Squishy Robotics’ goal is to commercialize prior research, hardware and testing performed under an Early Stage Innovation (ESI) grant from NASA Ames through UC Berkeley with Dr. Agogino as the PI. Currently, the NASA-funded spherical tensegrity robots were designed to perform missions on the Moon. Although some of the surface and mission conditions of the Moon are different from disaster relief requirements on Earth (e.g., gravity, communication mechanisms, soil properties) there are many similarities between the two. This research provides the foundation for developing the technology platform for our commercial applications.
Our R&D plan will begin with the technology specifications needed to transfer academic research to our proposed commercial applications. By pushing current technological limits, we believe we have the foundation and a research plan to develop a ground-breaking technology platform that could disrupt the current market in robotics. Its success will de-risk the project and provide proof-of-concept validation.
Benefits of Tensegrity Robots
Tensegrity (tension-integrity) structures were first introduced in the mid-1960s in architecture and art. The structures’ passive combination of cables-in-tension and rods-in-compression became a significant design feature in several architectural and sculptural structures.
Challenging environments for robot locomotion have motivated recent research into robots using tensegrity structures. These robots consist of rigid rods held together in a network of cables in tension. Tensegrity robots can be made as spheres that roll on a variety of terrains, snake-like robots which crawl along the ground, or as part of four-legged robots. All of these robots are designed to exploit the various beneficial properties of tensegrity structures: low mass, variable stiffness, redundancy to failure, withstand high impact forces, easily transportable, among other benefits.
Tensegrity robots change their shape by adjusting the lengths of their cables eliciting the moniker as “shape-shifting” robots. Many different types of tensegrity robots have been created, including robot designs that use pneumatic actuators, shape-memory alloy actuators, linear motors to pull on cables, direct actuation via servomotors, as well as motors attached to spools. Regardless of the actuation method used, a tensegrity structure must have all tensile elements in tension to maintain a stable structure.
Dr. Agogino’s Prior Work in Tensegrity Robots
Led by Dr. Agogino, the University of California’s Berkeley Emergent Space Tensegrities (BEST) Laboratory has been collaborating with the National Aeronautics and Space Administration’s (NASA) Ames Research Center on using tensegrity structures as the basis for the next generation of space exploration robots. These spherical structures are robots that are designed to land and roll over a range of different terrains.
In particular, a spherical tensegrity robot has the potential to be used as both a lander and a rover since it has the ability to passively distribute forces across the entire structure. The tension network provides shock protection from the impact of landing without requiring complex parachute systems while also serving as a mobility platform for exploring unpredictable environments. This makes them ideal for deployment from an aerial vehicle, such as an unmanned aerial vehicle (UAV).
Five different actuated spherical tensegrity robots have been developed by NASA Ames and Dr. Alice Agogino’s UC Berkeley team: the SUPERball at NASA Ames, the TT-1 and TT-2 robots at UC Berkeley, the TT-3 robot at UC Berkeley (Fig. 1), and the new TT-4mini (Fig. 2). Each of the four ”TT” robots from UC Berkeley have results in improvements in design, actuation, and control. The TT-4mini contributes a major step in manufacturing and assembly for these robots.
|FIGURE 1: Tensegrity robot TT-3 prototype. The rod-center modules contain the electronics and motor device to control the length of each cable .||FIGURE 2: The TT-4mini prototype, the first tensegrity robot that uses the elastic lattice platform. This robot moves by adjusting the lengths of its cables with respect to its elastic lattice It is also able to roll up an inclined surface of 24 degrees.|
The UCB-NASA collaboration has extended the research of spherical tensegrity robots to 12-bar tensegrity structures, which represent the next largest symmetric form. We have simulated and created rapid prototypes of two geometric forms of 12-bar structures in order to learn more about their mobility, impact, and payload characteristics. The 12-bar structure will be an option in our development of tensegrity robots for exploration on rough terrain.
Finally, tensegrity spine robots have been developed to assist the walking of four-legged (quadruped) robots over uneven terrain. The Underactuated Lightweight Tensegrity Robotic Assistive Spine (ULTRA Spine) developed at UC Berkeley is a tensegrity robot with five independent vertebrae that can bend and twist, emulating a back-bone’s motions. Simulations, controllers and physical prototypes have been developed for the ULTRA Spine.
Two patents have been filed and a third is under a provisional filing. The SBIR team has secured a licensing arrangement through UC Berkeley for this intellectual property.
- DNA Structured Linear Actuator – PCT/US2016/032899 (Patent Pending)
- Modular Rod-Centered, Distributed Actuation and Control Architecture for Spherical Tensegrity Robots – PCT/US2016/061353 (Patent Pending)
- Elastic Lattices for Design of Tensegrity Structures and Robots – Provisional – BK-2017-078 (provisional filed; in process of patent filing)