自行车功率计
 | 此条目目前正依照其他维基百科上的内容进行翻译。 (2024年11月30日) |
自行车功率计（cycling power meter）是自行车上量测驾驶者输出功率的装置。 大部份的功率计会用应变片来量测力矩，若有角速度的资讯，也可以量测功率[1]。
此技术是在1980年代后期应用在自行车上，也在职业自行车比赛中测试过，当时测试的队伍是Power Pacer原型（Team Strawberry），选手是格雷格·莱蒙德，使用的设备是SRM。此设备已在1989年起商品化，越来越多人使用功率计进行自行车训练。
功率计也可以用无线通讯的方式，传输资料到自行车电脑、智能手机和智能手表。自行车功率计可以即时回馈给自行车运动员，可以精准分析骑车过程，也是训练时很好用的工具。
电动自行车里也会加装自行车功率计，根据驾驶者的出力调整的电动机的动力。
介面
[编辑]较早期的自行车功率计是使用信号线传输功率资讯到自行车电脑，此系统的缺点是自行车上需增加电线，不容易清洁，也需要固定电线的相关机构。
自从2009年起的趋势是改用无线通讯。自行车功率计常会使用ANT+或是蓝牙低功耗协定，也会和标准自行车电脑结合，显示驾驶者所产生的功率。
技术分类
[编辑]大部份的自行车功率计用应变片来量测力矩，若再加上角速度的资讯，可以计算功率。 使用应变片的功率计会安装在中轴、后freehub或牙盘。 有些较新型的功率计不使用应变片，而是用装在手把上的装置，利用牛顿运动定律，量测自行车驾驶者受到的反向力（重力、风阻、惯性、滚动阻力） ，再结合速度资讯计算驾驶者的功率输出。
曲柄或是齿爪
[编辑]
安装在曲柄或齿爪（spider）上的功率计透过应变片量测二个从踏板所施加的力矩。从应变片的形变量以及踏板的踏频可以计算功率。大部份安装在曲柄上的功率计只能量测单侧踏板的力矩，或是需要第二个感测器才能量测两侧踏板的力矩，而安装在齿爪上的功率计可以量测两侧踏板的力矩。
这种功率计需要特殊的曲柄或是齿爪，不过相容性较高的产品，比较容易从自行车上拆下，再装在其他自行车上。
Pedals
[编辑]
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
[编辑]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
[编辑]
A freehub 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
[编辑]At the heart of Bicycle chain 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.
反向力
[编辑]反向力功率计会量测坡度（重力）、自行车加速度（惯性），有时也会量测风速。根据这些资讯间接算出驾驶者输出的功率。
相关条目
[编辑]参考资料
[编辑]外部链接
[编辑]- cycling shoes
- Book: Training and Racing with a Power Meter, 2nd Ed.
- DC Rainmaker - The Power Meters Buyer’s Guide–2016 Edition
- Anhalt, Tom. What's up with those funky rings...?. January 12, 2013.
- Sullivan, Mark. Bicycle Crank Power Meters and Round and Non-Round Chainrings. October 3, 2014.
- Abbiss, C.; Quod, M.; Levin, G.; Martin, D.; Laursen, P. Accuracy of the Velotron Ergometer and SRM Power Meter. International Journal of Sports Medicine. 2009, 30 (2): 107–112. PMID 19177315. doi:10.1055/s-0028-1103285.
- Cullen, L.; Andrew, K.; Lair, K.; Widger, M.; Timson, B. Efficiency of Trained Cyclists Using Circular and Noncircular Chainrings. International Journal of Sports Medicine. 2008, 13 (3): 264–9. PMID 1601563. doi:10.1055/s-2007-1021264.
- Hopker, J.; Myers, S.; Jobson, S. A.; Bruce, W.; Passfield, L. Validity and Reliability of the Wattbike Cycle Ergometer (PDF). International Journal of Sports Medicine. 2010, 31 (10): 731–6. PMID 20665423. doi:10.1055/s-0030-1261968.
- Driss, Tarak; Vandewalle, Henry. The Measurement of Maximal (Anaerobic) Power Output on a Cycle Ergometer: A Critical Review. BioMed Research International. 2013, 2013: 589361. PMC 3773392
. PMID 24073413. doi:10.1155/2013/589361 . - Bini, Rodrigo Rico; Dagnese, Frederico. Noncircular chainrings and pedal to crank interface in cycling: a literature review (PDF). Revista Brasileira de Cineantropometria e Desempenho Humano. 2012, 14 (4): 470–82. doi:10.5007/1980-0037.2012v14n4p470 .
- Strutzenberger, Gerda; Wunsch, Tobias; Kroell, Josef; Dastl, Jacqueline; Schwameder, Hermann. Effect of chainring ovality on joint power during cycling at different workloads and cadences. Sports Biomechanics. 2014, 13 (2): 97–108. PMID 25122995. S2CID 812286. doi:10.1080/14763141.2014.908946.
- powerpod depth review
