Hans Moravec
Robotics Institute
Carnegie Mellon University
5000 Forbes Avenue
Pittsburgh, PA 15213-3891

(412) 268-3829 - FAX: (412) 268-5895
hpm@cmu.edu www.frc.ri.cmu.edu/~hpm

September 30, 2002

This letter is to announce commercialization of my work on free range robot navigation, and to solicit interest in participating in the opportunity.

The point of the work is robot perception good enough to let mobile machines free range reliably indoors for long distances without route-specific preparation. This seemingly straightforward functionality has eluded everybody to this day: I’ve been at it for three decades. Lessons from those 30 years (summarized in the accompanying illustrated sheets), along with a 1000x increase in computer power at 1/1000 the price, have finally put it in reach. It’s surely an “enabling technology.”

Today the parts cost is over $5,000, for high-end computing and stereoscopic cameras to do dense 3D statistical perception and mapping. For this reason, high-value AGVs (Automatic Guided Vehicles for factories and warehouses) may be the most plausible early application. We are contacting major suppliers of varied AGV navigation systems (AGV Electronics in Sweden, Siemens Dematic in Michigan) to explore that option. For AGVs, a camera-based mapping module, resembling a laser navigation unit, could provide significant advantages over existing guidance methods. Without need of bar code targets or floor embedded wires, magnets or patterns, a mapping AGV could be installed in new locations or rerouted with small effort, perhaps just led through a new route by a worker. Mapping is potentially more accurate and reliable than laser navigation, because a dense 3D sense gives a firmer statistical grip on the surroundings than the three or four points of a laser localization. The rich map opens the possibility of extra functionality, for instance long-range obstacle negotiation, locating movable destinations and large object recognition.

By my numbers, the cost of computation has recently been halving each year, a combination of increasing computer performance and decreasing unit price. Camera costs are falling almost as rapidly. Within five years the parts cost should be well below $1,000, with significantly increased performance. By developing expensive products now for the near term, we achieve a head start in the creation of algorithms for hardware expected to be available in 5 years. Additionally, the development cost will be largely amortized within the early (2 to 3 year) target market. The cost reductions will make it possible to use the approach with smaller, less-expensive, vehicles, where the advantages are much greater and the market orders of magnitude larger. While million-dollar AGV systems must be carefully preplanned, inexpensive small transport vehicles could be used casually. A mapping vehicle might be taught new routes at any time by being led through once, and remember several destinations. It could then function as a junior employee, transporting where and when required on command. The comprehensive 3D sense enables straightforward programming to deal with unexpected route hazards, and to locate destinations that move unpredictably. Easily installed security robots are a related application.

Another is industrial floor cleaning robots—there are a few today, but most require specialist installation and routing. Denning, a now-defunct company I was affiliated with in the 1980s, made the navigation system for one such. Siemens recently began to offer a navigator called Sinas based on a 2D mapping laser from Sick, AG (many robot research projects are using it also) that is more nearly self installing—it doesn’t have the potential of 3D mapping and probably won’t drop as fast in cost, but it shows that things are heating up. We’re contacting a cleaning robot manufacturer (Kärcher in Germany—they make the radar-guided BR 700 Robot floor scrubber) who inquired about collaborating with me a few years ago. A machine able to automatically map a new space could be programmed to locate the boundaries of a room and the major obstacles, and to plan and execute a systematic cleaning trajectory on the spot. A supervisor might be able to shepherd a group of such machines down an industrial corridor, and drop them off one by one in rooms to be cleaned, like human workers, trusting each to do its job automatically and reliably, then directing them to new rooms, and collecting them at the end of the shift. On subsequent nights the machines might repeat the entire routine without any external guidance.

Further cost reductions enabled by the economics of a growing mid scale market for industrial machines should then open even larger possibilities in consumer markets. Kärcher has a prototype consumer robot vacuum cleaner that’s very small and can self-charge and empty its dust contents at a docking station. Electrolux is having initial success in Sweden with their less ambitious model and iRobot, Dyson, Hoover and others may not be far behind. But the simple-minded navigation of these machines is a serious impediment. Severe cost constraints and limitations in their technology prevent them from understanding their surroundings or even knowing their location. They move randomly, miss areas and easily become lost or stuck. A mapping machine could keep track of exactly where it had been, what remained, identify and work around navigation hazards and reliably find its docking station, thus work completely autonomously, recharging and emptying itself repeatedly while moving from room to room.

In turn, useful single-purpose machines lead naturally to a truly exciting, enormous market for more advanced utility robots with arms, programmable for multiple tasks. Then robots will truly begin to live up to their promise, as their range of potential application grows to cover almost every physical task. (The rest of the story is for books, not business plan.)

My research on the mapping and navigation problem has been conducted in the open for thirty years. Finally the results are sufficient to support long-term reliable free ranging. It will take a few years more to develop them into a complete demonstration that convinces every casual observer. Unfortunately, doing this last stage of the work in the open would likely compromise the commercial value of the result, and it is not the fastest route to the goal. Various branches of robotics research are experiencing great ferment as functionalities long out of reach rapidly approach practicality. Competition will soon become great and fast-moving. For these reasons I’ve decided to start the commercial effort now, to build such a prototype in a focused, accelerated effort, followed immediately by a product.

