Humanoid Robot: Honda has got one which has been walking around better than your grandma for some three years now.

Fictional Star Wars droid C-3PO may be quite a smooth walker and talker, but up until now, robots built by scientists around the world have not been nearly so neat on their feet. Enter Honda.

Fictional Star Wars droid C-3PO may be quite a smooth walker and talker, but up until now, robots built by scientists around the world have not been nearly so neat on their feet. Enter Honda.

Human movement, especially walking, is an amazing combination of co-ordination, balance and speed and as far as robotics is concerned, it has proved difficult to recreate. In Japan a team of scientists lead by Kazuo Hirate, Head of Honda Research and Development, have managed to build a robot that walks with stability and balance. It’s taken fourteen plus years and many prototypes.

The first attempt staggered backwards and forwards, the next was faster but had to gyrate its hips to stay up! Once they’d managed to get some robotic legs working, they added a torso to make it look more human and less like something out of Wallace and Gromit. They created two more prototypes, P1 and P2.

It was 1986 when Honda commenced the humanoid robot research and development program. Keys to the development of the robot included “intelligence” and “mobility.” The basic concept at that time was that the robot “should coexist and cooperate with human beings, by doing what a person cannot do and cultivating a new dimension in mobility both of which would result in added value to society.” This, in other words, provided a guideline for a new type of robot that would be used in our daily life, rather than being purpose-built for specific special operations.

Approximately one year was spent exclusively on initially determining how the robot should be like in order to build the concept. The robot that was aimed at should ensure such functions as moving through furnitured rooms and going up and down the stairs because it was to be designed for home use. And, at the same time, the design team came up with a conception that the robot would be compatible to most terrains, including severely rough surfaces if the two-foot/leg mobility technology could be ensured for the robot.

Based upon the aforementioned, Honda engineers begun the program by focusing on a “foot/leg-walking mobile function,” which corresponds to our basic measure of mobility. As you probably imagine, there have been a number of technical challenges to be cleared before creating the robot intended.

Special attention was thus paid to our own legs and feet. To begin with, the first phase of the program was dedicated to the analysis of how a human walks with the legs and feet.

So what’s the one beating grandma at badminton

The model that’s really strutting its stuff, is the P3. It’s 1.6 metres tall, about the size of a Japanese woman, but much heavier at 130 kg!

P3 has the electronic equivalent of a nervous system, sensors in different parts of its body that send messages to its ‘brain’, with an on-board computer hidden in its backpack. The six sensors in its feet send messages about its movement and the sensors in its tummy tell it what angle it’s at, so it can counterbalance any movements it makes. Whatever happens, P3 is determined to stay upright!

Result

P3 can walk at 2 km per hour on a battery which lasts 25 minutes. All it needs is an engineer to programme it when to start and stop and warn it about difficult terrain ahead like stairs. The robot does the rest. It can decide whether to step over an obstacle or to find an alternative route. It can work out the exact depth and height of each step and re-adjust its stride if it finds the size of the step varies.

Not content with this, however, Kazuo Hirate has more plans, “First of all, the robot is still too heavy so I’d like to make it lighter. Secondly I’d like to add more functions to it to make it able to do as many human-like tasks as possible, and thirdly I’d like to give it artificial intelligence so it can make more decisions.”

Future Development

In terms of hardware, the program in the future will be focused on;

— Further dimensional and weight reduction.

— Improved dynamic performances.
— Improved operability.

It is extremely important to ensure a physical autonomy by improving dynamic performances and adaptability to wider variations of working conditions through the evolution of hardware. Similalry important is encouragement of studies in artificial intelligence systems, which will provide a solution for improved autonomy. If all of them are ensured, a robot does not require minute correcting operations done by a human.

And, in terms of software, we should be aimed at promoting a social infrastructure where humanoid robots will be accepted widely and easily. The issue is deemed significant considering the appearance of the humanoid robot.

Honda hopes that a time will come when humanoid robots play an important role in serving us and making our lives and society more enriched.

