Patent ID: 9146175
Filing Date: 2015-09-29
Classification: F16H,G01M

Abstract:
1. A method for detecting abnormal changes in play in a transmission unit configured to transfer rotational movements of a motor, having a speed of rotation that depends on a torque reference signal, to a movable mechanical unit, wherein the method comprises, in a device for detecting abnormal changes in play in the transmission unit, computer implemented steps of: a. saving torque reference values for the motor at least in a time interval during which the motor is running at a steady state rotation speed, b. retrieving measured rotation speed values of the motor at least during said time interval, c. identifying the steady state rotation speed of the motor based on the retrieved rotation speed values, d. calculating a power spectrum of the torque reference signal, e. calculating an energy generated around a second harmonic in a selected frequency band surrounding the identified steady state rotation speed, wherein the selected frequency band is around a peak value of the second harmonic in the calculated power spectrum,