Imagine if you could have a robot that could drive around on crazy terrain for ground surveillance, then lift off for aerial surveillance. That would be a pretty versatile little robot.
Obviously there would be some practical concerns. For instance, the wheels required for ground travel might make the robot too heavy and unwieldy for flight. The next best solution? Two robots that can work in tandem.
The University of California Berkeley's VelociRoach is a robot created by a team of researchers at the university's Biomimetic Millisystems Lab, which focuses on building robots inspired by nature.
Rather than running on straight legs, it has a rolling gait on six C-shaped legs, which lets it travel at a remarkably high speed. A version of the VelociRoach, the X2, broke the robot speed record for robots of its size, reaching velocities of up to 4.9 metres per second.
A different version of the VelociRoach has been modified to work in collaboration with another of the laboratory's robots, the bird-inspired H2Bird ornithopter. The 32-gram roachbot was fitted with supports that enables it to carry the 13.2-gram H2Bird ornithopter micro-aerial vehicle, and can reach speeds of 2.7 metres per second -- more than fast enough to provide takeoff velocity.
The MAV cannot take off from a stationary position. Its wings, which do flap, are not large enough to provide enough thrust to counter its weight and the drag caused by contact with the ground. It could be launched by being thrown like a paper aeroplane, which could provide a better take-off angle and enough velocity for the MAV to continue on its own.
To determine the best speed and pitch angle would be best to launch the MAV, the UC Berkeley team -- graduate researchers Cameron Rose and Ron Fearing, and student Parsa Mahmoudieh -- used a wind tunnel to collect data. This allowed them to build a custom rig to be fitted to the back of the VelociRoach, pointing the MAV's nose in the air.
Trial and error then determined that the minimum speed at which the MAV will successfully launch is 1.2 metres per second. Although launch can fail at this speed, it is usually caused by improper positioning in the cradle, which can be jolted when the VelociRoach starts moving.
The team also discovered some interesting side effects of carrying the MAV on the VelociRoach. The weight and bulk of the MAV increases the power consumption of the VelociRoACH by around 24.5 percent. On the other hand, the MAV stabilises the VelociRoach. Pitch and roll velocity, the team observed, is about 90 percent less when the MAV is in its cradle, and overall velocity is increased by 12.7 percent when the MAV flaps its wings while the roach runs.
Further experimentation on these effects will be the next step in the research to try and create perfect launch conditions with as few failures as possible.