2 Ağustos 2007 Perşembe

servo future columns

In previous SERVO columns, we have touched upon a number of issues related to careers in the robotics space, with particular attention applied to high growth markets. The educational robotics market serves as an example. Other ‘hot’ robotics sectors include medical and consumer robotics. One of the fastest growing robotics sectors is military robotics, the subject of this column. Given the focus of SERVO Magazine (largely ground based robots) and the length constraints of the column, let’s limit the discussion of military robots to unmanned ground vehicles (UGVs). Let me apologize beforehand for the number of acronyms, but to discuss military vehicles, we must use military speak.
The US military — like the militaries of most developed countries — understands the value of applying robotics technology to military requirements and are willing to spend time and money to deliver operational
systems. Unmanned aerial vehicles, which are now proving their worth over the skies of Afghanistan and Iraq, were under development for more than 40 years and cost plenty in R&D dollars. Unmanned ground vehicles, too, are receiving much interest from the military (read funding), and this interest translates into career opportunities.
At this time, there are approxi-mately 4,000 ground robots employed by the US military (13 systems), up from less than 100 in 2001. These robotics systems are in action in multiple theaters including the European Command (EUCOM), Iraq, Afghanistan, and Central Command (CENTCOM). Improvised explosive device (IED) detection, reconnaissance, and explosive ordnance disposal (EOD) are typical applications.
The Army’s key defense acquisi-tion program to develop and field light, medium, and heavy unmanned ground vehicles is the Future Combat Systems (FCS) initiative, a $161B mod-ernization program (the Pentagon’s second most costly program, behind the $276B Joint Strike Fighter). UGV development efforts have also been supported by the Army’s Joint Ground Robotics Enterprise (JGRE) and the Defense Advanced Research Projects Agency’s (DARPA) Unmanned Ground Combat Vehicle (UGCV) Perception for Off-Road Robots Integration (UPI) program. The UGVs include fielded systems and prototypes, as well as commercial off-the-shelf (COTS) purchases. Classes of unmanned ground vehicles under these programs include:
• Armed Reconnaissance Vehicles (ARV) — These systems provide reconnaissance, surveillance, and target acquisition (RSTA), as well as force protection services (the armed version).
• Unmanned Ground Combat Vehicle — Large, weaponized UGVs designed for ground combat.
• Soldier Unmanned Ground Vehicles
(SUGV) — These are small, man-
packable robot systems that can be
configured for a large number of
missions including reconnaissance and
explosive detection and disposal.
• Multifunction Utility/Logistics
Equipment Vehicles (MULE) - These
systems support the soldier in the field,
providing transportation services for
equipment and supplies.
More Than the War
The war in Iraq drives much of the military’s current robotic activity. However, ever since 1990, Department of Defense (DoD) ground robotics investments have steadily increased over the years and will continue to do so. For example, since 1990, the level of annual JGRE appropriations has increased from approximately $20M to almost $50M in FY2006. Moreover, it is projected that DoD research investments during FY2006-2012 will approach $1.7B. More importantly for those evaluating military robotics as a career, this research will transition to acquisition programs.
More Than Casualty Reduction
There are many reasons for the military’s interest in unmanned ground vehicle systems. This is a good thing for those considering a career in military robotics as it reduces risks. And risks there are with any career choice. Although there have been efforts at scaling back the Army’s Future Combat Systems initiative, the benefits of the military application of robots and robotic technology are so compelling that projects will continue even if

