A Method for Disturbance-Tolerant “Sensorless” Angle Measurement of DC Motors
“Sensorless” measurement of the angle of rotation or speed of direct current motors using periodic oscillations in the electrical signals is usually very susceptible to errors. This is caused by the occurrence of frequencies in the signals that do not correspond to the expected frequency. In this article, a new method is presented, which is robust against these influences and is, thus, able to provide a much more reliable angle or speed signal. For this purpose, the causes of the frequencies occurring in the electrical signals are discussed first. Based on general considerations incorporating these effects, the derivation of a general scheme and the associated requirements are presented. The algorithm is then developed in detail and implemented within the context of an application example using an electric parking brake of a motor vehicle. Finally, the process is experimentally validated using three different motor types under different operating conditions and the specific properties of the method are discussed.