| Unmanned Aerial Vehicle Guidance & Control | May 20-22, 2014 | Columbia, MD |
| Unmanned Air Vehicle Design | Apr 22-24, 2014 | Dayton, OH |
Austria was the first country to use unmanned aerial vehicles for combat purposes. In 1849, the Austrian military attached explosives to five large balloons and sent them to attack the city of Venice. Some of the balloons were blown off course, but others managed to hit targets within the city.
The concept of pilotless aerial combat units resurfaced during World War I when military scientists began building devices such as the Hewitt-Sperry Automatic Airplane. This craft was essentially an airborne bomb and was controlled using gyroscopes. After witnessing the capabilities of the Automatic Airplane, the U.S. military began working on precursors to modern cruise missiles called aerial torpedoes. The first aerial torpedo was dubbed the Kettering Bomb. Developed in 1918, the Kettering Bomb could be guided by an onboard gyroscope toward targets located up to 75 miles from its launch point.
Aerial Torpedo attached to Aircraft
A British World War I veteran namedReginald Denny opened a model plane shop in Hollywood in 1934. Denny eventually began producing radio-controlled aircraft that could be used for training purposes by anti-aircraft gunners. The Army hired Denny and produced thousands of drones for use during World War II. The Navy also began producing radio-controlled aircraft around this time. In 1942, a Navy assault drone successfully hit an enemy destroyer with a torpedo.
After World War II, Reginald Denny’s company continued to build target drones for the U.S. military. The drones became increasingly advanced to keep up with manned combat aircraft. During the Cold War, some of these drones were converted for reconnaissance purposes. Based on the successful Ryan Firebee target drone model, the Ryan Model 147 Lightning Bug series of drones was used to spy on targets in China, Vietnam, and Korea in the 1960s and ’70s. The Soviet Union developed its own photo reconnaissance drones, although little is known about these devices. Drones were also used as decoys during combat operations.
Unmanned aircraft vehicles were largely seen as impractical, unreliable, and expensive until 1982 when Israel successfully used the devices against the Syrian Air Force. The Israeli Air Force used the drones for video reconnaissance, distractions, and electronic jamming of Syrian equipment. They were also used to destroy Syrian aircraft without risking the lives of Israeli pilots. The success of Israel’s UAV project convinced the United States military to start developing more unmanned aircraft. The U.S. now has a large fleet of UAVs used to deceive detection systems such as radar and sonar.
General Atomics Predator RQ-1L UAV
Figure 1: Basic op-amp series regulator.
The opposite action occurs when the output voltage rises because of an increase in the unregulated input voltage or a decrease in load current. The negative feedback causes the error amplifier to reduce the drive to the base of the NPN transistor, causing Vout to decrease until the sampled feedback voltage seen at the inverting input equals the zener voltage.
In effect, any variation in the output voltage is absorbed by the transistor’s collector-emitter voltage resulting in a regulated supply rail.
The operation of a shunt regulator is similar to the series design except that regulation is achieved by controlling the current through a transistor in parallel with the load. The shunt regulator is less efficient than the series type, but offers some inherent short-circuit protection as the load current is limited by an internal series resistor.
For both designs, the regulating element is realised using a power pass-transistor operating in its active region, e.g., where IC = βIB. Conceptually, this transistor can be considered as a dissipative, variable-controlled resistor, and hence this type of linear regulator always steps down the input power and voltage.
Regulation is achieved by the purposeful conversion of excess power as heat and the pass transistor must have the required thermal rating to operate at the worst-case input voltage and full load. If an excessive amount of current is drawn, the transistor can be damaged unless some form of limiting or protection is implemented.
From the block diagram shown in Figure 2, the power dissipation in watts of a linear regulator can be expressed as:
(Vin-Vout)* Iload + (Vin * Iq)
and the efficiency in percent as:
η = Pout / (Pout + Plosses) = Vout/Vin = (Iload * Vout) / (Iload + Iq) * Vin
Figure 2: Linear regulator inputs and outputs.
The quiescent current is the difference between the input and output currents and a low value is desired to maximise efficiency. The biasing of the band-gap reference, sampling resistors and the error amplifier all contribute to the ground current adversely affecting the efficiency of the overall power conversion.
Low quiescent current, dropout voltage and the voltage difference between the input supply and regulated output rails must be minimised to optimise converter efficiency.
The pass transistor operates in its linear mode which requires a certain minimum voltage drop (headroom) between its input and output to function. If Vin become too close to Vout and reaches the dropout voltage, the circuit ceases to regulate.
Many improvements can be made to the basic series and shunt designs to improve overall efficiency. An NPN regulator is unconditionally stable (critically damped) as the pass transistor is being used in a non-inverting, common-collector mode offering high bandwidth and low output impedance. This places a pole in the feedback loop at high frequency making the NPN design relatively insensitive to capacitive loading.
Several designs use a unity-gain error amplifier to avail of the highest bandwidth and fastest transient response independent of the magnitude of the output voltage. Multiple devices can be connected in parallel to share a larger output current with access to both the inverting and non-inverting inputs allowing the design engineer to validate the gain and phase margins.
Other types of pass transistors are used to reduce the headroom voltage and quiescent current to improve overall efficiency. Linear regulators which use either a PMOS FET, a single PNP, or a combination of an NPN and PNP, offer lower dropout voltages as the pass devices operate at saturation.
For FETs, the quiescent current is almost constant with respect to load current since this is voltage driven. However, these transistors are used in their inverting common-emitter/source mode which presents high source impedance to the load. This adds a low-frequency pole to the feedback loop whose response then becomes dependent on both load resistance and output capacitance.
