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A humanoid robot is a robot with its body shape built to resemble that of the human body. A humanoid design might be for functional purposes, such as interacting with human tools and environments, for experimental purposes, such as the study of bipedal locomotion, or for other purposes. In general, humanoid robots have a torso, a head, two arms, and two legs, though some forms of humanoid robots may model only part of the body, for example, from the waist up. Some humanoid robots may also have heads designed to replicate human facial features such as eyes and mouths. Androids are humanoid robots built to aesthetically resemble humans.
Humanoid robots are used as a research tool in several scientific areas.
Researchers need to understand the human body structure and behavior (biomechanics) to build and study humanoid robots. On the other side, the attempt to simulate the human body leads to a better understanding of it.
Human cognition is a field of study which is focused on how humans learn from sensory information in order to acquire perceptual and motor skills. This knowledge is used to develop computational models of human behavior and it has been improving over time.
It has been suggested that very advanced robotics will facilitate the enhancement of ordinary humans. See transhumanism.
Although the initial aim of humanoid research was to build better orthosis and prosthesis for human beings, knowledge has been transferred between both disciplines. A few examples are: powered leg prosthesis for neuromuscularly impaired, ankle-foot orthosis, biological realistic leg prosthesis and forearm prosthesis.
Besides the research, humanoid robots are being developed to perform human tasks like personal assistance, where they should be able to assist the sick and elderly, and dirty or dangerous jobs. Regular jobs like being a receptionist or a worker of an automotive manufacturing line are also suitable for humanoids. In essence, since they can use tools and operate equipment and vehicles designed for the human form, humanoids could theoretically perform any task a human being can, so long as they have the proper software. However, the complexity of doing so is deceptively great.
They are becoming increasingly popular for providing entertainment too. For example, Ursula, a female robot, sings, play music, dances, and speaks to her audiences at Universal Studios. Several Disney attractions employ the use of animatrons, robots that look, move, and speak much like human beings, in some of their theme park shows. These animatrons look so realistic that it can be hard to decipher from a distance whether or not they are actually human. Although they have a realistic look, they have no cognition or physical autonomy. Various humanoid robots and their possible applications in daily life are featured in an independent documentary film called Plug & Pray, which was released in 2010.
Humanoid robots, especially with artificial intelligence algorithms, could be useful for future dangerous and/or distant space exploration missions, without having the need to turn back around again and return to Earth once the mission is completed.
Sensors can be classified according to the physical process with which they work or according to the type of measurement information that they give as output. In this case, the second approach was used.
Proprioceptive Sensors 
Proprioceptive sensors sense the position, the orientation and the speed of the humanoid's body and joints.
In human beings inner ears are used to maintain balance and orientation. Humanoid robots use accelerometers to measure the acceleration, from which velocity can be calculated by integration; tilt sensors to measure inclination; force sensors placed in robot's hands and feet to measure contact force with environment; position sensors, that indicate the actual position of the robot (from which the velocity can be calculated by derivation) or even speed sensors.
Exteroceptive Sensors 
Arrays of tactels can be used to provide data on what has been touched. The Shadow Hand uses an array of 34 tactels arranged beneath its polyurethane skin on each finger tip. Tactile sensors also provide information about forces and torques transferred between the robot and other objects.
Vision refers to processing data from any modality which uses the electromagnetic spectrum to produce an image. In humanoid robots it is used to recognize objects and determine their properties. Vision sensors work most similarly to the eyes of human beings. Most humanoid robots use CCD cameras as vision sensors.
Sound sensors allow humanoid robots to hear speech and environmental sounds, and perform as the ears of the human being. Microphones are usually used for this task.
Actuators are the motors responsible for motion in the robot.
Humanoid robots are constructed in such a way that they mimic the human body, so they use actuators that perform like muscles and joints, though with a different structure. To achieve the same effect as human motion, humanoid robots use mainly rotary actuators. They can be either electric, pneumatic, hydraulic, piezoelectric or ultrasonic.
Hydraulic and electric actuators have a very rigid behavior and can only be made to act in a compliant manner through the use of relatively complex feedback control strategies . While electric coreless motor actuators are better suited for high speed and low load applications, hydraulic ones operate well at low speed and high load applications.
Piezoelectric actuators generate a small movement with a high force capability when voltage is applied. They can be used for ultra-precise positioning and for generating and handling high forces or pressures in static or dynamic situations.
Ultrasonic actuators are designed to produce movements in a micrometer order at ultrasonic frequencies (over 20 kHz). They are useful for controlling vibration, positioning applications and quick switching.
