**2. A brief history of humanoid robotics research**

Our fellow roboticist Rob goes back in time in order to trace the roots of his passion. He finds out that attempts to create automated machines can be traced back to the first century of our era with the inventions of Hero of Alexandria, a Greek mathematician and engineer from Roman Egypt. Among the first human-like automata he found one created by another polymath inventor from Mesopotamia in the 12th century known as Al-Jazari. His group of "robots" used water to drive their mechanisms and play four different instruments.

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(a) ASIMO (b) HUBO2 (c) HRP-4

(d) iCub (e) Robonaut2 (f) Twendy-One

The RobotCub Consortium formed by 11 European institutions created iCub, a child sized humanoid robot which until 2010 was only able to crawl, Fig. 1(d). This robot has 53 DOF, weights 22kg and has a height of 104cm (Tsakarakis et al., 2007). A remarkable feature of this project is that everything developed within it was made available as open source, including the mechanical design and software products. This move has created a growing community

General Motors joined NASA for the second version of NASA's project Robonaut (Ambrose et al., 2000). This upper body humanoid robot (Fig. 1(e)) is a very dexterous robotic platform with 42 DOF, 150kg and 100cm (waist to head). Another upper-body robotic platform worth including as state-of-the-art is Waseda University's TwendyOne, a very dexterous and

One common characteristic of all the above mentioned platforms is the use of electric torque motors in their joints. There have been, however, new attempts to use hydraulic and pneumatic actuators such as the ones in Anybots' biped Dexter which is also able to jump (Anybots, 2008); or Boston Dynamics' PetMan which introduces a much faster and more human-like gait (Petman, 2011). These two examples make use of pneumatic and hydraulic actuators respectively but there is also a growing interest around the use of pneumatic artificial muscles or air muscles. Shadow Robot's pneumatic hand (Shadow Robot Company, 2003) performing highly dexterous movements and Festo's use of artificial muscles (Festo, 2011) are also worth mentioning as state-of-the-art due to the high accuracy of these otherwise

Fig. 1. Some state of the art humanoid platforms.

that actively collaborates at all levels of research.

difficult to control kind of actuators.

high-power robot with 47 DOF, 111kg and 147cm height, Fig. 1(f).

Among others who designed and/or created human-like machines he discovers that:


Rob also comes across some interesting information about the word "robot". It has its origins in the 1921 play "R.U.R." (Rossum's Universal Robots) created by the Czech writer Karel Capek, although he later credited his brother Josef Capek as the actual person who coined the word. In Czech, the word "robota" refers to "forced labor"; in this sense a robot is a machine created to perform repetitive and expensive labor. In 1942 Isaac Asimov introduces the word "robotics" in the short story "Runaround". His robot stories also introduced the idea of a "positronic brain" (used by the character "Data" in Star Trek) and the "three laws of robotics" (later he added the "zeroth" law).

However it wasn't until the second half of the 20th century that fully autonomous robots started being developed and used in greater numbers. Following the rhythm of a demanding industrial revolution the first programmable (autonomous) robot was born. Unimate was used to lift and stack hot pieces of die-cast metal and spot welding at a General Motor plant. From then on, other single arm robots were created to cope with larger production requirements. Nowadays industrial robots are widely used in manufacturing, assembly, packing, transport, surgery, etc.

Humanoid robotics, as a formal line of research was born in the 1970s with the creation of Wabot at Waseda University in Japan. Several projects around the world have been developed since then. The next section will briefly describe the current state-of-the-art in anthropomorphic robots.

#### **2.1 State of the art**

This section starts by presenting HONDA's project ASIMO, Fig. 1(a). HONDA's research on humanoid robots began in 1986 with its E-series, a collection of biped structures that developed, without doubt, the most representative example among state of the art humanoid robots (Hirose et al., 2001). Today's ASIMO has 34 degrees-of-freedom (DOF), weights 54kg and has a total height of 130cm. This robot is able to walk and run in straight or circular paths, go up or down stairs and perform an always increasing set of computer vision routines like object tracking, identification, and recognition, localization, obstacle avoidance, etc.

