The U.S. Army loves its toys and pays a lot of money for them, so it naturally gets disappointed when it can’t bring its expensive gadgets everywhere it wants to go. In the 1980s, the Army figured that around half of the landmass on the planet was impassable by conventional wheeled or tracked vehicles, a.k.a. its entire ground fleet. This was clearly a problem, so it partnered with Ohio State University and a few outside contractors to develop the Adaptive Suspension Vehicle: a truck-sized, six-legged hydraulic robot manned by a solo operator.
Although it was very complex and equally slow, it was a successful attempt to get artificial legged locomotion off the pages of science fiction and into reality, beating Boston Dynamics to the creepy mechanized animal game by a good two decades.
Funded by the Defense Advanced Research Projects Agency (DARPA), the ASV project began at OSU in January of 1981. Under the lead of Robert McGhee and Kenneth Waldron-both professors at the university-the machine was developed over the next nine years. Unlike other more crude experiments that came before it, OSU’s machine would incorporate an array of 17 computers to ensure the vehicle’s operator wasn’t physically and mentally exhausted after a day of managing every step taken by the ASV’s six legs.
Keep in mind thputers are incredibly weak by today’s standards. Those massive rectangular boxes you see above the vehicle’s metallic shoulders are not some sort of hydraulic reservoir, they each house one of the six Intel “86/30” 128k, 8-bit computers that controlled the legs.
The rest, 11 in total, did various other tasks, like controlling the CRT displays inside the cockpit, analyzing all of the data gathered from the legs and the pressure sensors in the feet, and determining the best footing for the machine based on data from a 128×128-pixel scanning rangefinder mounted above the cab. All of this data was then interpreted by the vehicle’s operating software-written in Pascal and consisting of 150,000 lines of source code-to make the ASV saunter along.
That’s where the computerized element ends, and the mechanical and human elements begin. The vehicle is described as being more “supervised” than really driven. The operator instructs the ASV where to go with a keypad and joystick, and then it sets off in that direction. It’s implied in some of the literature that the end goal was to make this machine autonomous, however, the OSU team was clearly limited by the processing power at the time-even though they were receiving a million bucks from DARPA every year to fund the project.
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That money was not just put to use on the vehicle’s computers, of course, because the mechanical systems to make the ASV walk were equally complex.
At the heart of the machine was a 900cc motorcycle engine with a peak output of 91 horsepower, but it wasn’t just powering one massive hydraulic pump. Between the engine and the 18 variable displacement pumps-yes, 18-driving the vehicle’s hydraulic cylinders was a 100-pound flywheel. It spun up to 12,000 rpm and could store .25 kWh of energy. That means it could output 250 watts worth of power-about one-third horsepower-for one hour, or a much larger amount of power for a much shorter period of time.
This was useful because the ASV’s 18 pumps were driven by a rather complex system. The engine delivered power from its output shaft to three separate driveshafts via toothed belts. These ran the entire length of the vehicle, which, in turn, transferred power to the pumps-three per leg-via more toothed belts. To complete particularly high-energy maneuvers in this high-friction system, the vehicle needed more power than the engine could produce.
This is when the energy stored in the flywheel was utilized. The flywheel also allowed the vehicle to recuperate some energy from the pumps when the…