Servo - August 2008

was usually left to his or her own imagination when it came to using these types of parts for robots.

Early Robot Designs

Robots were frequently built upon plywood bases, held together with wood screws, nails, and glue in the ‘50s. Most of the earlier robotic creations were fairly large so wood seemed natural for the shells of robots. There were few sources for aluminum angle extrusions so most people used steel for the inner structures. Wheels may have come from lawn mowers, the occasional scooter, large toy, or roller skates. Most motors available to experimenters were not geared down so belt and chain reduction systems connected the motors to the wheels. Many of the early robot designs used the ‘Ackermann’ type of steering that is used in all cars instead of the differential type of steering popular today in robots. In this configuration, the back (or front) wheels were used for forward or reverse movement and two of the wheels were connected together to steer right or left by another ‘steering’ motor. Sometimes a single wheel was steered by a steering motor and that single wheel could also be powered by a drive motor. Figure 1 shows Grey Walter’s Elmer robot and the gears that drive the front wheel in this configuration.

Good old Gilbert ‘Erector Sets’ had some of the best parts to experiment with mechanical configurations. Figure 2 shows a set from 1949. Notice that it features a remotely-controlled robot and you can see the AC motor sitting in the metal box with the red gear train behind. The motor supplied with these sets was not only a gearmotor, but it had several different geared output speeds. Since it was an AC shaded-pole motor, you were stuck with the speeds on the side of the gearbox. Few robots had any sort of variable speed control, whether for the base or for any sort of arms or other extremities. Cables and even fishing line were frequently used to transfer motion from one part of an arm to the ends to allow weighty driving motors to be located in areas

FIGURE 1. Grey Walter’s Elmer.

easier for the main arm motor to lift.

Early Robot Intelligence

robots with only relays, switches, CdS photo cells, and lots of hard-wired wire connections.

Early Robot Power

Not all of the earlier robots were designed to resemble bipedal humanoid forms as Grey Walter’s tortoise-like Elsie and Elmer typifies. Experimenters in these early days were just as interested in Artificial Intelligence as we are today; it’s just that there were absolutely no forms of ‘non-human intelligence’ (i.e., microcomputers) small enough to be placed on a mobile platform. In the ‘50s and even the ‘60s, computers filled complete rooms and drew thousands of watts. Any sort of intelligence had to be simulated by using some sort of sensors to feed back into an onboard relay or hard-wired network, or to an external computer.

Available sensors to the early experimenters could be microswitches with feelers to detect obstacles or CdS or phototube sensors to detect light sources or ambient light. The intelligence could be as simple (or complicated) as: “If bumper switch ‘c’ is in the closed position, and the CdS cell ‘2’ sees enough light to close its relay, then send a signal to relay ‘AA’ to drive the steering motor to the left.”

It wasn’t AI as we know it today, but Walter did some amazing things with two tubes in his amazing little robot. Those that followed also built some surprising

Early experimenters did not have the luxury of today’s vast array of battery chemistries, amp-hour capacities, and low costs. Many robots of that era used simple dry cells, usually the D sized carbon-zinc type. AA cells were called penlight batteries and there were no alkaline types at that time. C cells were smaller and less than half the capacity of a D, yet cost the same, so most experimenters used D cells. The other batteries were smaller six and 12 volt lead acid batteries, usually the smallest battery that you could find from a farm implement or similar.

There were no easily obtainable sealed electrolyte lead acid batteries so you just hoped your robot didn’t turn over and eat its innards and everything in sight with the spilled