Well welcome to the neighborhood, robot friend!

Click these links below to watch home video footage of the humanoid in action.

— Pushing a cart (878KB 12sec.)

— Tightening a nut (838KB 13sec.)

— Turning (1024KB 17sec.)

— Up and down stairs (1509KB 22sec.)

— Walking (974KB 16sec.)

The Research Background – The Study of Leg/Foot Functions of the Robot

— Movements of leg/foot joints when walking

Honda’s Research team has revealed that no significant effect is caused to walking even without toes. More important support is ensured by base sections of the toes, i.e., balls of feet, and joint areas. Without the feet joints, one cannot feel contact with the surface, being vulnerable to back-and-forth instability, as well as becoming less stable when crossing diagonally through an inclined surface. Also, it is impossible to ascend and descend stairs without the knee joints. No coxae condition makes autonomous walking extremely difficult. As a result of the examination, they opted for integrating coxae, knee joints and articulation pedis with their humanoid robot.

— Joint alignment

Joint alignment was determined so that it was ‘equivalent’ to the human skeletal structure.

— Movable ranges of joints

The movable ranges of joints while walking were defined in accordance with walking test measurements on flat surfaces and stairs.

— Dimensions, weights and centers of gravity of each leg and foot part

The center of gravity of each part was determined by referring to that of the human body.

— Torque application to the joints when walking

Torque acting on the joints was optimized based on the measurements of human joint movement during walking and reaction vectors from the contact surface.

— Sensor systems required for walking

Our sense of equilibrium is ensured by three sensing mechanisms. A detection of acceleration is provided by statoliths. Three semicircular canals detect angular velocity. Bathyesthesia provided from muscles and skins is responsible for detecting angles, angular velocity, muscular dynamism, pressures on plantae and sense of contact. Also important is visual sense, which supports and sometimes compensates for the sense of equilibrium, as well as provides information required for normal walking.

As a result, the robot system should incorporate G-force and six-axial force sensors to detect the conditions of legs/feet while walking, and an inclinometer and joint-angle sensors that detect the overall posture.

— Landing impact when walking

A human eases the impact of walking with a combination between structures and functions of movement. The former includes soft skin, ankles and arch-like structures comprised of several bones at the toe joints. The latter is ensured by the bending motions at joints when the plantae comes into contact with the surface.

Studies on human walking revealed that the reaction from the surface tends to increase along with an increase in walking speed, even with the shock-easing functions mentioned above. When walking at a speed of 2-4km/h, the load to the leg/foot is measured to be 1.2~1.4 times greater than the body weight. At a speed of 8km/h, the reaction load exceeds 1.8 times the weight.

Although the robot must feature similar shock-absorption mechanisms, the structural measure was not welcome because it might deteriorate the robot’s stability. Impact absorption was thus ensured through precise control of each component.

Based on analytical results, the Honda Research team felt confident in having determined the specifications for the robot legs and feet.

Development of Two-legged Robot

Based on a prototype design which was manufactured for the leg/foot function studies, they established three functions to be satisfied;

1. Walking speed corresponding to that of a human (i.e., 3km/h).
2. Providing structural support for the upper mechanisms, namely arms and hands.
3. Capable of going up and down ordinary stairs.

The program began with “static walking*l,” which later was shifted to “dynamic walking*2,” a dominant factor in human walking. Naturally, the walking program for the robot was complied according to the data of a human’s walking procedure. The active walking program was then integrated into the robot’s management system.
The continuous study program gradually allowed for a determination of specifications, which was followed by ensuring stable dynamic two-leg/feet walking operations and, finally, autonomous two-leg/feet walking.

(*1) Static walking: The center of gravity is maintained within the supporting leg base area. A smaller footstep and slow speed.

(*2) Dynamic walking: The center of gravity is outside the supporting leg base area. Walking maneuver where a static balance is intentionally destroyed.

