High Precision Dexterous Manipulator

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Under sponsorship of the U.S. Army Tank Automotive Research, Development and Engineering Center (TARDEC), Square One is working on increasing both the functionality and dexterity of their current robotic platforms. The goal is to allow soldiers to interrogate questionable items at a safe distance with minimal compromise of situational awareness.

Square One is incorporating haptic sensors into the manipulator design, this allows a feel of the object in question. In addition, utilizing inverse kinematics that allow a user to fly-the-end-effector. "Point and Get" behaviors automate the process of grasping an object, users are able to interrogate questionable items at a safe distance with unprecedented dexterity.

Recently, the Tri-Sphere concept has been adapted to serve as the basis for an innovative new type of dexterous manipulator. A compact, high-precision version was built and tested. All six of this unit’s actuators were created using commercial off-the-shelf (COTS) linear actuators driven by DC stepper motors. The manipulator was fitted with a standard two-jaw gripper, and a small digital camera and distance measuring interferometer were integrated into the gripper’s palm.

Point and Get automated behavior:

Tri-Sphere’s inverse kinematic equations form the basis of a sophisticated, LabView-based controls architecture. This control system provides the system’s operator with almost unlimited operational flexibility. The manipulator can be instructed to execute pure translations or pure rotations, commands can be de-magnified to provide micron-level resolution or the end effector can be smoothly “flown” along any arbitrary path. The controls system also provides a high level of supervised autonomy. It can analyze the gripper’s video feed and determine the size, shape and location of any object within the camera’s field of view. An operator need only click on the image of an object and the manipulator will automatically acquire that object. This “point and get” capability is just one example of the many augmented tele-operations that the Tri-Sphere manipulator can perform.

While serial-jointed manipulators have larger work envelopes than parallel manipulators, this advantage fades when a manipulator is paired with a modern, high-functioning mobility platform. In these applications, the superior speed, precision and power of the parallel design make it the better solution. A variety of parallel manipulators are used by industry; by far the most common of these is the hexapod. While the proposed Tri-Sphere manipulator is a descendent of the same family tree, its novel design offers major performance advantages over its more conventional parallel brethren. The Tri-Sphere’s rigid, prismatic geometry endows the manipulator with an exceptional strength-to-weight ratio. Unlike the hexapod, it is possible to create Tri-Sphere manipulators with strongly asymmetric work envelopes. Also, instead of its actuators being distributed along six pivoting struts, all of a Tri-Sphere’s actuators are clustered together making it much easier to “ruggedize” the manipulator. These advantages strongly suggest that an enhanced version of the Tri-Sphere manipulator might be harnessed to an existing unmanned ground vehicle to create a counter-explosive technology having unprecedented capabilities.