The figure depicts selected aspects of a six-legged robot that moves by hopping and that can be steered in the sense that it can be launched into a hop in a controllable direction. This is a prototype of hopping robots being developed for use in scientific exploration of rough terrain on remote planets that have surface gravitation less than that of Earth. Hopping robots could also be used on Earth, albeit at diminished hopping distances associated with the greater Earth gravitation.
Each leg includes an upper and a lower aluminum frame segment with a joint between them. A fiberglass spring, connected via hinges to both segments, is used to store hopping energy prior to launch into a hop and to cushion the landing at the end of the hop. A cable for loading the spring is run into each leg through the center of the universal joints and then down along the center lines of the segments to the lower end of the leg. A central spool actuated by a motor with a harmonic drive and an electromagnetic clutch winds in all six cables to compress all six springs (thereby also flexing all six legs) simultaneously. To ensure that all the legs push off and land in the same direction, timing-belt pulley drives are attached to the leg segments, restricting the flexing and extension of all six legs to a common linear motion.
In preparation for a hop, the spool can be driven to load the spring legs by an amount corresponding to a desired hop distance within range. The amount of compression can be computed from the reading of a shaft-angle encoder that indicates the amount by which the spool has been turned. When the robot is ready to hop, the electromagnetic clutch disengages the motor from the spool, thus releasing the cable restraints on the springs and allowing the springs to extend all six legs simultaneously.
When the robot lands, the springs in the legs are compressed as they absorb much of the impact. As the legs retract, a constant-force spring motor attached to the spool winds in the leg cables to keep them taught. A unidirectional clutch in line with the spool and the spool motor drive allows the spool to quickly overrun the motor drive when winding up the cable, but locks when the springs in the legs try to pull the cable back out. This action prevents bouncing after landing and provides for storage of energy for reuse on the next hop. A motor-driven gyroscope mounted on the lower hexagonal frame helps to prevent tumbling of the robot during hopping and was tested through computer simulation.
This work was done by Paulo Younse and Hrand Aghazarian of Caltech for NASA’s Jet Propulsion Laboratory. For more information, download the Technical Support Package (free white paper) at www.techbriefs.com/tsp under the Mechanics/Machinery category. NPO-45062
This Brief includes a Technical Support Package (TSP).
Steerable Hopping Six-Legged Robot
(reference NPO-45062) is currently available for download from the TSP library.
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Overview
The document presents a technical disclosure of NASA's Steerable Hopping Six-Legged Robot, identified as NPO 45062. The primary motivation behind this development is to create a hopping mechanism that is steerable, allowing for precise aiming during hops and safe landings. The design addresses the need for stability while the robot is on the ground, during the hopping phase, and upon landing, thereby minimizing the risk of damage from falls.
The solution involves a unique configuration of six legs connected through a pair of hexagonal frames, utilizing two universal joints for coordination. This design allows all six legs to be driven simultaneously with just two motors. Each leg is constructed with an aluminum frame and a strip of unidirectional fiberglass, which serves to store energy for hopping and cushion the landing. The cabling system used to load the springs is routed through the universal joints, enabling leg compression regardless of their orientation.
A centralized spool with an electric clutch is employed to manage the winding and release of the cabling for all legs during the hopping process. Additionally, a unidirectional clutch and spring motor are integrated to prevent bouncing during landing. The six-legged configuration enhances the robot's stability on the ground, distributes loads more effectively during hopping and landing, and reduces disturbances throughout these phases.
The document details the successful testing of a prototype, which achieved a vertical hop of 35 cm when the electric clutch was disengaged. The robot demonstrated motorized steering capabilities over a 40-degree range and performed angled hopping at a fixed 60-degree angle. Notably, gyro stabilization was tested through a simulation of the robot in lunar gravity, showcasing its ability to maintain balance during hops and landings.
The novelty of this technology lies in its steerable six-legged mechanism, which combines advanced engineering with practical applications in robotics. The document emphasizes the potential for broader technological, scientific, and commercial applications stemming from this development, highlighting NASA's commitment to innovation in aerospace-related fields. Further assistance and information are available through NASA's Innovative Partnerships Program.
