Home Chapter 10 Mobility: Servo motors, photo resistors, and PULSOUT
Mobility: Servo motors, photo resistors, and PULSOUT

 

You’re walking and you don’t always realize it, but you’re always falling. With each step you fall forward slightly and then you catch yourself from falling. Over and over you’re falling and then catching yourself from falling. This is how you can be walking and falling at the same time.
~Laurie Anderson

 

Question: Are there positional motors that can be easily controlled by a microprocessor?

 

Mobility


Humans seem to take their mobility for granted. From our youngest years, we instinctively learn to grasp objects and we begin to distinguish our own bodies from the external world. Without a thought, we reach out, grab objects and begin to manipulate and shape the world around us.

 


 Gunther von Hagens has invented a plastination system that allows you to see the amazing distributed nature of the muscular and vascular systems of the human body. He uses actual human bodies and plasticizes them; a process that coats and preserves the tissue. The techniques used and the poses Professor Hagens selects have many of these scientific works residing comfortably in the realm of art. Image copyright and photographer Landahlauts from Flickr photostream.

 

 

Humans have evolved complex neurological and musculoskeletal systems that allow us to take action quickly and fluidly. Not to say that our conscious actions are always intelligent, but our cells have another kind of intelligence.

The distribution of oxygen and nutrients to the heart, as well as to the leg muscles that allow us to walk, have been relegated to the autonomic nervous system. For walking (or falling) our legs do not need to receive step-by-step instructions, though, certainly as infants, our cells need to learn to walk.

 

The autonomic nervous system controls involuntary muscle movements in the body.

 

The evolution of the neuromuscular system for mobility, as well as distribution of oxygen and nutrients through our vascular systems, have allowed humans to focus on higher thought while our autonomic nervous system buzzes along in the background.

The science of biomorphic engineering allows researchers to understand, model, and mimic animal locomotion, adaptation, learning, and perception. These lessons are then utilized in technological systems.

Artists and engineers have been working for a long time to understand and mimic these living system models, and figurative art from our earliest human ancestors could be thought of as a formal variant of biomorphic engineering research. A relatively new variant is behavioral mimesis. Behavioral mimesis is the study of animal behavior and the symbolic representation of it in art and literature.

Some robots utilize microprocessors and actuators to mimic these animal perceptions and actions. Some of these systems learn to adapt to their environments utilizing the programming techniques of artificial life techniques such as the Autotelematic Spider Bots 2006 by the author.

Other formal variants of machine nervous systems can be seen in work like Tim Hawkinson’s Organ 1977. In this work a deconstructed organ reveals the wires remaining after all the supporting material and keys were removed. It created a wonderful anolog of a biological nervous system.

The contemporary artist Bill Vorn has created an interactive sculpture installation entitled STÈLE 01. The installation utilizes artificial life concepts and is composed of many systems and subsystems working in parallel. When heat sensors that sense humans activate the work, an anthropomorphic robotic form stands up while covering its face with its hands. Video imagery of human death is projected on the mosaic of Stele's body, which at times reflects the images onto the audience and at times receives the image on the revolving plates (mini screens) that constitute the body. Mortuary steles from Père Lachaise’s cemetery in Paris inspired STÈLE 01, and the work is designed to evoke a “dichotomy between the real and the virtual, life and death, movement and inertia, men and machines.” (Artists web site)

 


Stele 01 by Bill Vorn 2002. Montreal, Canada.

 

In this installation, Vorn used 32 microcontrollers to control very accurate positional motors called stepper motors. Stepper motors have multiple coils, which makes them extremely accurate, and can turn a full 360° continuously in either direction, as well as stop instantly.

Stepper motors differ from the servomotors you will be learning to use later in this chapter because they lack an internal position encoder, which is an integral part of servos. The encoder enables you to send a simple signal from the stamp to rotate the servo to a specific position. Servos are not as accurate as stepper motors, though, for their size they have a lot of torque.