System Design and Locomotion of Superball, an Untethered Tensegrity Robot

The Spherical Underactuated Planetary Exploration Robot ball (SUPERball) is an ongoing project within NASA Ames Research Center's Intelligent Robotics Group and the Dynamic Tensegrity Robotics Lab (DTRL). The current SUPERball is the first full prototype of this tensegrity robot platform, eventually destined for space exploration missions. This work, building on prior published discussions of individual components, presents the fully-constructed robot. Various design improvements are discussed, as well as testing results of the sensors and actuators that illustrate system performance. Basic low-level motor position controls are implemented and validated against sensor data, which show SUPERball to be uniquely suited for highly dynamic state trajectory tracking. Finally, SUPERball is shown in a simple example of locomotion. This implementation of a basic motion primitive shows SUPERball in untethered control

Design of a novel wheeled tensegrity robot: a comparison of tensegrity concepts and a prototype for travelling air ducts

Efforts in the research of tensegrity structures applied to mobile robots have recently been focused on a purely tensegrity solution to all design requirements. Locomotion systems based on tensegrity structures are currently slow and complex to control. Although wheeled locomotion provides better efficiency over distances there is no literature available on the value of wheeled methods with respect to tensegrity designs, nor on how to transition from a tensegrity structure to a fixed structure in mobile robotics. This paper is the first part of a larger study that aims to combine the flexibility, light weight, and strength of a tensegrity structure with the efficiency and simple control of a wheeled locomotion system. It focuses on comparing different types of tensegrity structure for applicability to a mobile robot, and experimentally finding an appropriate transitional region from a tensegrity structure to a conventional fixed structure on mobile robots. It applies this transitional structure to what is, to the authors' knowledge, the design of the world's first wheeled-tensegrity mobile robot that has been designed with the goal of traversing air ducts

Power-efficient adaptive behavior through a shape-changing elastic robot

The adaptive morphology of a robot, such as shape adaptation, plays a significant role in adapting its behaviors. Shape adaptation should ideally be achieved without considerable cost, like the power required to deform the robot’s body, and therefore, it is reasonably considered as the last resort in classical rigid robots. However, the last decade has seen an increasing interest in soft robots: robots that can achieve deformability through their inherent material properties or structural compliance. Nevertheless, the dynamics of these types of robots is often complex and therefore it is difficult to substantiate whether the cost like the required power for changing its shape will be worthwhile to achieve the desired behavior. This article presents an approach in the development and analysis of a shape-changing locomoting robot, which relies on the ability of elastic beams to deform and vibrate. Through a proper use of elastic materials and the robot’s vibration-based dynamics, it will be shown both analytically and experimentally how shape adaptation can be designed such that it leads to desirable behaviors, with better power efficiency compared to when the robot solely relies on changing its control input. The results encourage emerging direction in robotics that investigates approaches to change robots’ behaviors through their adaptive morphology. </jats:p

Morphological adaptation in an energy efficient vibration-based robot

Morphological computation is a concept relevant to robots made of soft and elastic materials. It states that robot's rich dynamics can be exploited to generate desirable behaviors, which can be altered when their morphology is adapted accordingly. This paper presents a low-cost robot made of elastic curved beam driven by a motor, with morphological computation and adaptation ability. Simply by changing robot's shape and the rotating frequency of the motor that vibrates the robot's body, the robot is able to shift its behavior from showing a tendency to slide when it needs to perform tasks like going under confined space, to have more tendency to hop diagonally forward when the robot stands upright. It will also be shown that based on the proposed mechanism, the energy efficiency of the robot locomotion can be maximized

Evolution of linkages for prototyping of linkage based robots

Prototyping robotic systems is a time consuming process. Computer aided design, however, might speed up the process significantly. Quality-diversity evolutionary approaches optimise for novelty as well as performance, and can be used to generate a repertoire of diverse designs. This design repertoire could be used as a tool to guide a designer and kick-start the rapid prototyping process. This paper explores this idea in the context of mechanical linkage based robots. These robots can be a good test-bed for rapid prototyping, as they can be modified quickly for swift iterations in design. We compare three evolutionary algorithms for optimising 2D mechanical linkages: 1) a standard evolutionary algorithm, 2) the multi-objective algorithm NSGA-II, and 3) the quality-diversity algorithm MAP-Elites. Some of the found linkages are then realized on a physical hexapod robot through a prototyping process, and tested on two different floors. We find that all the tested approaches, except the standard evolutionary algorithm, are capable of finding mechanical linkages that creates a path similar to a specified desired path. However, the quality-diversity approaches that had the length of the linkage as a behaviour descriptor were the most useful when prototyping. This was due to the quality-diversity approaches having a larger variety of similar designs to choose from, and because the search could be constrained by the behaviour descriptors to make linkages that were viable for construction on our hexapod platform