Compliance, locomotion and local computation in (self-) reconfigurable modular robots

Animals display an enormous versatility and a remarkable ability to adapt to changes in environment and terrain. Research in bio-inspired robotics strives to transfer these skills to robots, including legged systems. Even though animals seemingly effortlessly perform most of their activities on rough terrain, this feature seems to be particularly difficult to achieve in their robotic counterparts. We hypothesize that perturbations caused by e.g. rough terrain are not handled by the central nervous system, but rather by local modifications of the locomotion system such as legs and feet. Modifications can include changing mechanical properties such as spring and damping characteristics, as well as adjustments in the movement pattern of the locomotion. In this thesis, we isolate instances where a specific component, in our view, needs such modifications to fulfill different functionalities in a locomotion cycle. Further, we introduce the concept of mode-switches: a local computation is performed to induce these changes in functionalities by changing the dynamical response of the component. We then present one mode-switch method in hardware, jamming of granular media, that can switch the functionality of a foot between impact damping'' and propulsion force transmission'', and we show how this regularizes step sizes on rough terrain. We then present one mode-switch method in control, a force feedback strategy named tegotae''. This switches the functionality of leg movement between displacing the leg'' and displacing the body'', and we show how this informs the controller about which legs are bearing less weight and thus are more suited to be moved. We suggest that these methods can be applied to any legged structure and use modular robots to demonstrate these concepts. In parallel, we also improved our previously developed self-reconfigurable modular robot platform Roombots'' such that they perform a variety of tasks centered around adaptive and assistive furniture with up to 12 modules. This includes demonstrations of self-reconfiguration, mobile furniture, object manipulation, interaction capabilities and the development of a user interface. With these improvements, this platform can in the future also be used for further locomotion research where the shape-shifting ability could be of major importance.