Patent ID: 8232758
Filing Date: 2012-07-31
Classification: G05B,H02P

Abstract:
1. A controller for controlling an electric motor driving a drive shaft of a machine tool or an industrial machine, comprising: sine wave instruction means for adding a sine wave instruction to a torque instruction or a speed instruction of the controller; electric current feedback value obtaining means for obtaining an electric current feedback signal of an electric current flowing in the electric motor as an electric current feedback value in every sampling period; speed feedback value obtaining means for obtaining a speed feedback signal of the speed of the electric motor as a speed feedback value in every sampling period; estimated electric current value calculation means for calculating an estimated electric current value from the speed feedback value obtained in every sampling period and estimated inertia and estimated frictional force of the drive shaft; estimated error calculation means for calculating an estimated error from the electric current feedback value obtained in every sampling period and the estimated electric current value; and updating means for updating the estimated inertia and the estimated friction of the drive shaft using the speed feedback value detected in every sampling period and the estimated error, wherein inertia and friction are simultaneously estimated, wherein the estimated electric current value calculation means comprising: speed difference calculation means for calculating the difference between a currently sampled speed feedback value and a previously sampled speed feedback value of the speed feedback detected in every sampling period; first calculation means for calculating the product of the difference of the speed feedback value calculated by the speed difference calculation means and the estimated inertia; second calculation means for calculating the product of the currently sampled speed feedback value and estimated viscous friction; and third calculation means for calculating the product of the polarity of the currently sampled speed feedback and estimated Coulomb friction, wherein the values determined by the first calculation means, the second calculation means, and the third calculation means are used to calculate the estimated electric current value.