An external, compensating capacitor is required whose equivalent series resistance value is critical to guarantee loop stability. ESA’s ECSS-E-ST-20C Space Engineering standard specifies at least 50° of phase margin and 10 dB of gain margin for worst-case, end-of-life conditions with representative loading. A large value of output capacitance specified in a datasheet is indicative of loop instability and careful part selection is required to comply with ‘the tunnel of death’ curve shown below.
Figure 3: The ‘tunnel of death’ stability curve.
Recent space-grade LDOs have replaced low-gain lateral PNPs with higher-gain vertical equivalents to lower the dropout voltage and reduce the quiescent current. The latest qualified regulators are exploiting the lower on-resistance and gate-capacitance benefits of LDMOS and GaN FETs to further improve efficiency, reliability and performance.
Radiation-induced transients on the output rails of a regulator can impact the electronics to be supplied, e.g., voltage undershoot can cause erratic operation of memories and microprocessors while excessive overshoot can completely destroy CMOS devices. As an example, a single-event transient appearing on the d.c. output exceeding the maximum supply voltage that can be tolerated by a $100k FPGA could end a mission! The addition of current-limiting resistors, transient-suppressing, low-inductance capacitors can mitigate against single-event transients.
Radiation testing of linear regulators has shown that the wide range of input voltages and output load conditions can make devices sensitive to both protons and heavy ions. Results have shown that the amplitude and duration of a transient is dependent on the value of the output capacitor and its ESR, such that the feedback loop can become unstable. To compound the problem, LDOs are commonly used to post-regulate the output from a switching regulator where additional components are included to suppress the high-frequency EMI spikes and spurs.
The impact of external, transient-suppressing components on overall efficiency, stability, reliability and performance needs to be assessed on a per mission basis.
Power transistors are also sensitive to catastrophic single-event burnout and gate rupture effects. The photograph below shows a single-event gate rupture in a power MOSFET that ‘killed’ the transistor.
Figure 4: Catastrophic gate rupture of a power MOSFET.
Imagine watching your children sleep each night on the floor instead of in a bed. Imagine them waking up each morning to pick their school clothes for the day out of a plastic garbage bag instead of a dresser. Imagine eating family dinner each night on the floor because you have no kitchen table. For hundreds of thousands of mothers, this is not something they have to imagine. This is their reality. It is a reality A Wider Circle is changing for families all over the DC Metro area.
A Wider Circle was founded by Mark Bergel in 2001 in response to the cycle of poverty he saw all around him. He was so moved by their deplorable living conditions that he couldn’t sit back and watch anymore.
The mission of the organization, A Wider Circle, is to help adults and children lift themselves out of poverty. Every day of the week, A Wider Circle provides basic need items to families transitioning out of shelters or simply living without life’s necessities.
Their largest program is called Neighbor to Neighbor, where they provide the furniture from their showroom, all of it donated from individuals like you and me, to families moving out of shelters or who might be living without it now. In the state of Maryland, children can be removed from their homes if they are not sleeping on a bed, and Neighbor to Neighbor helps keep those families together. A Wider Circle furnishes about 15-20 rooms each day for needy families through this program.
In additional to the Neighbor to Neighbor program, AWC works with numerous organizations to help individuals and families overcome their current challenges and enable them to be successful. One such organization is the United States Department of Agriculture (USDA) that operates the national Food Stamp Program (SNAP).
This nutrition assistance program helps low-income individuals buy items they need to maintain their health such as:
-Breads and cereals;
-Fruits and vegetables;
-Meats, fish, and poultry;
-Dairy products; and
-Seeds for planting.
Surprisingly, there are many items that may not be purchased under SNAP:
-Soaps and Shampoos;
-Cleaning Products;
-Vitamins and Medicines;
-Paper Towels; and
-Toilet Paper.
AWC recognizes there is a significant gap between the items available for purchase under SNAP and what people need to stay healthy. AWC addresses this shortage by collecting items for further donation to SNAP recipients.
Interested in supporting AWC’s program?
You can help by contributing these items to our donation box:
• Toilet paper
• Paper towels
• Diapers
• Cleaning products
• Toothpaste
• Bar of soap
• Shampoo
Interested in donating a bed?
Visit awidercircle.org for more details.
Call 301-608-3504
Email furnish@awidercircle.org
www.awidercircle.org 
The Washington Post had an article on June 30, 2013 titled “They said the sequester would be scary. Mostly, they were wrong.” It said the effects were largely mitigated by political means and methods after all.
Sequestration and recently introduced “Furlough Fridays” have affected a lot of our customers. Everybody deals with this situation differently, but some of us really embrace the meaning of the phrase “When life gives you lemon make lemonade”. Pentagon civilian employee, John Martin, did just that.
“Furlough Fridays” is a song set in the style of “Monday, Monday” by The Mamas & the Papas.
There are always men on the eyepiece of the other periscope and their stories (in English) are even rarer. In what may be a unique instance, we have the memories of two Cold War submarine captains on opposite sides of the periscope participating in the same events. Commander Minton has his story, as does Admiral Al’fred Simenovich Berzin, who as a Captain First Rank (K1R) commanded Echo II class SSGN K-184, the Guardfish’s target, in 1972 during its transit to Vietnam in response to the failure of the Paris Peace Talks.
This is his side of the story, “Guardfish vs. K-184”
| Mar 20-21, 2012 | Columbia, MD | |
| Apr 20-21, 2012 | Orlando, FL |
in Vehicles, Devices, and Equipment
