Synchronization of multiple serially actuated robotic legs using virtual damping control

Özen, Merve
Even though one-legged models have been found to be a useful fundamental basis for understanding and controlling the dynamics of running, animals and physical robots alike often use multiple legs for additional support, dexterity, and stability. In general, the dynamics of such multi-legged morphologies are more complex and their control is more difficult. A common problem in this context is to achieve a particular phase relationship between periodic oscillations of different legs, resulting in different locomotory gaits. This thesis focuses on a new method to achieve a desired synchronization pattern across multiple legs, using series elastic actuation to obtain virtually tunable damping coefficients of otherwise decoupled and independent legs. In the first part of this thesis, leg models are first considered separately from the synchronization structure. Subsequently, we consider a spring-mass-damper model as a basic oscillator and investigate how the use of the damping coefficient as a control input can enable multi-leg synchronization. Following the investigation of this model, we then proceed to consider the Spring-Loaded Inverted Pendulum (SLIP) model, which has been widely accepted in the literature as a powerful tool to support the design of running robots, in order to obtain a more robust and efficient control of relative phases of different legs. Damping coefficients are, once again, used as control inputs, using feedback from measured phase differences between pairs of legs. We provide simulation results to support that this is indeed an energy efficient way in which cyclic motions of multiple legs in a system can be coordinated. Finally, the thesis also introduces a physical platform design and construction that is based on series-elastic actuation and is expected to support experimental instantiations of the proposed synchronization mechanisms for future work.
Citation Formats
M. Özen, “Synchronization of multiple serially actuated robotic legs using virtual damping control,” M.S. - Master of Science, Middle East Technical University, 2018.