HUBO

HUBO is a humanoid robot developed at the Korea Advanced Institute of Science and Technology. The first HUBO, KHR-3, was the culmination of four years of research based on three earlier prototypes, and it was officially unveiled to the public on January 6, 2005. The name HUBO is short for "humanoid robot."

Development history
The first HUBO was developed by mechanical engineering professor Oh Junho and his Ph.D. student teams over the course of about 20 years. During much of this time, the technologies in HUBO were steadily developed, and involvement of amateurs resulted in a very low development cost of about $500,000. (In comparison, Honda is believed to have spent $300 million on its ASIMO from 1986 to 2000.)

Prototypes
The first prototype was the KHR-0 (KAIST Humanoid Robot), which essentially consisted of two legs without an upper body. It was built in 2001 for the purpose of investigating the specifications of actuators (devices that receive electric signals and perform mechanical actions), such as power, torque, and speed, and the optimal weight and size of a humanoid robot.

The second prototype, the KHR-1, was completed by January 2002. The KHR-1 was approximately humanoid in form without a head and two hands, which were not essential for simulating walking. Its purpose was to demonstrate autonomous walking that involves real-time motion control through sensory feedback. (This involves constant adjustments that are absent in walking as a playback motion adopted from an offline learning process and walking with partial online adjustments.) It could make right turns and walked at 0.8km/hr.

The project was continued with the development of KHR-2 from 2003 to 2004. The KHR-2 was built as a complete humanoid and featured better sensoring with the addition of CCD cameras, inertia sensors, and tilt sensors. It was used as a platform for simulation of vision-guided dynamic walking, in which the robot keeps focus on a moving red light for direction.

KHR-3 HUBO
Work on the KHR-3 HUBO was begun in September 2004. The internal components were covered with metallic grey plastic, and modifications were made to the joints and and the skeleton for greater stiffness and minimal mechanical uncertainty. The KHR-3's physical specs, such as height, weight, and the number of DOFs (degrees of freedom), were similar to Honda's ASIMO, which served as the benchmark for the project. In terms of AI and movements, HUBO lagged significantly behind the "next-gen ASIMO," which was unveiled around the same time as HUBO in December 2004; for example, HUBO could only walk half as fast as the ASIMO (1.25 km/h vs 2.5 km/h), which could also run at 3 km/h. A temporary shortcoming for HUBO was that it was unable to walk on the stairs like ASIMO until it was further developed for several months after its initial publicity. The unnerved KAIST researchers noted, however, that HUBO could play rock-paper-scissors, which was impossible for ASIMO since its fingers could not move independently of each other.

International Collaboration
The project increasingly became international with participation from the United States. The first collaboration involved Hanson Robotics in the development of Albert HUBO, which was completed in November 2005. The Albert HUBO had a white body derived from the KHR-3 HUBO with modifications to accommodate a human-like head of Albert Einstein from the Hanson lab. The head had a skin of Frubber that is often used in movie productions and was controlled by 35 joints to make realistic facial expressions. It also contained 2 CCD cameras for vision recognition.

The subsequent collaboration on the Jaemi HUBO (also known as KHR-4 and HUBO 2; "Jaemi" (재미) can mean "in the United States" in Chinese characters or "fun" in colloquial Korean) was a more extensive and strategic effort to combine Korea's expertise in humanoid design with US's strength in cognition, perception, navigation, and networking. It involved participation of KAIST, Korea University, and the Seoul National University in South Korea, and the Bryn Mawr College, Colby College, Drexel University, the University of Pennsylvania, and Virginia Tech in the United States under a $5 million dollar, 5-year program funded by the National Science Foundation.

The initial development of the Jaemi HUBO was begun at KAIST in 2008. The Jaemi HUBO was given a slimmer design with an aluminum endoskeleton and a polycarbonate frame, resulting in a slightly taller height but 20% lighter weight than its predecessors. Its movements were more realistic since the arms made quicker and more natural motions, and the legs could stretch to imitate human walking, which also consumes relatively less energy. Its walking speed was improved to 1.4 km/h, and it also acquired the ability to run at 3.3 km/h (which is still much slower than the new ASIMO's 6 km/h by comparison).

Design and engineering principles
For practical and efficient engineering, the robot was built at a child's height of 119 cm.

In order to simulate autonomous walking, the KHR-1 was built without external connections, and it was controlled wirelessly and operated on internal batteries with low-level consumption. All models were built with harmonic drives in order to avoid backlash in the gears and to achieve a light, compact design. The DOFs of the different axes in the joints of shoulders, waist, hips, and ankles were merged into intersections in order to attain a simple, closed-form solution (that is, comprised of well-known mathematical functions) of inverse kinematics (the computation of the robot's movements). The KHR-1's walking movement was based on the Zero Moment Point trajectory (points of contact on the ground where the total moment of inertia of the active forces equals to 0) predicted based on a simple model of the robot.