A Review of Self-Righting Techniques for Terrestrial Animals International workshop on bio-inspired robots - Nantes, April 6-8, 2011 – Poster N°49 M. Davis, C. Gouinaud, J.-C. Fauroux, P. Vaslin Self-Righting ? The need :

The constraints :

- Emergency reconnaissance - Rapid surveillance - Swift payload delivery - Ballistic phases

- High-speed movement - Uncertain terrain - Conservation of angular momentum

Twisting with no initial angular momentum Complementary approaches : - Multi-step twisting, continuous twisting, or both

Marey 1894 – Twisting by halves Pouzols et al. 2006 – Pitch attitude correction by throttling or braking the wheels

Before leaving the ground Last chance for angular momentum modification : - Frogs : Highly compliant feet, long take-off phase - Gymnasts : Optimization of joint activation timings

Jusufi et al. 2008 – Gecko continuously twisting

Frohlich 1979 – Continuous twisting

If all else fails A posteriori self-righting :

Wong et al. 2008 – Importance of the take-off phase in frog jumps

King & Yeadon 2004 – Model for joint torque activation timings optimization for performance maximization

- Cons : Suspension systems not facing the ground - Grasping (agile creatures) - Jumping - Rolling

Limb motion Two strategies : - Partial angular momentum exchange - Modification of inertia tensor components Várkonyi & Domokos 2006 – Mono-monostatic body and Indian Star Tortoise (Geochelone elegans)

Conclusion

Frohlich 1979 – Initiation of a twisting maneuver

Yeadon 1993 – A backward somersault with one twist

- Vital to protect vehicle and payload - Robotic survival of the fittest - Several phases each with particular opportunities - A wide array of strategies to choose from - Necessity for rapid sensing, computing and actuating

Fauroux et al. 2011 – Last chance before ballistic phase