Moonraker, a robot designed by Pauls Robotics of Worcester, MA, recently won the 2009 NASA Lunar Regolith Excavation Challenge. The event, a NASA Centennial Challenge, attracted 23 teams from the United States and Canada to compete for the top prize of $500,000. Organized by the California Space Education and Workforce Institute (CSEWI), the event took place at NASA Ames Research Park in California on October 17 and 18, 2009.
The Pauls Robotics team, led by Worcester Polytechnic Institute (WPI) undergraduate student Paul Ventimiglia, began as a labor of love in early 2008. After Paul learned about the challenge from his high school physics teacher, he gathered a team of friends to compete in the challenge. The team, consisting of Marc DeVidts, software engineer from Miami, Brian Loveland, WPI Alumni 07 and graduate student, and Colleen Shaver, WPI Alumni 04 and WPI Manager of Robotics Initiatives, got a late start compared with the other competitors. After an unsuccessful appearance at the 2008 challenge, the team were not deterred. Taking what they learned, they reevaluated the challenge and recruited additional members Mike Ciaraldi, WPI Computer Science Professor-of-Practice, and Jennifer Flynn, WPI Alumni 04, to bring the latest version of Moonraker to reality.
Paul’s Robotics team members following their successful run (left to right): Mike Ciaraldi, Brian Loveland, Paul Ventimiglia, Colleen Shaver, Marc DeVidts, Jennifer Flynn. (Credit: Jamie Foster/CSA)
ABOUT THE NASA CHALLENGE
The NASA Centennial Challenges were created three years ago to help inspire innovative solutions to technical challenges in the aerospace industry. The Regolith Excavation Challenge began in 2007. Regolith refers to the loose layer of material covering a planet, in this case the moon, and its commonly known as moon dust. Lunar regolith has very unique mechanical properties that can cause problems for astronauts, space vehicles, and robots that have to operate on the moon. The fine particles are abrasive and small enough to find their way into small areas and cause problems for mechanical and electrical components.
For this challenge, teams built robots that had one chance to excavate as much regolith as possible in 30 minutes and deposit it in a collection bin. The robots had to operate in a 4×4-meter box containing 8 tons of JSC-1A regolith simulant. Four moon rocks were randomly placed throughout the course for the robots to navigate around. For the first two years of the event, fewer than 15 teams total were able to finish their robots and
SIZE: 45x45x70 inches (WxLxH)
FRAME CONSTRUCTION: 1/4-in., 7075 aluminum plate cut by Tom Gravel of Hydro-Cutter.com
HOPPER: Thin polycarbonate sheeting with 6061 aluminum tubes and angles riveted on for reinforcement
MISCELLANEOUS PARTS: 6061 aluminum tubes, flanges, sprockets and hubs tig-welded by Jake Cutler of Barnstorm.us; 40+ shielded ball-bearings; 3/8- and 1/2-in. bore for the entire robot to prevent dust from harming rotating shafts
ELECTRIC DRIVE SYSTEM: 2 CIM drive motors driving a 45:1, custom, three-stage, 20-pitch spur gear; 6061 enclosed gearbox with a final 2.5:1 reduction through no. 25 roller chain; 100-200 watts for the drive system
TANK TREADS: 45 aluminum cleats for each tread fixed to two rows of no. 35 attachment chain (400 nuts and bolts for the treads alone); max. drive speed of 7 in./sec.
DIGGING SYSTEM: 1 CIM motor driving the scoops through a 3.6:1 custom, single-stage, 20-pitch spur gear, Delrin enclosed gearbox with a final 4:1 reduction through no. 25 roller chain to a nylon sprocket; 150 watts for the digging system
MAIN POWERED AXLE: Â½-in.-diameter 7075 aluminum
DIGGING SCOOPS: Total of 20; each is 30 inches wide of 1 inch C-channel, 1/16 in. wall thickness with further pocketing for weight reduction; spaced approximately 5 in. apart, mounted on each end to no. 35 attachment chain.
DIGGING MECHANISM NOTES: Polycarbonate sprockets and reinforcing tubes; entire digging system/hopper rotates up and down 90 degrees, actuated by a 1,000-lb., 12-inch travel, ball screw from SurplusCenter. Two 250-lb. gas springs assist the ball-screw to lift when the hopper is loaded with regolith.
SOFTWARE: Robot programmed in Java
BRAINS: Acer Netbook running Linux operates as onboard server, sending out sensor messages to the control laptop using the built-in Wi-Fi.
Custom GUI developed in Visual Basic running on a Windows laptop used as the client to send out command messages.
Communication occurs over UDP owing to the 4-second roundtrip signal delay.
