A walking robot connected to external instrumentation via a tether has been proposed to enable visual inspections, retrieval of loose objects, and some repairs inside thin-wall round ducts. The ducts in question are made of sections about 4 ft (1.2 m) long, joined by flexible seals that accommodate axial gaps and lateral misalignments of as much as 1/4 in. (6 mm) between sections. The sections can be oriented horizontally or vertically. Some duct sections include, variously, changes in diameter, bends, and openings into side ducts. The robot is required to negotiate all such sections at distances up to 60 ft (18.3 m) from the point of entry, without damaging the thin duct walls. The robot is required to be able to enter a duct through an opening as small as 4.5 in. (11.4 cm) and to move along the duct.

Bladders Would Be Inflated to support the robot gently within the main duct. In addition to enabling visual inspection of the interior of the main duct, the robot could extend a probe for inspection of an adjacent portion of a side duct.

To prevent damage, the load exerted by the robot at a location of contact with a duct wall must be limited to 2.5 psi (17 kPa) or less. The total weight of the robot (including repair and retrieval tools and inspection video cameras but excluding the tether, tether reel, and external instrumentation) must be less than 20 lb (9 kg). The tether [61 ft (18.6 m) long] must weigh less than 10 lb (4.5 kg).

The basic requirements for gentle support, tolerance of misalignment between sections, and ability to accommodate bends would be satisfied by use of bladders that would be inflated after the robot had been placed inside the duct (see figure). The inflation pressure would be just enough to support the robot approximately centrally within the duct and to generate sufficient friction between the bladders and the duct wall to keep the robot from sliding along the duct wall when motion was not desired.

The robot would walk in a quasi-inchworm fashion by a combination of electrical and mechanical actuation, which would include alternate inflation and deflation of the fore and aft bladders in coordination with alternate lengthening and shortening of the structure between the bladders. Moreover, the inflation of both bladders during a stop would orient the axis of the robot approximately along the local ductaxis, thereby providing a directional reference for interpretation of images from the cameras.

This work was done by Dimitrios Apostolopoulos and Warren C. Whittaker of RedZone Robotics, Inc., for Kennedy Space Center. In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to

David White,
VP Business Development
RedZone Robotics, Inc.
2425 Liberty Ave.
Pittsburgh, PA 15222-4639
(412) 765-3064

Refer to KSC-12001

NASA Tech Briefs Magazine

This article first appeared in the September, 1998 issue of NASA Tech Briefs Magazine.

Read more articles from the archives here.