At Expo 2005 in Aichi, Japan, humanoids are one of the star attractions. Indeed, human-like robots are prominently featured at the first world's fair of the 21st century.

Of course, robots have appeared at international exhibitions in the past. For instance, the Westinghouse Electric pavilion at the 1939 New York World's Fair featured a humanoid called Elektro that thrilled visitors by smoking cigarettes and walking across a stage on command.

But, this year's crop of high-tech wonders are hauntingly human. They move about the fairgrounds autonomously and interact with visitors. Some serve as mobile "help" desks, while others collect trash, scrub floors and work as security guards. The goal is to show that robots and people can coexist.

Japanese manufacturers are at the forefront of developing humanoids and they're eager to showcase their technology. Indeed, several leading automakers, such as Honda Motor Co. (Tokyo) and Toyota Motor Corp. (Aichi, Japan), have unveiled humanlike robotic devices that walk upright and feature two arms, two legs and a head.

Some day, when humanoid technology is perfected, the robots may be suitable for manufacturing applications, such as working alongside humans on an automotive assembly line. However, most humanoids are initially being developed for routine household applications, such as floor cleaning, entertainment and security. Eventually, the devices may be used to assist the elderly.

Humanoid Roll Call

While many different types of humanoids are being developed in research laboratories around the world, several robots have already made their public debut. But, it's a recent phenomenon.

"When we started our humanoid robot research 10 years ago, there was no commercial humanoid robot available," says Kazuhiko Kawamura, director of the Center for Intelligent Systems at Vanderbilt University (Nashville, TN). "So, like other humanoid groups, we had to design and build our own. We started out with a simple robot, consisting of one arm and a simple industrial gripper, with a limited set of sensors." Today, Kawamura's group is working with NASA to develop Robonaut, an autonomous humanoid for space applications. Michael Lutomski, risk and mission assurance manager for the International Space Station program at Johnson Space Center (Houston), will be delivering a keynote speech on the project at this year's Assembly Technology Expo in Rosemont, IL, on Tuesday, Sept. 27.

However, Kawamura says Japanese manufacturers are investing more time and effort into developing humanoids than their American and European counterparts. He believes this is due to three distinct cultural differences:

• Social. "Japanese historically have considered machines to be their friends, not their enemies," says Kawamura. "Humanoid robots seem to be a natural extension of industrial robot development for the Japanese."
• Government policy. "The Japanese government and, in particular, the National Institute of Advanced Industrial Science and Technology (AIST, Tokyo), has been pushing advanced manufacturing technology development for the last 50 years," explains Kawamura.
• Corporate environment. "Japanese companies love to invest in advanced research and long-term technology projects," Kawamura points out. Many Japanese manufacturers have a long history of developing in-house automation.

Honda publicly claims that Asimo is being developed for personal assistance applications, but many observers believe the company is also exploring potential manufacturing uses. The automaker hopes to have Asimo working side by side with Honda workers by 2010.

Honda engineers are trying to speed up Asimo's movement and make its coordination more fluid. For instance, the robot currently pauses briefly before switching between walking and climbing stairs. The next stage is to enable Asimo to develop the ability to "think" for itself. Engineers are also developing new vision and force sensors to allow smoother interaction with people.

Honda recently unveiled a next-generation version of Asimo. It can maneuver toward its destination without stopping, by comparing any deviation between the input map information and the information obtained from the surrounding area from its floor-surface sensor. The robot can now autonomously change its path if its sensors detect any obstacles. In addition, a new thumb joint with its own motor allows Asimo to hold objects of various shapes. Previously, one motor operated all five fingers.

Some of the new technology developed for Asimo is already being used in other applications. For instance, Honda's work on machine intelligence is being applied to develop an accident-prevention system for its automobiles.

Last year, Toyota unveiled two types of humanoids that it calls "partner robots." A biped version stands 48 inches tall and features 29 joints. Its wheeled cousin is 40 inches tall and has 17 joints. The rolling model is intended for manufacturing applications and it is able to use its hands to carry out a wide variety of tasks.

