An electromechanical device implements a unique method of actuating a fabric joint in an inflatable structure  in particular, the joint in an astronaut's pressure suit. The method is based on the principle that power from an external source can be applied to a non-constant-volume joint in a pressure suit to actuate the joint without human force. Actuation of the joint by power from an external power source enables the astronaut to conserve energy for tasks that require more dexterity.

The design of the device is relatively simple. The figure shows the device installed as part of a pressure-suit glove, but the device can be applied to any similar inflatable structure. A drive shaft made of flexible cable or rigid segments, driven via internal and external ball hex couplings, is positioned to intersect a palm bar, which is on the palm side of the glove at the metacarpal joint. The drive shaft goes through several drive hubs, rotating within mountings that include a band and a spacer block. Retracting panels are wrapped around the drive shaft. When torque is applied via the drive shaft, the panels wind around the shaft; this causes the panels to pull on anchor points, thereby retracting the joint (closing the palm). Thus, by use of this device, the wearer can flex the metacarpal joint without using any muscle power.

This Electromechanical Device Attached to a Pressure-Suit Glove uses power from an external source to assist the wearer in flexing the metacarpal (palm) joint. In response to the wearer's hand motion, the input sensor generates an input to the control system.

An input sensor positioned either inside or outside the pressure suit exhibits changing electrical resistance in response to control movement of the wearer's hand. The sensor output signal is fed as input to an external control system that drives an electric motor. The motor, in turn, drives the flexible shaft and a gear drive unit. A feedback sensor is incorporated into the gear drive unit for additional response.

This device is potentially applicable beyond the U. S. Space Program. Devices like this one could easily be applied to other pressure-suit joints, or could be used on inflatable mobility joints for individuals who suffer from joint diseases and have partially or fully lost the use of the affected joints. The device could restore the full range of motion to a diseased joint or optimize the motility of a healthy joint being used under extreme conditions like zero gravity. In a case of therapeutic use on an inflated mobility joint to restore movement to a nonfunctioning limb, the input sensor could be placed on another limb or digit that is functional. Clearly, this device is a significant advance in the field of bionics and of potential benefit to both public and private sectors.

This work was done by Daniel G. Cencer of Johnson Space Center. No further documentation is available.

This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to

Patent Counsel
Johnson Space Center
(281) 483-0837

Refer to MSC-22797


NASA Tech Briefs Magazine

This article first appeared in the October, 1999 issue of NASA Tech Briefs Magazine.

Read more articles from the archives here.