Pneumatic actuators operate on the basis of gas compressibility. As they are inflated, they expand along the axis, and as they deflate, they contract. If one end is fixed, the other will move in a linear trajectory. These actuators are intended for low speed and low/medium load applications. Between pneumatic actuators there are: cylinders, bellows, pneumatic engines, pneumatic stepper motors and pneumatic artificial muscles.
Planning and control 
In planning and control, the essential difference between humanoids and other kinds of robots (like industrial ones) is that the movement of the robot has to be human-like, using legged locomotion, especially biped gait. The ideal planning for humanoid movements during normal walking should result in minimum energy consumption, like it does in the human body. For this reason, studies on dynamics and control of these kinds of structures become more and more important.
To maintain dynamic balance during the walk, a robot needs information about contact force and its current and desired motion. The solution to this problem relies on a major concept, the Zero Moment Point (ZMP).
Another characteristic of humanoid robots is that they move, gather information (using sensors) on the "real world" and interact with it. They don’t stay still like factory manipulators and other robots that work in highly structured environments. To allow humanoids to move in complex environments, planning and control must focus on self-collision detection, path planning and obstacle avoidance.
Humanoids don't yet have some features of the human body. They include structures with variable flexibility, which provide safety (to the robot itself and to the people), and redundancy of movements, i.e. more degrees of freedom and therefore wide task availability. Although these characteristics are desirable to humanoid robots, they will bring more complexity and new problems to planning and control.
Timeline of developments 
|This section's factual accuracy is disputed. (June 2010)|
|c. 250 BC||The Lie Zi described an automaton.|
|c. 50 AD||Greek mathematician Hero of Alexandria described a machine to automatically pour wine for party guests.|
|1206||Al-Jazari described a band made up of humanoid automata which, according to Charles B. Fowler, performed "more than fifty facial and body actions during each musical selection." Al-Jazari also created hand washing automata with automatic humanoid servants,[verification needed] and an elephant clock incorporating an automatic humanoid mahout striking a cymbal on the half-hour. His programmable "castle clock" also featured five musician automata which automatically played music when moved by levers operated by a hidden camshaft attached to a water wheel.|
|1495||Leonardo da Vinci designs a humanoid automaton that looks like an armored knight, known as Leonardo's robot.|
|1738||Jacques de Vaucanson builds The Flute Player, a life-size figure of a shepherd that could play twelve songs on the flute and The Tambourine Player that played a flute and a drum or tambourine.|
|1774||Pierre Jacquet-Droz and his son Henri-Louis created the Draughtsman, the Musicienne and the Writer, a figure of a boy that could write messages up to 40 characters long.|
Nikola Tesla publically demonstrates his "automaton" technology by wirelessly controlling a model boat at the Electrical Exposition held at Madison Square Garden in New York City during the height of the Spanish-American War.
|1921||Czech writer Karel Čapek introduced the word "robot" in his play R.U.R. (Rossum's Universal Robots). The word "robot" comes from the word "robota", meaning, in Czech and Polish, "forced labour, drudgery".|
|1927||The Maschinenmensch (“machine-human”), a gynoid humanoid robot, also called "Parody", "Futura", "Robotrix", or the "Maria impersonator" (played by German actress Brigitte Helm), perhaps the most memorable humanoid robot ever to appear on film, is depicted in Fritz Lang's film Metropolis.|
|1941-42||Isaac Asimov formulates the Three Laws of Robotics, and in the process of doing so, coins the word "robotics".|
|1948||Norbert Wiener formulates the principles of cybernetics, the basis of practical robotics.|
|1961||The first digitally operated and programmable non-humanoid robot, the Unimate, is installed on a General Motors assembly line to lift hot pieces of metal from a die casting machine and stack them. It was created by George Devol and constructed by Unimation, the first robot manufacturing company.|
|1969||D.E. Whitney publishes his article "Resolved motion rate control of manipulators and human prosthesis".|
|1970||Miomir Vukobratović has proposed Zero Moment Point, a theoretical model to explain biped locomotion.|
|1972||Miomir Vukobratović and his associates at Mihajlo Pupin Institute build the first active anthropomorphic exoskeleton.|
