NASA Space Robotics Challenge - Phase 2

Another NASA Centennial Challenge began earlier this year. It will be the 3rd I've entered. I also entered the 2019 ARIAC competition which makes 4 competitions. The current competition is the Space Robotics Challenge - Phase 2 (SRC2). In this competition robotic mining rovers explore the Moon to detect volatiles and collect them, detect a low orbiting cube sat, and position one rover aligned with a fiducial on a processing station.

Links to Follow-on Posts

• SRC2 - Explicit Steering - Wheel Orientation for Turning
• SRC2 - Explicit Steering - Crab, Straight, and Pivot Movements
• SRC2 - Explicit Steering - Wheel Speed

In the following posts I'll explain what I can about this topic. There are a number of research papers available however my posts will provide a simplified explanation. 

Explicit Steering

The biggest challenge in this competition is controlling the rover. It is the size of a small SUV with Explicit Four Wheel Steering, i.e. each of the four wheels is steered separately. If you've seen the Mars rover it is a similar design. That's the base rover, above.

Explicit steering allows flexibility in movement of the rover. It can turn all four wheels to the same angle to move sideways in a crab movement. This also provides straight forward movement. By orienting the wheels at different angles the rover can turn. An extreme example of this is pivoting in place.

Robot Operating System

The base software for the competition is the Robot Operating System (ROS) which consists of the fundamentals for communicating amongst software nodes and a large number of packages that provide useful capabilities. Unfortunately there isn't one for controlling the SRC2 rover.

There are two ways of controlling the wheels for locomotion. The predominant one is issuing a speed command. A number of ROS controller packages provide this capability. Another specified the effort or torque. There are effort controllers but none directly apply to the SRC2 rover.

The location of the rover on the surface is required for reporting the position of volatiles, moving to them, and generally controlling the rover's movement. This requires deriving odometry from wheel movement, vision processing via stereo cameras and an inertial measurement unit (IMU). Again, this is not provided. It is especially challenging due to the low friction between the wheels and simulated Moon surface which allows slippage of the wheels.

The Autonomous Roboticist

Since September 2016 I've been competing in the NASA Space Robotics Centennial Challenge (SRC). The challenge had a qualifying period and the final competition. I was one of the twenty teams from an international pool who qualified for the final competition. In mid-June the competitors ran their entries on a simulation in the cloud. The last few days, June 28 -30th capped the competition with a celebration at Space Center Houston, an education and entertainment facility next to the NASA Johnson Space Center.

On Thursday, the 29th, teams were invited to give presentations to the other teams, the NASA people who organized the challenge, and others. I used the opportunity to speak about my approach to the competition but also to raise the question of how an amateur roboticist, like myself, can make a meaningful contribution to robotics. 

Two ways are through competitions like this and by contributing software to the Robot Operating System (ROS). There aren't always competitions to work and ROS contributions don't fulfill my desire. In part, ROS misses the mark because before adding a new, usable package, I need to develop something new and useful. Now perhaps there are existing topics that need software and ROS packaging but how do I learn about them? 

And underlying issue for the amateur is knowing the state of the art in academia and industry. Often current academic material is behind paywalls. The amateur is also lacking in the background that lead to the current work. 

One of the reasons for this entry, and a possible new blog with the title, is to see if a third way can be found or created.