The motorcycle's balanced future

  • 20-Jul-2017 09:14 EDT
HondaRidingAssist concept at CES17.jpg

Honda's award-winning, self-balancing Riding Assist concept motorcycle was a showstopper at CES 2017. (Honda)

Where do motorcycles and scooters—that now require the rider to take a totally active role in piloting the machine—fit into the looming autonomous-and-connected vehicle ecosystem? A recent visit to a nondescript high-rise building in central Tokyo revealed a glimpse of the two-wheeled future.

In this office, a team of Honda R&D Co. engineers and computer scientists are developing autonomous machines and robotics. Officially called the Honda Innovation Laboratory, the independent think-tank is more commonly referred to as “Center X.” It is an open laboratory collaborating with outside research and academic institutions, as well as with venture enterprises and individuals and is linked with Honda Xcelerator open-innovation programs based out of the company’s Silicon Valley Lab.

Honda has been researching automated driving and related technologies for more than 30 years, noted R&D President Yoshinobu Matsumoto. He cited development of “Gyro-cater,” the world’s first in-vehicle navigation system offered for the Accord in 1981. Knowledge from that program eventually led to Honda’s extensive bipedal (two-legged) locomotion studies—which in turn led to ASIMO, the now-famous and beloved robot that has become an icon of Honda’s controls and artificial-intelligence expertise.

Technology developed at Center X for ASIMO and for the racetrack now is helping Honda develop two-wheelers that can stand up by themselves, Matsumoto told Automotive Engineering. The small gyro sensor originally used in ASIMO inspired development of sensors that recognize the attitude (lean angle) of a racing motorcycle, helping to govern engine power under extreme G forces while the machine is leaned hard in a corner. The technology was incorporated in Honda’s factory RC-V series MotoGP bike in 2011, he explained.

Engineers’ analysis of the rider’s thoughts and movements, rather than the behavior of the bike, led to the new electronic attitude controls that make the rider’s work easier. On the opposite end of the performance spectrum, Honda’s Uni-Cub self-balancing, two-axis personal mobility device first demonstrated in 2013 enables the seated rider to control speed, move in any direction and stop, all by simply shifting body weight.

The next step is software that can control the Uni-Cub via an “app” from mobile devices—expanding the machine’s value and functionality. Uni-Cub creator Shinichiro Kobashi has indicated the compact little two-wheeled unit may be released in time for demonstration at the 2020 Tokyo Olympics.

Toward the autonomous motorcycle

An obvious technology pathway from the MotoGP and Uni-Cub learnings is toward the autonomous motorbike and the 'personal transporter' capable of being summoned from their parking areas and sent back after the day’s riding/mobility duties are finished. More sensors and control technologies like those being integrated into passenger vehicles (cameras, radar and obstacle detection, lane keeping, etc.) are required, of course. And challenges related to packaging such hardware within the limited space on two-wheelers are significant.

Earlier this year, at CES 2017, Honda showed its latest step in the autonomous-bike journey: Riding Assist (https://www.youtube.com/watch?v=VH60-R8MOKo). The excitement it created among CES show-goers always began with, “Did you see the motorcycle that can balance itself? That's cool!” and "Honda has a robo-bike!"

And the machine, based on a production NC750S [a sporty 750cc twin-cylinder commuter bike sold in Europe] does just that.

Riding Assist is particularly effective and useful in such taxing situations as stop-and-crawl traffic or the common parking-lot fall when the rider, perhaps fatigued or distracted, is caught off-balance and lets the bike fall onto the ground. The Riding Assist prototype stands upright when stopped and at speeds less than 3 to 4 km/h (about 1.9 to 2.4 mph) with no manual input from the rider. If the rider dismounts the motorcycle, it remains standing as long as the balancing system is engaged.