|1973||In Waseda University, in Tokyo, Wabot-1 is built. It was able to walk, to communicate with a person in Japanese and to measure distances and directions to the objects using external receptors, artificial ears and eyes, and an artificial mouth.|
|1980||Marc Raibert established the MIT Leg Lab, which is dedicated to studying legged locomotion and building dynamic legged robots.|
|1983||Using MB Associates arms, "Greenman" was developed by Space and Naval Warfare Systems Center, San Diego. It had an exoskeletal master controller with kinematic equivalency and spatial correspondence of the torso, arms, and head. Its vision system consisted of two 525-line video cameras each having a 35-degree field of view and video camera eyepiece monitors mounted in an aviator's helmet.|
|1984||At Waseda University, the Wabot-2 is created, a musician humanoid robot able to communicate with a person, read a normal musical score with his eyes and play tunes of average difficulty on an electronic organ.|
|1985||Developed by Hitachi Ltd, WHL-11 is a biped robot capable of static walking on a flat surface at 13 seconds per step and it can also turn.|
|1985||WASUBOT is another musician robot from Waseda University. It performed a concerto with the NHK Symphony Orchestra at the opening ceremony of the International Science and Technology Exposition.|
|1986||Honda developed seven biped robots which were designated E0 (Experimental Model 0) through E6. E0 was in 1986, E1 – E3 were done between 1987 and 1991, and E4 - E6 were done between 1991 and 1993.|
|1989||Manny was a full-scale anthropomorphic robot with 42 degrees of freedom developed at Battelle's Pacific Northwest Laboratories in Richland, Washington, for the US Army's Dugway Proving Ground in Utah. It could not walk on its own but it could crawl, and had an artificial respiratory system to simulate breathing and sweating.|
|1990||Tad McGeer showed that a biped mechanical structure with knees could walk passively down a sloping surface.|
|1993||Honda developed P1 (Prototype Model 1) through P3, an evolution from E series, with upper limbs. Developed until 1997.|
|1995||Hadaly was developed in Waseda University to study human-robot communication and has three subsystems: a head-eye subsystem, a voice control system for listening and speaking in Japanese, and a motion-control subsystem to use the arms to point toward campus destinations.|
|1995||Wabian is a human-size biped walking robot from Waseda University.|
|1996||Saika, a light-weight, human-size and low-cost humanoid robot, was developed at Tokyo University. Saika has a two-DOF neck, dual five-DOF upper arms, a torso and a head. Several types of hands and forearms are under development also. Developed until 1998.|
|1997||Hadaly-2, developed at Waseda University, is a humanoid robot which realizes interactive communication with humans. It communicates not only informationally, but also physically.|
|2000||Honda creates its 11th bipedal humanoid robot, able to run, ASIMO.|
|2001||Sony unveils small humanoid entertainment robots, dubbed Sony Dream Robot (SDR). Renamed Qrio in 2003.|
|2001||Fujitsu realized its first commercial humanoid robot named HOAP-1. Its successors HOAP-2 and HOAP-3 were announced in 2003 and 2005, respectively. HOAP is designed for a broad range of applications for R&D of robot technologies.|
|2002||HRP-2, biped walking robot built by the Manufacturing Science and Technology Center (MSTC) in Tokyo.|
|2003||JOHNNIE, an autonomous biped walking robot built at the Technical University of Munich. The main objective was to realize an anthropomorphic walking machine with a human-like, dynamically stable gait |
|2003||Actroid, a robot with realistic silicone "skin" developed by Osaka University in conjunction with Kokoro Company Ltd.|
|2004||Persia, Iran's first humanoid robot, was developed using realistic simulation by researchers of Isfahan University of Technology in conjunction with ISTT.|
|2004||KHR-1, a programmable bipedal humanoid robot introduced in June 2004 by a Japanese company Kondo Kagaku.|
|2005||The PKD Android, a conversational humanoid robot made in the likeness of science fiction novelist Philip K Dick, was developed as a collaboration between Hanson Robotics, the FedEx Institute of Technology, and the University of Memphis.|
|2005||Wakamaru, a Japanese domestic robot made by Mitsubishi Heavy Industries, primarily intended to provide companionship to elderly and disabled people.|
|2005||Nao is a small open source programmable humanoid robot developped by Aldebaran Robotics, in France. Widely used by world wide universities as a research platform and educational tool.|
|2005||The Geminoid series is a series of ultra-realistic humanoid robots or Actroid developped by Hiroshi Ishiguro of ATR and Kokoro in Tokyo. The original one, Geminoid HI-1 was made at its image. Followed Geminoid-F in 2010 and Geminoid-DK in 2011.|
