The Next Robot
The next RoMeLa project that Hopkins is working on involves software development for a firefighting robot called SAFFiR. Another ECE student, Steve Ressler, is doing the embedded systems and electronics development. This robot will be able to walk in unstable environments: through obstacles, on uneven flooring, on a rocking ship.
Most robots, including the CHARLI and DARwIn models, use position control rigid walking. For this kind of movement, “you plan out the precise trajectory for the feet to keep the center of pressure within the support polygon of the foot. This requires the floor to be totally flat.”
SAFFiR, however, will be using force control walking. Instead of planning a precise trajectory, they will apply torques at all the joints. “The legs will swing naturally using force control with custom series-elastic actuators. The actuators are attached to titanium beams which act like springs,” says Hopkins. Only a few robots in the world are using this kind of walking. It will, however, allow SAFFiR to walk on uneven terrain.
It’s not just about walking. Humanoid robots also must think and react, and Bradley Fellow Mike Hopkins is working on this robotic brainpower.
Hopkins and others from Virginia Tech’s Robotics and Mechanisms Laboratory (RoMeLa), guided by Dennis Hong of mechanical engineering, led their humanoid robots to victory at the 2011 RoboCup, an international robotic soccer competition that was held in Istanbul, Turkey last summer. Winning five awards, including first place in both the Adult Size and Kid Size humanoid soccer leagues, the RoMeLa team has brought the Louis Vuitton Humanoid Cup to the United States for the first time. In previous years, the cup has been held by Japan and Germany.
Their adult-sized robot, Cognitive Humanoid Autonomous Robot with Learning Intelligence, known as CHARLI-2, competed in one-on-one soccer matches where it had to locate the ball behind him, dribble it to the other half, then kick it into a goal guarded by its opponent robot. It also had to be able to guard the goal when another robot was on offense. CHARLI-2 has also been named one of “Time” magazine’s 50 Best Inventions of 2011.
Hopkins was the lead software developer for CHARLI-2. His first year with the RoMeLa team was the first year that RoboCup had an adult-sized humanoid robotic soccer competition, and RoMeLa brought CHARLI-L1 to the competition. CHARLI-2 was the victorious redesign.
“Most of the students on our team are mechanical engineers, but robotics is one of the most multidisciplinary fields in engineering,” says Hopkins, who is advised by ECE’s Lynn Abbott. “It includes mechanical design, electronics, software, controls and artificial intelligence.”
There are two main challenges for any autonomous task, according to Hopkins. The first is state estimation (where is the robot on the field? where is the ball? what obstacles are in the way?). The second is decision-making. “Once the robot knows what state it’s in, it can make the best decisions to score a goal.”
“At the lowest level, you have the communication system which allows the robot to talk to its sensors and actuators,” Hopkins explains. “You want the communication to be as fast as possible in order to achieve robust control over the system. At the next level, you have the control system for motion tasks such as walking, kicking, tracking the ball with the head, etc. At the highest level, you have the perceptual and behavioral code for making decisions based on the current state of the world.”
The RoMeLa team collaborates with the University of Pennsylvania for their software needs. Virginia Tech was in charge of the CHARLI-2 code, and the University of Pennsylvania was responsible for the code for DARwIn-OP: the kid-sized robot that won its division at RoboCup last summer. “There is a shared software framework between the two teams,” Hopkins says.
According to Hopkins, the great challenge is time: “getting all the components working together in the short amount of time that we have for these competitions. Both years, we’ve built the entire platform from scratch. A year before RoboCup 2011, there was no CHARLI-2 robot. There wasn’t even a design.” It took approximately nine months to design and build CHARLI-2, leaving only three months for the full development process. They had to make the robot walk, have vision, and play soccer.
One thing that makes all this possible is that the entire system is designed in the lab. “We have a really good environment for collaborating, and everyone in the lab is really close. Working closely with the mechanical designers makes software development easier.” For CHARLI-2, Hopkins requested that the design of the neck joints be simpler so that the vision tasks would be easier.
Hopkins enjoys seeing his work in action. He explains that a lot of labs work on just one part of the system: for example, simulation, hardware, or code. “In our lab, we work on pretty much everything. We can create a whole robot and have the reward of seeing it play soccer,” he says.