Command and Control

The recent integration of the Make controller with Flash, its scripting language and image processing capabilities, solves many of the problems I was dealing with, from the choice of microcontroller to the controlling software.

The program currently reads the position of the performer on stage and even the distance from head to ground, all with only one cheap webcam as an input device. There is so much information that can be acquired through image analysis that effectively eliminates the need for a variety of sensors that I had planned to use.

The only limitation is the amount of servo ports in the controller. I will have to daisy-chain at least two, to handle all the servos I think I need.

The servo that supports the weight of the marionette most of the time needs much higher torque than the ones I have. I have not calculated the minimum torque yet, but need to do that ASAP to order it and start testing the software that Philip and I are designing. I am very excited and happy with the progress so far. At first I had my doubts that the solution he proposed would work, but now I see it can, and in a very simple and elegant way.

The two sizes of spools we currently use (5 and 8 cm diameter) happen to be just perfect to provide most of the travel that I need without using continuous rotation motors instead of standard servos. This simplifies programing. We found out by testing a variety of "identical" modified servo motors that the speed of rotation, given equal parameters, is quite different, which implies writing routines to address each one of them to synchronize, a royal pain!

The fish-line spools with their bushings in place

The only continuous rotation motors I need are for the arms since they travel a much greater distance.

Stage Hands

Assembling the motion section and adjusting the elements so they fit.

I love that time when you have to finally begin working on the stage for a play. It means the performance is imminent (unless the producer pulls out!). It is also time to listen carefully to the director, designer, performers, lighting and sound people and stage hands and riggers to make sure all points of view are represented and taken into consideration. (if only it was like that in real life...)

Since the hole pattern in the VeX system is not really well designed (unless someone proves the contrary) I had to notch and cut lots of pieces so that they overlapped correctly in the configuration I needed. As I said before, I think the engineer/s who designed the system probably did it with a preset number of projects in their mind.

I would go back to the drawing board. It seems strange to me that in this age of CAD and relational tools, they could not test at least a few thousand combinations and optimize the design for that. So anyway, the metal is soft enough that it doesn't take that long to adjust.

The Vex control modules, servos and power supply.

Except for Lorena, who is the human performer, choreographer and costume designer for the project and who makes sure her needs and demands are met:-), the rest of the crew is me with occasional help from my friends, like Philip who is working on a Flash interface to control the microprocessors and sensors. I have my doubts about the speed of the image processing functions in the new Flash, but it is worth a try.

For now I am using VeX to build the stage support and to prototype the motion and control system. Ideally I would like to use a faster microprocessor, perhaps Propeller by Parallax which is a multi processor where each one of the 8 processors can operate simultaneously giving you the ability to respond in real time to performer actions, which is what I need to do.

Easier said than done, since programming is not my forte, but my friend Philip, who is in his final year in Architecture, loves coding and we have done great work together. I need to complete the prototype so that we can start programming and optimizing. Everything simpler, easier, faster. Like Ars Electronica 2006 theme said, SIMPLICITY - the art of complexity.

The Creator's new feet

I am also getting so much more familiar with the marionette I've created, since while you are whittling away at blocks of wood and dealing with joints, balance and many other issues, it is difficult to meet the creature on its own terms. Although it is not awake yet I can already see a bit of its character. This is an experience which every puppeteer, or for that matter any artist goes through as it transitions from production to contemplation or analysis and finally to understanding or appreciation.

This process is not so familiar to the engineering folks, since for them, in the majority of cases, everything must be defined or though in toto in advance and there is usually little room for improvisation