ASIMO

(CC) Photo: Honda
The New ASIMO introduced in 2005.

ASIMO (アシモ ashimo) is the world's most advanced humanoid robot, developed by the Japanese company Honda. The first ASIMO was completed after 15 years of research, and it was officially unveiled on October 31, 2000. The robot resembles a small astronaut wearing a backpack, and is capable of performing a variety of tasks, including running, kicking a ball, walking up and down stairs, and recognizing people by their appearance and voice. The name is short for "Advanced Step in Innovative MObility" and is also known as an abbreviation of ashita no mobility, meaning 'mobility in the future.' It was named in reference to Isaac Asimov, an American professor and science fiction writer who is credited with coining the term robotics and proposing the Three Laws of Robotics.

Design concept

"Following in the steps of Honda motorcycles, cars and power products. Honda has taken up a new challenge in mobility - the development of a two-legged humanoid robot that can walk."

Bipedal movement has been the primary focus of Honda's humanoid robotic research to create general-purpose, intelligent robots that can "coexist and cooperate with humans", since it began in 1986 with the development of the 'E0' prototype. While there existed many different visions of futuristic robots, such as R2-D2 and C-3PO from Star Wars, it was recognized that human-like robots with bipedal mobility are the most ideal for operating and interacting with humans in human surroundings.

Based on this concept, ASIMO's design concerns three main elements, which are human-friendliness, adaptability to the human environment, and engineering feasibility. The robot's height was set at 120 cm (or 130 cm in the case of second-generation ASIMO), which is similar to a child's, as this would be practical both on the engineering aspect (since a smaller and lighter robot is less challenging than an adult-sized robot such as the P2 prototype) and the question of operability in the environment, where light switches are normally located 110 cm from the floor. With less bulk, the robot would be able to move more efficiently in handling obstacles and narrow passages, and it would also be less overwhelming presence to humans and, in case of accidents, less hazardous.

(CC) Photo: Honda
The New ASIMO serving refreshments.

Its humanoid form that is not only functionally but also proportionally similar to the human body was meant to enhance its human and environment-friendly qualities by allowing it to make gestures and communicate face-to-face, as well as using the stairs or taking seat in a car. Its strikingly minimalist appearance, which lacks a detailed face and toes on its feet, provides fewer moving parts as rooms for error, while being clearly discernible to humans as consisting of a head, torso, arms, hands, legs, and feet. ASIMO being a popular icon, its design has contributed to the conceptual diversity of futuristic robots, based on a very unique design language of modern Japanese aesthetics.

Honda has suggested several future uses for robots like the ASIMO, which, despite its impressive list of feats and features, remains an experimental technology demonstrator that needs to operate in controlled, predictable environment. With further advances, ASIMO could be engaged in useful tasks such as elderly care assistance, firefighting, and toxic cleanup. At the present, the ASIMO is being leased to companies for receptionist work.

On August 12, 2011, the Japanese newspaper Asahi Shimbun reported that Honda was seeking to develop a robot based on the ASIMO to handle the radiation leakage at the Fukushima nuclear power plant that resulted with the earthquake and tsunami that hit Japan in March, 2011:

If successful, in another year or two, an improved version of the Asimo could be taking over the work at the Fukushima site... Adjustments can be made to the degree of strength that is applied in the robot's shoulder, elbow and wrists that are operated by motors. While using the Asimo as the base, Honda officials want to create a robot devoted exclusively for working at the nuclear accident site by taking advantage of the arm technology of the Asimo. Because the footing at the Fukushima site is treacherous due to rubble that could topple the robot, the biped aspect of the Asimo would be replaced by either tires or crawlers used on tanks.

(CC) Photo: Don Nunn
The original ASIMO unveiled in 2000.

According to the AFP, US Honda spokeswoman Lauren Ebner denied the report, dismissing it as a mere "speculation."

Technology

ASIMO v1

System structure

ASIMO's control system includes approximately 20 CPUs and sensors that are grouped into several independent sub-systems interacting asynchronously through an internal message board. Each sub-system is essentially a PC with different operating system and are responsible for audio-visual sensory and recognition, communication with the operator, actuation of movement, and power management. The internal message board is updated at different frequencies due to the different processing load and power of each sub-system. Contrary to the popular belief, the system activities are event-driven without a central, intelligent AI to handle unexpected situations.

