UCLA

The field of legged robotics has made significant advancements and shown potential practicality in various applications. Although these robots are becoming more popular, they are still not widely used due to the inherent danger when malfunctioning as well as their high cost. BALLU, Buoyancy Assisted Lightweight Legged Unit, is a robot that never falls down due to the buoyancy provided by a set of helium balloons attached to its lightweight body. This platform solves many issues that hinder current robots from operating close to humans while also providing affordability. However, the advantages gained also lead to the platform's distinct difficulties caused by severe underactuation and nonlinearities due to external forces such as buoyancy and drag. This dissertation presents a motion planning approach using data-driven techniques motivated by these challenges and its application to BALLU. The paper describes the concept of the platform, the hardware design of different generations of BALLUs, the software architecture, the nonconventional characteristics of BALLU as a legged robot, and an analysis of its unique behavior. Based on the analysis, a data-driven approach is proposed to achieve non-teleoperated walking: a statistical process is proposed to form low-dimensional state vectors from the simulation data, and a deep neural network-based controller is trained. The controller is tested on both simulation and real-world hardware. Its performance is assessed by observing the robot's limit cycles and trajectories in Cartesian coordinates. The controller generates periodic walking sequences in simulation as well as on the real-world robot, even without additional transfer learning. It is also shown that the controller can deal with unseen conditions during the training phase. The resulting behavior not only shows the robustness of the controller but also implies that the proposed statistical process effectively extracts a state vector that is low-dimensional yet contains the essential information of the high-dimensional dynamics of BALLU's walking.