How the ASIMO Robot Operates

Would you like a robot to prepare your meals, assist with your studies, tidy your home, or even handle your shopping? Robots already take on many tasks that humans either prefer to avoid, cannot perform, or simply aren't as efficient at. In factories worldwide, robotic arms work tirelessly assembling cars, placing candies into boxes, and handling numerous repetitive jobs. Some robots even focus entirely on tasks like vacuuming the floor or cutting the grass.

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Many of us grew up watching robots on television and in films: We saw Rosie, the robot housekeeper from The Jetsons; Data, the android crew member from "Star Trek: The Next Generation"; and of course, C3PO from "Star Wars." While today's robots are still a far cry from Data or C3PO, there have been incredible strides in their technology. For over 20 years, Honda's engineers have been perfecting the ASIMO robot. In this article, we will explore what makes ASIMO the leading humanoid robot of our time.

The Honda Motor Company created ASIMO, which stands for Advanced Step in Innovative Mobility, making it the most sophisticated humanoid robot globally. ASIMO, as described on its website, is the first robot capable of walking autonomously and ascending stairs.

In addition to walking like humans, ASIMO can comprehend preprogrammed gestures and verbal commands, recognize voices and faces, and interact with IC Communication cards. Equipped with arms and hands, ASIMO can perform tasks like flipping light switches, opening doors, carrying items, and pushing carts.

Honda's goal was not to build another toy robot, but one that could serve as a helper — assisting in the home, aiding the elderly, or supporting those in wheelchairs or bedridden. At 4 feet 3 inches (1.3 meters), ASIMO is ideally sized to meet a person at eye level when sitting, making it approachable and functional without appearing too large or intimidating. Often described as resembling a "kid in a spacesuit," ASIMO’s friendly design and manageable size align perfectly with Honda's vision for a helpful companion.

ASIMO can also take on tasks that are too hazardous for humans, such as entering dangerous zones, defusing bombs, or even fighting fires.

ASIMO's Movement: Walking Like a Human

To enhance ASIMO's walking ability, Honda researchers examined the legs of insects, mammals, and the movements of a mountain climber with prosthetics. This research was crucial to understand the complex mechanics of human walking, especially at the joints. For example, the way we shift our weight with the help of our arms for balance was vital in perfecting ASIMO's walking motion. The role of our toes in maintaining balance was also taken into account. ASIMO's feet have soft extensions that mimic the function of human toes when walking. These soft materials also reduce impact on the joints, similar to how our tissues cushion the joints during movement.

ASIMO's body includes hip, knee, and foot joints. In robotics, these joints are known as "degrees of freedom." A single degree of freedom allows movement either horizontally or vertically. ASIMO has 34 degrees of freedom spread across its body, enabling fluid movement. There are three degrees of freedom in its neck, seven in each arm, and six in each leg. The required number of degrees of freedom in ASIMO's legs was determined by studying human joint movement during activities such as walking on flat surfaces, climbing stairs, and running.

ASIMO is equipped with a speed sensor and a gyroscope sensor attached to its body. These sensors carry out the following functions:

These sensors operate similarly to our inner ears, helping to preserve balance and spatial orientation.

ASIMO also includes floor surface sensors in its feet and six ultrasonic sensors in its torso. These devices allow ASIMO to better interact with its surroundings by detecting objects in its vicinity and comparing the gathered data with maps stored in its memory.

To replicate the sensory functions our muscles and skin perform in detecting muscle strength, pressure, and joint angles, ASIMO is equipped with joint-angle sensors and a six-axis force sensor.

Unless you're well-versed in robotics, you might not fully appreciate the remarkable achievement that ASIMO walking like humans is. The most impressive aspect of ASIMO's movement is its ability to turn smoothly. Rather than halting, shifting, stopping, and shifting again, ASIMO leans and turns effortlessly, just like a person. In addition, ASIMO can modify its steps when it stumbles, gets pushed, or encounters obstacles that disrupt its normal stride.

To achieve this, ASIMO's engineers had to figure out how to manage the inertial forces that arise during walking. For instance, gravity and walking speed both exert a force, referred to as the 'total inertial force.' There's also the force when your foot makes contact with the ground, known as the 'ground reaction force.' These forces must be balanced, with posture playing a key role in ensuring stability. This balance is what engineers call the 'zero moment point' (ZMP).