The Riding Assist program’s chief engineer, Hiroyuki Nakata, is a veteran engineer-development-rider (with specialist background in braking) at the Honda Motorcycle R&D Center at Asaka. Nakata also is responsible for advanced-safety technologies. He acknowledges that it has for several years been an ongoing project at Honda to enhance motorcycle safety by combining robotics research with the company’s championship-winning motorcycle technology. He reasons that the formidable combination could realize “dream technologies for new mobility.”

To create Rider Assist, Nakata’s small team (fewer than ten, excluding fabricators) was joined by two “young blood” Ph.Ds in control systems: Makoto Araki and Kazushi Akimoto, an expert in bipedal robotics and “novel mobility” research. They were aided by veteran Atsuo Ota, who directed Honda’s recent CES showcase for Rider Assist.

From the onset, the team decided not to employ gyro devices—they were deemed too heavy, too large and likely to hinder the motorcycle’s inherent dynamics. “We are catering to the most discriminating and selfish clientele,” Nakata observed, “including us engineers, who may be the worst of the lot! [Riders] A and B do not ride the same way. There are as many riding styles as there are riders. Motorcycles are designed and built to please them. We cannot rob any of the fun factors.” So they chose to leave the virtues alone, but to remove some of the unpleasantness.

On the geometry ‘trail’

The Riding Assist motorcycle differs from the conventional in that it has variable trail; “trail” on a motorcycle being the distance between the point of the front wheel’s contact with the ground and a line drawn through the axis of the steering head. Under normal operation, this contact point is always some distance behind the projected line—typically between 2 and 4 in (51 and 101 mm). Think of it as how far the contact patch trails behind the steering axis. Too much (positive trail) makes the machine difficult to turn; too little (negative trail) makes it unstable.

The “sweet spot” of positive trail effectively points the tire patch straight forward, stabilizing the bike. When standing still or moving very slowly, the motorcycle begins falling and steering efforts cannot correct the situation because of the geometry.

In Honda’s Riding Assist, at standstill and speeds less than 4 km/h, the tire’s road contact point is moved forward by actively altering the front fork angle, producing a negative trail (leading versus trailing). In this state, the system-determined steering moment counters and the bike maintains an upright posture.

The system uses three electric servo motors. One is responsible for variably altering trail—i.e., front fork inclination. A second motor handles the steer-by-wire and the third motor performs the “balancing act” by producing appropriate corrective steering moment.Two roll-related sensors are also employed; one is for roll angle and the other roll rate. If the rider is aboard, the weight and mass distribution are compensated on a roll-sensing signal.

On a conventional motorcycle, an expert rider may keep the machine motionless by wiggling the handle bars; the Riding Assist system does it faster and with greater precision via moment input of the steering and its attendant software controls.

Fun to accompany functional

A charming feature of the Riding Assist prototype is called “follow the walking master,” shown in a video at CES. Speaking with Automotive Engineering, Nakata’s team was candid and admitted that in the video, while no brake intervention was employed, the bike was following a pre-programmed indoor route. This technique also has been employed to demonstrate some autonomous-driving cars on handling and race courses. One engineer remarked that such capability is advancing rapidly thanks to equally-fast-advancing features such as optical recognition.

The Riding Assist system’s added weight is mostly offset by careful design and construction. About two-thirds of the prototype machine is a stock NC750S. Moving out of the standstill, ultra-low-speed operating parameters for Riding Assist, the motorcycle delivers the expected fun and pleasure of a conventional motorcycle, the team assured.

Nakata affirmed autonomous operation of motorized vehicles, be they two-wheeled, four-wheeled or whatever number, must be seriously considered for the future. And for two-wheelers, which formed the genesis of Honda Motor Co. and still account for considerable profits today, adopting autonomous capabilities is a matter of survival. Future bikes may retain the looks and functions of today, he observed, or completely transform to another entity.

“Motorcycle riders generally dislike automatization, but the world is changing rapidly," Nakata asserted. "And we must seriously search better solutions.”

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