This paper provides a sensorless method to control the position of keys passing through a linear actuator used in an industrial textile machine. The presented method describes how to find out the position of the key using two cascading discrete Kalman filters, the first for filtering the speed and the second for filtering the impedance measurement in other to retrieve the position. Due to the thickness difference from one textile machine to another, an actuator model, to evaluate impedance in function of position, is obtained by using parameter identification.