To regulate ASIMO's posture, engineers concentrated on three key control mechanisms:

ASIMO's Motion: Smooth Moves

ASIMO is capable of detecting and reacting to falling movements quickly, but its engineers aimed for more. They wanted to equip the robot with not just a smooth gait but also the ability to do something other robots can’t—turn without stopping.

When we walk around corners, we shift our center of gravity to follow the turn. ASIMO uses a technology known as "predictive movement control," also referred to as Honda's Intelligent Real-Time Flexible Walking Technology, or I-Walk, to achieve the same result. ASIMO predicts how much it should shift its center of gravity inside the turn and for how long to maintain the shift. Since this system operates in real time, ASIMO doesn’t need to pause between steps, unlike other robots.

In essence, with each step ASIMO takes, it must assess its inertia and forecast how to shift its weight for the next step, ensuring smooth walking and turning. It adjusts factors like the following to maintain balance and proper position:

While recreating a human-like walk is already an impressive feat, ASIMO can now run at a speed of up to 3.7 miles per hour (6 kilometers per hour). To truly be considered a running robot, ASIMO must have both feet off the ground for a brief moment with each stride. ASIMO manages to stay airborne for 0.08 seconds during each running step.

Honda’s engineers faced a whole new set of challenges when they worked on giving ASIMO the ability to run. They provided ASIMO’s torso with extra flexibility to allow bending and twisting, helping it adjust its posture while airborne. Without this capability, ASIMO could lose control mid-air, potentially spinning out or stumbling when it lands.

To make turning while running smooth, the engineers enhanced ASIMO’s ability to tilt its center of gravity into the turns, helping it maintain balance and counteract centrifugal force. ASIMO can even anticipate a turn, starting to lean into it before it even begins, much like a skier or skater would do.

In the following section, we’ll explore how ASIMO is able to recognize images and sense its surroundings.

ASIMO's Senses

In robotics, vision refers to an image captured and interpreted using pre-programmed templates. In controlled environments like manufacturing, where robots build cars or inspect microscopic components of semiconductor chips, the lighting and angles remain constant, and the number of objects to process is limited. In contrast, the real, unstructured world presents an exponentially larger variety of things to perceive and understand.

A humanoid robot tasked with navigating through homes, buildings, or outdoor spaces must be capable of understanding the many objects it "sees." It must comprehend shadows, odd angles, and movement. For instance, a robot venturing into an unfamiliar space would need to recognize and identify objects in real time, selecting features like color, shape, and edges for comparison against a database of known objects or environments. This memory can contain thousands of items.

ASIMO's vision system is built around two video cameras located in its head. With stereoscopic vision and a proprietary vision algorithm, ASIMO can see, recognize, and avoid obstacles, even if their lighting or orientation differs from what’s in its memory. These cameras are capable of detecting multiple objects, measuring distance, perceiving motion, recognizing faces, and interpreting hand gestures. For instance, when you raise your hand in a "stop" gesture, ASIMO halts. The facial recognition feature enables ASIMO to recognize and greet familiar faces.

ASIMO can detect moving objects by analyzing the images captured by the cameras in its head. It can determine the distance and direction of a moving object, enabling ASIMO to follow a person, pause to let something pass, or greet you as you approach.

The cameras transmit the images they capture to ASIMO's controller. This allows someone controlling ASIMO from a PC to see exactly what ASIMO sees.

In addition to its head-mounted cameras, ASIMO is equipped with multiple sensors that help it navigate through environments and interact with people and objects. Floor sensors detect objects and changes in the ground surface, while ultrasonic sensors help ASIMO detect surrounding obstacles. These sensors work together to help ASIMO match the real-world environment with its preprogrammed internal map.

ASIMO also has a sense of touch, to an extent. The force sensors in its wrists allow ASIMO to gauge how much pressure to apply when picking up objects, handing over items like files, or even shaking hands. By combining data from its cameras and force sensors, ASIMO can move in harmony with a person, such as when holding hands. When pushing a cart, the force sensors help ASIMO adjust the amount of force based on conditions, like increasing force when detecting an incline.