I’ve linked up with a small company (incorporated as “Botfactory”) of 6 individuals with technical backgrounds pursuing this purpose. We hope to raise about $5 million to develop a prototype navigation unit in two years, and a first sellable product a year after that. The product would be a retrofittable unit something like AGV laser navigation devices (which scan a laser horizontally at about 10 Hz, detecting retroreflective bar code targets on walls and pillars. Three or more targets allow the machine to triangulate its position and orientation), but with a wide-angle stereo camera head scanning 360 degrees at about 1 Hz. Onboard processing of 1000 MIPS or more will permit dense stereoscopic range images to be generated at several Hz and digested into probabilistic 3D maps used for localization, possibly several times per scan, and available for more advanced functions. (We would prefer to use four fixed camera sets instead of a scanner, but cost at present favors a scan. That is likely to change within a few years as inexpensive CMOS cameras advance. The approach would also work well with an imaging rangefinder instead of stereoscopic cameras, but cameras are today more compact and less expensive. Stereoscopy requires more processing, but only about a quarter of the total needed for mapmaking and other functions, and the fraction will decline as the system computer power increases.)


Hans Moravec
Principal Research Scientist
Robotics Institute
Carnegie Mellon University

Chief Technology Officer
Botfactory, Inc.

3D Perception and Mapping for Free-Ranging Robots
Research History: Hans Moravec, September 2002

The following is a brief summary of work leading to a soon-practical dense 3D mapping system for mobile robots that reliably self-install in novel routes. It supplements capsule summaries found on the accompanying illustrated pages.

Further information can be obtained from my web page

http://www.frc.ri.cmu.edu/~hpm (Or simply Google for Moravec)
Lower left of the web page has recent technical reports
Mobile Robots since 1963 link at top has biography and full CV
Presentations link at right has animated illustrations (needs good bandwidth)

Links to printable PDF versions of these documents follow:
Summary letter
Research History and Business Goal
1979 Illustration: Stereo Navigation
1984 Illustration: Grid Mapping
1990 Illustration: Sensor Model Learning
1996-2002 Illustration: 3D Mapping and Learning

Research History & Innovations

Hans Moravec is a Principal Research Scientist in the Robotics Institute of Carnegie Mellon University. He has been thinking about robots since a child in the 1950s, building his first robot, a construct of tin cans, batteries, lights and a motor, at age ten. In high school he won two science fair prizes for a light-following electronic turtle and a tape-controlled robot hand. As an undergraduate he designed a computer to control fancier robots, and experimented with learning and automatic programming on commercial machines. During his master's work he built a small robot with whiskers and photoelectric eyes controlled by a minicomputer, and wrote a thesis on a computer language for artificial intelligence. He received a PhD from Stanford University in 1980 for a TV-equipped robot, remote controlled by a large computer, that negotiated cluttered obstacle courses, taking about five hours. Since 1980 his Mobile Robot Lab at CMU has discovered more effective approaches for robot spatial representation, notably 3D occupancy grids, that, with newly available computer power, promise commercial free-ranging mobile robots within a decade. His books, Mind Children: the future of robot and human intelligence, 1988, and Robot: mere machine to transcendent mind, 1998, consider the implications of evolving robot intelligence. He has published many papers and articles in robotics, computer graphics, multiprocessors, space travel and other speculative areas.

A pioneering start and long persistence on the navigation mapping problem allowed us to succeed where others were deterred. Many of the results below were be achieved only after subtle sources of error were carefully identified and corrected, and unobvious fast implementations found for multiple components . There is no sustained industrial effort in this area yet, and typical five-year research projects provide insufficient time for the requisite care, leaving first exploration of this new territory to us. "First" below means "first ever, anywhere."
First use of computer vision to guide an outdoor robot (tracking horizon features to maintain heading).
First "Interest Operator" to select suitable image features. (Stanford Cart)

First use of stereoscopic vision to map obstacle fields. First multi-ocular stereoscopic vision (9 viewpoints) to reduce errors. First multi-resolution stereo system.

1979   (click for illustrated description)
First demonstration of robot stereoscopic indoor and outdoor obstacle avoidance, navigation and 3D mapping (maps were a sparse scattering of several dozen points on objects in the scene).  

1984   (click for illustrated description)
First occupancy evidence grid maps, in 2D, giving greatly improved reliability for robot mapping (primarily using sonar sensors, but a demonstration using stereoscopic sensing).  

1989   (click for illustrated description)
First learning of sensor models for 2D grid mapping, greatly improving maps, especially in mirrorlike locations where most sonar measurements were misleading.  

First very fast implementation of 3D grid map sensor evidence projection, using a combination of new techniques (integer log-odds representation of evidence, cylindrical sweep of sensor evidence cross-section, pre-calculation of generic sensor cylinder map plane intersection addressing, sorting of intersection addresses by radius so only significant cone is processed).

1996   (click for illustrated description)
Center of radial distortion method (image dewarping) for rectifying camera images, especially from wide-angle lenses. First use of stereoscopic vision to build 3D evidence grids.  

