Browsing by Author "Weiss, Nathan"

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    Design of a series articulated bipedal robot capable of agile and transient maneuvers
    (Stellenbosch : Stellenbosch University, 2023-03) Weiss, Nathan; Fisher, Callen; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    ENGLISH ABSTRACT: For legged robots to effectively emulate the dynamic maneuverability, mobility and agility presented by animals in nature, highly dynamic and robust legged locomotive systems are required. In achieving transient legged mobility, legged robots are capable of employing static and dynamically stable motions, including walking, running and jumping, to navigate various topographic terrains and overcome obstacles in unknown environments. However, due to the numerous complexities and non-linearities involved in legged locomotion; researchers in the past have struggled to produce robotic systems that embody the same level of dexterity and maneuverability seen by their biological inspiration. The aim of this thesis was to design and develop a series articulated bipedal robot capable of performing agile and transient maneuvers. In accomplishing this objective, the designed robots would serve as a platform for future research candidates at Stellenbosch University to explore legged locomotive compliance on various terrains. However, the main focus of this research involved the investigation and implementation of key design principles, identified through literature to have contributed to the advancements seen in existing legged robots. To aid the design process of the bipdeal robot, named Q-Bert, an analytical analysis was employed to investigate the jumping performance of a two link articulated leg model for various link lengths and actuators. This resulted in the selection of an appropriate link length, along with a Quasi-Direct Drive electric actuation transmission. Thereafter, an iterative mechanical design process was conducted to produce an initial monopedal prototype; while ensuring adequate structural integrity and minimized system mass and inertia. Furthermore, the planar motion of both, the monopod and biped platforms were constrained within the sagittal plane and supported by a developed vertical planarizing cart system. Q-Bert’s dynamic motions were embodied through the implementation of a virtual model controller inspired by Raibert’s control framework. The performance of these dynamic motions were evaluated and verified through a performance metric known as vertical specific agility. This showed the agility of Q-Bert to surpass some existing dynamic robots; however, was unable to compete with the most agile legged systems. The transient capabilities of Q-Bert were compared to long-time-horizon trajectories generated through a trajectory optimisation simulation and verified Q-Bert’s suitability for transient maneuvers. Q-Bert’s verified suitability was achieved through periodic hopping maneuvers that showed the steady-state hopping frequency and height of the robot to align with the simulated trajectories. Lastly, the maximum recorded jumping height attained by Q-Bert successfully surpassed the analytical jumping height determined during the design analysis and validated the robots design process.