Between 1990 and 2000 there was a short period in robotics which was working different from academic robotics. So called BEAM robots were invented by Mark W. Tilden and according to the self description, it works with analog electronics like solar cells and mechanical beauty.[2] Indeed, most of the robots are looking completely different than any robot before. The most dominant property is the absence of a program controlled computer.
Unfortunately, the BEAM movement has stopped after the year 2000, in favor of classical DIY robotics projects based on the Lego NXT brick and Arduino microcontrollers. What is possible from today's perspective it to reverse engineer the former BEAM movement with the goal to understand why it was started.
Around the year 1990 there was no robot available in the university domain who was able to walk with 2, 4 or even 6 six legs. In contrast, BEAM Robots were able to do so. A BEAM walker can walk while a BEAM snake imitates the locomotion of an animal. The explanation for these advanced movements are located in the nv neurons, which is special term for the logic inside a BEAM robot.
In a more elaborated language a BEAM robot is an oscillator realized in hardware. Components like capacitors, resistors and triggers are combined into analog circuits known as Central Pattern Generators. These pattern generators are normal phase modulated feedback loops. From a mathematical standpoint such a pattern is equal to the sinus function on the time axis which produces a certain behavior for the servo motors.
The interesting situation is, that the same rhythmic movement can be generated without an analog circuit but with a classical MS excel sheet which calculates the Sinus function and has some parameters to adjust the height and length of the output. After adjusting the parameters the resulting function will make the robot legs walk forward.
In other terms, Mark W. Tilden has invented a sinus tone generator build in analog circuits. That is the reason why a BEAM walker doesn't need a complex computer program but the motor signals are realized with a more simpler principle, similar to early analog music synthesizer.[1]
[1] https://en.wikipedia.org/wiki/Analog_synthesizer
[2] https://en.wikipedia.org/wiki/BEAM_robotics