Segway's Centaur Fun on Four Wheels 4/25/2007
By Bryan Harley
The company that gave us the Personal Transporter (PT) is at it again. Segway continues to innovate with its creation of the Centaur, a highly maneuverable, four-wheeled all-terrain vehicle. Rest assured, the Centaur is not your typical quad.
Before die-hard ATVers dismiss it as a bunch of wasted bits and bytes of techno gadgetry, know that the Centaur is capable of popping the ultimate wheelie. It doesn't even require hours of riding practice and numerous bruises and broken bones from failed attempts. The Centaur is configured so you pop up at about a 45-degree angle and the vehicle is capable of holding itself there without throwing you off the back. Of course, riders are denied the adrenaline-filled moment precariously balanced between tipping over backwards or riding it out. Then again, you won't end up flat on your back with the wind knocked out of you as your bike continues without you either.
The hi-tech Segway Concept Centaur has Nieman Marcus' Christmas catalog appeal. The contraption arouses curiosity, stimulates the nucleus accumbens and would be fun to ride, but few will ever get the opportunity because it remains solely a Segway prototype vehicle.
The four-wheeler's minimalist design betrays the intricate technology that mobilizes the machine. At first glance, you see a long, banana-style bicycle seat, similar in shape to the one on my first Schwinn 3-speed. The seat is mounted on lightweight, thin bicycle-type tubing in a compact X-shaped frame. Steering is by means of mountain bike-style handlebars that pivot on a short neck. You place your feet on small, round foot pegs while assuming an aggressive forward-leaning riding stance, similar to tucking in on a sportbike. It has four big wheels and a short wheelbase and no visible means of propulsion. Part of the aesthetic appeal of the Centaur is its clutter-free, rudimentary design.
But look closer through the simple-looking framework of the Centaur and you find revolutionary technology, like the advanced electric propulsion system that provides power without pollution. Inspect the Centaur further and there is much to appreciate about Segway's four-wheeled machine that has the ability to recognize a rider's body position and attempts to maintain the optimum balance between man and machine using tilt sensors, gyroscopes, and microprocessors.
One of the first marvels of the Centaur's capabilities is its Smart Steering. There are two sensors in the steering column that calculate speed. The first sensor's readings come from the twist of the throttle. The second readings come from the angle of turn received through the sensor in the handlebar. Mechanical linkage connected to the handlebar controls the left and right movement of the front wheels.
When the front wheels are in the air, the Centaur performs like Segway's PT and senses a rider's body position. Despite having two wheels in the air, it maintains the ability to maneuver thanks to a combination of simultaneous mechanical and drive-by-wire steering; the rider still steers with the handlebar.
The Centaur's performance on two wheels is based on Segway's patented dynamic stabilization technology (DST) it initially developed for the PT. It is enabled when the vehicle's front wheels come off the ground. The rider stands similar to the way they would on a PT by placing their feet on the platform constructed at the base of the frame between the two rear tires. The DST is centered upon tilt sensors set in an electrolytic fluid that form a ring and track which way is down. Five micro-machined electric gyroscopes work in conjunction with the tilt sensors to detect changes in external motion. Inside the gyroscopes, a conductive ring formed by a constantly pulsing magnet senses disturbances in the ring's pattern, such as a shift in a rider's balance. Two accelerometers recognize any changes in terrain and body position and measure the degree of the rider's lean at 100 times-per-second. The computerized controller boards combine this info with the data from the tilt sensors and adjust the wheel speed to maintain optimum balance for a rider. In short, the bike senses which way you're leaning and makes the mechanical adjustments to keep you vertical.
When it's on four wheels, the forward and backward movement is controlled by pushing a thumb throttle located on the underside of the right-hand handlebar. When the handlebar is turned, it activates both manual (front wheels) and drive-by-wire (rear wheels) steering. The readings from the sensors in the steering column, which measure throttle pressure and handlebar angle, are sent to the control boards. From this data, the sophisticated software computes how fast to spin the outside rear wheel in relation to the spin of the inside rear wheel. The wheels have the ability to spin at different rates according to what direction the rider is steering and based on the center of the rider's balance.
When examining the Centaur's exterior, there is no engine visible. But listen to the teaser video on the Segway website and you hear the mosquito-like buzzing of the four-wheeler's electric motors. Information was scarce regarding the makeup of the motor except for the fact that the Centaur is powered by its lithium-ion batteries. The batteries use regenerative braking, which recharges them during deceleration and hill descents.
If it's like the PT, propulsion is achieved by a combination of two identical sets of microprocessor-based electronic controller circuit boards, the batteries, and motor windings that function together and share the load of driving the wheels. The motors are quiet in comparison to an ATV. Most impressive of all there are no emissions because it's all electric and there is no exhaust.
Scott Waters, manager of industrial design, stated that the Concept Centaur is capable of approximately 25 mph top speed, has a range between 10-15 miles on a single charge, and carries a maximum payload of 400 lbs. It measures 58 inches long by 35 inches wide and weighs a scant 140 lbs. But that is not the most impressive stat.
"It is a blast. I love riding it," said Carla Vallone, Segway's Communications Manager.
But don't be ready to trade in your quad just yet. Serious ATVers would surely miss the rumble of their exhausts and the smell of spent fuel. And there's definitely no cargo area for mounting a buck during hunting season.
On the serious side, it seems to have a high center of gravity, so there's the possibility of the rider being thrown performing a quick, tight turn. Segway claims that it has the capacity for two-up riding, but this is never demonstrated in its test video. It's hard to discern if riding two-up on the Centaur is practical. We don't know how well the essential sensors and microprocessors to the Centaur are protected from hard impacts, like hitting a curb or rock. The last point of contention would be in the area of repairs. With the sophistication of the circuitry, it seems a safe bet that there would be no quick, inexpensive fixes.
Despite its possible shortcomings, if it's unadulterated fun you're looking for, the Segway Centaur would seem to fit the bill. If Segway decides to go public with it, we hope they put us on the list for a thrill ride.