How a first attempt at an autonomous road vehicle came from a

blocked Moon Rover project with some help from football

By Lester Earnest (les at cs.stanford.edu)

2014.05.10


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The Stanford Cart has had a career of ups and downs over fifty years. It was born as a research platform for studying the problem of controlling a Moon Rover from Earth. It then was reconfigured as an autonomous road vehicle for research in visual navigation, then went into show business for a few years. It now is on display in a home for retired robots at the Computer History Museum .

Moon Rover Test Vehicle

Stanford Cart with cable, 1961

1960-61 - The Stanford Cart was originally constructed by Mechanical Engineering (ME) graduate student James L. Adams to support his research on the problem of controlling a remote vehicle using video information. He had been working at the Jet Propulsion Laboratory on a NASA project called Project Prospector, which was proceeding with the assumption that someone on earth could drive around the Moon using a TV camera on a vehicle and a radio control link However Adams showed that assumption to be false.

The Cart had four small bicycle wheels with electric motors powered by a car battery and carried a television camera with a fixed view in the forward direction. Tests were conducted using both 2-wheel steering, like a car, and 4-wheel steering, in which the wheels and television camera swivel together. The cart was connected by a very long cable to a control console with a television display and controls for steering and speed. A magnetic tape loop made it possible to vary the time delay of steering commands, to simulate communication delays.

Adams explored the controllability of the vehicle while avoiding obstacles with various combinations of communication delay and speed. When steering commands are delayed by communications there is a tendency for the operator to over-steer and lose control. Among other things, Adams showed in his dissertation that with a communication delay corresponding to the round trip to the Moon (about 2 1/2 seconds) the vehicle could not be reliably controlled if traveling faster than about 0.2 mph (0.3 kph).

Stanford Cart with radio links, 1963 

1962-63 - Mechanical Engineering graduate student Paul W. Braisted devised a scheme to improve the controllability of the vehicle by adding an analog computer that functioned as a predictor that took into account preceding steering commands and put a bright dot on the television screen at the predicted location of the cart when a current steering command would begin to take effect. With this addition the vehicle could be controlled at 5 mph (8 kph). Still there was a fundamental limitation on teleoperation in that if the travel during the time delay is greater than the distance from the vehicle to an unseen obstacle there is no way to avoid hitting it. Braisted completed his dissertation in 1963.

However, the immediate prospect of applying this technology was put off as a result of President John F. Kennedy's announcement on September 12, 1962 of the U.S. manned mission to the Moon.

How football kicked off the first attempt at an autonomous road vehicle

In late 1965 Lester Earnest came to Stanford and joined Prof. John McCarthy's Artificial Intelligence Project as Executive Officer. He then designed and managed a new computer research facility in the foothills above the Stanford campus and in 1971 named it the Stanford Artificial Intelligence Laboratory (SAIL), which by then included several additional research projects.


Site of SAIL research facility, 1966-79

James Adams, who had originally created the Cart for his PhD dissertation, had returned to Stanford as a Professor of Mechanical Engineering. Given that he and Earnest had been football teammates at Caltech in the early 1950s, Earnest looked him up and visited Adams' lab where he noticed the Cart stored in the corner of the room and asked about it. It occurred to Earnest that this vehicle could be used in an attempt to build a self-steering road vehicle based on visual input so he asked if he could borrow it and was granted that privilege.

Earnest had in mind trying to drive on the circular road surrounding the SAIL facility using the road center line and other visual references. However he knew that the Cart would be unable to carry a big enough computer to do that, so he planned to use a transmitter on the cart to send images from the TV camera to the SAIL computer (which by that time was a DEC KA10 system occupying an area about the size of a basketball half-court) and another radio link to send guidance commands from the computer to the Cart. The KA10 ran at a speed of about 0.65 MIPS, quite slow by modern standards.

Unfortunately the two radio links, which had been used in the earlier experiments with the Cart had since disappeared, so Earnest sought and recruited an Electrical Engineering PhD student named Rodney Schmidt, who built a low power television transmitter and radio control link. The Federal Communications Commission granted a low power TV license for Channels 22 and 23 and experimental operations began with a human operators controlling the cart via the computer using television images. Earnest had a long ramp built down the front steps that allowed the Cart to travel from the lab to the road. That allowed students to drive it around the neighborhood while seated at a desk watching the television screen, which became a popular pastime.