A joint project between the University of Tokyo and Kawada Industries gave birth to the Humanoid Robot "H6" and ended up with HRP-3 in 2007 (Kaneko et al., 2008). The National Institute of Advanced Industrial Science and Technology (AIST) continued this project and developed today's HRP-4, Fig. 1(c), a 34 DOF walking robot weighting 39kg and measuring 151cm in height. This light-weight full size robot was designed with a reduction of production costs in mind, thus allowing access to the average robotics research group around the world to a pretty advanced research tool.

Korea's Advanced Institute of Science and Technology (KAIST) started working on humanoid platforms in 2002 with KHR-1. Today's KAIST humanoid is known as HUBO2 (KHR-4) and has a total of 40 DOF, a height of 130cm and weight of 45kg, Fig. 1(b). HUBO2 is also able to walk, run and perform an increasing set of sensor-motor tasks (Park et al., 2005).

2 Will-be-set-by-IN-TECH

• Leonardo Da Vinci designed a mechanical knight at the end of the 15th century. This

• Hisashige Tanaka, a Japanese craftsman in the 19th century, created several extremely

• In 1929, Japanese biologist Makoto Nishimura designed and created *Gakutensoku*, a robot

Rob also comes across some interesting information about the word "robot". It has its origins in the 1921 play "R.U.R." (Rossum's Universal Robots) created by the Czech writer Karel Capek, although he later credited his brother Josef Capek as the actual person who coined the word. In Czech, the word "robota" refers to "forced labor"; in this sense a robot is a machine created to perform repetitive and expensive labor. In 1942 Isaac Asimov introduces the word "robotics" in the short story "Runaround". His robot stories also introduced the idea of a "positronic brain" (used by the character "Data" in Star Trek) and the "three laws of

However it wasn't until the second half of the 20th century that fully autonomous robots started being developed and used in greater numbers. Following the rhythm of a demanding industrial revolution the first programmable (autonomous) robot was born. Unimate was used to lift and stack hot pieces of die-cast metal and spot welding at a General Motor plant. From then on, other single arm robots were created to cope with larger production requirements. Nowadays industrial robots are widely used in manufacturing, assembly,

Humanoid robotics, as a formal line of research was born in the 1970s with the creation of Wabot at Waseda University in Japan. Several projects around the world have been developed since then. The next section will briefly describe the current state-of-the-art in

This section starts by presenting HONDA's project ASIMO, Fig. 1(a). HONDA's research on humanoid robots began in 1986 with its E-series, a collection of biped structures that developed, without doubt, the most representative example among state of the art humanoid robots (Hirose et al., 2001). Today's ASIMO has 34 degrees-of-freedom (DOF), weights 54kg and has a total height of 130cm. This robot is able to walk and run in straight or circular paths, go up or down stairs and perform an always increasing set of computer vision routines like

A joint project between the University of Tokyo and Kawada Industries gave birth to the Humanoid Robot "H6" and ended up with HRP-3 in 2007 (Kaneko et al., 2008). The National Institute of Advanced Industrial Science and Technology (AIST) continued this project and developed today's HRP-4, Fig. 1(c), a 34 DOF walking robot weighting 39kg and measuring 151cm in height. This light-weight full size robot was designed with a reduction of production costs in mind, thus allowing access to the average robotics research group around the world

Korea's Advanced Institute of Science and Technology (KAIST) started working on humanoid platforms in 2002 with KHR-1. Today's KAIST humanoid is known as HUBO2 (KHR-4) and has a total of 40 DOF, a height of 130cm and weight of 45kg, Fig. 1(b). HUBO2 is also able to

object tracking, identification, and recognition, localization, obstacle avoidance, etc.

walk, run and perform an increasing set of sensor-motor tasks (Park et al., 2005).

Among others who designed and/or created human-like machines he discovers that:

machine was able to sit up, wave its arms and move its head and jaw.

complex toys able to serve tea, fire arrows and paint kanji characters.

driven by air pressure that could move its head and hands.

robotics" (later he added the "zeroth" law).

packing, transport, surgery, etc.

to a pretty advanced research tool.

anthropomorphic robots.

**2.1 State of the art**

Fig. 1. Some state of the art humanoid platforms.