Sensory

ASIMO's sensors are responsible for visual, auditory, and tactile functions, as well as those relating to movement, such as the gyro sensor, force sensor, and inclinometer. In human terms, it is limited to three senses as it lacks particle detectors that can substitute for the nose or tongue and the emotional capacity to react in the manner of either appreciation or disgust.

ASIMO's vision system is responsible for processing spatial perception, object-mapping, human tracking, facial recognition, and gestural-postural detection. It relies on stereo images (of two views from slightly different angles) provided by the frame grabber that is connected to the two color board cameras on the head unit of the robot. 3D and moving objects are identified by calculating depth of space based on the Sum of Absolute values of Differences (SAD) method using the images that are captured in black-and-white and callibrated for lens distortion. A local map of 3D objects is constructed and provided to the agent programs for walking and movement. The vision system also identifies moving parts of the moving objects, from which the recognition of human gestures and postures is processed and provided to the agent programs for human-robot interaction and eye control.

ASIMO can identify multiple people in a scene by using the snake algorithm to distinguish the contours of human shapes. When in motion, ASIMO tracks humans by using an optical flow-based algorithm to lock on their changing positions in the image data. 2D gesture recognition algorithm can identify handshake, hand-circling, farewell, hand swing, high hand, and come here-call based on the probabilities for a given position of the hand using the Bayes statistical model. 3D gesture recognition algorithm can identify where a person is pointing at based on the relative positions of the person's head and hand from the depth map data. Face is recognized by applying the Eigenvector Method on the face contour and eye image data.

ASIMO relies on the sound data to be situationally aware of the surrounding outside its field of vision. The sound's direction is calculated based on the volume and time differences of the signals at two separate microphones. It can discern human voices and footsteps from the sound data and look when a person calls its name, or something falls on the floor.

Movement

(CC) Diagram: Chunbum Park
(a) With intelligent real-time flexible walking or "i-WALK," walking cycle and stride are adjustable. (b) Prototypes were unable to make small directional changes while in motion but needed to pause between straight and turning phases because their walking cycle and stride were unchangeable.

ASIMO's bipedal movement comprises of highly sophisticated functions involving "dynamic" walking based on real-time sensory feedback and predictive movement planning, which allow ASIMO to flexibly adjust its course while continuing to move in real time. This contrasts with earlier ways of walking demonstrated by ASIMO's prototypes that followed pre-programmed walking patterns with fixed time per step.

(CC) Diagram: Chunbum Park
Zero Moment Point is where floor reaction minus total inertial force equals 0. Loss of balance occurs when the target ZMP and the center of ground reaction misalign.

Humans rely on information regarding the linear and angular speeds provided by the ears' inner parts (otolith and semicircular canals respectively) and the sensations from the muscles and skin relating to joint angle, angular speed, muscle power, and pressure. In the ASIMO, the joint angle sensors are used to determine the positions and angles of the body parts; 6-axis force sensors, the force and torque of each motors in the x, y, z coordinates; speed sensor, the overall movement speed of the robot; and gyroscope (and inclinometer), the overall orientation relative to the artificial horizon.

Unlike WABIAN-2 by Japan's Waseda University or HUBO 2 by KAIST which are capable of "straight-legged walking" like humans, ASIMO bends its legs to maintain a stable movement pattern based on Zero Moment Point trajectories that are simple but versatile for the purpose of predictive movement planning. Zero Moment Points are mathematically-conceived contact points where the ground reaction force to the position of the supporting leg equals the total inertia force (i.e. gravity and forward accelerating or decelerating force).

ZMP dictates ASIMO's stable movement pattern through a three-layered system consisting of "floor reaction control", "target ZMP control", and "foot planting location control". Floor reaction control absorbs irregular floor impact by adjusting the feet to align the point of floor reaction to the target ZMP. Target ZMP control activates when the floor reaction control fails, and the soles of the feet cannot plant firmly to the ground. In that case, the target ZMP is itself changed by deviating from the ideal movement pathing by accelerating the upper torso (which contains most of the robot's mass) in the direction of the falling force. Foot planting location control corrects the irregular outcome of target ZMP control by changing the length of stride to accommodate for the changed torso speed.