CAMERAS: 3 Logitech webcams mounted on the robot: two front-facing, high up looking straight ahead and other down at the regolith; one back-facing
SENSOR NOTES: Controlled through 2 USB hubs, 1 for all cameras, 1 for all other sensors. Two U.S. Digital encodersone for each side of the drivetrainhooked up through Phidgets encoder boards. Yaw Rate Gyro to measure the angle of the robot as it moved. 10k rotary potentiometer for measuring the angle of the digger and hopper, assisted by two limit switches that detect when the left and ride sides of the digger have been lowered to the maximum depth. Limit switches mounted on the back left and right sides tell when the robot has backed up flat against a wall. All limit switches and potentiometers are hooked up to a Phidgets I/O board.
POWER-SYSTEM NOTES: Three fanless Victor Thors and one Sidewinder ESC to control all motors; 12V electrical system powered by 12, 10-cell 2400mAh Ni-Cd battery packs wired in parallel (recycled from Heavyweight Battlebot Brutality); 45-, 30- and 15A Anderson Powerpoles used extensively on all parts of the robot; 15A fuses required by the event for each battery; Team Whyachi MS-2 main power switch.
Moonraker robot in competition box right at the end of its official run. (Credit: Jamie Foster/CSA)
make an official attempt. None was able to move the minimum 150kg to qualify for the prizes.
For the 2009 challenge, two significant changes were made to the rules. First, teams were allowed to teleoperate their robots instead of requiring them to be fully autonomous as in previous years. The teams drivers were isolated in a room separate from the robot and field and had to control their robot through a competition-provided two-second delay on the sending and receiving of commands. This was designed to simulate delayed communication to the moon. Teams were limited to 1000kbs communication bandwidth averaged over their 30-minute run. Second, competitors were required to provide their own onboard power. In previous competitions, robots were tethered to a competition power source that limited them to 30 watts in 2007 and 150 watts in 2008. To account for the onboard power requirement, the weight limit was increased from 70kg to 80kg.
MOONRAKER 2.0: DESIGN & DEVELOPMENT
Moonraker was designed primarily by team leader Paul Ventimiglia and sponsored by WPI. The basic idea was to implement a full-size, fast-digging robot that could hold close to the minimum amount of required regolith on board. With its front rake and rock rollers, the overall strategy for Moonraker was to move the rocks out of its path and then dig a series of approximately five-foot-long paths fanning out from the starting cell. It would return to the collector to deposit the regolith and then head out again for collection.
Polycarbonate sprockets CNC-milled by the team for the digging system.
In the control room, the team had a custom graphical user interface that included live video, preset commands, macros and bandwidth monitoring as well as feedback on all robot sensors, including a gyro, encoders, potentiometers and limit switches. The interface allowed the team to queue up a series of tasks, remove tasks from the queue, send an emergency stop to the robot in case of a problem and adapt to situations with ease and fluidity. Unlike driving an RC car, Moonrakers operator had a series of automated tasks to select from when sending commands, including begin digging, drive three feet, turn left 15 degrees, dock and dump. When any of these commands were queued, the robot would execute a preprogrammed sequence and use its wide variety of sensors to automatically complete the action. As the team conducted full sandbox tests before shipping their robot, this level of automation proved essential for control and effective time use owing to the delayed communications.
Team leader Paul Ventimigla solders power connectors.
THE COMPETITION UNFOLDS
On arrival at the event, the team was nervous at the sight of so many strong competitors. They prepped throughout the day on Friday before sending their robot into impound for Saturday morning. Team names were drawn one by one to ensure random fair play. The first team of the day posted a qualifying run, exciting the entire crowd. From that point on, many of the competitors were plagued with technical issues, mainly getting their communications up and working.
Moonrakers name was drawn in the middle of the events second day. Like many other competitors, its run did not go as smoothly as planned. The team made weight and setup efficiently, and all six team members followed predetermined checklists to ensure no problems or failures. But during the middle of the run, the robot got high-centered, and it took the team several minutes to navigate out of the situation. Additionally, three of the digging scoops were bent and broken very early on in the run. This meant that the team were losing a significant quantity of regolith on each pass, although they could not see this from the control room.
Despite these challenges, Moonraker was able to make seven digging runs and dumps into the collector for a total of 440kg of regolithoverloading the competition scale. The team waited anxiously for the rest of the competitors to finish their runs; almost all moved regolith,
Close-up view of tank tread during assembly.
but only one other was able to meet the minimum requirement.
Pauls Robotics and all the competitors appreciated the opportunity provided to them by NASA and the CSEWI to demonstrate their lunar diggers on the main stage. Throughout the three days at the event site, teams shared stories of their trials and successes while building their competition robots. This sharing of knowledge, expertise and experience helped to make the entire event even more interesting and valuable than just a showcase of robots.