Evolution of Fin Undulation on a Physical Knifefish-inspired Soft Robot

Frank Veenstra, Jonas Jørgensen, Sebastian Risi

Research output: Conference Article in Proceeding or Book/Report chapterArticle in proceedingsResearchpeer-review


Soft robotics is a growing field of research and one of its challenges is how to efficiently design a controller for a soft morphology.
This paper presents a marine soft robot inspired by the ghost knifefish that swims on the water surface by using an undulating fin underneath its body.
We investigate how propagating wave functions can be evolved and how these affect the swimming performance of the robot.
The fin and body of the robot are constructed from silicone and six wooden fin rays actuated by servo motors.
In order to bypass the reality gap, which would necessitate a complex simulation of the fish, we implemented a Covariance Matrix Adaptation Evolution Strategy (CMA-ES) directly on the physical robot to optimize its controller for travel speed.
Our results show that evolving a simple sine wave or a Fourier series can generate controllers that outperform a hand programmed controller.
The results additionally demonstrate that the best evolved controllers share similarities with the undulation patterns of actual knifefish.
Based on these results we suggest that evolution on physical robots is promising for future application in optimizing behaviors of soft robots.
Translated title of the contributionEvolution af finne-undulation på en fysisk knivfisk-inspireret blød robot
Original languageEnglish
Title of host publicationGECCO ’18 : Genetic and Evolutionary Computation Conference, July 15–19, 2018, Kyoto, Japan
EditorsJennifer B. Sartor, Theo D’Hondt, Wolfgang De Meuter
Number of pages8
Place of PublicationNew York, NY. USA
PublisherAssociation for Computing Machinery
Publication date15 Jul 2018
ISBN (Print)978-1-4503-5618-3
Publication statusPublished - 15 Jul 2018


  • Soft Robotics
  • Evolutionary Algorithms
  • Evolutionary Robotics


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