Sensor Companies Gain By Emphasizing Market-Focused R&D
SBD has consistently encouraged sensor companies to aim their research and product development efforts at addressing key sensing needs in significant markets and applications that would benefit from enhancements in the sensor's ability to measure an important parameter. To maximize the opportunities for their newly developed sensors, sensor developers and producers should constantly strive to obtain the latest information about major developments and trends that impact the prospects for sensors in a particular industry or market segment. They should also seek feedback from users in a wide range of industries in order to develop a sensor that is capable of effectively addressing a variety of applications.
BEI Precision Systems & Space Division (Maumelle, AR, 501-851-4000)--a division of BEI Technologies, Inc., and a motion control company with considerable experience in providing high-accuracy and aerospace-quality encoder/motors, encoders, subsystems, servo accelerometers, inertial sensors, and scanners--is strategically expanding opportunities for their new and existing sensor products in varied markets in addition to the aerospace, aviation, military, and government sectors.
Bob Riebe, business development manager, explained that BEI Precision Systems & Space Division (which provides the pointing system for the Hubble telescope) is focusing on using their engineering capabilities and product expertise to enter new, high-growth markets in the industrial and commercial sectors. Such target markets include, for example, telecommunications, semiconductors, and robotics. To optimize their market expansion strategy, BEI Precision Systems & Space Division is analyzing opportunities in many industries in order to find the best fit for their capabilities, Riebe noted. Moreover, BEI Precision Systems & Space Divison seeks to partner with companies and organizations that do development work; and they are also looking for potential acquisition candidates.
BEI Precision Systems & Space Division's optical linear gap displacement transducer (LGDT)(U.S. Patent #5,017,772) has been designed to address expanding needs in the marketplace for displacement and proximity sensors that are capable of sensing components of shrinking size, able to sense objects comprised of virtually any material, and can operate in diverse and harsh environments over a variety of ranges with high resolution. The LGDT was introduced at Sensors Expo, held in Chicago, IL from June 5th-7th, where the product won an award. Feedback from attendees was valuable for ascertaining key market opportunities for the device. Based on feedback from attendees, the LGDT may be further refined.
Andrew Chouinard, design engineer at BEI Precision Systems & Space Divison, explained that, originally, the LGDT was considered to have applications in, for example, magnetic levitation for bearings, such as those provided by Kimco Magnetics (San Marcos, CA), a division of BEI Technologies, Inc.
However, BEI Precision Systems & Space discovered that the ability of the non-contact optical LGDT to work with a plethora of target
materials renders it an attractive solution for numerous, diverse displacement/proximity sensing applications in addition to voice coil
actuator closed-loop control, including fast-steering mirror displacement sensing, web position sensing in web processing, real-time concentricity measurements, bearing runout measurements, sensing mechanical displacement under dynamic load, and vibration measurements.
Moreover, Riebe added that the LGDT is suitable for a plethora of applications that require very fine resolution and precise distance
measurements, such as manufacturing highly accurate gas turbine components and copying machine manufacture.
Chouinard noted that bearing runout (the amount of "wobble" in the bearing) is a very important parameter in optical encoders (which need to have a very small bearing runout). The LGDT would, for example, be beneficial for measuring runout on a bearing assembly before the assembly is built into the optical encoder.
BEI Precision Systems & Space Division has expanded the capabilities of the LGDT, including broadening its measurement range, using probes of different sizes for different measuring ranges, and developing more thermally-stable electronics. Their linear gap displacement transducer offers such features as high resolution, excellent repeatability, broad linear range, and adaptability to numerous types of targets (i.e., those with a reflectivity down to about 3%). The LGDT, which employs a patented fiber-optic probe, is capable of performing effectively and reliably in harsh environments. Unlike inductive displacement sensors, the LGDT is not limited to conductive (e.g., ferrous metal or aluminum) targets.
Since it utilizes a ratiometric optical technique, the LGDT can be used with bare and finished metals, paint, plastics, glass, paper products, and any materials that reflects light (including diffuse surfaces). Since it uses optical technology, the probe can be placed in strong electric, magnetic, and radio frequency (RF) fields without suffering performance degradation. The length of the fiber bundle does not affect the measurement, allowing for remote placement of the electronics.
The LGDT, which consists of a fiber-optic probe and an electronic module, measures the distance from the probe tip to a flat surface. The fiber-optic probe, consisting of concentric fiber rings, is used to illuminate the target's surface, measure the reflected light, and derive a measurement of the distance to the target. The LGDT is designed to measure target surface movement over a small range very precisely. The device has an analog voltage output that varies with the distance of the target to probe's tip minus the standoff distance (the minimal distance from the object to the probe tip that is required to obtain a measurement).
The linear range, sensitivity, and resolution of an LGDT probe primarily depend on the probe's geometry; therefore, probes can be designed to address the requirements for specific applications.
