Position Measurement & Control - Summer 1997 (SU97)

Position Measurement & Control is published for the customers of SpaceAge Control and the engineering and instrumentation community. Subscriptions are free. To subscribe at no charge, submit a Newsletter Subscription Request.

Contents

• How SpaceAge Control Started
  
• Looking for a Better Fit: Prosthesis Lining Movement Monitored
  
• Boeing/UCLA Unmanned Air Vehicle Completes First Flight Tests
  
• Placing the Displacement Cable Connector
  

What were you doing in the late 1960's? During that time in Palmdale, California USA, SpaceAge Control, Inc. was getting its start as a provider of sensors, instrumentation, and components to the space and aviation industries. One of the first products the company produced was the "LDT" (linear displacement transducer), used to measure various moving components on flight test aircraft at Edwards AFB for NASA, the U.S. Air Force, and the U.S. Army.

The LDT, now referred to as a position transducer, was developed to provide a flexible means of measuring flight control surfaces, pilot control inputs, landing gear, and other aircraft systems. Before the LDT, aircraft instrumentation technicians and engineers had to design and fabricate special-purpose measurement devices each time a new measurement requirement came up.

Today, aircraft and aerospace applications continue to be significant uses of SpaceAge Control position transducers. Over the past 10 years, there has been increasing use of these products in the vehicle, transportation, industrial control, and OEM fields. These markets generally select these products to obtain the same benefits aircraft instrumentation professionals have for nearly 30 years: flexibility, small size, durability, and accuracy.

Editor's Note: Thanks to Norm Foster, founder of SpaceAge Control, Inc., for providing background information. SpaceAge Control will be celebrating its 30th anniversary next year.

Bending a limb may seem like a simple motion to most people but to prosthetists and prosthesis users, limb movement is a very complex subject. Developing a prosthesis that simply attaches to the limb while remaining fully functional has occupied the minds of top doctors and researchers since the first prosthesis was developed.

A particularly difficult aspect of prosthesis development is ensuring the limb liner motion tracks the motion of the human skin it is in contact with. Any movement between the limb liner and the human skin results in poor biofidelity, skin irritation, and general dissatisfaction by the amputee.

In an effort to better understand how limb liners interface with the skin, Engineered Silicon Products, LLC measured negative compliance of below-knee prostheses during swing phase and compared the performance of various silicone limb liners, including those that use a stiffening material to reduce non-compliance.

Lou Haberman, Certified Prosthetist and Orthotist for Engineered Silicon Products, chose a SpaceAge Control Series 160 position transducer to measure the liner movement. The transducer was mounted laterally onto a pre-fabricated molded pelvic belt. The displacement cable was secured to an outrigger installed on the prosthesis (see photos above). The maximum displacement monitored was 0.815 inches (20.701 mm). The transducer output was sent to both a chart recorder and PC-based data acquisition system.

According to Haberman, a SpaceAge Control transducer was selected for use after a long search for an appropriate measurement tool. "These products are very compact and mount easily while still giving consistent and accurate data", noted Haberman.

An analysis of the test results confirmed previous less sophisticated clinical testing. In addition, a test involving amputees' redundant (fleshy) limbs was surprising in that a matrix liner reduced compliance by a statistically insignificant 0.026 inches (0.66 mm) compared to non-matrix liners. This lack of difference between matrix- and non-matrix-based liners has led to other studies to understand amputee perception and prosthesis design.

For more information on the company or prosthesis design and development, please contact:

Sandwiched between November rainstorms, a crew of Boeing engineers successfully launched and flew the UCLA-Boeing (formerly Rockwell North American) Unmanned Air Vehicle (UAV) during tests on Nov. 19 at El Mirage Dry Lake in the Mojave Desert of California.

Flying with an array of SpaceAge Control instrumentation, the battery powered, 44-foot-wing-span craft was released from its remote launch vehicle and flew perfectly for about three minutes at around 100 feet altitude. Jubilant engineers chased the aircraft across the dry lake in a convertible. Two more successful tests were completed before an early winter storm soaked the lake, making it unfit for vehicles.

We're quite pleased," said Boeing project manager Gerry Miller. "The performance of the aircraft was essentially flawless, and verified the flight dynamics we expected."

Boeing/UCLA UAV (Photo by Scott Quintard of ASUCLA Photography)

SpaceAge Control Model 173-0241 position transducers were used to provide actuator feedback on the wings and inverted-V ruddervator. In addition, a SpaceAge Control Model 100400 mini air data boom provided angle-of-attack and sideslip. A custom mini-turbine provided airspeed data.

Darrell Dennell, Instrumentation Team Leader for Boeing, selected the SpaceAge Control products because, "We had good luck with these products in the past including extensive use on the B-1."

The purpose of the aircraft is to provide a platform for communications or environmental sensing that is self-powered (solar), automatic, and permanent. This is only achievable if more than one aircraft flies in formation, like a flock of geese. In this lead-follow manner, each aircraft can take advantage of turbulent upwash coming off the plane in front to reduce its workload. This additional energy is the key to enabling aircraft to stay aloft permanently, powered only by the Sun.

UCLA and Boeing engineers will soon begin construction of two more UAVs. With these three aircraft, the team hopes to begin a series of demonstration flights this summer to achieve autonomous formation flying. If these tests are successful, the aircraft will be fitted with solar panels to prove high-altitude solar-powered flight, and then solar-powered formation flight (SPFF). In SPFF, five or more ultralight UAVs would fly at approximately 65,000 feet and stay in formation autonomously.

