Creating Motion

The process began by attempting to imitate happy, sad and angry faces using simple motions of the mouth, ears and eyebrows of the lion, and the mouth, nose and eyebrows of the demon. We built a mouth that could open and close, a nose that could flare or hang normally, ears that could be folded down or upright, and a brow that could be straight, tilted down(sad) or tilted up(angry). All of these motions are possible to imitate with relatively simple gear trains and can be seen in the gallery.

We built preliminary skulls for our robots and were able to fit our own motion modules and motors into these skulls with very little tinkering to the design to lead us to our very first versions of our gargoyles.

Sensors

The next step was to place sensors in the appropriate places on the skull so the robots would be able to tell when each part of their face had reached a particular state. Since there were only two states for the mouth, ears and nostrils we were able to use two touch sensors per part to let the robot know whether the mouth was open or closed, whether the ears were up or down, and whether the nostrils were flared or not. The biggest problem here was being able to get the correct range of motion for each piece of the face. It was not always possible to have as large or as small a difference in the two states for as you would like. Another problem was that if the motor wasn't powerful enough, even though the sensors were lined up to be pressed at the right stage, it might not be powerful enough to click it, or it might click it too vigorously and bounce back to a less extreme state. These problems could have been fixed by increasing the torque, but since we had such a limited amount of time we were unable to fix the problems once we had realized they would affect to robot as much as they did.

Since we wanted to have three distinct states for the eyebrows we needed to have break-beam sensors. This is an infrared light and sensor set up so that when the motor turns, a lego breaks the beam from the light to the sensor causing the reading on the sensor to increase significantly for a small amount of time. If the lego is turning fast enough we can judge how what state the eyebrows are in by how many times the lego has broken the infrared beam.

Arts and Crafts

At this stage we had two functional robots which did not at all convey emotion because they didn't have actual faces yet. In order to create the finished version of the gargoyles we made patterns out of paper which we then cut out of a tan muslin and stitched in the forms of a lion and an demon face. We made the demon face less scary than our original plans because we didn't want to scare all the children at the exhibition with something that actually looked like a demon. With a little extra felt, stuffing and paint we had two heads that resembled the gargoyles we had envisioned for so long. Afterwards, we found two similarly sized boxes which were painted to look as much like a wall as was possible. The gargoyles were mounted onto the boxes, which had little shelves on the inside for the handyboards and small boxes to keep the communication lights and sensors out of the way of any light that might get inside the boxes otherwise.

Design Problems

Our major misstep in the design process was to fit the motion modules we built into the original skulls that were built without considering if there would be a better design for the skull that would make more sense with the different movements that were necessary. Had we considered rebuilding at this stage we could have made a more stable and robust robot that was able to support the motors and gear trains that were causing us so much trouble by becoming loose and disconnected from one another. Lyn was able to help our angry gargoyle at the last minute, which made him more stable than the lion, which we did not have time to do the same to. This allowed for our angry gargoyle to work for a good portion of the exhibition, while the lion was in repairs throughout the entire thing. Had we considered redesigning at this stage we may have also avoided our sensor problems which in the end caused us to get rid of the mouth movement entirely.

If we had more time would could have also spent a little longer making our angry gargoyle look more like we wanted him to. We could have added ears and horns, and changed the brow and mouth a little. Sadly we ran out of time and were unable to do any of these things in time for the exhibition.

Last Modified: January 29, 2009