Carnegie Mellon University > Robotics Institute > Garth Zeglin > Kinetic Fabric Sculpture
My robotic art practice includes the creation of kinetic fabric sculptures which combine actuators, sensing, and control with lightweight suspended fabric structures. My main art documentation is located at garthzeglin.com, but this page includes a more technical discussion of the ideas behind the work.
Currently in development, ‘Shelter’ is a commissioned work to be shown at the Carnegie Library Main during July 2008 in Pittsburgh, PA as part of Robot 250.
A conceptual illustration of the idea appears below:
The proposed piece comprises two concentric rotating tent-like silk forms suspended over a round couch or reading chair. The bottom panels of the structure are low and flutter in the air as the structures rotate; visitors should feel welcome to step under them and sit to experience the piece at close proximity, touching the fabric and seeing the interplay of the light, fabric and motion. The overall effect is intended to provide a small sanctuary, a colorful, peaceful shelter in the midst of the library.
The piece does not move continuously, but is controlled through both choreographed motions and algorithmic behaviors. Each tent can independently stop or rotate in either direction, varying in response to the the passage of time, the presence of people, or changes in the lighting. The sensors are used to regulate the motion, which makes this an interactive fabric robot; as visitors touch the piece and sit on the couch, the effects of their contact and presence will indirectly affect the behavior of the piece as it attempts to compensate for their disturbance.
This work is first and foremost an art piece but also involves some fundamental robotic principles. For example, the upper fabric panels serve as a state-dependent variable transmission between the motor at the top and the inertia of the hoop in the middle. Since the hoop lifts against gravity as the fabric twists, the effect is similar to a series-elastic transmission. At rest, the fabric provides little coupling between the motor and hoop, but as the motor rotates, the twist angle increases and provides torque coupling. This is an important factor for the drive design, since reversing the applied drive torque requires unwinding the fabric twist and winding in the opposite direction. For this reason the drive uses a low transmission ratio and low-inertia spindle to operate as a high-speed torque actuator.
On the human-robot interaction side is an exploration of how the simple presence of feedback creates the illusion of a responsive system. There are no sensors directly dedicated to sensing people, just proprioceptive sensing of the fabric motion and ambient light sensors. But my hypothesis is that the normal control response to the disturbance of a visitor's touch will be perceived as an animate response. This also provides an opportunity to build a model-based classifier to detect human presence based upon the disturbance signals, which could serve as a cue to the algorithmic behaviors to create a narrative response.
Just to give a sense of my engineering design style, I've listed a few of the parts used in the project: the microcontroller is an LPC2129 ARM7 chip on an Olimex LPC-P2129 prototyping board; the motors are Pittman 14204S006 24V servomotors; the amplifiers are AMC Z12A8DDC units with digital PWM interface; the hoops are assembled from Easton aluminum tent pole segments; the fabric drive features a custom-machined spindle with tent-pole spokes; the transmission is a 6:1 timing belt reduction using a custom laser-cut large pulley; the motor supports are laser-cut ABS plastic tabbed and screwed together. The sensor suite is still being worked out but could include Sharp optical rangefinders, various sonars, and a RGB color sensor.
Advanced Motion Controls provided discounted motor amplifiers in support of the project.
My prior kinetic fabric pieces include Albatross and Window. In brief, Albatross uses four direct-drive capstan winches to move a counterweighted fabric structure through a space. The motion was algorithmically generated to create slow, silent non-repeating motions which moved through a cycle of different tempos and rhythms. Window is an exploration of using a bank of computer-controlled fans and lights to provide a delicate motion of a few fabric panels.
Page revision: 2008/05/06 15:58:45.
Garth Zeglin, Robotics Institute, Carnegie Mellon University.