"Toyota had to develop a humanoid, since Honda was getting all the publicity," says Kawamura. The automakers' engineers developed the robots using technology that they perfected through car manufacturing, such as ultra compact motors that move fingers, arms and other joints; sensors for detecting body inclination; and mechanisms to correct body posture to the upright position.

According to a statement released by Toyota, the partner robots "have human characteristics, such as being agile, warm and kind and also intelligent enough to skillfully operate a variety of devices in the area of personal assistance, care for the elderly, manufacturing and mobility."

Toyota is currently in the process of establishing a new division staffed with several hundred engineers specializing in the development of humanoid robot technology, which it intends to commercialize by 2010. The new division will be established within Toyota's production technology headquarters, which handles the development and improvement of the company's manufacturing plants. Toyota engineers will be joined in the project by colleagues at Denso Corp. (Aichi, Japan), who are developing new sensors, motors and other technology.

Toyota claims that its humanoid project will be contributing to society because "birthrates and a rapidly aging population are underscoring concerns regarding the need to secure a stable labor force for the future in order for people to be able to enjoy comfortable standards of living."

Non-automotive manufacturers are also busy developing humanoids. For instance, Fujitsu Ltd. (Tokyo) has created a humanoid for open architecture platform (HOAP). Its HOAP-2 robot can be connected to a personal computer as a research tool for studying movement control and communication with humans. However, Kawamura claims it can't compare to the Honda or Toyota humanoids in terms of performance.

Hitachi Ltd. (Tokyo) recently unveiled a humanoid at Expo 2005 that it calls EMIEW ("excellent mobility and interactive existence as workmate"). The 4-foot tall robot features a self-balancing, two-wheel-motion mechanism that enables it to move about compact spaces. Sensors measure gradients and help the humanoid balance. It shifts its center of gravity by swinging its body from left to right. That allows the robot to make agile changes in direction, unlike humanoids that use human-like feet.

Kawada Industries Inc. (Tokyo), a leading builder of aircraft and bridges, and Yaskawa Electric Corp. (Fukuoka, Japan) have developed a humanoid called HRP-2P, which feature 30 degrees of freedom, including two hip-joint axes. By using a high-density electronics package, engineers were able to eliminate the bulky backpack that other humanoids use to store batteries and computers.

Researchers across the Sea of Japan are also busy developing humanoids. For instance, a team of engineers at the Korea Institute of Science and Technology (Seoul) have unveiled a 5-foot-tall robot that they claim is the "first network-based humanoid in the world."

Unlike other humanoids whose intelligence capabilities are fixed with built-in circuits, the Korean humanoid is linked with an outside computer through a high-speed wireless telecom network. That enables the robot to exchange information with the server and quickly receive directions, allowing it to interact with people and the environment.

Numerous Challenges

Despite those advances, many barriers must still be overcome before humanoids can be mass produced. For instance, Vanderbilt's Kawamura says perception, processing and action must be embodied in a recognizably anthropomorphic form.

One major roadblock to widespread humanoid use is the robots' inability to react to change or unprogrammed events. To be effective on an assembly line, humanoids would need to duplicate the hand-eye coordination of humans.

"One of the unsolved research issues in robotics is learning," says Kawamura. "We do not want to, nor can we, program robots to face every kind of situation. So, obviously, we would like robots to learn behaviors and new knowledge by interacting with the environment directly, [instead of] being programmed by humans. Humanoids need to go out and learn from their mistakes. We have made limited progress on this."

Kawamura and his colleagues have developed flexible control software called intelligent machine architecture (IMA). "One of the key IMA agents we have been developing is called the self agent," he explains. "Self agent represents a robot self. Just like a human, a future robot must be aware of itself as well as the environment to become an effective partner to humans. This concept is very complex and we are talking to cognitive psychologists, neuroscientists and others to help us model this internal agent. An emerging area called ‘machine consciousness' is closely related to this line of work."

