Wireless technology will play a new and unexpected role this Olympic season, as cyclists use it to measure the power they produce on biking courses in Beijing.
The new wireless phenomenon, spreading gradually through the ranks of professional cyclists, is being enabled by the emergence of transceivers and strain gages that tell athletes how much power — in watts — they produce with each push of the pedals. The “power meters,” as they're called, are changing the face of cycling because they tell athletes virtually everything they need to know about their workouts, from velocity to force to wattage. Cycling coaches now say they can't imagine how they once got along without it.
“This has become incredibly important in cycling because it provides a completely objective measure of an athlete's fitness,” says Hunter Allen, CEO and founder of The Peaks Coaching Group, Inc., which trains world-class cyclists. “With this, there's no lying. A watt is a watt is a watt.”
Indeed, Allen says his athletes use the wireless systems to examine their power output over periods of an hour or more. They then break the numbers down further, analyzing such factors as pedal force and angular velocity. In one case, Allen says, U.S. mountain biker Jeremiah Bishop learned he was pedaling too fast on his training runs and not producing enough force, based on his power meter's “scatter plots.” With a few adjustments to his workouts, Bishop improved his race times.
“If you had just one piece of data you could get for a cyclist, it would be power,” says James Meyer, president and founder of Quarq, a manufacturer of a bicycle power sensor. “From a training standpoint, it all comes down to power. That's what really matters.”
The launch of the wireless power meter phenomenon occurred after engineers and cyclists began to simultaneously work on different parts of the puzzle. At least four companies played major roles in the development of subsystems, including the power sensor, handlebar computer, communications software stack and silicon radio transceiver.
To be sure, the idea of providing power data was not new when those firms set out to create their technologies. Several companies previously made bicycle power meters. Those meters, however, sent data from the sensors to the handlebar computers through hard wiring, a concept that was less than thrilling for some world-class cyclists.
“Some cyclists have $6,000 bikes that are essentially works of art, and here you are, taping wires to the frame,” Meyer says.
Moreover, many cyclists and their coaches worried about the practical problems associated with the hard-wire technique. “You've got all kinds of spinning parts close by,” Allen says. “And if your chain falls off, you've suddenly got all these wires wrapped around your chain. It's one more link in the chain to break.”
Meyer, a former bicycle mechanic and triathlete, was one of the first to see the value in a wireless alternative (German sports device manufacturer SRM, saw it, as well). “I started looking for a power meter but wasn't impressed with the options,” he says. “I felt there was a market need that wasn't being fulfilled correctly.”
As a result, Meyer set out on a quest to develop his own power meter — a wireless version. While examining wireless technologies, he came across an ad for a Garmin bicycle computer in a cycling magazine. The ad introduced him to a wireless communications protocol known as ANT, used on the Garmin computers. Meyer learned that ANT, which is designed for communication between sensors and sports computers, provided a lower-power alternative to Bluetooth and ZigBee wireless networks. He also found that the hardware, reference drawings and communications setup were already done, so he quickly gravitated toward it.
In 2006, all the companies began collaborating on products that could work with one another. Quarq developed its crankshaft-based power meter and collaborated with Dynastream Innovations Inc. (which makes ANT) on using the wireless communications protocol to send data from the power meter to a “head” computer on the handlebars. To accomplish that, though, both firms had to work with Garmin, which makes the handlebar computer. At the same time, Nordic Semiconductor ASA collaborated with Dynastream to implement the multi-channel ANT communications protocol onto its silicon transceiver and microcontroller.
“Most of the work was on Dynastream's side to tweak the (communications) protocol onto our new MCU,” says Thomas Soderholm, a business development manager for Nordic Semiconductor. “Our job was to help them as best we could to get their protocol onto our product.”
Low Power the Key
The result of all the collaboration is a standard methodology that can be shared by a wide variety of bike component manufacturers.
No matter which company's technology is used, the method of operation is the same: A biker generates force by pushing on the pedals. That force is transmitted into the bike's crank arm and moves from there to the so-called “spider,” which connects to the bike's chain rings and doubles as a power sensor. Quarq's sensor, known as CinQo, uses strain gages at each of its five arms to measure the strain and, by inference, the torque, which is proportional to the strain. While the unit's microcontroller computes torque, the spider employs Reed switches to count revolutions as the wheel passes a magnet mounted on the bike's frame. Using the torque and velocity data, an onboard microcontroller calculates the power generated by the rider.
CinQo, which consists of an aluminum part in a molded plastic case, accomplishes that by employing its onboard Nordic Semiconductor nRF24AP1 transceiver and microcontroller. After the MCU calculates the power numbers, the unit's 2.4-GHz transceiver uses the built-in ANT communications protocol to send the data to the handlebar computer, a Garmin Edge 705. A separate transceiver in the computer gathers the wireless data for the display.
“Since we already had the radio in there to pick up the heart rate, we could easily use it to pick up the power data, too” says David Downey, software engineering team leader for Garmin Fitness Products. “Once the speed and cadence sensors started going wireless, this was a logical evolution.”
Many engineers familiar with the technology, however, say the “logical evolution” wouldn't have happened without the ANT protocol. ANT, they say, enables use of a wireless system in bike applications because it consumes so little power. Dynastream engineers, creators of the wireless network, say they did that by configuring the communications code into time-based slots, where each channel is responsible for managing its own slot. Because the system departs from the traditional method of using a global manager, it needs no global clock. That, in turn, means it uses less power.
“Our stack is an order of magnitude smaller than other communications stacks, such as Bluetooth or ZigBee,” says Rod Morris, engineering manager for the Wireless Div. of Dynastream Innovations Inc., a wholly owned subsidiary of Garmin. “And the low power results in low cost because it equates to cheaper parts.”
Moreover, ANT has added a dimension of interoperability to the design of such wireless systems. By creating a so-called “managed network” called ANT+Sport, Dynastream enables developers of wireless sports products to use a de facto standard that provides specifications for their product designs. Dynastream says 43 sports equipment manufacturers, including such major brand names as Garmin, Timex, SRM, Trek, Beurer and Quarq, have already joined the ANT+Sport network. With so many companies in, equipment manufacturers can now focus on the design of a single component, instead of an entire system.
“If you're designing a bike head (computer) and you're a member of ANT+Sport, you could make your bike head work with other heart rate monitors and bike speed sensors,” Morris says. “It's a win-win. You get to sell more bike heads because you have more features. And the makers of the power meters get access to better head computers than they could have made on their own.”
The emerging wireless power meter configurations also benefit consumers. With interoperability, consumers can now select among a variety of bike heads, power meters and heart rate monitors.
“All cyclists have their own idiosyncrasies and preferences,” Morris says. “This lets them select the device that's best for them.”
The technology is also expected to trickle down from the realm of world-class cyclists to the world of weekend warriors and gadget lovers. Suppliers say they expect the wireless power meter to eventually gain rapid adoption in the amateur cycling community.
For now, though, the technology is expected help elite, Olympic-level cyclists. Allen of The Peaks Coaching Group says the wireless power meters are being used by all of his athletes, including Olympic hopefuls such as Bishop and UK road racer Daniel Lloyd, as well as motocross cyclist Amanda Geving.
“When we were in Atlanta (in 1996), you could inspect the course, but you couldn't clearly define the demands of the race,” Allen says. “With power meters, we now know the workload demands. It's a much more quantifiable process.”