The RobotCub Consortium formed by 11 European institutions created iCub, a child sized humanoid robot which until 2010 was only able to crawl, Fig. 1(d). This robot has 53 DOF, weights 22kg and has a height of 104cm (Tsakarakis et al., 2007). A remarkable feature of this project is that everything developed within it was made available as open source, including the mechanical design and software products. This move has created a growing community that actively collaborates at all levels of research.

General Motors joined NASA for the second version of NASA's project Robonaut (Ambrose et al., 2000). This upper body humanoid robot (Fig. 1(e)) is a very dexterous robotic platform with 42 DOF, 150kg and 100cm (waist to head). Another upper-body robotic platform worth including as state-of-the-art is Waseda University's TwendyOne, a very dexterous and high-power robot with 47 DOF, 111kg and 147cm height, Fig. 1(f).

One common characteristic of all the above mentioned platforms is the use of electric torque motors in their joints. There have been, however, new attempts to use hydraulic and pneumatic actuators such as the ones in Anybots' biped Dexter which is also able to jump (Anybots, 2008); or Boston Dynamics' PetMan which introduces a much faster and more human-like gait (Petman, 2011). These two examples make use of pneumatic and hydraulic actuators respectively but there is also a growing interest around the use of pneumatic artificial muscles or air muscles. Shadow Robot's pneumatic hand (Shadow Robot Company, 2003) performing highly dexterous movements and Festo's use of artificial muscles (Festo, 2011) are also worth mentioning as state-of-the-art due to the high accuracy of these otherwise difficult to control kind of actuators.

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to successfully tackle different areas of vision while keeping their low cost Cartesian cameras (Fig. 2(a)) and solve their algorithms with software. Nonetheless, Rob welcomes the attempts to reproduce the high resolution area at the center of the visual field, fovea, with hardware and/or software. He thinks that nature developed this specific structure for our eyes throughout evolution and it may be wise to take advantage of that development.

(a) Cartesian (b) Log-Polar (c) Hemispheric (d) Microsoft's Kinect

Rob identifies several challenges for the hardware component of vision sensors. Potentially the most important is the need to widen the field of view of current cameras. Normal limits for the human field of view are approximately 160 degrees in the horizontal direction and 135 degrees in the vertical direction. A typical camera used in robotic applications has a field of view around 60 degrees for the horizontal direction and 45 degrees for the vertical direction. Important information is lost in those areas where current cameras can not reach in a single stimulus. Adaptation to changes in light conditions is also a complex and difficult process for artificial vision, especially when working within a dynamic environment. Rob is considering a few options from the video security market based on infra-red and Day/Night technology that could be adapted for use in humanoid robots. Finally, the robotics community has experienced a growing interest on using RGB-D (Red-Green-Blue-Depth) cameras after the release of the low-cost motion capture system Kinect by Microsoft (Shotton & Sharp, 2011), Fig. 2(d). This technology combines visual information and high-resolution depth, opening therefore new possibilities for overcoming the challenges of 3D mapping and localization,

Even though touch sensors are being used on few specific points of humanoid platforms (e.g. tip of fingers, feet, head), Rob thinks that an efficient solution to acquiring information from large surfaces is needed in order to be able to exploit the richness of textures, shapes, temperatures, firmness, etc. Therefore he argues the importance of developing skin-like

In robotic applications, Rob has used his imagination to create solutions for detecting objects in the path of an arm, finger or leg. One of these solutions has been the detection of peaks of current in their electric motors or using torque and force sensors. This approach could be considered tactile sensing as well but within the area of proprioception since measurements are made as relative positions of neighbouring parts in static and dynamic situations. In humanoid robots, exteroceptive sensors include dedicated pressure sensors placed on points of interest. The technology used in most pressure sensors so far include: resistive, tunnel-effect, capacitive, optical, ultrasonic, magnetic, and piezoelectric. Resistive and capacitive sensors are certainly the most common technology used not only in robotic but

Fig. 2. Samples of different configurations for image sensors.

object identification and recognition, tracking, manipulation, etc.

sensors as another future challenge for humanoid robotics.

in many consumer electronic applications (Dahiya et al., 2010).

**3.1.2 Tactile**
