extending the control period because of the small amount of the calculation time required by the dc motor software servo. According to experimental results, we found that the proposed feedforward method is efficient in controlling the motor current and has a compact hardware system.