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A Dynamical System for Online Learning of Periodic Movements of Unknown Waveform and Frequency


Conference Paper


The paper presents a two-layered system for learning and encoding a periodic signal onto a limit cycle without any knowledge on the waveform and the frequency of the signal, and without any signal processing. The first dynamical system is responsible for extracting the main frequency of the input signal. It is based on adaptive frequency phase oscillators in a feedback structure, enabling us to extract separate frequency components without any signal processing, as all of the processing is embedded in the dynamics of the system itself. The second dynamical system is responsible for learning of the waveform. It has a built-in learning algorithm based on locally weighted regression, which adjusts the weights according to the amplitude of the input signal. By combining the output of the first system with the input of the second system we can rapidly teach new trajectories to robots. The systems works online for any periodic signal and can be applied in parallel to multiple dimensions. Furthermore, it can adapt to changes in frequency and shape, e.g. to non-stationary signals, and is computationally inexpensive. Results using simulated and hand-generated input signals, along with applying the algorithm to a HOAP-2 humanoid robot are presented.

Author(s): Gams, A. and Righetti, L. and Ijspeert, A.J. and Lenarčič, J.
Book Title: 2008 2nd IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics
Pages: 85--90
Year: 2008
Month: October
Publisher: IEEE

Department(s): Movement Generation and Control
Bibtex Type: Conference Paper (inproceedings)

DOI: 10.1109/BIOROB.2008.4762850

Address: Scottsdale, USA
URL: https://www.researchgate.net/profile/Andrej_Gams/publication/224376112_A_Dynamical_System_for_Online_Learning_of_Periodic_Movements_of_Unknown_Waveform_and_Frequency/links/0fcfd50bdd21bc0637000000.pdf


  title = {A {Dynamical} {System} for {Online} {Learning} of {Periodic} {Movements} of {Unknown} {Waveform} and {Frequency}},
  author = {Gams, A. and Righetti, L. and Ijspeert, A.J. and Lenarčič, J.},
  booktitle = {2008 2nd {IEEE} {RAS} \& {EMBS} {International} {Conference} on {Biomedical} {Robotics} and {Biomechatronics}},
  pages = {85--90},
  publisher = {IEEE},
  address = {Scottsdale, USA},
  month = oct,
  year = {2008},
  url = {https://www.researchgate.net/profile/Andrej_Gams/publication/224376112_A_Dynamical_System_for_Online_Learning_of_Periodic_Movements_of_Unknown_Waveform_and_Frequency/links/0fcfd50bdd21bc0637000000.pdf},
  month_numeric = {10}