Patent ID: 8541972

Claim:
A method for suppressing a speed ripple occurring during an operation of an AC motor by using a torque compensator based on an activation function, the method comprising: (a) calculating a speed error ω err based on a reference speed ω ref and an actual speed ω act ; (b) calculating a controller output T rm by using the speed error ω err as an input of a PI control and an operation of a compensated torque T com ; and (c) determining a torque variation based on the controller output T rm and a reference torque T ref and operating the torque variation in relation to an anti-windup gain K a to use the torque variation as an input of an integral (I) control, wherein in step (b), an output of the compensated torque T com is determined based on f ⁡ ( ω err · ⅆ ω err ⅆ t ) = 0 ⁢ ⁢ ( when , ( ω err · ⅆ ω err ⅆ t ) < 0 ) ⁢ ⁢ and ⁢ f ⁡ ( ω err · ⅆ ω err ⅆ t ) = 1 ⁢ ⁢ ( when , ( ω err · ⅆ ω err ⅆ t ) > 0 ) .