Robust and Economical Bipedal Locomotion

For bipedal robots to gain widespread use, significant improvements must be made in their energetic economy and robustness against falling. An increase in economy can increase their functional range, while a reduction in the rate of falling can reduce the need for human intervention. This dissertation explores novel concepts that improve these two goals in a fundamental manner. By centering on core ideas instead of direct application, these concepts are aimed at influencing a wide range of current and future legged robots. The presented work can be broken into five major contributions. The first extends our understanding of the energetic economy of series elastic walking robots. This investigation uses trajectory optimization to find energy-miminizing periodic motions for a realistic model of the walking robot RAMone. The energetically optimal motions for this model are shown to closely resemble human walking at low speeds, and as the speed increases, the motions switch abruptly to those resembling human running. The second contribution explores the energetic economy of the real robot RAMone. Here the model used in the previous investigation is shown to closely match reality. In addition, this investigation demonstrates a concrete example of a trade-off between energetic economy and robustness. The third contribution takes a step towards addressing this trade-off by deriving a robot constraint that guarantees safety against falling. Such a constraint can be used to remove considerations of robustness while conducting future investigations into economical robot motions. The approach is demonstrated using a simple compass-gait style walking model. The fourth contribution extends this safety constraint towards higher-dimensional walking models, using a combination of hybrid zero dynamics and sums-of-squares analysis. This is demonstrated by safely modifying the pitch of a 10 dimensional Rabbit model walking over flat terrain. The final contribution pushes the safety guarantee towards a broader set of walking behaviours, including rough terrain walking. Throughout this work, a range of models are used to reason about the economy and robustness of walking robots. These model-based methods allow control designers to move away from heuristics and tuning, and towards generalizable and reliable controllers. This is vital for walking robots to push further into the wild.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/153459/1/nilssmit_1.pd

Acoustic measurements using a microphone array

A microphone array is designed, built and used for analyzing the radiation of a single test instrument, an oud. Two analysis algorithms are implemented for this purpose, radiation mapping and delay and sum beamforming. Radiation mapping is used to determine the spatial radiation intensity of the instrument, while beamforming is used to map the source locations on the instrument’s soundboard. In this report, the mechanical design history of the microphone array is presented, as well as a detailed overview of the finalized design. The development and testing of the beamforming algorithm is then summarized, followed by a detailed description and analysis of the final algorithm. Radiation maps for the 5 largest vibration modes of the oud are produced and presented, as well as beamforming results for various frequencies. Some investigations are subsequently made into the validity of the results, and recommendations are given for their further verification and improvement. It is concluded that beamforming can consistently and successfully locate single monopole sound sources. While the results of beamforming for the more complicated sources found in the oud soundboard remain far from conclusive, their consistency and intuitive placement suggest that they hold some valid results. In order to fully support this hypothesis, it is concluded that modal analysis should be performed on the oud, comparing the results with those produced by beamforming.Science, Faculty ofPhysics and Astronomy, Department ofUnreviewedUndergraduat

An Overview on Principles for Energy Efficient Robot Locomotion.

Despite enhancements in the development of robotic systems, the energy economy of today's robots lags far behind that of biological systems. This is in particular critical for untethered legged robot locomotion. To elucidate the current stage of energy efficiency in legged robotic systems, this paper provides an overview on recent advancements in development of such platforms. The covered different perspectives include actuation, leg structure, control and locomotion principles. We review various robotic actuators exploiting compliance in series and in parallel with the drive-train to permit energy recycling during locomotion. We discuss the importance of limb segmentation under efficiency aspects and with respect to design, dynamics analysis and control of legged robots. This paper also reviews a number of control approaches allowing for energy efficient locomotion of robots by exploiting the natural dynamics of the system, and by utilizing optimal control approaches targeting locomotion expenditure. To this end, a set of locomotion principles elaborating on models for energetics, dynamics, and of the systems is studied