Semester Project Defense: Locomotion in Modular Robots: YaMoR Host 3 and Roombots. Simon Lépine Supervisors: Auke Ijspeert Alexander Spröwitz

Task definition Reactivate the software framework around YaMoR Host 3. Model a Roombots (RB) module in Webots. Create several different robots exploring different locomotion principles, such as legs or wheels. Interface the robots with YaMoR Host 3, add CPGs and run optimization processes.

The YaMoR project YaMoR stands for « Yet another Modular Robot » Identical modules that can be connected in many different ways Controlled with a Central Pattern Generator (CPG) Each module of the robot contains one oscillator

Central Pattern Generator « A CPG is a network of neurons, capable of producing oscillatory signals without oscillatory inputs. » Network of coupled non- linear oscillators. Source: J. Buchli and A.J. Ijspeert. Distributed central pattern generator model for robotics application based on phase sensitivity analysis. In A.J. Ijspeert, M. Murata, and N. Wakamiya, editors, Biologically Inspired Approaches to Advanced Information Technology: First International Workshop, BioADIT 2004, volume 3141 of Lecture Notes in Computer Science, pages Springer Verlag Berlin Heidelberg, 2004.

Oscillator model Phase oscillator with controlled amplitude. Phase Amplitude Offset Output Where vi and Ri are the intrinsic frequency and amplitude of the oscillator i, and ai a positive constant. Couplings between oscillators are defined by the weights wij and phase biases φij. Source: Jérôme Maye, « Control of Locomotion in Modular Robotics », Biolologically Inspired Robotics Group, Swiss Federal Institute of Technology of Lausanne, Master thesis.

YaMoR Host 3 Can be seen as a driver for the robot. Is able to control the real robot or a Webots simulation without requiring the user to take care whether he is using the real robot or not.

YaMoR Optimizer Interface providing a convenient way of performing optimizations to the optimizers (not an optimizer itself). Able to load optimizers dynamically, to process several instances of the same optimizer with different parameters. Uses YaMoR Host 3 to interact with Webots or the real robot. Source: Michel Yerly, « YaMoR Lifelong learning », Biolologically Inspired Robotics Group, Swiss Federal Institute of Technology of Lausanne, Master thesis.

Debugging… Lots of problems (CD version was not working, program trying to copy files in an unreachable directory…) Slow advancements, because the communication by with Michel Yerly just can’t be fast. Michel Yerly came: all problems solved at once.

Roombots New Modular Robot under development Inspired by Molecubes 3 DOF Particularity: axis B and C can be either orthogonal or parallel during the same movement

Webots implementation Used Masoud Asadpour’s work on Molecubes Changes on motor torques and DOFs principally

Robot configurations

Gait search (snake) Not a « standard » snake gait Rolls on the side using extremities as supports.

Gait search (tripod)

Gait search (walking quadripod)

Gait search (Car) Using the 360° rotation property of Roombots

Things forgotten in the report… Some systematic searches were not complete: range should have been twice broader (tripod for instance). Time of one « period » for a set of parameters during searches is 10 sec.

The final word Roombots possibilities are vast Interfacing Roombots with YaMoR Host 3 would probably be very interesting Didn’t have time to implement CPG… 

Questions?