Tri-Sphere Multi-Mode Mobility Platform

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Robotic Mobility

The Tri-Sphere design has also been adapted to serve as the foundation for a holonomic walking frame: two platforms, each with three fixed legs, are joined by the manipulator.

The Tri-Sphere design has also been adapted to serve as the foundation for a holonomic walking frame: two platforms, each with three fixed legs, are joined by the manipulator.

The resulting system is capable of moving via a tripod gait along any compass heading and can also make use of the manipulator’s yaw to pivot in place. These motion capabilities are identical to those of sophisticated six-legged robots but are achieved with a fraction of the mechanical complexity.

The use of the Tri-Sphere manipulator endows the walking frame with several powerful capabilities. Because the relative motion between the two platforms can be any subset of the Tri-Sphere’s generous work envelope, the length of the robot’s gait can be adjusted in real time and its center of mass can be shifted fore and aft and from side to side. In addition, the functional flexibility of the design supports the implementation of “adaptive” walking algorithms automatically adjust the foot orientation and placement to accommodate obstacles and surface irregularities. This ability to dynamically tune key motion parameters allows the robot to move nimbly in cluttered, unstructured environments.

In addition to enhanced mobility, the robot’s design allows it to also function as a highly dexterous manipulator. When the three legs attached to the lower platform are provided with the ability to pivot, that platform is transformed into a six-axis gantry. Because its parallel/prismatic design, a Tri-Sphere robot can employ this gantry to dig, grasp, lift and carry objects weighing many times its weight.

The third important component of the Tri-Sphere Robot’s functionality is its ability to dynamically control the pose of its upper plate. When the upper platform’s legs are allowed to pivot, they can be spread to deploy solar cells or communication surfaces. The robot is then able to adjust the upper plate’s elevation and azimuth to precisely aim these surfaces toward any point in space.