Efficient frequency selective signal filtering

A signal filter and an efficient procedure are presented, which enable the online filtering of interferences with known frequencies with a minor or rather no phase loss and accordingly without signal delay.


The processing of signals with interferences of variable frequency can be challenging. This affects in particular applications, which are dealing with one or numerous dominant parasitic oscillations with a discrete frequency. Compensation methods, such as phase locked loop or short-term Fourier transformation, can have an inaccurate phase detection, which enable only an imperfect compensation. Conventional approaches often need long settling times, have major delays and/or cannot take variable frequencies into account. Such challenges can occur in a positioning action of an actuator, such as an electrical waste gate actuator of an exhaust turbocharger in a combustion engine. Pulsations of the exhaust from the combustion engine can be problematic, as they can induce external stresses on the waste gate. Another example, in which the above mentioned challenges can occur, is the torque control in a drive train of a vehicle, which can comprise a complex regulation of the initial and output shaft speed.

Our Solution

Inventors from the University of Hannover and IAV GmbH have developed a method for signal processing in combination with a frequency selective signal filter, which corresponds to an expanded Kalman filter. The expanded Kalman filter, which can be used to remove disturbances or spurious vibrations that overlay a signal, features an integrator with an alteration of a set value as incoming (system model) and a single mass oscillator without incoming with a variable, definable resonance frequency (interference model). According to the invention, the algorithm is able to operate online and can free a signal from one or several dominant interference frequencies, without inducing a significant delay. Hence, according to the invention, a kind of notch filter is formed, but for variable frequencies and practically without any time lag.

Fig. 1: Signal filter and filtering procedure applied on a control circuit, e.g. position regulation of an electrical waste gate actuator of an exhaust turbocharger in a combustion engine (adaptation from patent application DE102017003033B4).

CPA 1893 HsH Fig. 2Fig. 2: Expanded Kalman filter as a suitable observer for time-variant systems (adaptation from patent application DE102017003033B4).


  • Efficient removal of interferences with known, variable frequency
  • Low or no phase loss and accordingly no signal delay
  • Online operation


  • Suitable for any kind of technical systems and/or processes
  • Electrical waste gate
  • Machines with variable rotational speed (e.g. drilling machine, milling machine, winder etc.)
  • Clutch and power transmission systems (e.g. torque transmission in vehicles)

Development Status

Technology successfully developed. System functionality approved.

Patent Status

Germany patent application granted: DE102017003033B4

Patent holders:
University of Hannover – University of Applied Sciences and Arts
IAV GmbH Ingenieurgesellschaft Auto und Verkehr


Dr. Mirza Mackovic
Patent Manager Technology
E-Mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Tel.: +49 551 30724 153
Referenz: CPA-1893-HsH

Tags: IT and Software, Physics and Technology & Software


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