An important but easily unnoticed characteristic of ASIMO's bipedal movement is that it involves bending of the legs, which lowers the center of gravity and keeps constant the height of the hips. This is contrary to the widely-spread thinking that ASIMO's "...walk is modeled on a human being's." The constant height of the hips, which makes simpler the inverse kinematics of movement, makes feasible the real-time predictive movement-planning technology featured on the ASIMO. When ASIMO walks, it predicts an ideal movement path consisting of Zero Moment Points and tilts its body sideways or forward to shift its center of gravity in anticipation. Real-time predictive movement-planning enables ASIMO to make minor adjustments to its movement path rather than changing gears between different walking patterns as in the earlier ways of walking.

Other basic movements of ASIMO, some of which were also demonstrated on previous prototypes, include climbing and descending stairs, pushing a cart, carrying things, passing through doorways, and shooting a ball.

ASIMO v2 changes

The New ASIMO was introduced on December 13, 2005 with a host of new features over the original ASIMO. To enable quicker movement, ASIMO's body was made more responsive with the addition of high-speed processing circuit, high-power and highly responsive motors, and lighter and more rigid leg structure. The New ASIMO walks at speeds up to 2.7 km/h and runs at 6 km/hour.

Continuous movement independent of the head (which contains the vision sensor) was enabled with the addition of extra sensors around the waist area, namely the laser and infrared sensor and the ultrasonic sensor units. Laser sensor detects the ground surface and obstacles within two meters, while the infrared sensor identifies floor markings. Ultrasonic sensor detects obstacles three meters ahead, including glass which cannot be detected with the image data from the stereoscopic camera. The use of multiple sensors allows New ASIMO to sense its surrounding more acccurately by self-correcting and adjusting the sensitivity of each sensor depending on the situation.

New abilities were added to the ASIMO's receptionist system, such as walking with a person while holding hands and carrying objects using a cart. A total control system was developed to enable ASIMO to automatically perform the tasks for reception, including escort and delivery service.

ASIMO v3 changes

The All-new ASIMO was unveiled on November 8, 2011, becoming the world's first to autonomously choose its behavior without control by an operator, based on a comprehensive analysis of visual, auditory, and tactile input data and predictions about the surrounding. The All-new ASIMO will pause and change its behavior according to the other person's intention, such as changing its course to avoid collision.

With new hands that were made more dexterous by enabling fingers to move independently of each other, the All-new ASIMO is able to twist off cap of a bottle or make sign language expressions.

The All-new ASIMO also acquired the ability to run backward and hop on its legs by changing the landing position of its legs in middle of motion. The All-new ASIMO can run at 9 km per hour.

Prototype development history

Honda's humanoid robot development began in 1986 at the Wako Fundamental Technology Research Center under the lead of Masato Hirose (who is currently the Executive Chief Engineer at Honda R&D).

The E0, the first prototype, was a basic two-legged machine that demonstrated "static walking" by taking a step every 30 seconds. The slow speed of static walking meant that the center of gravity was placed within the soles of the feet as it shifted places between the left and right foot.

Research involved the E1, E2, and E3 prototypes between 1987 and 1991. E1 prototype walked at an improved speed of 0.25 km/h.

"Dynamic walking" was achieved on the E2 prototype by improving the speed to 1.2 km/h. With faster dynamic walking, static balance was intentionally terminated as next steps were taken before the shifting center of gravity could center onto the soles of the feet. The E3 prototype could walk at 3 km/h.

Research continued with the E4, E5, and E6 prototypes between 1991 and 1993. E4 could walk at 4.7 km and was the first prototype to walk on uneven surfaces. Unlike the previous prototypes, the E4 was surefooted and not liable to stumbling as it could recover from a fall by leaning forward its upper body. Falling forward by the hips was a digression from the mainstream theory of the day, which was mainly concerned with maintaining an ideal movement pattern in which the robot stands upright after landing, by correcting deviations with the toes pressing down and the heels lifting up.

E5 was the first autonomous locomotion model. It incorporated the three-layered ZMP control system to achieve stable walking even on stairs and slopes.

Prototypes P1, P2, and P3 were the final models that underwent development between 1993 and 1997. P1 was the first man-like model with an upper body. It could turn external electrical and computer switches on and off, grab doorknobs, and pick up and carry things. P2 achieved independent operation with built-in battery and wireless technology. It was able to walk up and down stairs and push carts. P3 was a slenderized version of the P2 with smaller components and reduced weight.