substantial program funding cuts are made.
Casualty reduction is one of the primary reasons for the military’s battlefield robotics initiatives. Robots can be used in place of humans for many of the dangerous and life threatening tasks that soldiers perform on a daily basis. Also, robots are able to accomplish some tasks better than their human counter¬parts, or undertake tasks that humans simply cannot perform. That is, robotic systems can increase battlefield operational effectiveness, in addition to lives.
In fact, Army officials have request-ed that research in UGV functionality should focus on what robots can do better that humans, as opposed to what humans already do well. For their part, the Army has developed an ordered list of areas where they need support. Robotics technology can be applied to meet many of these require¬ments (see Figure 1).
Robotics in the form of unmanned ground vehicles can also be used to completely change the way in which military force is applied. The Army’s current transformation from a slow moving, heavily armored (and heavily armed) force to a high¬ly flexible, responsive, and agile entity provides an additional driver for the increased use of robotics within the military. As it is now envisioned, the Army’s ‘Future Force’ will rely heavily upon unmanned ground sys¬tems to extend percep¬tion (reconnaissance, surveillance, and target acquisition) and affect action (counter-mine operations, transport, as well as weapons platforms, extraction of the wounded, etc.) on the battlefield.
Reducing Costs
At this time, cost savings does not appear to be a driving force in military robotics acquisition programs. First, the individual robots themselves are expensive. Second, for the near term, the employment of robots will not result in a reduction of military personnel. In fact, they could increase the number of Army personnel as the robots themselves require operators and maintenance teams. There is also concern in some quarters that the systems themselves will not be able to fulfill mission goals due to limited functionality and a lack of robustness.
As robotic systems increase their perception and reasoning capabilities — and therefore become more autonomous — operator demand will decrease. Similarly, as the systems themselves become more functional and robust (and standardized), the maintenance load will drop and the systems can be applied in an increasing number of areas. It can be seen, therefore, that advances in autonomy,functionality, and robustness will act to increase mission capabilities and reduce costs.
Where the Jobs Are
When evaluating career opportuni-ties, a sound approach is to look where there is the greatest need (What are the critical requirements?). Military robotics is similar to all other careers in this respect.
Requirements prioritization is a thorny and uncertain undertaking, and the criticality of unmanned systems make that effort that much more difficult. However, it can be seen that much of the UGV program’s success is predicated on the ability of the systems to be able to work autonomously (after all we are talking about ‘unmanned’ ground vehicles). As we have seen, increases in the level of autonomy will increase the operational effectiveness of the systems, and will eventually reduce overall costs.
Currently, the Army’s unmanned systems are teleoperated, but the goal is to have some systems become fully autonomous over time. This will occur in a stepwise fashion beginning with adding semiautonomous mobility capabilities to current systems. Degrees of autonomy can be described as follows (see Figure 2):• Teleoperation — Dedicated, continu-ous remote operation without exception handling. Human operator makes all decisions.
• Teleoperation w/Exception Handling — Continuous remote operation with exception notification when problems occur (‘wheels spinning, unable to proceed’).
• ‘Directed’ Autonomy - Systems
directed to ‘go there’ and ‘go there
next’ with minimal, non-continuous,
direct control. Operator guidance
provided when problems arise.
• Autonomy w/Oversight - Systems ‘go there’ with no direct, continuous control by human operators making path following decisions by themselves.
• Autonomous Operation - Complete autonomy, problem resolution, and correction capability (‘go there, perform this task, and return’).
High end robotics technologies such as military robotic systems are characterized as having significant technical and production risks. These technical challenges must be addressed before unmanned ground systems can become a fixture in the Army’s Future Force. Power management,

FIGURE 2. Levels of Autonomous Operation in Unmanned Vehicles.
human-machine interfaces, and integration with other UGV and manned systems are just a few of the UGV functional areas in need of solutions. Technical hurdles in these areas and many more (particularly those related to achieving autonomy), must be addressed to realize the Army’s vision for Future Force UGVs.
Conclusion
The United States is the world leader in the area of military robotics, but many other industrialized countries are embracing robots and robotic technology as a means to increase the efficacy of their militaries and to reduce casualties. Robust, practical military robots are now deployed in the field and new technologies and systems are under development (and test). Cost reduction is not a driver at this time, but could be realized as systems become more autonomous, functional, and durable.
If you are considering military robotics as a career or a direction for your company, the news is all good ... roadmaps are in place for the develop¬ment and deployment of UGV systems and funding is available. Moreover, the technical challenges for developing unmanned ground systems are daunting, and therefore, there will be no shortage of work, especially in the area of autonomous mobility.
For those of you uneasy with the notion of working for the military, take heart. The same work can be applied to first responder systems and autonomous transportation for commercial markets.
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Cascode stage
or “collector follower”
Jean-Paul Brodier
All microprocessors from the 8051 family have inputs and outputs that are ‘quasi-bidirectional’. This means that when power is first applied, the ports behave as inputs with a logic high level and a weak pull-up.,

