4The Structure of Petit Mal
My goal was to build a robot that was robust, ran for long periods of time without attention, explored its environment and interacted with people, and gave the impression of sentience, with the absolute minimum of mechanical hardware, sensors, code and computational power. I wanted to build a device in which its physiognomy was determined by brutally expedient exploitation of minimal hardware.
The two wheeled design offered the most expedient motor realisation for drive and steering: two pulse-width-modulated DC gearheard motors. This two wheeled design then demanded a low center of gravity to ensure stability. This swinging undercarriage then demanded a solution to the problem of stabilisation of the sensors so that they wouldn't swing radically, looking first at the ceiling then at the floor.The second internal pendulum provided this stability. In this way the structure specified the necessary extrapolations to itself, the development of the mechanical structure was not a gratuitous design but a highly constrained and rigorous elaboration based on the first premise of two wheeled locomotion. The double pendulum structure then implied a separation between logic and motor voltages, the lower or outer pendulum carries motors, motor battery and motor drive electronics, the inner pendulum carries the sensors at the top, the accelerometer in the middle and processor ( a Coactive GCB11 microcontroller board) and power supplies as counterweight in the lower part. The batteries are not dead weight but in both cases also function as the counterweights. It then became clear that the angle between the two pendulums could be measured and this angle could be used as an expedient measure of acceleration and also could indicate a 'problem' situation in which the motors were applying torque but the robot was not moving. The analogy to the semi-circular canals of the inner ear as the primary sensor of balance in humans is clear: the accelerometer is a rudimentary proprioceptive sensor, it measures relationships between parts of the robot's 'body'. It was important to me that this robot was 'aware' of its body, for reasons which will become clear shortly.
This holistic, almost biological approach to design extends into the software. From the outset I wanted to approach hardware and software, not as separate entities but as a whole. Data collection requirements necessitated the development of the stable inner pendulum, likewise the physical structure, together with the basic requirements of navigation and interaction with humans, determined the software. I wanted the software to 'emerge' from the hardware, from the bottom up, so to speak. The code would make maximal utilisation of minimal sensor data input.
I must emphasise that as an artist, I am an amateur and an impostor in fields of robotic engineering, artificial intelligence and cognitive science. However my outsider status has allowed me an overview of research in these fields. It became clear during the project that the project had much in common with research into artificial life, bottom-up robotics and autonomous agents. Curiously, I have discovered that some of my basic assumptions align me with the more progressive research in those fields. Coming from an artistic background, I have a strong sympathy for an 'embodied' approach. I also have an holistic approach to design and construction. I have designed and built most of the robot myself.