2000   (click for illustrated description)
First sensor model learning by color projection of multiple scene images into trial 3D grids (low color variance indicates high grid quality). Demonstrated with binocular stereoscopic sensor, producing near-photorealistic grid maps.  

Parallel-ray reformulation of fast 3D grid map sensor evidence projection program further doubles speed and improves edge clipping (code is also simplified).

2002   (click for illustrated description)
First combination of textured-light, trinocular stereoscopic vision with 3D grids, color projection learning, vernier-search stereoscopic matching to make navigation-ready maps of a test area. The near virtual-reality quality of the maps is probably sufficient for tasks beyond navigation, up to small-object recognition.  

Work underway Supplementary local least-squares local image dewarping correction (allows use of inexpensive, imprecise, cameras and lenses). Probing developing grids to obtain statistical occupancy priors to improve stereoscopic estimation (should greatly reduce remaining noise in reconstructed grids). Use of dual occupied and empty thresholds to evaluate grid quality in color-projection learning (should ensure grids are correct for path planning and object recognition, not just visualization). Color projection and grid visualization by ray propagation through grid cells, accelerated by multi-resolution grid representation (much better scaling properties than the conventional surface-based graphics algorithms we have been using).

Business History & Goal

In 1983, despite misgivings about the effort being premature, I agreed to join Denning Mobile Robotics as a founder, consultant and director. The company was active active from 1983 to 1995. They produced a several dozen security, transport, cleaning and research robots, valued about $50,000 each, using a variety of navigational techniques, but never became profitable. The involvement produced the occupancy grid idea and many practical lessons about the business, including the observation that utility robots should run without problems for at least six months to achieve customer acceptance.

I am now part of a newly formed company incorporated as “Botfactory” of 6 individuals with technical backgrounds pursuing the goal of commercializing 3D grid mapping for free ranging robots. A full prototype should be possible within two years, an initial industrial product within three.

The goal is mobile robots that can reliably free range, that is safely find their way from point to point in novel areas without advance preparation of either robot or route. To nearly everyone's surprise, achieving this straightforward functionality has proven extraordinarily difficult. Several commercial efforts in the 1980s and 90s eyeing applications such as automated material transport, floor cleaning, and security patrol, began by promising machines that would automatically learn their routes. Unable to deliver on the promise, those companies that survive produce robots that must be carefully installed by specialists who program a each route segment, and usually pepper it with navigational markers. Struggling mobile robot makers join a dozen larger traditional AGV (automatic guided vehicle) manufacturers, who, since the 1950s, made transport machines for factories and warehouses that followed buried wires. Since the 1980s, using microprocessors, AGV makers added navigation by optical patterns or magnets on the floor, and laser-read bar codes on walls. Installation remains time-consuming, expensive, intrusive and inflexible, and for two decades worldwide AGV annual sales have been saturated at about 1,000 vehicles ($400 million value) worldwide, 250 ($100M) in the US.

Reliable free-range navigation would expand existing robot vehicle applications and enable new ones, eventually even in mass markets. I've spent a thirty-year research career pursuing this goal. In the 1970s my PhD work at Stanford, using one of the very first computer-controlled mobile robots, was first to navigate normal indoor and outdoor clutter by computer vision, building, without prior knowledge, sparse 3D maps to locate (localize) itself, detect obstacles and plan its moves. It was wildly impractical with our 1 MIPS (million instructions per second) mainframe computer, taking five hours to travel 30 meters and losing its way about once every 100 meters. In the 1980s my CMU research group invented a much better, error-mitigating, dense grid map technique that, used in 2D, allowed robots to free range hallways and offices at walking speed for a day or more. Many other research groups adopted this approach in the 1990s. Unfortunately, an error per day is still too many for most practical applications. Different parts of 2D maps are too similar for trustworthy localization, and obstructions that vary with height are poorly represented. 3D grid maps promised to be much better, but seemed out of reach at 1,000 times the computer speed and memory. In 1992 we discovered representational and algorithm innovations that together improved speed about 100 times, just as our computers reached 30 MIPS, allowing us to begin experiments with 3D maps. Now, ten years and additional inventions later, our programs turn robot camera images of arbitrarily complex surroundings into 3D maps that look like virtual reality. With 1,000 MIPS, now available in laptop computers, and optimized code, it takes about 1 second to process each glimpse, fast enough for some indoor applications. Soon the rate will be much better: computers are almost doubling in performance every year. Further improvements are underway, but we have already demonstrated mapmaking ability more than good enough for long-term free ranging.

A year of focused comercially-oriented software and hardware development by a small group should suffice to assemble a system, to be retrofitted to existing vehicles, that drives in real time. Existing mapping software would be optimized and modularized. New programs to memorize, replay and plan routes would be added (we have demonstrated these functionalities in earlier systems: they are straightforward and reliable if the maps are good). The hardware effort would integrate scanning stereo cameras and perhaps 2,000 MIPS of processors in a compact package. A second year effort could then refine the design and develop software for specific applications, for a complete prototype. We anticipate an a additional year for testing, refinement and marketing effort before first products are sold.