Pig robot

Category: Inventions
Collaborators: Zoran Srdić Janežič

Pig robot cover picture

Through a common friend (thanks Ra!), I heard that Zoran Srdić of The Gulag Institute for Contemporary Arts and Cultures needed some assistance with electronics. He was already involved in a long series of works about pigs and men, and for the newest part he wanted to create machine pigs and machine men. As I had never really built a robot before, I though this would be a great opportunity to have some impact on that field as well. So I signed up for the project.

The first display of our work was to be in the 8th edition of Bienale lutkovnih ustvarjalcev Slovenije, a festival of puppet theatre in Maribor. The main program of this festival consistes of puppet plays. Our show was to be a bit different, an amalgram of three different methods of animation: traditional puppet play (acted by Aja Kobe), augmented reality, and robotics. The whole thing got the name Corporis animati. My part, working together with Zoran, was to create a self-moving pig robot as the main character, supplemented by stationary human characters who would somehow react to proximity of the pig.

For a month we met almost every afternoon in the workshop of Ljubljana puppet theater and worked until 21 or 22 or 23. As we both also have an “ordinary” job, this was a bit crazy schedule, causing some stress every now and then. Nevertheless, the results are great.

Zoran was working with the mechanical and structural parts. The atmosphere in the studio was a bit grotesque with him walking in with various pig parts, to be cast in silicone and other materials. Maybe the suffering of the pigs was worth it, because the casts ended up looking great. Meanwhile, I was doing mainly electronics and programming.

What we ended up with was an about real-size pig creature, propelled by two windshield wiper motors (really strong, easy to acquire, and mechanical reduction included — very good for diy work) moving the hind “legs”. In the awareness and intelligence department, the pig turned out smart enough to detect a white line in the ground, position itself in relation to it, and back off. This way it knew how to remain within a circular (or nearly so) white line. This felt like an imitation of real domestic pigs bound by a fence.

Showing emotion was also an objective. For this, we got the pig to wiggle its tail in a touching way. This was realized using a stepper motor retrieved from an old photocopy machine we demolished. Unfortunately, our attempts to move the pig’s nose with a coil were unsuccessful.

The casts of human bust look great, and are actually casts of Zoran himself. They were supposed to detect the presence of pig’s “headlights” by a virtue of some sensor, light up, and do some weird and grotesque movements. For the movement we attached motors to the busts. The sensor is a differential sensor built out of two photoresistors and an operational amplifier.

The sensor part gave us quite a bit of trouble. In principle the sensors do work, but the setup is very sensitive to ambient lightning conditions. It happens very easily that the human figures become so sensitive that they self- trigger or trigger spontaneously, or that they become so insensitive that they do not really ever trigger. I think the solution to these problems would be to ditch photoresistors in favor or infrared receiver based setup, akin to remote controls. That should be more dependable.

In addition to the first show in Ulu, the pig has now made appereances in 2015 edition of mfru-kiblix festival in Maribor and in Layerjeva Hiša in Kranj.