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The increasing complexity of soft and hybrid-soft robots highlights the need for more efficient methods of minimizing machine learning solution spaces, and creative ways to ease the process of rapid prototyping. In this paper, we present an initial exploration of this process, using hand-chosen morphologies. Four different choices of muscle groups will be actuated on a tensegrity quadruped called...
Tensegrity robots, composed of rigid rods connected by elastic cables, have a number of unique properties that make them appealing for use as planetary exploration rovers. However, control of tensegrity robots remains a difficult problem due to their unusual structures and complex dynamics. In this work, we show how locomotion gaits can be learned automatically using a novel extension of mirror descent...
The Underactuated Lightweight Tensegrity Robotic Assistive Spine (ULTRA Spine) project is an ongoing effort to develop a flexible, actuated backbone for quadruped robots. In this work, model-predictive control is used to track a trajectory in the robot's state space, in simulation. This is the first work that tracks an arbitrary trajectory, in closed-loop, in the state space of a spine-like tensegrity...
From the viewpoint of evolution, vertebrates first accomplished locomotion via motion of the spine. Legs evolved later, to enhance mobility, but the spine remains central. Contrary to this, most robots have rigid torsos and rely primarily on movement of the legs for mobility. The force distributing properties of tensegrity structures presents a potential means of developing compliant spines for legged...
This work presents a 10 kg tensegrity ball probe that can quickly and precisely deliver a 1 kg payload over a 1 km distance on the Moon by combining cable-driven rolling and thruster-based hopping. Previous research has shown that cable-driven rolling is effective for precise positioning, even in rough terrain. However, traveling large distances using thruster-based hopping, which is made feasible...
Most traditional robotic mechanisms feature inelastic joints that are unable to robustly handle large deformations and off-axis moments. As a result, the applied loads are transferred rigidly throughout the entire structure. The disadvantage of this approach is that the exerted leverage is magnified at each subsequent joint possibly damaging the mechanism. In this paper, we present two lightweight,...
Tensegrity robots are a class of compliant robots that have many desirable traits when designing mass efficient systems that must interact with uncertain environments. Various promising control approaches have been proposed for tensegrity systems in simulation. Unfortunately, state estimation methods for tensegrity robots have not yet been thoroughly studied. In this paper, we present the design and...
In this paper, we present a lightweight, multi-axis compliant tensegrity joint that is biologically inspired by the human elbow. This tensegrity elbow actuates by shortening and lengthening cables in a method inspired by muscular actuation in a person. Unlike many series elastic actuators, this joint is structurally compliant not just along each axis of rotation, but along other axes as well. Compliant...
Duct exploration and maintenance is a task well suited for small agile robots, which must be capable of navigating complex and irregular systems of ducts. Previously, we presented a tensegrity robot, DuCTT (Duct Climbing Tetrahedral Tensegrity), which demonstrated the plausibility of such a robot for duct exploration but was never able to successfully demonstrate climbing. Here we present DuCTTv2,...
Using a new hardware implementation of our designs for tunably compliant spine-like tensegrity robots, we show that the NASA Tensegrity Robotics Toolkit can effectively generate and predict desirable locomotion strategies for these many degree of freedom systems. Tensegrity, which provides structural integrity through a tension network, shows promise as a design strategy for more compliant robots...
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...
Co-robots that can effectively move with and operate alongside humans in a variety of conditions could revolutionize the utility of robots for a wide range of applications. Unfortunately, most current robotic systems have difficulty operating in human environments that people easily traverse, much less interact with people. Wheeled robots have difficulty climbing stairs or going over rough terrain...
We are developing impedance controlled twisted string actuators (TSA) for use in tensegrity robots, as an alternative to traditional spooled cable actuation. Tensegrity robots are composed of continuous tension and discontinuous compression elements, with no rigid joints between elements, which give them unique force distribution properties. The use of tensegrity robots is strongly motivated by biological...
Tensegrity robots are composed of compression elements (rods) that are connected via a network of tension elements (cables). Tensegrity robots provide many advantages over standard robots, such as compliance, robustness, and flexibility. Moreover, sphere-shaped tensegrity robots can provide non-traditional modes of locomotion, such as rolling. While they have advantageous physical properties, tensegrity...
A robot with the ability to traverse complex duct systems requires a large range of controllable motions as well as the ability to grip the duct walls in vertical shafts. We present a tensegrity robot with two linked tetrahedral frames, each containing a linear actuator, connected by a system of eight actuated cables. The robot climbs by alternately wedging each tetrahedron within the duct and moving...
NASA Ames Research Center is developing a compliant modular tensegrity robotic platform for planetary exploration. In this paper we present the design and evolution of the platform's main hardware component, an untethered, robust tensegrity strut, with rich sensor feedback and cable actuation. Each strut is a complete robot, and multiple struts can be combined together to form a wide range of complex...
In order to produce a new mode of robust robotic locomotion and better understand how vertebrates coordinate motion with a compliant spine, we are developing a modular tensegrity robot inspired by the spine. The robot, called Tetraspine, is composed of rigid tetrahedron-shaped segments connected by six strings. Distributed impedance controllers coupled with central pattern generators (CPGs) generate...
The FootFall Planning System is a ground‐based planning and decision support system designed to facilitate the control of walking activities for the ATHLETE (All‐Terrain Hex‐Limbed Extra‐Terrestrial Explorer) family of robots. ATHLETE was developed at NASA's Jet Propulsion Laboratory and is a large, six‐legged robot designed to serve multiple roles during manned and unmanned missions to the moon;...
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