From Photocopiers and Cars To Space Probes, Immobots Take Control

By Roland Piquepaille

These new robots have more brain than brawn. Each possesses a detailed picture of its own inner workings -- encoded in software-based models -- that gives it the ability to respond in novel ways to events its programmers might not have anticipated. Because many of these inward-focused, self-reconfiguring machines don't move, some computer scientists call them immobile robots, or "immobots."

Immobots are already beginning to crop up in situations where autonomy is important. They are needed either because direct operator control is impossible (for example, in space probes so distant that radio signals take minutes or hours to reach them) or because humans lack the skill or the desire to oversee all the details (in such down-to-earth systems as office machines, water treatment plants, and internal combustion engines).

Before giving different industrial examples, from NASA to the water utility in Porto Alegre, and from Toyota cars to some new Xerox photocopiers, Wade Roush looks at the programming model behind the immobots.

To make machines behave autonomously, most practitioners in robotics and control engineering have long used "heuristic" programs that amount to lists of rules for accomplishing a goal and dealing with contingencies. For example, "If A is true, then do B. If C is true, then do D." The trouble, many artificial-intelligence experts assert, is that traditional, hand-coded software can be either reliable or affordable. Not both.

A model-based program that reasons like [NASA's Deep Space One] Remote Agent isn't built that way at all. It looks like a picture of the machine it was designed to control, painted in the logical language of computers. Both mobile and immobile robots can use this picture to model themselves and choose the fastest, safest, or most cost-effective way to implement an operator's instructions or deal with an emergency. "The idea is very simple," says Brian Williams, a former NASA researcher who coinvented Deep Space One's autonomous software. "Provide the program with a physical plan of the system and let the software deduce what to do."

Here is an example of what an immobot could do for your car.

Say the air conditioning in your vehicle won't work. An onboard immobot might quickly deduce that the problem is a malfunctioning fuel-level sensor in the gas tank. "What's the interdependency?" asks Peter Struss, a computer scientist at the University of Technology at Munich. In some cars, he explains, "the AC control system has to ask the engine control unit whether, as a consumer, it's allowed to come on. The engine management system will check whether there's enough fuel. And if not, it will deny the request."

A model-based diagnostic system knows such details in advance. Therefore, if you've got a full tank and the air conditioning still won't work, the model-based diagnostic makes an educated guess at the cause. "Workshop people can read out the diagnostics from control units and see six or seven trouble codes, but it may not be obvious what the ultimate cause is," says Struss. "They cannot see all the interactions." But an immobot can.

Source: Wade Roush, Technology Review, December 2002/January 2003 Issue