In his doctoral thesis, Benjamin Jenett from the Center for Bits and Atoms (CBA) at MIT describes how such relative robots can work together to build complex structures from small base elements known as voxels. Together with Amira Abdel-Rahman and Kenneth Cheung, he wrote an article for "IEEE Robotics and Automation Letters," which Aron Becker, Associate Professor of Electronics and Computer Engineering at the University of Houston, describes as a breakthrough because it combines the latest mechanical design methods, new robots, and simulations with over 100,000 design elements. "We are in the process of opening up a whole new area, the field of hybrid material-robot systems," explains Professor Neil Gershenfeld, Director of the CBA.
According to him, there have only been two types of robot so far: One is made up of expensive, specifically manufactured parts. These types are precisely tailored to their respective tasks. The second type of robot consists of relatively inexpensive modules that are produced in large quantities. However, they are less efficient.
According to Gershenfeld, the "relative robots" form a new category. They have a simpler structure than the application-specific robots but are still much more powerful than the robots made from standard components. They have the potential to revolutionize the construction of large structures - from aircraft and bridges to entire buildings. The big difference between robots and other robots would be their relationship to the materials they handle: "The difference between robot and structure becomes blurred, both work together as a system". A major advantage: today's mobile robots must have an accurate navigation system in order to be able to precisely determine their respective positions. Relative robots only need to know their position in relation to the voxels.
The underlying idea: Just as an image can be composed of pixels, physical objects can be constructed from three-dimensional basic elements, the voxels. The robots can pick them up and join them together to build larger, more complex structures.
The robots themselves resemble an arm with two long segments connected in the middle by a joint. At the ends of each segment there is a gripper. It is used by the robot to hold on to a voxel on one side and to pick up a voxel on the other side to bring it to the desired positions and add it to the structure. Jenett named his robot BILL-E (Bipedal Isotropic Lattice Locomoting Explorer).
He has built several types to show that they work, as well as the associated voxels, which have snap-in mechanisms to easily assemble or disassemble. Now the robots can already build two- and three-dimensional linear structures. "We didn't integrate precision into the robots, but it results from the structure that is created step by step," explains Jenett. "The robot only knows what to do in the next step. That's the big difference to existing robots. This eliminates a large part of the complexity previously required in robots. As long as the robot does not omit a step, it always knows where it is."
Engineers working on the construction of space stations and buildings on the moon or other planets are particularly interested in how large structures can be constructed from simple basic elements. No wonder NASA and Airbus SE supported the project.
What is particularly interesting is that damage to the complex structures can be repaired very easily: The affected voxels are simply removed and replaced by new ones. After that the structure is as robust as the original one. "The robots will "live" in the structure and continuously perform maintenance and repair tasks," says Jenett.
Sandor Fekete from the Institute for Operating Systems and Computer Networks at the Technical University of Braunschweig is also impressed: "Ultra-light, digital materials like these open up the possibility of efficiently constructing large and complex structures, such as those of major importance in the aerospace industry. With their original work, Jenett and his colleagues have taken a huge step forward in the construction of dynamically adaptable aircraft wings, solar sails and even reconfigurable stations in space.