Chapter 3: BEAM robotics

Robotics in the BEAM (biology, electronics, aesthetics, and mechanics) tradition eschew the use of a microprocessor in favor of simpler analogue circuits like comparators to create novel mechanical forms. BEAM robotics, while not as adaptable as microprocessor-based robots, can be reliable and effective when used for their intended purpose.

To better respond to its working environment, BEAM robots may use a set of analog circuits that mimic biological neurons.

The foundation of BEAM is a machine's capacity to respond to stimuli. The underlying mechanism, wherein the circuit (or an Nv net of Nv neurons) is used to simulate biological neuron behaviors, was invented by Mark W. Tilden. Ed Rietman published a number of experiments on artificial neural networks that were reminiscent of this work. Tilden's circuit is similar to a shift register, but it has a few key improvements that make it more suited for use in a mobile robot.

Included additional regulations (and to varying degrees applied):

Reduce the number of electronic components you use as much as possible ("keep it simple")

Reuse and recycle technoscrap

Make use of light rays (such as solar power)

Many BEAM robots are equipped with small solar arrays to power a "Solar Engine," making them fully autonomous and usable in a variety of lighting environments. In addition to Tilden's "Nervous Networks'" basic computational layer, BEAM has added a wealth of new resources for roboticists. The BEAM community has documented and shared a variety of circuits, including the "Solar Engine" circuit, numerous H-bridge circuits for small motor control, tactile sensor designs, and techniques for building meso-scale (palm-sized) robots.

BEAM robotics, which takes its cues from Rodney Brooks's "reaction-based" approaches, seeks to mimic the traits and actions of living things in an effort to tame the "wild" robots it creates. BEAM robots' aesthetics are based on the "form follows function" principle, which is then modified by the designer's decisions as they work to implement the robot's intended functionality.

The true meaning of BEAM is open to interpretation. Biology, Electronics, Art, and Mechanics are the most common interpretations.

Mark Tilden first used this term in a 1990 panel at the Ontario Science Centre. Mark was showing off a few of the unique robots he developed while employed there.

Many other, less common names are in use, though:

Biotechnology Ethology Analogy Morphology

Construction of Anarchy, Evolution, and Modularity

In contrast to many other microcontroller-based robot architectures, BEAM robots are designed around the idea of multiple simple behaviors linked directly to sensor systems with minimal signal conditioning. The seminal work "Vehicles: Experiments in Synthetic Psychology" shares similar design principles. This book delves into how simple inhibitory and excitatory sensor links to the actuators can lead to the development of complex robot behaviors through a series of thought experiments. Due to the very low-level hardware-centric design philosophy, microcontrollers and computer programming are not typically included in a traditional ("pure") BEAM robot.

Combining the two technologies has resulted in successful robot designs. These "hybrids," like the "horse-and-rider" topology BEAMbots, satisfy a demand for robust control systems while also providing the flexibility afforded by dynamic programming (e.g. the ScoutWalker 3). Traditional BEAM technology is used to implement 'horse' behavior, but a microcontroller-based 'rider' can steer that behavior to achieve the rider's goals.

BEAMbots come in many "-trope" varieties, each with its own set of goals it hopes to accomplish. The phototropes are the most common of the series because a solar-powered robot would benefit most from a light-seeking behavior.

The audiotropic response.

Audiophiles gravitate toward playback devices.

Those who are audiophobic avoid noise.

"Light-seeking" phototropes are attracted to illumination.

Light attracts photophiles, also called photovores.

Those who are photophobic avoid bright lights.

Radiotropes are sensitive to radio waves.

Enthusiasts of radio frequency radiation (RF) tend to congregate near such devices.

Those who are afraid of radio frequency radiation avoid it.

Thermotropes are temperature sensors.

Thermophiles are drawn to high temperatures.

Those who are afraid of heat avoid them.

BEAMbots can move and position themselves in a number of different ways. Among these are:

Robots that sit still and do nothing are known as "sitters.".

Beacons: Send out a signal (typically a directional blip) that other BEAMbots can use to find their way.

