Method and device for determining the rotational speed and the angle of rotation of a motor shaft of a mechanically commutated dc motor

Abstract

A method for determining the rotational speed and the angle of rotation of a motor shaft of a mechanically commutated DC motor from the measured progression of time of the ripple in the motor current and in the motor terminal voltage occurring during the commutation. A motor state model of the DC motor, to which the measured motor terminal voltage and the measured motor current, an estimated load torque, an estimated rotational speed and an estimated angle of rotation of the DC motor are supplied to a Kalman filter as input variables. By running the motor state model, the Kalman filter provides an estimated current, an adjusted rotational speed and an adjusted angle of rotation of the DC motor as output variables. From the ripple in the measured motor current and the rotational speed, adjusted by the Kalman filter, a ripple detection unit determines the commutation times and, from the latter, derives an estimated rotational speed and an estimated angle of rotation of the DC motor and provides same to the Kalman filter as the input variables.