Stanford Cart configured as an autonomous road vehicle

Earnest also had a metal “CAUTION ROBOT VEHICLE” sign posted on the entrance road to the lab, which turned out to be a problem because it was repeatedly stolen and was expensive to replicate. He figured out too late that it should have been printed on cardboard and offered for sale at the Stanford Book Store, which could have made some money.


SAIL was granted an experimental TV license by the Federal Communications Commission for Channels 22 and 23 and experimental operation began with a human operator controlling the cart via the computer based on television images. This initially allowed students to drive it around the neighborhood while seated at a desk, which became a popular pastime.

Once the system was working John McCarthy became interested and took control of the project. However he eventually backed away from the road vehicle goal and settled for following a high contrast white line under controlled lighting conditions at a speed of about 0.8 mph (1.3 kph), an experiment didn't even require a vehicle. Schmidt completed his dissertation in 1971.

Getting through a crowded room

Stanford Cart with slider, 1979

The cart was next changed from 4-wheel to 2-wheel steering. Hans Moravec, who had come to Stanford specifically to work on visual navigation, stayed with it but suffered a setback in October 1973 when the cart toppled off an exit ramp while under manual control and ended up with battery acid throughout its electronics.

Moravec was able to enlist the aid of roboticist Victor Scheinman in 1977 to build a “slider,” a mechanical swivel that moved the television camera from side to side allowing multiple views to be obtained without moving the cart. Using the KL10 processor then available, which ran at about 2.5 MIPS, Moravec was eventually able to use multi-ocular vision to navigate slowly around obstacles in an indoor environment. The cart moved in one meter spurts punctuated by ten to fifteen minute pauses for image processing and route planning. In 1979, the cart successfully crossed a chair-filled room without human intervention in about five hours.  Moravec completed his dissertation in 1980 and there is a short video of the cart in action. Upon completion of his PhD, Moravec moved to Carnegie Mellon University’s Robotics Institute which had been founded earlier by Prof. Raj Reddy, another SAIL graduate.

Show Business

After SAIL shut down in 1980 the cart again went into storage until 1987 when, at the request of the Digital Computer Museum in Boston, a number of retired robotic devices were sent to a new exhibit there. The Smart Machines Theater, later renamed Robot Theater, was a collection of artifacts on stage, lit up in sequence with some moving in their moments of glory, synched to a video, proving that even old robots can have a second career in show business.

The Smart Machines Theater in Boston exhibited the Cart in the center

After the Boston museum shut down, the robots and other artifacts were sent to its successor, the Computer History Museum in Mountain View, California. Beginning in 2011 it was put on static display at the Museum, where it can be seen today. Perhaps some day it will again be allowed to roam the world.

The next generation

Stanley gloating after winning the Grand Challenge

In 2003 Sebastian Thrun, who had participated in the Robotics Institute at Carnegie Mellon University, moved to Stanford, revived SAIL and initiated a new autonomous road vehicle project. He initially developed a robot car called Stanley that in 2005 won the DARPA Grand Challenge, a race across the Nevada desert. In 2007 the SAIL team took second in the DARPA Urban Challenge, which simulated an urban driving environment.

Sebastian Thrun and some of his colleagues then moved to nearby Google and created the Google driverless car which is still under development there, though Thrun has gone elsewhere.

A Google Autonomous road vehicle

Acknowledgment

Thanks to James Adams, Bruce Baumgart, Hans Moravec, Oliver Strimpel and Sebastian Thrun for providing information for this account.

References 

The following Ph.D. dissertations at Stanford University came out of research with the Stanford Cart.

[1] Adams, James Lowell, Remote control with long transmission delays, PhD in Mechanical Engineering, 1961.

[2] Braisted, Paul Wilder, Study of a predictor for remote control systems operating with signal transmission delays, PhD in Mechanical Engineering, 1963.

[3] Schmidt, Rodney Albert, Jr., A study of the real-time control of a computer-driven vehicle, PhD in Elecetrical Engineering, 1971.

[4] Moravec, Hans Peter, Obstacle avoidance and navigation in the real world by a seeing robot rover, PhD in Computer Science, 1980.