Glitch
a relay or some other load such as When driving an optocou-pler or LED, there is a problem
at power on: the NPN transistor in the common emitter connec­tion (Figure 1) causes an unde­sirable excitation of the load from the moment power is applied until the microprocessor has had the chance to turn the output low. In addition, logic high outputs are seldom able to deliver enough current to drive the transistor into saturation because they have been designed to be active low.
Figure 1. An NPN transistor drives a load.
To solve both of these problems in one hit, we have to make the active level logic low. This can be done in three different ways: use an emitter follower as a buffer stage (Figure 2a), an inverter in a common emit­ter circuit (Figure 2b) or an inverter/open collector circuit (Figure 2c). The disadvantage of solution 2a is the fact that the voltage to the load is reduced. In the case of a relay with a 5-V coil there is the risk that the resulting voltage is too low. The disadvantage of examples 2b and 2c is that they require more parts.
Collector follower
That leaves the open collector buffer in the form of an IC type 7404. This solution, however, also has a few disadvantages. You do not always need all of the 6 buffers in one IC. Also, the SMD version can only handle 12 V. This is too low and dan­gerous if we happen to supply the load from an unregulated voltage.
The solution presented here com­bines in one transistor the advan­tages of the emitter follower (inactive when power is first applied) and open collector (higher power supply voltage, lower current). This circuit has been known since the valve era by the name cascode (drive via the cathode). The goal was to reduce the Miller-effect of the internal (parasitic) capacitances. Not having the option of reduc­ing the capacitance between the internal electrodes, a lower volt­age was used instead. The cas-code circuit is often used in pow­erful transmitters (tens of kW) to minimise the Miller-effect. This circuit was also used to limit tran­sistor conduction and to keep the dissipation within bounds, which increased the life of bipolar tran­sistors. This was in the IGBT and VMOS era.
The transistor conducts only when the output from the micro­processor is low (refer Fig­ure 3). The base current is lim­ited by resistor R. This current is determined by the current flow­ing through the load. When the power is switched on, both the base and emitter see the same potential, VCC, so the transistor remains blocked. One thing we have to keep in mind: we may not exceed the current rating of the microprocessor output because it has to cope with all the current flowing in the emitter of the transistor.
In the case of the quite common 80C51, this maximum current is typically 3.2 mA (two LS TTL loads). This is sufficient to drive an LED without overloading the 5-V regulator, or for driving a PNP power stage at the high side (Figure 3b). The parallel Philips PCF88574 I2C interfaces can handle 25 mA. For the Atmel AT89Cx051 as well as for the Philips P89LPC9xx the limit is 20 mA. For the latter type the cascode circuit or ‘collector fol­lower’ is even more interesting when the outputs are configured as open-drain because the nom­inal voltage is only 3.6 V. In all cases we have to make sure that the maximum dissipation of the
Figure 3. Cascode driver stage with discrete transistor.
package is not exceeded. 24 V is sufficient to energise its are determined by the power
Should this be the case, then the half Watt relay coil, which in PNP (or VMOS) transistor.
number of open collectors turn can drive a load of 16 A at The cascode transistor can be a required will probably justify 230V. ‘digital’ type with integrated resorting to a 7404. For loads driven from the positive base and emitter resistors.A current of around 20 mA at side, the voltage and current lim-


