One of the fastest-growing general areas of technology, of which robotics is just a part, is the ability to control things using increasingly sophisticated theory and algorithms, and the ability to run non-trivial simulation models as part of the control process. Consider this use of compressed air jets:
From the report at IEEE Automation blog:
Aaron Becker and Robert Sandheinrich, with help from professor Timothy Bretl, built a computer-controlled air jet system that can make spherical objects like ping-pong balls not only float in place but also move along pre-programmed trajectories, ascending or descending and moving left or right in mid-air — even performing some acrobatic maneuvers like passing through metal rings. Their robotic air blower can also sort balls of different weights and precisely propel balls toward a target. And it can lift an apple and non-spherical objects like a water bottle.
… The system consists of a gimbaled air jet with two degrees of freedom. The air jet is supplied up to 620 kPa through a DC motor-controlled valve. Stereo vision cameras track the objects, and a control algorithm uses the position data and a fluid dynamics model to adjust the air jet, varying its speed and direction to keep the object in equilibrium.
Making a plastic ball “levitate” using compressed air is an old trick (the fast moving air creates a low pressure zone around the ball that traps it), but the UIUC guys had to solve a number of hurdles in engineering their system. The design of the control system, in particular, was a big challenge because the dynamics of the air flow can exhibit chaotic behavior, which is hard to model, and also because adding more than one ball changes the flow field in complex ways. Still, the system can manipulate spheres of various sizes (12 to 97 mm in radius and 2.6 to 188 g in mass).