Pummers, put on a "light show" or a musical sequence for us. Pummers are typically solar-powered, nighttime robots that store energy during the day.

Ornaments are a generic term for tabletop accessories other than beacons and pummers. These are typically examples of electronic art.

Squirmers are interesting, stationary robots that squirm (usually by moving some sort of limbs or appendages).

Magbots: animating themselves with magnetic fields.

Flagwavers are people who change the position of a sign (or "flag") at a set interval.

Turn your and move in the direction of an easily observable object, like a flash of light. (In the BEAM subculture, these are quite common. They can function as independent robots, but are more commonly found as components of larger machines.

Vibrators: move around by shaking themselves with a small pager motor and an off-center weight.

Robots that move by sliding their body parts along a surface while maintaining contact with that surface are known as sliders.

Use a horizontal wave motion, like a snake.

Longitudinal wave motion is used by earthworms.

Crawlers are robots that can move along tracks or by rolling their bodies with an attachment. The robot's chassis doesn't drag along the floor.

All turbots use their arms and flagella to perform a full body roll.

Inchworms are vehicles that only move their chassis, not their entire bodies, forward.

Robots with tracked wheels, like those on a tank.

Robots that use a vertical takeoff and landing to get around are called "jumpers.".

Vibrobots: make a trembling noise while moving in a random pattern across a flat surface.

Springbots: Advance by bouncing forward in a predetermined path.

Robots that get around by rolling all or some of their body are known as rollers.

Symets: Powered by a single motor whose shaft makes contact with the ground; direction of motion is determined by which of several symmetric contact points around the shaft is in contact with the ground.

Solarrollers are single-motor, one- or two-wheeled vehicles powered by solar energy and optimized for speed over a flat, short distance.

Two motors powered by independent solar-powered generators; reliance on differential sensors for action.

To make miniballs roll, you must alter their center of gravity.

Robots with legs capable of differential ground contact are referred to as walkers. BEAM walkers are typically unprogrammed Nv networks that walk and react to their surroundings based on the resistance of their motors.

Leg motion is powered by motors (typically 3 motors or less).

Leg actuators are powered by muscle wires made of Nitinol (nickel-titanium alloy).

Aquabots or aquatic herbivores are another name for swimmers. Surface- and submerged-moving robots for use in liquid environments (typically water).

Bots that function on the water's surface are called "boats.".

Functioning below the surface of a liquid, subbots are able to.

Fliers are robots that can fly for extended periods of time.

For lift and forward motion in helicopters, a single powered rotor is used.

Planes can create lift with either stationary or moving wing surfaces.

Flying saucers: float on a neutrally buoyant balloon.

Climbers are robots that are able to scale or descend a vertical surface using some sort of guide, typically a rope or wire.

Commercial use of autonomous robots is currently limited to a few niche products like the iRobot Roomba robotic vacuum cleaner and a few autonomous lawn mowers. Most commonly, BEAM has been used for the rapid prototyping of motion systems and in educational and hobby settings. Wow-Wee Robotics' B.I.O.Bug and RoboRaptor are two examples of how Mark Tilden has used BEAM to successfully prototype products. Hobby and educational products based on BEAM have also been released by Solarbotics Ltd., Bug'n'Bots, JCM InVentures Inc., and PagerMotors.com. Hexbugs are miniature BEAM robots created by Vex.

Problems arise when aspiring BEAM roboticists attempt to exercise direct control over "pure" BEAM control circuits, which is not the case in most cases. Biomorphic techniques, which are inspired by natural systems, are currently being studied for their potential to outperform conventional methods. Numerous examples demonstrate that insect brains, despite their small size, can outperform even the most sophisticated microelectronics.

The perceived random nature of the 'nervous network,' which necessitates the builder learning new techniques to successfully diagnose and manipulate the characteristics of the circuitry, is another obstacle to the widespread application of BEAM technology. Mark Tilden was previously a regular participant in a group of international academics who gather each year in Telluride, Colorado to discuss this very...