pot as interrupt generator

In battery-powered, microcon­troller driven circuits, as well as with microcontrollers operating in cars, it is desirable to switch the micro into power-down mode once a task has been completed. An interrupt request is then required to wake up the micro. This circuit allows an interrupt to be generated in a simple way using a common potentiometer. In the example circuit, the pot may also copy its spindle position to the ADC. This enables the pot to be used for continuously variable settings (like volume) as well for getting the micro out of its power-down mode.
IC1A is configured as a differen­tiator with R3 preventing oscillation by keeping the gain down to 10 times. Because the opamp oper­ates off a single-rail supply voltage, an 18k/10k potential divider (R1/R2) is able to create a virtual ground level at +1.75 V. This can be done because the LM358 can handle input levels of up to 3.5 V when supplied at 5.0 volts. IC1A supplies a brief High pulse at a falling input voltage, and a similar Low pulse when the input voltage rises. In order to get a High pulse when the potentiome­ter spindle is turned cw or ccw, IC1B is set up as an inverter. Next, each opamp output drives the base of a BC547 transistor. The 5 V-to-0 V transitions at both collector outputs are shaped and combined into a usable interrupt pulse by three NOR gates IC2A, IC2B and IC2C.If the potentiometer spindle is turned very slowly, it is possible that the circuit does not respond
That is why an LED has been added that lights briefly when a pulse is generated. Finally, a tip: a 100-pF capacitor may be connected in parallel with R5 for additional suppres­sion of self-oscillation.

elektor time standart


Elektor Time standard (1988)
Jan Buiting

The Elektor Time Standard and associated Slave Unit were spin-offs of another hugely successful project, the DCF77 Receiver / Locked Frequency Standard. The receiver was published in the January 1988 issue, the Time Standard and Slave display in the next two issues. All units were housed in then very fash­ionable and (expensive!) Ver-obox two-part ABS enclosures which had also been used for a number of Elektor test instrument designs published between 1984 and 1987. The Time Standard box was designed to process seconds pulses received from the VLF (77.5 kHz) DCF77 time standard transmitter in Mainflingen, Ger­many, and display time (with atomic accuracy) and date on an LC display. The circuit was based on then extremely popular 8052AH-BASIC microcontroller from Intel, a device, we can safely claim, that made it to fame & glory thanks to Elektor Electron-
ics. The 40-way DIL chip con­tained a BASIC interpreter capa­ble of executing ‘tokenised’ code from an external EPROM. This, we were told by our resident designer Peter Theunissen, made writing the DCF77 time signal decoding routines ‘a doddle’ using his specially adapted BASIC computer and interpreter. For example, when concerns were raised (by myself) that not all of Europe was in the time zone served by DCF77 (i.e., CET or GMT+1h), a menu option was quickly added to allow users to select between UTC and GMT+1h. As a relative novelty, a ready-made self-adhesive front panel foil with built-in membrane keys was designed into the proj­ect. This expensive item had been produced specially for Elektor. However, when the article went into print (using a rather glum page layout and black & white print), there were yet other con­cerns regarding the range of the DCF77 transmitter. This is offi­cially claimed as “approximately 1,000 km by groundwave propa-

gation”. A quick use of a com­pass and a map of Europe sug­gested that the signal would only cover the south-eastern part of the UK, possibly including Greater London. For a couple of months we waited with baited breath for readers’ responses, only to receive two enthusiastic reception reports, one from the East coast of Ireland and another from Riyadh, Saudi Arabia! The latter report came from a reader work­ing at a chemical laboratory. I remember he wrote that DCF77 could be received for a few min­utes a day only, synchronising the clock, usually around nightfall despite heavy ‘static’. A huge wire antenna was used (nothing like the 1-inch ferrite rods we used in our lab, which is less than 100 km away from Mainflingen). Although the BASIC program list-
ing for the Time Standard was freely distributed to interested readers (on paper, in an enve­lope, by snail mail!), only very advanced readers were able to compile the program into tokenised code and burn it into an EPROM. Most other readers had to rely on a ready-pro­grammed 27C64 supplied through our Readers Services. Apart from displaying time and date at atomic accuracy, the Time Standard was also capable of outputting time/date information

in the form of ASCII character strings for other (intelligent) equip­ment to use, for example, a timer or switching clock. Although sales figures of the PCB and EPROM were in the hundreds, I never heard from anyone actually hav­ing enjoyed the wonders of the ASCII output so extensively described in the article. The Slave unit published in March 1988 was connected to the Time Standard via screened (micro­phone) cable, the idea being that one or more Slave units could be installed on walls in rooms at some distance from the main clock unit. Central timekeeping deluxe for offices, labs, schools and workshops, but at what an expense and design effort! Not too many PCBs were sold for this extension of the Time Standard.