Patent ID: 7289915

Claim:
A method of estimating load inertia for a motor comprising the steps of: calculating an acceleration feedback difference Δa n between a value for an acceleration feedback signal which has passed through a low-pass filter and a value for a previous acceleration feedback signal which has passed through the low-pass filter, multiplying a previous estimated inertia J n−1 by the acceleration feedback difference Δa n to obtain a value of Δa n J n−1 , obtaining a torque feedback difference ΔT n from the value of Δa n J n−1 , calculating a torque command difference ΔT cn between a value for a torque command signal which has passed through another low-pass filter and a value for a previous torque command signal which has passed through the another low-pass filter, calculating an error e n between the torque feedback difference ΔT n and the torque command difference ΔT cn , multiplying the error e n by an estimated inertia gain K n to obtain a value of e n K n , and obtaining an estimated inertia J n , by adding the value of e n K n to the previous estimated inertia value J n−1 , wherein the estimated inertia gain K n is multiplied by a coefficient α, wherein when vibration in the acceleration feedback signal is equal to or more than a predetermined level, said coefficient α has a value greater than 0 but less than 1, and, wherein when the vibration in the acceleration feedback signal is less than the predetermined level, said coefficient α has a value of 1.