Showtime for the cable robot

German actor Dietmar Bär, known for his recurrent role in a popular crime series, visited the Max Planck Institute for Biological Cybernetics for a TV programme

For the “Große Show der Naturwunder“ (Great Show of Natural Wonders), which was aired on 26 May on German Channel 1, the actor Dietmar Bär climbed into the Institute’s unique cable-driven parallel robot. Inside this motion simulator, he experienced the virtual world of a helicopter flight and was able gain insights into the development of this technology.

A pod constructed from carbon-fibre rods is suspended by eight stout steel cables that are anchored in the walls of a large hall and are equipped with powerful motors. This, along with modern computer technology and the software designed at the Institute, forms the essential components of a new cable-driven parallel robot for production technology and automation that scientists at the MPI for Biological Cybernetics have developed in cooperation with colleagues at the Fraunhofer-Institut. For the first time, this cable-based system can now also transport humans.

The pod can be moved to any point in space. This achieves two things: very complex motion sequences can be realistically simulated, and the manner in which humans deal with those motions – for example, how the senses interact  during the take-off of an aircraft − can be recorded using special measurement techniques.

For the past six months, this cable robot, which can also perform very gentle movements approaching the human perception threshold, has been available for research purposes. When a subject is seated in the simulator, he wears a head-mounted display, i.e. data goggles for virtual reality (VR), which transports him into the relevant scenario.

Hovering in a helicopter

When Dietmar Bär climbed into the simulator in mid-March, the scientists started the VR program of a helicopter cockpit. Bär looked down on a rugged landscape with snow-covered mountains and trees. The actor was able to control the movements of the cable robot himself by means of a joystick. However, the scientists did give him a bit of help: he didn’t have to take off himself.

His task was to hold the cable robot stable and to hover in the virtual helicopter. This was no child’s play. There were a number of difficultly levels as the researchers gradually tweaked various parameters. For example, they were able to change the gravitation from “moon-like” to “earth-like”, which resulted in slower or quicker system response. “Gravitation as on the moon causes the system to respond sluggishly,” explains Philipp Miermeister, research engineer in the Department of Max Planck Director Heinrich Bülthoff. The viscosity of the ambient medium could also be changed and ranged from honey-like to air-like. This affects the stability and control of the helicopter, Miermeister says: “The motion is damped, the helicopter doesn’t sway back and forth as much, and it doesn’t tilt away so quickly.”

Constant compensatory movements are also necessary to control a helicopter in real life, says Miermeister. “As soon as the pilot releases the joystick, the system becomes unstable and begins to drift.”

After several minutes, the scientists were astonished at how deftly Bär was able to hold the helicopter in hovering flight. He was even able to keep the motion simulator stable despite increasingly difficult conditions: in the virtual world, the helicopter flew into fog that reduced visibility, and the helicopter began to lurch. Despite all the adversities he had to contend with, the “Tatort” inspector landed safely.

Curious about science

The filming was also a special moment for the scientists. After all, when filmmaking encounters research, two worlds meet. Scientists are used to speaking in technical jargon, whereas film teams address the lay public. To bridge the gap, the filming was planned well in advance. In addition, some compromises were made. “We modified the flight simulation somewhat and concentrated on individual aspects,” says Max Planck Director Heinrich Bülthoff. Filming took place on several simulators, and interviews were conducted with the researchers. “Generally speaking, in the broadcast we wanted to convey how our senses work together and how people are able to solve difficult control tasks, especially when information from the eyes and the balance organ have to be combined,” says Bülthoff.

The result was aired at 8:15 p.m. on 26 May on German Channel 1 when presenters Frank Elstner and Ranga Yogeshwar hosted the “Große Show der Naturwunder” (Great Show of Natural Wonders). Prominent guests on the program were singer Ute Lemper, presenter Andrea Kiewel, singer Thomas Anders and, of course, Dietmar Bär. The segment from Tübingen were alse shown. In addition, one of the quiz questions related to Bär’s experience in the motion simulator. The actor-inspector from the Cologne-based “Tatort” also expressed keen interest in the science on site and took time out for chats, during which it was revealed that he has a special relationship to Tübingen: he played his very first role in the city’s regional theatre, where he subsequently worked for three years.

cbo/je