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自行車功率計

維基百科，自由的百科全書
在腳踏車踏板曲柄上的功率計，在左踏板曲柄後方的小盒子有應變片

自行車功率計（cycling power meter）是自行車上量測駕駛者輸出功率的裝置。 大部份的功率計會用應變片來量測力矩，若有角速度的資訊，也可以量測功率[1]。

此技術是在1980年代後期應用在自行車上，也在職業自行車比賽中測試過，當時測試的隊伍是Power Pacer原型（Team Strawberry（英語：Team Strawberry）），選手是格雷格·萊蒙德，使用的設備是SRM（英語：Schoberer Rad Meßtechnik）。此設備已在1989年起商品化，越來越多人使用功率計進行自行車訓練。

功率計也可以用無線通訊的方式，傳輸資料到自行車電腦（英語：Cyclocomputer）、智能手機和智能手錶。自行車功率計可以即時回饋給自行車運動員，可以精準分析騎車過程，也是訓練時很好用的工具。

電動自行車裡也會加裝自行車功率計，根據駕駛者的出力調整的電動機的動力。

介面

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較早期的自行車功率計是使用信號線傳輸功率資訊到自行車電腦，此系統的缺點是自行車上需增加電線，不容易清潔，也需要固定電線的相關機構。

自從2009年起的趨勢是改用無線通訊。自行車功率計常會使用ANT+（英語：ANT+）或是藍牙低功耗協定，也會和標準自行車電腦結合，顯示駕駛者所產生的功率。

技術分類

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大部份的自行車功率計用應變片來量測力矩，若再加上角速度的資訊，可以計算功率。 使用應變片的功率計會安裝在中軸、後freehub（英語：freehub）或牙盤。 有些較新型的功率計不使用應變片，而是用裝在手把上的裝置，利用牛頓運動定律，量測自行車駕駛者受到的阻力（重力、風阻、慣性、滾動阻力） ，再結合速度資訊計算駕駛者的功率輸出。

已隱藏部分未翻譯內容，歡迎參與翻譯。

Crank or spider

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Spider based power meter.

Crank and spider based power meters measure the torque applied through both pedals via strain gauge/s positioned within the crank or crank spider. A calculation of power is derived from the deflection of the strain gauge/s and pedaling cadence. While most crank-based power meters measure the power output of one leg only or need a second sensor to measure the power output of both legs, the spider-based power meters always measure the total power output of both legs.

These units require specific cranks or cranksets but can be relatively simple to interchange between bikes, depending on compatibility.

Pedals

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Pedal based power meters.

Pedal-based power meters can be located either in the pedal axle or in the pedal body. This type of cycling power meter measures the cyclist’s force exactly where it is applied, through one or both pedals. Power meters with sensors on both pedals can provide a real dual-sided power measurement, that is power data gathered individually on both legs. This feature is useful to observe and correct penalizing differences in performance between legs.

Power meter pedals are easy to install and swap across bikes.

Bottom bracket

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File:Ergomo Bottom Bracket.JPG
Bottom bracket with connection cables

Bottom bracket power meters rely on the torsional deflection in the BB shaft. This is done by the shaft having a disc at each end with perforations. These perforations are detected using non-contact photo-electric sensors that detect when torque is applied to the left pedal and then doubled. Data is sent digitally to a handlebar mounted computer unit.

These units are difficult to interchange and require a different bottom bracket unit for each bike.

Freehub

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Hub based power meter.

A Lua錯誤：bad argument #1 to 'gsub' (string expected, got nil)。 power meter uses the same strain gauges that are present in the crank power meters, but it is located in the rear wheel hub and measures the power at the rear wheel. The power measured by a freehub power meter will be slightly less than the power measured by a crank-based power meter due to power losses in the chain, pedals, and bottom bracket. Because freehub power meters are built into the rear wheel, it is simple to interchange them among bikes so long as the wheels are compatible.

Chain

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At the heart of Lua錯誤：bad argument #1 to 'gsub' (string expected, got nil)。 units is essentially a guitar pick-up that mounts to the cycle's chain stay. The pick-up detects chain vibration from which it calculates chain tension which, along with chain speed, gives power output. Finnish company Polar was the first to bring a chain-based power meter to market.

Opposing force

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Opposing force power meters measure hill slope (gravity), bike acceleration (inertia), and sometimes, wind speed. From this, power can be indirectly calculated.

相關條目

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參考資料

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  1. ^ Cycling with a Power Meter. 

外部連結

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取自「https://zh-two.iwiki.icu/w/index.php?title=自行車功率計&oldid=85456099」