The LGDT's fiber-optic probe contains three fiber bundles. At the sensor end of the probe, the bundles are arranged in concentric rings, with separation bands between the rings. At the opposite end of the probe, the bundles are separated into independent fiber cables for coupling to the electronic module.
The target surface is illuminated by a 880 nm infrared LED (light emitting diode) via the central fiber bundle. Divergent light emitted from the central fiber bundle is reflected from the target's surface back to the probe end and is collected by the two outer fiber bundle rings. As the target moves further away from the probe end, the outer fiber ring receives an increasing amount of reflected light, while the inner ring receives a decreasing amount. Each of the receiver rings transmits the collected light to a silicon photo diode detector in the electronic module. An analog divider provides the ratio of the detector signals, which is multiplied by a gain factor. An offset voltage is subtracted to yield the final analog output.
The output characteristics of the LGDT probe can be varied based on the sensor's gain and offset settings. A low-gain configuration (where the gain is 5 V and the offset is 0 V) provides the greatest dynamic range from a given probe. A high-gain configuration (which uses increased gain and an offset voltage to provide an output of 0-10 V over just the linear range of the probe) provides the highest sensitivity for a 0.375" diameter probe (2 V/mm).
An LGDT unit with a 0.375" diameter probe provides a resolution to 150 nm over a 5 mm range, with an output noise of only 0.3 mV RMS (root mean square). A particular probe's dynamic and linear measurement range depends on its opto-mechanical geometry. Smaller diameter probes have shorter ranges and higher sensitivities, yielding to higher resolution. In testing, the LGDT had an average repeatability over a 7 mm range of 2.7 mV; and its true repeatability is expected to be less than this value.
In testing of the LGDT with a 0.375" diameter probe to various target lighting conditions (i.e., darkness, ambient sunlight within the room, fluorescent room lights, low-intensity spotlight, high-intensity spotlight), normal lighting conditions did not measurably affect the LGDT's response, while high-intensity target illumination caused an offset voltage. This phenomenon is expected to occur. The outer receiver ring, which has a larger cross-sectional area than the inner receiver ring, picks up more external light than the inner ring. This causes a greater proportional increase in the signal from the outer ring than from the inner ring, resulting in a positive shift in the LGDT's output voltage.
Ambient lighting conditions have virtually no effect on the LGDT's sensitivity, but do cause a signal offset. For applications where only target movements are measured, the LGDT can be used without calibration for external lighting, as long as the amount of external light remains constant during measurements. For absolute distance measurements in high-light environments, the LGDT requires calibration for lighting conditions. It should be noted that the aforementioned results apply pertain to an LGDT unit without optical filtration. For applications where ambient light effects must be eliminated, optical bandpass filters can be inserted between the receiver bundles and detectors.
In testing involving target reflectivities of 98%, 75%, 42%, and 3% at the wavelength of the LED, the LGDT performed well with respect to targets of virtually any reflectivity. While the LGDT uses a ratiometric measurement technique, and, therefore, has an output that is independent of illumination intensity, the automatic LED power control increases the LED's output as target reflectivity decreases. This phenomenon increases the light level, and, therefore, the signal-to-noise ratio, for low-reflectivity targets. Below a certain reflectivity (which depends on the optical probe used), the LED's power limit is reached and the signal-to-ratio begins to degrade. This effect begins to appear with a target of 3% reflectivity.
"Diffusivity" is the target characteristic that has the greatest effect on the LGDT's response. The LGDT has been tested on the following targets, listed in order of their increasing diffusivity: an aluminum front-surface mirror (least diffusive); bare aluminum with surface oxidation; aluminum scoured with 120 grit sandpaper; and plain white paper (most diffusive). In testing, the LGDT performed effectively with either specular or diffuse targets. Increasing target surface diffusivity results in a positive offset voltage and greater sensitivity, compared to specular targets.
Light is typically reflected from a specular target in a manner corresponding to Fermat's reflection principle (i.e., the angle of
reflection is equal to the angle of incidence). The pattern of light reflected from the target is constrained by the divergence angle of the light emitted from the probe's illumination bundle.
In contrast, highly diffuse targets scatter rays in random directions about the theoretical reflection angle, thereby spreading the reflected light. As a result, more light strikes the outer receiver ring at closer target distances, increasing the LGDT's output. The effect also becomes greater with increasing target distance, resulting in higher sensitivity for diffuse, as opposed to, specular, targets.
The LGDT has been tested with respect to target angular misalignment using the four diffusivity test targets. The degree to which angular misalignment affects the LGDT's response depends on the target's diffusivity; and the effect of the target's angle is much greater for highly specular targets than for diffuse targets. Since highly specular targets reflect light in a specific direction that depends on the incident light angle, rotation of the target causes twice-greater rotation of the light rays leaving the target, shifting the reflected light pattern across the probe.
