Software tool makes custom robotic design possible

The primary challenge of the research project was to design the robot’s movements so that they would also work outside the digital realm. “That’s the hard part of this work, the part where technical innovation is needed,” says Bernhard Thomaszewski of Disney Research Zurich. From a user’s perspective, he says, the tools offered by their program are comparable with those used in the animation of purely digital figures.

However, unlike in digital animations, the robots must obey the laws of physics. In particular, physical robots cannot balance in every pose that is digitally possible, and there is a limit to the accelerations that can be produced by the motors.

“Without support from a computer, it is extremely difficult for users to take these restrictions into account when planning the movements, and this quickly becomes frustrating for the layman,” says Thomaszewski. “This is precisely the task that our software automates through simulation and numerical optimisation. The user can therefore focus entirely on the creative aspects of the design.”

In order to design the motion of a robot, the user specifies simple motion goals such as “walk forward” or “turn left”. Megaro’s program automatically converts these high-level commands into low-level control signals for the motors such that physical figure is able to walk stably. Whenever the user changes the robot’s skeleton or its motion goals, the computer automatically adapts the time-dependent motor values. This process is very fast such that the user receives immediate feedback on the resulting motion, as predicted by simulation.

Once the user is satisfied with the robot, the program automatically generates three-dimensional building plans for all segments of the body and for the connecting parts, which house the electric motors. Stored in the program are standard sizes of various commercially available motors, so the user need only select the one that matches in order to obtain the connecting parts.

The parts are fabricated on a 3D printer and, finally, the robot is assembled by hand. The electric motors, cables, battery and control unit for the robot are available commercially, and Megaro was able to buy these components cheaply online. On the other hand, a greater financial burden is associated with manufacturing the robot limbs on a high-quality 3D printer.

The ETH doctoral student manufactured the first two prototypes using the in-house printer. This was cheap, he says, but the quality of the body parts was not particularly good. Apparently, the shin bones broke in the first prototype, which was a four-legged robotic dog. In contrast to this, he commissioned an outside company to produce his insect-like masterpiece. This, he says, is of excellent quality and made of sturdy, high-grade plastic. “That quality comes at a price,” says Megaro.

The robotic creatures that Megaro and his colleagues designed, are intentionally kept simple. They can only adopt gaits that the user has first created using the software. Megaro’s five-legged robotic insect can move forwards and sideways using various techniques.

It cannot, however, identify obstacles, as the robots neither have sensors installed nor are they designed to travel independently. They also cannot be controlled remotely, something which could potentially be achieved using a smartphone app. “It also wasn’t the project’s aim to create an autonomous robot,” points out the young researcher.

Until now, it was difficult to develop legged robotic creatures with almost any desired morphology, says the ETH doctoral student. “In addition to research, this effort also involved a great deal of development work and engineering know-how.” He says that, until now, no system existed that simplified this process and allowed even the layman to make a creature based on their own ideas. “We have succeeded in filling this gap.” The software is still in development and is not publicly available to interested parties.