Darts machine scores a bull`s-eye every time (almost)

It is answer to every pub darts player`s dream - a dartboard that will almost guarantee a bull`s-eye every time. This fantasy has become a reality thanks to a group of German engineers and computer scientists.

They have developed a system (shown above) that uses machine vision cameras to track the flight of a dart and then moves a dartboard rapidly and accurately enough for it to be in the right place for the dart to score a bull`s-eye.

At first, nobody thought that it would be possible to determine the dart`s flight path, calculate the point of impact, and move the board to the correct position, within the 250ms flight time of a dart. Despite this, about a year ago, a group of students from the Munich Technical University (TUM) formed a multidisciplinary team to determine whether the dart machine would be feasible.

First, they had to find out whether commercially available vision systems would be fast enough to acquire the image of the flying dart, and to work out how to arrange the actuators needed to move the board quickly and precisely. They calculated that 100ms was needed to acquire of the dart data and position the board, and a further 50ms was needed to allow for communications between the components and for the various movements to be co-ordinated.

The team decided to limit the movement of the dartboard to half its diameter in both the vertical and horizontal axes. This would mean that the dart-thrower was going to hit the board anyway, but the system would help to ensure that the dart would score a bull`s-eye.

Several German automation suppliers, including igus, Leuze Lumiflex, and Softing provided equipment for the project. Festo supplied the servomotors and the electrical toothed belt axes that move the board, while Bosch Rexroth provided the supporting profiles.

Two cameras - one looking down on the dart from above, and the other viewing it from the side - track the dart`s motion in three dimensions. This information is fed to an industrial PC, which calculates the trajectory and sends commands via CANbus to the motion controllers that supervise the servo-driven axes.

The dartboard is mounted on horizontal and vertical beams which are propelled by co-ordinated pairs of belt-driven axes at either end. This design was chosen to minimise the moving mass.

The developers completed the project within four months. They claim that the dartboard machine will "score" a bull`s-eye at least nine times out of ten. Since the machine was completed, it has drawn crowds at several trade shows and can be seen again at the Hannover Fair in April this year, and at the Automatica show in Munich in May.

A short video of the dartboard in action can be seen on the development team`s Web site.