Technologies

Single Coil Absolute Position Sensor (SCAPS) with Inductive Gap Sensor (GapSyn) and Add-On Technologies

A novel position sensor with gap sensing capabilities and a suite of three associated technologies that can be incorporated into the lead technology to enhance sensing and other functions

This technology suite, developed by NASA’s Marshall Space Flight Center, includes a Single Coil Absolute Position Sensor (SCAPS) with Inductive Gap Sensor (GapSyn) and three associated technologies that can be incorporated into the primary technology to perform additional sensor functions and serve as a short-range antenna and close proximity transmitter and receiver. Applications for these technologies span a broad range of industries and they can be combined to perform a variety of functions.

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Technology Suite Benefits

Robust: Relies on printed circuit board (PCB) technology, which is well established and highly reliable
Economical: Uses components that have a low manufacturing cost
Effective: Incorporates a limit switch, which provides advantages over other commercially available sensors
Flexible: Includes primary technology that has unique functionality and can be augmented to perform a variety of functions

Single Coil Absolute Position Sensor (SCAPS) with Inductive Gap Sensor (GapSyn)

Benefits
Applications
How it works
Why it is better
Patents

This technology (MFS-32224-1) combines NASA’s GapSyn innovation (MFS-32218-1) with existing NASA SCAPS technology (MFS-32213-1), creating a novel position sensor with gap sensing capabilities. This innovative combination significantly improves the SCAPS technology and produces a sensor with the ability to self-calibrate and operate in a wireless or true non-contact configuration. Depending on the application, this sensor technology can provide absolute position in various forms and can be easily integrated into user designs.

Benefits

Precise: Provides absolute position and provides improved precision when compared with conventional position sensing techniques
Low-cost: Uses inexpensive components
Reliable and self-calibrating: Exhibits data correlations of 0.99999 or better
Non-contact: Allows coils to be completely sealed against the environment
Simple: Uses only two active components
Scalable: Adjusts to meet application requirements
Flexible: Integrates easily into several applications and supports other NASA technology

Applications

CNC, water jet, and laser milling machines
Pick and place machines for semiconductor manufacturing and automated biotech operations
Inkjet and raster printers
Home and office scanners
Profilometers
Industrial robots in which raster, head, and substrate are in close proximity
Rotary and linear positioning of automotive engine components
Robot-assisted surgery, biotech micro array, and assay procedures

How It Works

The SCAPS technology is a small, non-contact, absolute position sensor that can be used as a linear position sensor, x-y position sensor, limit switch, and/or gap sensor, either independently or in combination. In SCAPS, which is used where there is relative motion between two components or structures, an excitation coil is mounted on one component, and it induces a signal in a sensor coil that is mounted on another component. The magnitude and phase of the sensed signal unambiguously define a precise position.

GapSyn is a unique inductive gap sensor that measures the absolute magnitude of the gap between two members that move relative to one another. A signal is induced in a planar “sensor synchronizer” coil, parallel and close to the emitter coil. The strength of this signal is directly proportional to the gap between these two coils.

One purpose of this innovation is to provide the excitation signal phasing information to the sensor side of the SCAPS technology. This allows the two components to not be directly wired together and allows for wireless operation of the SCAPS sensor technology. A second purpose of this innovation is to provide the sensor electronics a means by which sensor calibration can be independently achieved. In-situ calibration allows the sensor to be self-calibrated initially and then be re-calibrated autonomously at any time.

Several other discrete inventions developed by NASA innovators comprise this technology, including:

An Absolute Limit Switch (MFS-32192-1) takes advantage of the value of the induced voltage and uses a predetermined value of the sensed signal to determine an absolute limit switching point, such as to stop a movable carriage.

A ferromagnetic metal backing layer (MFS-32219-1) provides a flux return path, thus enhancing the signal-to-noise ratio and signal linearity, as well as increasing the usable range of the position sensor. The metal backing is ideally "mu-metal," a nickel-iron alloy that has a very high magnetic permeability.Depending on the application, a thin, lightweight mu-metal foil may be appropriate, which would add little mass or volume.

A miniature housing (MFS-32000-1) with a sealable cover contains a small circuit board with electronics and a communications interface.

Why It Is Better

Integration of the GapSyn coil into the SCAPS technology allows the sensor unit to be completely separate from the excitation unit. It allows for wireless operation of the sensor coil, produces a constant voltage, and can be packaged in the same location as the SCAPS sensor. The device can be easily integrated into various applications because it can be designed to be self-calibrating; the basic sensor utilizes only two active and inexpensive components; and the sensor can be attached by an adhesive or can be inside or underneath the outer skin of a component. The sensor technology can be physically scaled up or down in size and can be designed with redundant coils without adding additional volume. Tested prototypes have achieved accuracies of four microns, and greater accuracies are possible with other sensor configurations. The emitter can use excitation frequencies ranging from several kilohertz to the megahertz region. The sensor is extremely reliable and repeatable and exhibits data correlations greater than 0.99999.The SCAPS technology with GapSyn can be combined with three other NASA technologies to create additional applications and benefits (see below).

Patents

NASA’s Marshall Space Flight Center has received patent protection for this technology: U.S. Patent Nos. 7,116,098 (link opens new browser window), 7,081,730 (link opens new browser window), and 7,134,885 (link opens new browser window).

Short Range Antenna/Close Proximity Transmitter and Receiver

Benefits
Applications
How it works
Why it is better
Patents

This technology (MFS-32228-1) is an inexpensive and effective method of exchanging information over a short distance between two devices when each is equipped with a coil. This short-range, non-contact data communication method is ideally suited for use in conjunction with NASA's GapSyn technology.