|2006||REEM-A, a biped humanoid robot designed to play chess with the Hydra Chess engine. The first robot developed by PAL Robotics, it was also used as a walking, manipulation speech and vision development platform.|
|2006||iCub, a biped humanoid open source robot for cognition research.|
|2006||Mahru, a network-based biped humanoid robot developed in South Korea.|
|2007||TOPIO, a ping pong playing robot developed by TOSY Robotics JSC.|
|2007||Twendy-One, a robot developed by the WASEDA University Sugano Laboratory for home assistance services. It is not biped, as it uses an omni-directional mobile mechanism.|
|2008||Justin, a humanoid robot developed by the German Aerospace Center (DLR).|
|2008||KT-X, the first international humanoid robot developed as a collaboration between the five-time consecutive RoboCup champions, Team Osaka, and KumoTek Robotics.|
|2008||Nexi, the first mobile, dexterous and social robot, makes its public debut as one of TIME magazine's top inventions of the year. The robot was built through a collaboration between the MIT Media Lab Personal Robots Group, Xitome Design UMass Amherst and Meka robotics.|
|2008||Salvius (robot), The first open source humanoid robot built in the United States is created.|
|2008||REEM-B, the second biped humanoid robot developed by PAL Robotics. It has the ability to autonomously learn its environment using various sensors and carry 20% of its own weight.|
|2009||HRP-4C, a Japanese domestic robot made by National Institute of Advanced Industrial Science and Technology, shows human characteristics in addition to bipedal walking.|
|2009||Turkey's first dynamically walking humanoid robot, SURALP, is developed by Sabanci University in conjunction with Tubitak.|
|2009||Kobian, an robot developed by WASEDA University can walk, talk and mimic emotions.|
|2010||NASA and General Motors revealed Robonaut 2, a very advanced humanoid robot. It was part of the payload of Shuttle Discovery on the successful launch February 24, 2011. It is intended to do spacewalks for NASA.|
|2010||Students at the University of Tehran, Iran unveil the Surena II. It was unveiled by President Mahmoud Ahmadinejad.|
|2010||Researchers at Japan's National Institute of Advanced Industrial Science and Technology demonstrate their humanoid robot HRP-4C singing and dancing along with human dancers.|
|2010||In September the National Institute of Advanced Industrial Science and Technology also demonstrates the humanoid robot HRP-4. The HRP-4 resembles the HRP-4C in some regards but is called "athletic" and is not a gynoid.|
|2010||REEM, a humanoid service robot with a wheeled mobile base. Developed by PAL Robotics, it can perform autonomous navigation in various surroundings and has voice and face recognition capabilities.|
|2011||In November Honda unveiled its second generation Honda Asimo Robot. The all new Asimo is the first version of the robot with semi-autonomous capabilities.|
|2012||In April, the Advanced Robotics Department in Italian Institute of Technology released its first version of the Compliant huManoid robot CoMan which is designed for robust dynamic walking and balancing in rough terrain.|
See also 
- Archie Humanoid Robot
- ASIMO first humanoid robot to walk on its own
- Ibn Sina Robot
- Salvius (robot)
- Shadow Hand
- Toyota Partner Robot
- Uncanny valley
- "A Ping-Pong-Playing Terminator". Popular Science.
- "Best robot 2009". www.gadgetrivia.com.
- "Shadow Robot Company: The Hand Technical Specification". Retrieved 2009-04-09.
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- Fowler, Charles B. (October 1967), "The Museum of Music: A History of Mechanical Instruments", Music Educators Journal 54 (2): 45-9
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- DLR press release 2008
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- Department of Advanced Robotics, IIT
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- Everett, H. R. (1995). Sensors for Mobile Robots: Theory and Application. AK Peters. ISBN 1-56881-048-2.
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Further reading 
- Carpenter, J., Davis, J., Erwin‐Stewart, N., Lee. T., Bransford, J. & Vye, N. (2009). Gender representation in humanoid robots for domestic use. International Journal of Social Robotics (special issue). 1 (3), 261‐265.The Netherlands: Springer.
- Carpenter, J., Davis, J., Erwin‐Stewart, N., Lee. T., Bransford, J. & Vye, N. (2008). Invisible machinery in function, not form: User expectations of a domestic humanoid robot. Proceedings of 6th conference on Design and Emotion. Hong Kong, China.
- Williams, Karl P. (2004). Build Your Own Human Robots: 6 Amazing and Affordable Projects. McGraw-Hill/TAB Electronics. ISBN 0-07-142274-9. ISBN 978-0-07-142274-1.
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