For Freer Walking

Foundation for the two-leg/foot operation was ensured with specifications determined for straightforward dynamic movement on a flat surface.
The next logical step was to conduct a research and development program for freer walking. The robot developed in the following stages must be capable of walking through undulations and bumps, inclined surfaces, stairs, as well as more stable autonomous walking without the risk of falling.

Technical challenges for ensuring robot stability are concentrated on the following three items;

1. A controlling technology to ease landing impacts without being affected by bumps on the surface. Such a function should be ensured by the overall mechanisms of the components.
2. A posture controlling strategy to restore the robot’s unfavorable movement when it nearly falls.
3. A variable and adaptive controlling strategy that puts the leg/foot exactly on the point of landing in accordance with the circumstance. The landing point is automatically determined as a result of various management factors.

The Honda Research team attempted to complete each technology before combining them to ensure comprehensive autonomous two-leg/foot management.

Technical Clues to Stable Walking

A human attempts to restore their posture by applying pressure to a part (and some parts) of the plantae to avoid falling while walking and at a standstill. If they judge that the pressure application is not enough, they can change the location of the center of gravity by a structural movement and/or stepping out.

It was required to ensure a similar action for the robot in order to maintain posture stabilization.

Basic Principles for Posture Control

The robot was, basically, controlled to follow the joint angle to meet a specific walking pattern. A resultant force from the inertia and gravity determined by the pattern is called “target overall inertia.” A point where the moment of the target overall inertia becomes zero is defined as “target ZMP.” Also, a combined force between the reaction from the floor to the left and right plantae is called “actual overall floor reaction.” A point where the moment of actual overall floor reaction is at zero is regarded as a “central point of the actual overall floor reaction.

The target ZMP coincides with the central point of the actual overall floor reaction as long as the robot is ideally walking. The two points, however, tend to differ from each other during actual walking because of the effects of bumps and inclination, even though the upper body posture conforms to the target and the joint angle is exactly controlled according to the target.

Under this condition, there is a difference in the line of action resulted from the floor reaction and point of action of the target overall inertia.This leads to the generation of couple, which acts on the robot by inclining it. The couple of the forces is defined as a “moment of falling force,” one of the most difficult problems before ensuring a stable walking control.
Honda’s strategy is based on an innovative conception to making the best use of the falling force moment. More specifically, the difference in the target ZMP and central point of the actual overall floor reaction is dynamically controlled through the use of falling force moment. The body inclination is thus compensated by the falling force moment, which is originally a problematic factor in posture control.

Evolution to Humanoid Robot

Last but not least, Honda engineers should integrate the leg/foot mechanism, which could walk stably and autonomously, with the upper body to achieve a humanoid design.

The functions of Honda’s humanoid robot were defined as follows;

— An operational system that autonomously performs typical operations under known circumstances, and if an extraordinary operation is required under unknown circumstances, the robot will be supported by an operator.

The first prototype, P1, was measured 1,915mm in height with a weight of 175kg.

The P1 was developed to identify the most appropriate way to ensure for synchronous arm/leg movements. Being so, the prototype did not feature an integrated power source. With the P1 , we achieved basic functions, including turning switches on/off, grasping a door knob and transporting objects held by two hands. Also achieved was the synchronized movements between the arms and legs.

The P1 was followed by the humanoid-type autonomous prototype, P2 , whereby wireless techniques were adopted. The, P2, 1,820mm in height and 210kg in weight, features a computer unit, motor-drive system, battery and wireless apparatus inside the body section. This more sophisticated robot can achieve freer movement, go up and down the stairs and push a vehicle, all of which functions are triggered via a wireless transponder. Naturally, the level of adaptation to autonomous operation is greater with P2 than Pl.
The latest version of the prototype robot is the P3, which was completed in September 1997. Efforts for downsizing resulted in a more compact and lighter design with a height of 1,600mm and a weight of 130kg.

Author: thee_InVection_report

News Service: TheExperiment Network

URL: http://www.honda.co.jp/english/technology/robot/index.html