Material and power breakthroughs are also needed before humanoids find widespread industrial applications. "Each joint in a humanoid requires numerous actuators," says Kawamura. "There can be hundreds of gears and motors, depending on how many degrees of motion are being used.

"Current materials are too heavy and not flexible enough," adds Kawamura. "It would be much better if we could develop a synthetic muscle-type material that could operate through signals or pulses."

In addition, new energy sources must be developed for humanoids. Most devices currently use batteries that require frequent recharging. Batteries also take up valuable space and add extra weight. In fact, Kawamura claims that half the weight of most of today's humanoids is from batteries. Fuel cells may eventually become a more efficient energy source.

Because of all those challenges, Kawamura believes it will be more than 10 years before humanoids are used for assembly applications. "Manufacturing requires speed, dexterity and precision," he points out. "Current humanoid robots contain too many unstable and primitive modules, such as sensors, actuators and grippers, to be trustworthy in manufacturing.

"Brain power is another problem," adds Kawamura. "In 10 years, we may be able to develop a humanoid with an equivalent of mouse-scale intelligence. Could you trust a mouse working with you? On the other hand, if you do not want a universal robot, then by modifying existing industrial robots to look like humans, I can see humanoid robots doing simple assembly jobs." However, Kawamura predicts it will be at least 30 years before there are factories full of humanoids. Of course, he also notes that it's difficult to predict the future when talking about evolving technology.

An Autonomous Quest

Humanoid robots currently lack the autonomous skills that most people take for granted. For instance, humans are able to automatically combine a series of basic movements, such as pushing, lifting or grasping, to perform new tasks on the fly. They can also adapt to unanticipated circumstances and incrementally acquire new knowledge.

A team of researchers at Purdue University (West Lafayette, IN) is currently in the midst of a 4-year project to enable humanoids to move more like people. Their goal is to make the robots adapt quickly to new situations so that they can complete a variety of tasks they weren't specifically programmed to perform.

"We are trying to give humanoid robots the ability to behave and move more like human beings, to have the skill-learning capabilities of humans," says George Lee, a professor of electrical and computer engineering who specializes in robotics. He and his colleagues are collaborating with researchers at AIST in Japan.

"What we are going to try to do is capture the essence of how people learn movement skills," adds Howard Zelaznik, a professor of health and kinesiology. "For example, if I asked you to open a door and you were carrying two bags of groceries, you would know how to do that the first time through because you have in your repertoire the flexibility to combine old skills into new ones.

"We'd like to see whether we can figure out if there is a computationally reasonable way for a robot to take a set of skills and combine them into new skills rather efficiently, flexibly and quickly," adds Zelaznik. "We are trying to figure out how best to make that robot adaptable so that it can learn new skills quickly."

Today's generation of humanoids do not move the way people do. "They are very stiff and mechanical," Lee points out.

The Purdue researchers are using special equipment to record human movements in three dimensions. Tiny coiled wire receivers are placed around certain body parts, such as fingers and arms, as a person moves in a low-level magnetic field.

The receivers induce a current, which is tracked by computers. By analyzing the basic movement patterns, the scientists hope to build mathematical models to make robots move more like people. The ultimate goal is to create software that enables humanoids to combine several of the most primitive skills to perform more complex movements.

"We are not trying to make the robot perfect," explains Zelaznik. "People are not perfect. When we move, we are variable, we are imprecise, we make errors. We don't exactly do the same thing time in and time out. We believe it is this imperfection that allows us the capability to be flexible."

Walking and Balancing

Researchers huddled in other school laboratories are addressing the challenge of making humanoids walk and balance more naturally. For instance, a group of engineers at Cornell University (Ithaca, NY) have built robots that closely mimic the human gait and match human efficiency. But, that's no easy task, because a human foot has 20 muscles that strengthen and react when they hit the ground.

