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Prototype Bicycle Power Meter
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Bolton Engineering, Inc. worked with CC Kinetics, Inc. to develop the first embedded prototype of a proprietary passive Bicycle Power Meter. Code named “The Twanger” during development, the Power Meter measures the power transmitted through the Bicycle drive chain by monitoring the chain resonant frequency and the chain speed. |
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System
Overview
The “Twanger” Bicycle
Power Meter uses Digital Signal Processing (DSP) to compute
power by passively monitoring a bicycle chain. Unlike competing
power meters that require users to replace key bicycle components
with custom ones containing strain gauges, the “Twanger”
measures the power transmitted through the Bicycle drive
chain by monitoring the chain resonant frequency and the
chain speed.
Power is the product of force and speed. In a bicycle, transmitted
power is the product of the tension of the upper chain run
and the chain speed. Speed can be directly detected by monitoring
the links as they pass a sensor. Chain tension can be derived
from the frequency of vibration of the chain, which depends
only on the tension, and the fixed parameters of mass and
length.
Project Scope
Bolton Engineering, Inc. worked with CC Kinetics
to develop a prototype based on a Texas Instruments (TI)
DSP that could be tested on an actual bicycle. A Bolton
Engineering software engineer took the original development
code and converted it to run on the chosen low-power Texas
Instruments DSP. TI signal processing libraries were used
to streamline the development process.
Bolton Engineering, Inc. also allowed CC Kinetics use of
its office space to demonstrate the product to prospective
investors and to prospective licensees. Subsequently, the
“Twanger” technology was patented (US patent
6,199.021) and licensed to Polar, and is now available as
the Polar “Power Tap.”
Note: Bolton Engineering did not play an active role in
the final design of the final Polar Power Tap, which was
designed from scratch by Polar Electro. See more information
here.
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Consumer and Computer