Ultimately, aircraft arrays could be deployed permanently over cities to carry microwave repeaters for cellular phones and wireless computers, or can be utilized for a number of applications, such as carrying accurate sensors for environmental studies of earth and air reconnaissance.

Most of the UAV's parts were fabricated at UCLA's Research & Development Machine Center. The aircraft was assembled at UCLA by Boeing engineers and faculty, staff, and students from the UCLA School of Engineering and Applied Science.

The prototype UAV's wing span is constructed of tubular spars and graphite-epoxy ribs covered with mylar. The inverted V-tail ruddervator is of the same composition as the wings, and both are attached to a one-piece, tubular fuselage. A payload compartment is mounted on the fuselage below the center of the wing span, and a "push" propeller is mounted aft of the V-tail.

Follow-on aircraft will be constructed with graphite-epoxy spars and fuselage, replacing aluminum components on the prototype. The prototype lacks solar cells, which will be added to aircraft after formation flight is demonstrated.

According to Professor Jason Speyer of UCLA's School of Engineering and Applied Science, the aerodynamics of formation flying have been known for years. "The fact is, when geese fly in formation, when they are gliding, each bird takes advantage of the upwash coming off of the bird in front to reduce its workload," Speyer said.

Fighter pilots can verify that their fuel tanks go dry slower when they fly in wingtip-to-wingtip formations for a length of time. In formation flight, the geese actually perform much like a single larger wing. We hope to essentially accomplish the same thing with the UAV, except that the aircraft would do it autonomously and stay aloft for weeks, months, or longer."

In SPFF, five or more ultralight UAVs would fly at approximately 65,000 feet and stay in formation autonomously. "Formation flying is inherently unstable without an active control system," said Speyer. "We believe that our system will control the relative position of each aircraft in the formation to an accuracy of less than one inch."

Speyer explained that the UAV's flight control system will accomplish this by combining information from air data sensors, an inertial measurement unit, infrared ranging sensors and signals fed by the Global Positioning Satellite network.

Boeing project manager Gerry Miller said the aircraft will maintain flight without the use of conventional ailerons or flaps by using actuators at the wing tips that twist the outer portion of the wing. The actuators will essentially twist the end third of each wing to change shape enough to maintain aerodynamic control, he said. SpaceAge Control position transducers measure the degree of twist and provide feedback to the actuators.

van packed with communications equipment and antennas will be used to remotely control the aircraft when they take off and land. Once the aircraft achieve flight, they will fly to altitude and assemble into a "V" formation by themselves (autonomously).

Miller said that once formation is achieved, each aircraft's engine will require one-half horsepower (373 watts) or less to maintain flight. The aircraft power system will include solar-cells that cover approximately 90 percent of the wing surface, and rechargeable batteries located in the fuselage. "The power system will provide from 500 to 4,000 watts, depending upon the efficiency of the photovoltaic panels used," Miller said. "This will allow the aircraft to fly under direct power from the Sun during the day, while at the same time recharging the batteries for flight at night."

In addition to the aircraft's native components, the payload compartment can carry more than 20 pounds of communications receivers/transmitters, or other sensing packages for a variety of applications. Thousands of simultaneous wireless data-transfers could be accomplished by each aircraft, or infrared, radar and other imaging sensors on each aircraft can be programmed to act as a very wide aperture lens for accurate scan of the earth's surface, such as for environmental studies. The aircraft could also be used by the military for high-altitude, low-cost surveillance of a battlefield.

Student engineers who worked on the aircraft are enrolled in UCLA's Integrated Manufacturing Engineering (IME) program. The IME Program develops manufacturing leaders capable of implementing integrated manufacturing in American industry in order to compete globally at the forefront of today's aircraft and ground-transportation production markets.

For more information on the SPFF program, please contact:

Standard SpaceAge Control position transducers are provided with a swivel or line connector and an uncrimped eyelet. This arrangement allows you to place the swivel or line connector on the displacement cable precisely where you need it.

To crimp the eyelet to the displacement cable, loop the displacement cable through the eyelet, through the swivel or line connector, and then back through the eyelet. Crimp the eyelet using a 4-pronged electrical connector crimping tool or equivalent. See Figure 1. NOTE: If you need to cut uncoated displacement cable, you should anneal the cable with a flame (a candle or match will work fine) at the cutting point to ensure the cable does not fray after cutting.

SpaceAge Control does not provide the crimping tools for crimping the eyelet to the displacement cable. There are numerous suppliers of these types of products worldwide. One company that we purchase from is:

If you require a crimping tool, feel free to contact Astro Tool Corp. and ask them for their Tooling Guide. We have used both their 615466 and 612548 microcrimp tools. For the standard 0.018-inch (0.4572 mm) diameter displacement cable, we use a 0.019-inch (0.4826-mm) gage pin to set the crimping diameter on the microcrimp tool and then do a pull test. For the 0.027-inch (0.6858 mm) diameter displacement cable, we use a 0.028-inch (0.7112-mm) gage pin. You may also purchase an appropriate calibrating tool from Astro Tool Corp.

If you would like us to place the swivel or line connector on the displacement cable for you, please specify your requirements on your purchase order. A drawing or sketch with tolerances would be helpful.

ISSN 1527-5108