According to Andy Ruina, a professor of theoretical and applied mechanics, humanoids such as Asimo move smoothly, but on large, flat feet. "And, compared with a person, it consumes much more energy," claims Ruina.

"Our robot seems to be at least 10 times more efficient than anybody else's," he explains. The Cornell biped uses energy only to push off, while Asimo and other humanoids "needlessly use energy to absorb work," claims Ruina. "In other robots, the motors are fighting themselves."

Unlike other robots, Ruina's machine supplies power to the ankles to push off. When the forward foot hits the ground, a microchip controller tells the rear foot to push off. "During the forward swing of each leg, a small motor stretches a spring, which is finally released to provide the push," says Ruina.

A team of scientists at Massachusetts Institute of Technology (MIT, Cambridge, MA) have developed a biped that can continually adapt to terrain as it walks. Customized learning software allows the robot to teach itself to walk in less than 20 minutes, or about 600 steps. The robot is called "Toddler," because it toddles as it learns to walk.

The machine "is one of the first walking robots to use a learning program, and it is the first to learn to walk without any prior information built into the controller," claims Russ Tedrake, a postdoctoral associate in MIT's department of brain and cognitive sciences. Among other things, the learning program allows Toddler to navigate efficiently over a variety of walking surfaces. Because the program works so quickly, the robot can continuously adapt to the terrain as it walks.

A team of researchers at the University of Michigan (Ann Arbor) and the Laboratoire Automatique (Grenoble, France) have developed a humanoid called RABBIT that they claim is "the first known robot to walk and balance like a human." According to Jessy Grizzle, who developed the control theory for the machine, the balancing ability programmed into the robot has many applications in the medical field, such as smart prosthetics that adapt to the wearer.

Gizzle, a professor of electrical engineering and computer science at Michigan, claims that bipedal robots in existence today walk flat-footed, with an unnatural crouching or stomping gait. "Up until RABBIT, scientists produced stability in two-legged walking machines largely through extensive trial and error experiments during development," notes Grizzle.

"Current walking machines use large feet to avoid tipping over and do not require the robot's control system to be endowed with a real understanding of the mechanics of walking or balance," adds Grizzle. "If you provided these robots with a pair of stilts or asked them to tip-toe across the room, they would just fall over."

RABBIT was built without feet. Its legs end like stilts so that it pivots on a point when it moves forward. According to Grizzle, the control theory for walking gives scientists an analytical method that can predict in advance how the robot will move.

"The concept of stability is reduced to two formulas," Grizzle points out. "It's a matter of understanding enough about the dynamics of walking and balance so that you can express with mathematical formulas how you want the robot to move, and then automatically produce the control algorithm that will induce the desired walking motion on the very fist try."

Out-of-this-world Applications

Scientists at NASA's Johnson Space Center (Houston) have developed a humanoid for extravehicular activities, such as building the International Space Station. The human-size Robonaut features advanced sensors that measure the movement of forearms and five-fingered hands. It is capable of exerting the correct amount of force and control to perform critical jobs, such as tightening fasteners with a pistol-grip screwdriver or a ratchet wrench.

Each arm contains more than 150 sensors that control and monitor force, position, temperature, torque and touch. Robonaut uses a fiber-optic sensor system that is immune to electrical noise. It also requires significantly less cabling to measure the bending of the "fingers" and force of the touch.

Michael Lutomski, risk and mission assurance manager for the International Space Station program, will deliver a keynote speech on Robonaut on Tuesday, Sept. 27, at this year's Assembly Technology Expo in Rosemont, IL. Lutomski will describe how the humanoid was designed and will discuss assembly applications. For more details, click www.atexpo.com.

Although Robonaut was designed for use in outer space, its technology may eventually be applied to more down-to-earth applications, such as building and maintaining undersea pipelines. Other industrial uses envisioned by NASA include automotive and aerospace manufacturing.