We’ve written before about the advantages of multi-modal robots: by combining two different forms of locomotion in one platform, you can take advantage of (say) the efficiency and endurance of a ground robot with the range and versatility of a flying robot. However, designing one robot that can walk and fly tends to be both complicated and inefficient, which is why hetergeneous robot teams are often more appealing. Instead of trying to cram every capability into one robot, you just use several different robots with different specializations and find some way of getting them to work together. Like this robotic cockroach that can serve as an aircraft carrier for a robotic bird.
You’re looking at UC Berkeley’s VelociRoACH (not the super speedy X2 version that we also wrote about today, just the normal speedy one) giving a running start to the H2Bird ornithopter micro aerial vehicle and successfully launching it off of a carrier framework. The H2Bird (which weighs a smidge over 13 grams and can fly for a minute and a half) can’t get itself off the ground on its own; it needs to hit about 1.3 m/s with an angle of attack of between 35 and 40 degrees, all of which can be provided by the carrier structure on top of a scurrying VelociRoACH.
The appeal of this little robotic team goes beyond the advantages of each robot operating separately, as the researchers found that there was significant benefit to the robots even when they’re attached. Obviously, hauling the H2Bird around on its back is going to make VelociRoACH less efficient, but it also improves stability, decreasing pitch and roll variances by up to 95 percent if H2Bird slowly flaps its wings (at 5 Hz) while VelociRoAch is running. At the same time, this slow flap reduces the effective weight of H2Bird, boosting VelociRoACH’s running speed by over 12 percent. There’s also an overall decrease in the cost of transport for both robots, as the researchers explain:
Placing the H2Bird on top of the VelociRoACH decreases the cost of transport of the VelociRoACH by approximately 16 percent. This decrease in the cost of transport would be useful in a situation where the VelociRoACH and the H2Bird had to both reach a point 80 meters away and the H2Bird had to fly 20 meters in the air, where the VelociRoACH cannot reach. In one case, both robots travel the 80 meters separately, and then the H2Bird continues the last 20 meters. In a second case, the VelociRoACH carries the H2Bird for the first 80 meters, then the H2Bird is launched and flies 20 meters. The second case consumes 25 percent less energy than the first. In situations such as these, cooperative locomotion would be more efficient than independent locomotion.
Right now, the launch of H2Bird off of VelociRoACH is being remote controlled by hand, so the next step is to make the launch system autonomous. We’re also hoping to see some sort of adaptation that’ll somehow allow VelociRoACH to pick H2Bird up again, enabling the team to fully leverage both aerial and ground locomotion.
“Coordinated Launching of an Ornithopter With a Hexapedal Robot,” by Cameron J. Rose, Parsa Mahmoudieh, and Ronald S. Fearing from UC Berkeley, will be presented this week at ICRA 2015 in Seattle.
[ UC Berkeley ]