ASIMO can also sense the environment using IC Communication cards. These cards use infrared signals to transmit and receive data. When you carry an IC card containing your information, ASIMO can detect your presence even if you're outside its camera’s line of sight. These cards enhance ASIMO’s interaction capabilities. For instance, when you visit Honda’s office and receive an IC card as a visitor pass, ASIMO can greet you and guide you to your destination by reading the information encoded on the card.

Managing ASIMO's Operations and Power

ASIMO is not capable of independent decision-making. It cannot simply enter a room and figure out how to move around. Instead, it must either be pre-programmed for specific tasks in areas marked with identifiers it recognizes, or be directly controlled by a human operator.

ASIMO can be operated through four different methods:

By utilizing 802.11 wireless technology along with a laptop or desktop computer, you can operate ASIMO and even view what it sees through its camera-equipped eyes. Additionally, ASIMO can use its PC connection to access the Internet and provide you with useful information such as weather updates and news.

The wireless joystick controller allows you to control ASIMO’s movements much like you would steer a remote-controlled car. You can direct ASIMO forward, backward, sideways, diagonally, or make it turn in place. It can navigate around corners or even run in circles. Although it may seem simple, ASIMO is capable of adjusting its steps automatically when encountering slopes or obstacles, ensuring it moves smoothly despite terrain changes.

ASIMO can identify and react to a variety of gestures and body movements, enabling nonverbal communication. For instance, if you point at a spot, ASIMO will follow your direction. If you wave, it will respond in kind. It even knows when you wish to shake its hand.

ASIMO is able to understand and follow simple, pre-programmed verbal commands. There’s virtually no limit to how many commands it can store. Additionally, you can register your voice, making it easier for ASIMO to recognize you specifically.

Beyond controlling ASIMO’s physical movements through voice, there are also verbal commands that prompt ASIMO to respond with speech. This capability has enabled ASIMO to function as a receptionist, where it greets guests and answers questions.

Much like other technologies in the robotics sector, ASIMO is driven by servo motors. These compact yet powerful motors feature a rotating shaft that adjusts the position of limbs or surfaces to a precise angle as commanded by a controller. Once the motor reaches the desired angle, it powers down until further instructions are given. For instance, a servo might control a robot's arm joint, maintaining the set angle until movement is necessary, after which it adjusts accordingly. Servos incorporate a position-sensing device (also referred to as a digital decoder) to verify that the motor's shaft is aligned correctly. They typically draw power in proportion to the mechanical load they bear. A lightly loaded servo, for example, consumes minimal energy.

ASIMO is equipped with 34 servo motors throughout its body, controlling the movement of its torso, arms, hands, legs, feet, ankles, and other moving components. ASIMO orchestrates a series of servo motors to manage each specific type of movement.

ASIMO operates on a rechargeable 51.8 volt lithium ion (Li-ION) battery that offers a runtime of one hour on a full charge. The battery is housed in ASIMO's backpack, weighing around 13 pounds. To recharge the battery fully, it takes about three hours, making additional batteries essential for prolonged operation. Users can either charge the battery while it's still attached to ASIMO via a power connector or remove the backpack to charge it separately.

ASIMO's Life Story

Honda initiated the development of its humanoid robot in 1986. The engineers recognized that for the robot to effectively navigate through homes or buildings, its walking technology had to be flawless. As a result, their initial prototypes were essentially boxes with legs. Once the walking mechanism was nearly perfected, they added arms, hands, and ultimately, a head.

The ASIMO Timeline

ASIMO's Peers

Aside from ASIMO, there are other advanced humanoid robots that perform similar tasks. However, most of these robots are much smaller in size and are mainly designed for entertainment purposes rather than practical service. Currently, ASIMO faces significant competition in terms of technology from:

Several robots are also employed in hospitals globally, navigating corridors and using elevators to deliver patient records, x-rays, medications, and other supplies. These robots operate on wheels and are either programmed with the hospital's layout or equipped to follow markers and barcodes on the walls.

Robots have been utilized in various fields since the 1960s. As computer processors continue to improve and robotics technology advances, it's only a matter of time before we have a real-life "Rosie" to cook meals and clean our homes.