The pattern of light reflected from a diffuse target is broadened by random fluctuations in the reflected light angle. If the magnitude of the random scattering angles is greater than the target's rotation angle, there will be a minimal change in the light pattern incident on the probe's receiver rings.
Target diffusivity can be exploited in applications where the target angle may change or is unknown. The use of a diffuse target reduces or eliminates target angle effects. However, it is important to balance target angle immunity with signal-to-noise ratio. Extremely diffuse targets can cause low signal levels and, therefore, low signal-to-noise ratios.
BEI Precision Systems & Space is also exploring new commercial and industrial markets for their inertial sensors and precision servo
accelerometers, which are now typically used in space and re-entry vehicles.
Major markets for BEI Precision Systems & Space's products include space, tactical military, range instrumentation, lab instruments,
and high-accuracy industrial applications.
BEI Precision Systems & Space's model 8301 precision fluid rotor inertial angular displacement sensor--which has been used in the Landsat thermatic mapper camera, as well as in GOES, GPS, and Defense Department satellites--detects angular motion or "jitter" from milliradians to below 1 nanoradian. Their model 4310 linear servo accelerometer--which has been utilized in numerous space or re-entry vehicles, including Skylab, Minuteman, Mercury, Survivor, Polaris, GOES, and Intelsat V and VI--has a resolution of less than 0.001% of full scale and a temperature range of -40° to +93°C.
BEI Technologies, Inc. (San Francisco, CA, 415-956-4477)(Nasdaq: BEIQ) was spun-off from BEI Electronics, Inc. in 1997. BEI Technologies offers electronic devices that provide vital sensory input for advanced machinery and automation control systems.
Through its divisions, BEI's products include: shaft encoders; precision potentiometers (used, for example, for throttle, steering, suspension, and seat and mirror position controls in automobiles and heavy equipment); magnetic actuators; brushless DC motors; accelerometers and rate sensors using traditional mechanical technology (i.e., a moving mass suspended by a pivot and jewel mechanism); and micromachined rate of rotation sensors and accelerometers, which use a crystalline quartz element, and address such applications as heading and attitude reference in aircraft and missiles, stabilization of satellites, pointing and control of antennae on aircraft, ships, and other moving platforms, navigation of oil well drill bit assemblies, and intelligent vehicle stability systems.
Additional products offered by BEI include: GyroChip® micromachined quartz rate sensors (which are used as yaw sensors in automobile stability control or spinout prevention systems (including GM's StabiliTrak® vehicle dynamic control system), and in such applications as navigation of autonomous guided vehicles, ocean buoy and sea-state monitoring, stabilization of pointing systems for antennas and optical systems, and stabilization platforms (e.g., wheelchairs)); silicon micromachined and thin-film pressure sensors; inertial measurement units (IMUs) for inertial navigation and position or attitude reporting systems; scanner assemblies in military night vision systems; servo systems that use an encoder or other sensor to control the position or velocity of rotating shafts or other parts; and trackballs used in such applications as ultrasound scanning machines, factory automation, and defense.
Moreover, SiTek (Campbell, CA), a BEI company, is engaged in the development of future MEMS (microelectromechanical systems) products
(including a micromachined silicon gyro); and OpticNet was established as a minority-owned BEI subsidiary and separate company last year to develop proprietary devices for MEMS-based fiber-optic telecommunications applications. During FY 2000, which ended September 30, 2000, BEI developed and introduced a non-contact angular position sensor (NCAPS(tm)), which uses inductive technology to sense angular position and is based on proprietary transceiver technology with digital signal processing techniques.
In May, BEI reported that its "smart actuator" (which integrates BEI's voice coil and position sensing technologies to provide actuation and position feedback) has been selected for use in a vehicle adaptive cruise control equipped with forward-looking radar detection technology.
The adaptive cruise control system can operate without the need to reset or resume cruise control operation when the driver approaches a vehicle that has slowed down or is traveling at a slower speed than the reference vehicle. The follow-on production order is for a model year 2002 vehicle and was awarded to BEI by HE Microwave LLC, a joint venture of Delphi Delco Electronics Systems and Raytheon.
Key market segments for BEI's products include factory automation, office automation, process automation, transportation (including cars, trucks, mass transit, construction and farm equipment), health care and scientific equipment, military, aviation, space, and telecommunications.
For FY 2000 ended September 30, 2000, BEI Technologies net sales reached about $219.2 million, a 37.5% increase over the prior year. After-tax net income from continuing operations was about $9.6 million, or $1.30 per share, a 76% gain in EPS over the prior year. In FY 2000, automotive sales increased 97.3% to $107.5 million, while sales to industrial customers rose $7.2 million to $93.0 million.
For the first six months of FY 2001, BEI Technologies had net sales of about $125.3 million, a 28% increase over the comparable period in FY 2001. Net income was about $6.75 million, or $0.47 per share, a 90% increase over net income reported in the first half of FY
2000.
