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Objective
The National Aeronautics and Space Administration (NASA) seeks qualified users and/or manufacturers to pursue commercialization of technologies associated Compliant Mechanism.
Description
Reproducing the strength, flexibility, and durability of a human joint is a task with which designers have long struggled. By using the inherent compliance associated with cables, NASA has developed for prosthetic, robotic, and industrial designers compliant mechanisms that are tough, strong, and flexible. The compliance technology that is the basis of these joint designs has been patented and licensed for robotics and medical applications. However, because the technology benefits numerous applications, NASAs Goddard Space Flight Center continues to seek qualified users and/or manufacturers to pursue further development and commercialization of cable compliance applications.
The NASA-developed Compliance technology was applied to a NASA gantry robot, which illustrates the joints ability to correct for misalignment as the gantry touches the target.
Cable compliance technologies use many segments of stranded wire rope (cable) to provide compliance and damping in coupling, mating, and force transmission operations. The cables are configured to make a joint that can be tailored to any desired degree of flexibility. The damping aspect of compliant technologies comes from the many strands in each cable rubbing against each other.
The compliant mechanism is comprised of two U-shaped mounting brackets that are mounted perpendicular to one another by means of swaged cables that interlock at a center block. By manipulating variables such as cable size, cable length, cable stranding, cable pretwisting, and cable material, the designer can control the degree of compliance within the cable. Thus, the flexibility can be adjusted for any joint.
Benefits
A compliant mechanism is capable of rotation and translation in all three planes. These capabilities enable the duplication of the rotational movement and flexibility of a natural knee or hip. Specific attributes of the joint include the following:
- Durable: no metal-to-metal or plastic hinging.
- Inexpensive: the cables are typically stainless steel.
- Compact: less bulky than typical joints capable of supporting comparable loads.
- Strong/Absorbing: provides compliance and vibrational damping in one system.
- Flexible/Compliant: an advantage for robotic applications that need to touch gently - the compliance can help correct for misalignment.
Compliant Mechanism
Potential Application(s)
- Physical Therapy: A walker that uses NASA’s cable compliance technology has been patented by NASA and licensed by Wheel Ring, Inc. This walker enables patients with limited use of their legs and lower backs to be supported for walking therapy.
- Joint Prosthesis: Prosthetic devices are typically expensive and short-lived, and only the most expensive provide "human-like" response. The compliant joint provides resistance similar to a human limb because of its nonlinear nature: as the cable in the joint bends the stiffness increases. Standard mechanical devices have constant stiffness. Figure 2 presents the compliant technology applied to a knee joint.
2-Knee-Joint Engineering Prototype
- Isolation of Sensitive Equipment: A compliant mechanism is being investigated for use in the delicate Orbital Replacement Units for maintenance and repair of the Hubble Space Telescope. The compliance of the cable enables isolation from stresses caused by thermal distortion and vibration.
- Offshore Platform Assembly: Barges used to build offshore platforms will move in all six degrees of freedom relative to each other. Tying them together induces strong forces. Cable compliance is the only technology that can accommodate this type of motion. NASA’s compliance technology provides flexibility during initial contact and increasing stiffness and strength as needed after linking.
- Vibration Damping for Power Tools: Reciprocating tools such as jackhammers, rivet guns, and hammer drills can cause repetitive motion injuries such as nerve damage and carpal tunnel syndrome. The damage is caused by the vibration transmitted from the tool while it is operating. Cable compliance technology can effectively reduce this vibration through shock isolation. Because it is small this NASA technology can also be applied to hand tools.
Technology Commercialization Status
Four U.S. patents have been issued for the compliant mechanism, two of which have already been licensed. However, two patents are still available for license: Compliant Joint (4,932,806) and Robot Cable-Compliant Devices (4,946,421). Because the technology benefits numerous applications, NASAs Goddard Space Flight Center continues to seek qualified users and/or manufacturers to pursue further development and commercialization of cable compliance applications.
Related Technologies
Contact
If your company is interested in this technology please contact:
Office Of Technology Transfer
GSFC
Phone: (301) 286-5810
FAX: (301) 286-0301
E-mail: Techtransfer@gsfc.nasa.gov
Public Release Date: 4/5/1999
Reference Number: TOP5-615
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