the Flock: Artificial Life Sculpture
The Flock is a group of musical interactive sound sculptures which exhibit behaviors analogous to the flocking found in natural groups such as birds, schooling fish or flying bats. Flocking behaviors demonstrate characteristics of supra organization, of a series of animals or artificial life forms that act as one creature. They are complex, interdependent interactions which require individual flocking members to be aware of their position in relation to other flocking members. Our Flock consists of three 9 1/2 foot long jointed robotic arms, constructed from grapevines, which hang from the ceiling and interact with viewers, participants and each other. Each dangling arm has an array of three infrared sensors, projecting out from the top of the arm, which function as active eyes and permit the sculptures to avoid participants walking around the installation. Another infrared eye at the tip of each arm functions to allow the sculptures to approach and simultaneously react to participants presence. Each arm also has an array of four microphones which function as ears allowing the sculpture to move toward participants. The microphones are placed so relative volume levels of viewer/participants voices can be monitored.
The artificial creatures of The Flock were also given their own language. They communicate among themselves with audible telephone tones. These telephone tones function as a musical and positional language allowing the sculptures to pass messages about a participants position in relation to other sculptures. For instance, an arm can sing its position to the other arms, allowing them to follow its lead. The output speaker which plays these tones is at the tip of each of the three arm joints closest to the floor. When the sculptures locate a person they sing with audible telephone tones to the other sculptures, which respond by repeating this tonal and positional sequence, and pointing in the direction of the arm that is closest to the participant. These simple behaviors set up a distributed flocking in the direction of the sounds coming from the participants. Telephone tones were selected as this language of intercommunication between sculptures because they consist of a main tone and an overtone which is unlikely to arise in normal human speech. This reduced the possibility that human intercommunication would mistrigger the system.
While these robotic sound sculptures are programmed to move in the direction of participants voices the active infrared eyes are programmed to allow the sculptures to avoid getting too close to participants. This creates a dynamic state of attraction and repulsion for each sculpture. Here the participants and other sculptures, as environment, affect the form and the form modifies the environment, which then affects the form again, ad infinitum.
The responses of each sculpture depend on the local interactions of the individual sculptures as they interact with the group (the other arms and the human participants). The software is designed to allow a range of learned and unpredictable behaviors, with an emphasis on cooperation to produce a group aesthetic. Each sculpture is controlled by a stand alone processor with intercommunication between sculptures only through the telephone tones. The main concept of this musical robotic series is emergence1, the coming together of systems with no central controller guiding their behavior. Behavior is allowed to arise from the bottom up. This distributed intercommunication permits the global behavior to evolve naturally out of all the local interactions. When the lower levels of the sculptures control system like self preservation (donÍt hit a participant) is satisfied the higher functions like flocking (sing to other sculptures with telephone tones about where the participant is located) are allowed to arise. The results are complex, chaotic, nonlinear and often lifelike. Christopher Langton2 has pointed out, a properly organized structure, need not be living or even physically embodied to display lifelike processes. By this token The Flock exhibits lifelike processes; and since it is a physical embodiment, it is subject to a far richer set of environmental stimuli and constraints than would a pure "in silico" organism. This helps bring the system dynamics into the realm where they can be better apprehended by participants.
Craig Reynolds 3 has had much success with creating on-screen flocking behaviors with artificial organisms he calls "Boids". These simulated birdlike entities have been able to display complex group motion while avoiding obstacles and generally displaying computational flocking. After setting out to create my own artificial life sculptures I discovered Ilhan Ihnatowicz4 had taken a step in this direction in 1972. He built a creature called Senster a computerized sculpture, which was able to dynamically sense it's environment and, under software control, modify its behavior based on past experience and current environmental inputs.
Each sculpture has three joints made of grapevines and bass wood, pulled into a tension/compression structure with steel wire and held together with a cyanoacrylate-based cement and baking soda. The top-most joint of the sculpture which is anchored to the ceiling is outfitted with an array of four microphone ears and three 40 Khz active infrared reflective proximity detectors modified from TV romote control sensors. A loudspeaker at the tip of each arm is used to output the telephone tones and pretaped sounds. The uppermost joint is anchored to a wooden box that houses four reversible DC motors each with an absolute shaft encoder used for arms positioning. Two motors activate the lower two joints and two activate the upper one joint. With this configuration a surprising range of motion is possible. A cord and pulley system much like that used for a radio dial was employed to keep the pull-strings tight. Above this box is the electronic control, a custom built HC68010 processor recycled from old Silicon Graphic Workstations. The audio circuit contains an analog to digital converter to grab human sounds from the environment and digital to analog converter to output human sound. The audio process also contains a telephone touch-tone receiver and sender(Dual Tone Modulated Frequency, DTMF) used for intercommunication between the arms.
The controller software itself is organized as a collection of cooperating real-time processes communicating through a central behavior state structure. Each process is in charge of a particular sensor input or control output. The Behavior State Variables are the repository for information needed by the individual processes. Since the guiding principle is to create bottom-up synthetic behavior, each state variable is for the most part accessed by only a single process. For instance, the influence of the shaft encoder positions over the motor speed is embodied in localized tables; the Audio Process adjusts its own noise threshold based on long-term average sound level; and the dual tone modulated frequencies process has enough intelligence to avoid publicizing its own tone output to back to itself so as not to confuse the system. However, the Behavior Process makes use of a cross section of the available state data to guide the "personality" of the arm, and to integrate the diverse sensor data to arrive at a generalized "feel" for the environment. This state evolves in real time to produce a theoretically infinite variation in an arms reactions.
By seamlessly integrating electronic and organic elements I am asserting the confluence and co-evolution of organic and technological cultures. The branching and joining of the physical forms echoes the temporal flow of interactions within The Flock and makes further reference to the bottom-up self similarity characteristics inherent in living systems. The Flock further demonstrates an imperative that technological systems be modeled on the principles of general living systems. They assert that technological systems have much to learn from the time tested interconnected symbiosis of matter energy and information processes which have evolved in natural living systems. This will permit technological systems, a necessity for human survival and evolution, and natural systems, also critical to our survival, to inherently fuse and create an interdependent co-evolving earth.
The three arms of The Flock was created by artist/engineer Kenneth Edmund Rinaldo and Engineer Mark Grossman. 2. Special thanks to Joe Kennedy, Silicon Graphics engineer, for his original HC 68010 processor design for this project and John Dawson for his ongoing support. Thanks to Liz Zivic for her amazing strobe shots of this project back in 1994.
1, Chris Langton, C. l (1987) "Artificial Life" (Redwood City, California, Addison Wesley Publishing Company, Inc.) The Key concept in Artificial Life is emergent behavior. Natural life emerges out of the organized interaction s of a great number of nonliving molecule, with no global controller responsible for the behavior of every part. Rather, every part is a behavior itself, and life is the behavior that emerges from out of all the local interactions among individual behaviors. It is this bottom-up distributed, local determination of behavior that AL employs in its primary methodological approach to the generation of lifelike behaviors.
Copyright KEN RINALDO 2000 All Rights Reserved