DARPA Urban Challenge: the race to save lives


AGV WENDY DARLING is a modified M-215 Army supply truck.

The DARPA Urban Challenge (DARPA URBAN CHALLENGE) really is about saving soldier’s lives in combat zones, and its civilian spin-off has great potential for saving many more lives on U.S. roadways. A 1997 Department of Transportation study found that hyper-intelligent computer Hal in Stanley Kubrick’s 2001: A Space Odyssey was right: people are the weak link. People are the cause of over 90% of fatal traffic accidents.

On large ships the AutoPilot is often referred to as Iron Mike.  Having reached the level of Chief Engineer in the US Merchant Marine, I have spent a lot of time studying steering engines and AutoPilots for large ships.  I have spent a lot of time keeping them running, repairing them and of course airplanes have had them for a long time too.  Isn’t it about time that trucks learned how to drive themselves?  Recognizing that the technology needed to allow supply trucks to drive themselves in war zones is within reach, the U.S. Congress has ordered the US armed forces to outfit 1/3 of their ground vehicles for "driverless operation as soon as possible and before 2015".  In the case of the US Army this amounts to 333,333 driverless systems, not counting any extras or spares that they will need.  No such system is available yet, so to stimulate the development of Truck AutoPilots that will allow US armed force’s vehicles to operate autonomously, the Defense Advanced Research Projects Agency (DARPA) created the Urban Challenge race.  The race puts demonstrating a driverless system in the form of a contest with cash prizes: $2 million for first place, $1 million for second place, $500,000 for third place.  Trophies, medals, and $11 million in development grant money are also part of this race. DARPA believes that once someone has demonstrated that it can be done, a flood of vendors will come forward offering a variety of driverless systems for the Army can choose from.  We here at AMERICAN INDUSTRIAL MAGIC have estimated this technology will save the lives of 30 Army drivers a month, reduce the need for a draft, and take some of the pressure off of Army recruiters.  

Recently designers have been adding automated systems to civilian cars, buses, and trucks, following the example of how aircraft designers improved commercial airliner safety. These systems, if all put together on one vehicle, could allow it to nearly drive itself. We are very close to vehicles having HorseSense. That is, vehicles that refuse to run into obstacles or each other, are smart enough to avoid dangerous situations, and know their own way home. A U.S. Department of Transportation study estimated that in the civilian sector, this technology would save 5,000 lives a month.  As a public health issue, this would save more lives in the 0 to 49 years age group than curing cancer would.  Imagine, engineers have an opportunity to become national heroes, by addressing one of the most important public health issues in the USA.

The 2007 DARPA Urban Challenge http://www.darpa.mil/grandchallenge is to take ground vehicle automation that next step. It is the logical follow-on to the DARPA Grand Challenge, which was completed in 2006. Most people remember the DARPA Grand Challenge as "the race in the desert with no drivers." The DARPA Urban Challenge is going to be a little different; the vehicles will have to find their way safely through 60 miles of simulated city traffic, making a series of stops along the way. In the DARPA Grand Challenge, it was “simply” a matter of getting from A to B while dodging obstacles. The DARPA Urban Challenge will test to see if the trucks can pass a follow California State Driver’s Rules Of The Road.  They will be required to get to their delivery stops — and back, dealing with normal traffic situations along the way.

The name Wendy was invented for the children’s story Peter Pan, it did not exist before then.  The family’s last name was Darling (we had to send a team member to the library to find that out).  What better name could there be for a type of truck that never existed before than Wendy?  AMERICAN INDUSTRIAL MAGIC’s vehicle is named  Automatic Guided Vehicle WENDY DARLING in honor of  the children’s story Peter Pan, and to honor women in technology.  To allow the truck to be controlled by the onboard computer system, we are creating a drive-by-wire system by automating the manual systems.

Since this is an experimental vehicle, we must give careful thought to how each part fails. I tried to pick the choice that was closest to "fail safe." For example in the case of the turning relay failure, we want the vehicle to turn to the right, away from oncoming traffic. Extensive testing of each system is done both on the bench and on the vehicle. Most everything on the vehicle is put together and taken apart many times for revision, measurement, and test of fit and function.  Periodic teardown inspections of critical parts are part of the routine.

The AIM Team has implemented a simple electric steering control system using reliable low-tech relays.

On this truck there are four control points: Steering (0 to 100%), Throttle (0 to 100%), Brake (0 to 100%), and Transmission (FWD or REV).  These are the minimum required to make it go. Additional control points are nice to have or or required by the rules but these are the most essential ones and first ones to consider carefully. After considering several steering system options that can be controlled by a computer, and comparing them to available parts donated to the team, team members constructed a simple electric steering system using high current relays.  Electric steering systems are gaining popularity in the automotive industry because they can be lighter, cheaper, and more reliable than other types. Electric steering also adapts easily to control by computer, which seems to be the direction car designers are going.  So far they don’t seem to have moved into the truck market yet, we may be leading the industry in this area.

In our home-brew version of the electric steering system for our truck, a series of relays control a high performance dc motor turning the steering shaft using #50 roller chain and sprockets.  The AIM Team is searching for the lowest-tech solutions where ever possible. Hydraulic steering had been considered but there was some difficulty getting the main control valve which forced to look for alternatives.  We discovered the advantages electric steering has over any other system.  Had we been able to get the valve we needed, we might not have looked so closely at electric steering for trucks.  

Software, when constructed using the right tools, is easier and less expensive to change than hardware is. Software can be used in place of many expensive hardware components which teams like AIM might not be able to get. All the critical functions f(x) are in the software. The driving software has incorporated in it all the relationships between variables and chooses setting for each that will achieve what a California driving license examaner would consider good driving. For instance, the faster the vehicle is traveling, the smaller the allowable steering adjustments are. Their relationship is based on the need to maintain stability and not roll the vehicle over, maintain traction, while making the best speed. Some interestng things have been done with adaptive flight controls and we are looking at what we might use from their example to create adaptive driving software to react to variations in driving conditions, much as people do. http://www.nasa.gov/centers/dryden/news/FactSheets/FS-076-DFRC.html  

The hardware for every system is as simple as possible, leaving the complexity to the less expensive and more easily changed software part of the hardware/software ballance..  The first relay R1 is the "low/high" speed-selecting relay, it chooses between two voltage sources: 12 V dc for low speed and 24 V dc for high speed. The default failure mode is "low." The second relay (R2) is the off/on relay, which fails to "off." The third relay (R3) is the "right/left" turning relay, which fails "right". The first limit switch (LS-1) interrupts power to the steering motor when the right limit is reached while turning right. The second limit switch (LS-2) interrupts power to the steering motor when the left limit is reached while turning left. The spring-set brake on the motor is released whenever there is power applied to the steering motor.


Paul F. Grayson - Chief Engineer
Racing to build technology that saves soldier’s lives.
390 4-Mile Rd. S.
Traverse City, MI 49686-8411
(231) 946-0187, (231) 883-4463 Cell
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Posted by Paul Grayson on April 17, 2007

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