1. Locomotion control for a quadruped robot based on motor primitives Verena Hamburger

2. Advantages of motor primitives Biologically inspired (mankind, frog etc.) Evasion of online trajectory planning Simple solution of Bernstein-Problem Facilitates the generation and perception of movements (-> mirror neurons) Robust classification of faulty movement pattern (even prediction in infants) Superposition comparable to linear approximation and Fourier analysis

3. Importance of morphology Behavioural diversity Cheap design Ecological balance Emergence of behaviours

4. Aim A methodology together with morphology and task independent measures which aims at the development of quality criteria and design guidelines for motor primitives and fitting morphologies

5. Proceeding 1.Preprogrammed experiments 2.Generation of vocabularies 3.Selection of morphologies 4.Behavioural diversity 5.Robustness against variation of morphology, position and inclines of 22.5° and 30° 6.Learning progress of Reinforcement Learning Development of morphology and task independent measures

6. Preprogrammed experiments to explore the potential of the given hardware

7. MiniDog6M 6 servo motors: shoulder, hind, spine Spring approximates artificial muscle Control cycle 1 sec because of self-stabilisation Identical leg design: one active and one passive dof Acceleration sensor (static and dynamic) in the head

8. Preprogrammed trajectories Red: Dynamic

9. Generation of vocabularies

10. Flexibility-Index Flx Some primitives do not specify all motors, but uses stop symbol/Don‘t- Care x instead => Flexibility-Index

11. Transfer into simulation & Selection of morphologies

12. Investigated morphologies Head has biggest influence on standing up Original can lie on left, right, back and head Vertical cannot roll over on back and not stand on head Round can roll over on the back most easily, but cannot lie on back nor stand on head => different numbers of possible initial positions => different effort for learning

13. Behavioural diversity & Robustness against variation of shape and posture

14. No uniform definition for intelligence, but behavioural diversity is part of all current definitions Increases adaptability Not only amount is important, but also a balance between heterogenity and homogenity of solutions Mean duration of solutions as non-functional criteria Behavioural diversity

15. Behavioural-Diversity-Index BDI BDI is the product of the total amount of legal sequences with the mean diversity factor D D is a measure for the heterogenity of sequences.

16. Flx > 0 results in higher BDI than Flx = 0 Compatibility of sequences heavily depends on vocabulary (Sometimes even symmetrical tendencies) Position stable: a sequence is successful for more than one initial position of the same head Form stable: a sequence is successful for more than one heads of the same initial position Results (1)

17. Results (2) Only vertical head supports position stability for all vocabularies Form OR position stable sequences involve primitives with and without Don't-Care (Flx ≥ 0) Form AND position stable sequences involve only primitives without Don't-Care (Flx = 0)

18. Robustness on inclines of 22.5° and 30°

19. Results Weight distribution and centre of mass are identical in all three heads Original and the round head perform equally or better than on flat terrain => most robust Vertical head: solutions for Left and Right are exchanged (sometimes one side behaves as if with original head) => Morphological effect which is purely grounded in the shape

20. Learning progress: Q-Function is linearly approximated on the basis of a RadialBasisFunction-Network

21. Results (1) BDI > 10 guarantees success within max. 100 of 200 given episodes Vocabularies with low BDI often do not find a solution for one or more initial positions

22. Results (2) Flx > 0 outweighs the higher learning effort through more initial positions Flx = 0 Flx > 0

23. Conclusion Only few vocabularies are equally good at all features and morphologies Use of Don't-Care (Flx > 0) is good for BDI and learning progress, but not for robustness Effects of shape and material must already be considered in the design phase No need for adaptation in case of proper design and enough behavioural diversity Currently cheapest design and control of a running quadruped

24. To Do Application of this methodology to many different tasks, morphologies, learning methods and vocabularies Examination of robustness on different ground properties e.g. elastic, irregular Additional investigations of sensory- motor-coordination

25. The end.