There are just a few companies in the world that need no introduction, and Disney is one of them. After all, who didn’t grow up watching Disney classics? But did you know that Disney does more than shoot box office hits, record terrible catchy songs and avoid theme park-related lawsuits? They also have an active Research Department charged with creating actual, rather than digital, creations which can be used for throughout the Disney imperium. And the department’s latest achievement is impressive: recreating the walking movements of animated characters in bi-pedal robots, which they have done using 3D printing technology.
As three scientists attached to the department in Pittsburgh – Seungmoon Song, Joohyung Kim and Katsu Yamane – explain, they set out to develop robotics that can be used to make Disney’s theme parks and toys more realistic and magical. After all, fit young heros from Disney’s movies and TV shows don’t exactly perform well when moving as stiffly as paraplegic grandmothers. ‘Creating robots that embody animation characters in the real world is highly demanded in the entertainment industry because such robots would allow people to physically interact with characters that they have only seen in films or TV. To give a feeling of life to those robots, it is important to mimic not only the appearance but also the motion styles of the characters,’ they write.
But this isn’t easy. As they write in an article entitled ‘Development of a Bipedal Robot that Walks Like an Animation Character’, the field of robotics struggles to capture life-like movement. ‘The main challenge of this project comes from the fact that the original animation character and its motions are not designed considering physical constraints,’ they write. And of course trying to tackle quirky and fast animated characters is even more difficult, as they movements are not typically designed to be physical correct. ‘[But in recent years] animation characters have evolved to be more realistic. Using computer graphic techniques, we can design 3D characters, and generate more natural and physically plausible motions with them.’
And you might be surprised to learn that their solution is somewhat similar to what you and I would do for a project: just 3D print it and add some servo motors. Of course it isn’t quite so simple, but to capture the exaggerated gait and movement of animated characters they first 3D printed leg components to match the structure of their potato-like character, which you can see in the clip below. ‘We start from animation data of a character walking. We develop a bipedal robot which corresponds to lower part of the character following its kinematic structure. The links are 3D printed and the joints are actuated by servo motors,’ they explain. All these parts were 3D printed using Stratasys’ Object 260 Connect 3D printer in RGD525 material.
Of course these need to be very specifically angled and positioned to ensure that 3D movement can be recreated. And Trajectory optimization software does most of the rest. ‘Using trajectory optimization, we generate an open-loop walking trajectory that mimics the character’s walking motion by modifying the motion such that the Zero Moment Point stays in the contact convex hull,’ they write. Now this process is more difficult than it sounds, but for a full description of data extraction and installing the mechanics you’ll have to dive into the full scientific article here.
But the results are obvious, though not perfect. The robot can definitely walk well, but doesn’t reproduce the digital models perfectly and has a tendency to wobble. ‘When we play back the optimized trajectory, the robot wobbles forward. It is because the robot does not produce the motion perfectly. For example, the stance leg flexes more and scuffs the swing foot at the beginning and end of the swing phase. This causes the swing foot to push against the ground and the stance foot to slip, which results in unstable walking,’ the scientists write.
One solution for this is slowing down the process. ‘We observed that the robot slips less as we play back the optimized motion slower, and the resulting walking looks closer to the optimized walking,’ they write, but conclude that the system just isn’t working optimal for now. While there are few options for more progress – including investigating structural materials and replacing 3D printed parts – it looks like we’ll have to wait a few years before running into mechanically-sound walking Disney characters at Disney world.
by Alec | May 27, 2015