ANT

## Overview

Team Buffalo decided early on to use an All-Terrain Vehicle (ATV) as its “motion” platform. The combination of low-cost and go-anywhere design were compelling attributes. Modifications to enable autonomous control and the guidance system were begun only after an extensive test-driving and break-in period. Burzynski was eager to gain in-depth knowledge of the vehicle’s handling capabilities. He said, “I need to know the vehicle’s limitations and handling characteristics so I can program the PLC to those limitations.” The vehicle was dubbed the ANT: Autonomous Non-Manned Transport.

Team Buffalo’s approach to the navigation and control system was fairly straightforward: a pair of commercially available GPS systems that acquire position data, and a “heading” (direction of travel) from geo-synchronous satellites. This navigational information is transferred to a Pentium-class single-board computer via an RS-232 serial link. The PC is used to preprocess and filter the navigational information before sending it to an AutomationDirect DL205 PLC. The PLC controls servo actuators for steering and throttle control, and a linear actuator for “shifting” the transmission. The PLC also accepts inputs from seven ultrasonic “obstacle avoidance” sensors, and plots the actual course of the ANT. To quote Schwartz, “In essence, the single-board computer tells the PLC where we are now, where we want to go, and our current heading. The PLC then uses that information, along with the obstacle and collision avoidance information, to steer the vehicle toward our desired destination.”

## Qualification

With a vehicle procured, sponsorships lined up, and a control system design in hand, Team Buffalo worked day and night—seven days a week—to modify the ATV, fabricate the control system, and program the PC and PLC. As part of the formal application process to DARPA, the team was required to submit a 5-minute video, detailing and demonstrating the vehicle, by March 11.

There were some hurdles, as Schwartz explains: “At first, we had some minor difficulty programming the analog inputs and outputs on the DL205 PLC. However, one quick call to AutomationDirect’s support line and we were back on track in no time at all. In fact, I was truly amazed at how fast we were able to get through to a knowledgeable support engineer. We had the answers and information needed to configure the analog inputs and outputs in less time than we typically spend on hold with some of the other PLC manufacturers.”

As detailed in the opening e-mail excerpt, Team Buffalo also learned a hard lesson about encoder feedback and limit switches for servo systems, but were up to that challenge as well. The two soon announced that they were one of 136 teams that had successfully completed the application process.

The Team continued working feverishly to complete and refine their design. On April 11, they were notified by DARPA that a formal site visit was being planned by the DARPA officials during the month of May. DARPA initially scheduled the visit for May 3. The team respectfully asked for more time, and DARPA denied the request. Then, lo and behold, DARPA decided to reschedule the visit for May 2!

The Grand Challenge rules stipulate that during the site visit, the team will have 3 hours to demonstrate the vehicle. The team is responsible for setting up a 200-meter course with at least two turns. Team Buffalo selected a 15-acre site of woods and fields behind several acres of lush lawn in a rural area of western New York. They had planned to set up the course in the woods. However, the wooded area was deemed too wet, so instead, a course was configured on the rain-soaked lawn between the road and the woods.

The weather did not cooperate before or during the site visit, as Schwartz describes in his report. “The day started with the weather being just cold and windy. However, before the site visit was over, I think we had experienced every kind of precipitation known to man – rain, snow, sleet and hail.”

The DARPA officials were patient and encouraging as the team spent 2-1/2 hours troubleshooting a loose pin in the cable connection to the PC. With only 30 minutes left in the visit, Team Buffalo put the ANT on the starting line, crossed their fingers and pushed the GO button.

Mark describes the moment: “We quickly moved the vehicle back to the starting line. After a brief safety orientation for all, we placed the vehicle back into Auto mode and stepped back to wait for our hard-coded time delay to kick in before the vehicle moved. Shortly after the mandatory 5-second audible alarm (horn) sounded, the vehicle gradually accelerated down the course. At first, everything looked great. But then all of a sudden, for no apparent reason, the vehicle stopped abruptly. As we watched anxiously, we could see the linear actuators on the transmission shift the vehicle into reverse. Brad and I looked at each other with stunned faces. We knew the vehicle’s onboard collision avoidance system had just kicked in, but neither of us knew why. Once the actuators stopped, the vehicle started to move again; but of course, it was going in reverse. We had hoped it would travel just a short distance in reverse. We assumed that once it cleared whatever obstacle it thought was there, it would automatically shift itself back into forward gear. Unfortunately, it continued in reverse, running over one of the orange safety cones on the left lateral boundary, and headed off toward the woods.”

Unfortunately for Team Buffalo, the remaining attempts proved to be equally disappointing. Weather conditions grew noticeably worse, with driving hail and sleet that made troubleshooting almost impossible. In the end they were unable to successfully navigate the course, but the DARPA officials were still encouraging and very interested in the vehicle and design approach. The Team was left to wait until June for a final decision from DARPA.

On June 6, DARPA released the names of the 40 teams that made the final cut, and Team Buffalo was not among them.

## Robot History

### DARPA Grand Challenge 2005

ANT was not selected for the Grand Challenge, but the team planned to continue development and enter the 2006 Grand Challenge if no one completed the 2005 course.

## See Also

* 2005 DARPA Grand Challenge (Automation Direct)