POWER MEASUREMENT AND ROAD LOAD DATA ACQUISITION FOR SPEED ... › sd › a › 1c9ee424-a2ae-4c05... · Power Measurement and Road Load Data Acquisition March 2015 Figure 2 / 15

Speed EPACPower Measurement and Road Load Data Acquisition

March 2015 Figure 1 / 15

Dr. Eric Groß, Jorrid Lund, Christoph Petershagen, A nne SchröderTechnische Universität Hamburg-Harburg

Institut für Zuverlässigkeitstechnik

[email protected]

http://www.tu-harburg.de/mec

POWER MEASUREMENT AND ROAD LOAD DATA

ACQUISITION FOR SPEED EPACS

Investigation regarding vehicle structure integrity for cycles designed to pedal

of vehicle category L1e-B and ratio of auxiliary propulsion power and actual pedal power

Refer to document COMMISSION DELEGATED REGULATION (EU) No 3/2014 of 24 October 2013



ANNEX XIX of Regulation (EU) Nr. 168/2013

Requirements regarding vehicle structure integr ity

1.1.1. Vehicles of category L1e-A and cycles designed to pedalof vehicle category L1e-B shall be designed and constructed as to conform with all prescriptions regarding strength and construction of front forks and frames as encompassed in standard EN 14764:2005, specifying safety and performance requirements for the design, assembly, and testing of bicycles and subassemblies intended for use on public roads.

Remark.: EN 14764 does not include „ Frame — Fatigue test with horizontal forces “

Type approval



Type approval

REGULATIONS COMMISSION DELEGATED REGULATION (EU) No 3/2014

of 24 October 2013 supplementing Regulation (EU) No 168/2013 of the European Parliament and of the Council w ith regard to vehicle functional safety requiremen ts for the approval of two- or three-wheel veh icles

and quadricycles

(11) The limitation to ‘four ’ of the ratio of auxiliary propulsion power and actual pedal power for cycles designed to pedal set out in Annex XIX should be subject to further scientific research and assessment. Upon availability of scientific data and statistics on vehicles placed on the market, the ratio ‘four’ referred to above may be revisited in a future revision of this Regulation.



Test vehicles and Metrology

Test vehicle 1: Production Speed-EPAC

• Type/category: Citybike• 500W back wheel hub motor (up to 40 km/h)• Aluminum frame, hydraulic rim brakes• Mass incl. battery 26 kg

Test vehicle 2: Speed-EPAC-Prototype• Type/category: Trekking bike• 350W bottom bracket motor (up to 45 km/h)• Fixed support ratios Pel/PPed from 2/1 to 6/1• Aluminum frame, hydraulic rim brakes• Hub gear• Mass incl. battery 26 kg



Test vehicles and Metrology

Test vehicle 3: Speed-EPAC-Prototype• Type/category: Trekking bike• 500W rear wheel hub motor (up to 45 km/h)• Bang-bang control possible, 900W max• Aluminum frame, suspension fork• Hydraulic disc brakes• Derailleur gears• Mass incl. battery 28 kg

Test vehicle 4: Production Speed-EPAC• Type/category: Fun bike / commuter• Back wheel hub motor (up to 45 km/h), no

power specification from manufacturer• Aluminum frame• Hydraulic disc brakes• Derailleur gears• Mass incl. battery 23,8 kg



Data acquisition

• Conditioning amplifier (strain gauges,current)

• Data logger (max. 16 channels, 4GB memory)

− Sample frequency 1 kHz

− Buffering of data

− read out of data using digital interface

• Analysis-Software

• Strain gauges using full Wheatstone bridge

• Loads on handlebar, front fork,frame and seat post

Load Data

• Inductive current sensor for electric motor

• Forces on crank measured bystrain gauges on frame

• rpm of crank to calculate human power

Power measurement



� Loads measured according to tests as defined in Standards ISO 4210 / EN 14764 / EN 14766 / prEN 15194

� Front fork horizontal – Handlebar – Seat post/saddle – Pedal force

Data acquisition



Intended (normal) Use

Definition: Service loads: Loads during normal use of the EPAC on typical tracks in combination with obtaining environmental conditions.

Special events: Events with a low number of appearances that are part of the normal use and in general can not be affected by the rider.

Test drivers: • female and male• 1,60 m to 1,86 m• 55 kg to 98 kg



Cobblestone irregular (Belgian block) and moved reg ularly, dirt road

Asphalt road and inner city traffic, paved trail (c linker)

Data acquisition – Overview of different road surfac es included in the measurement campaign



� Max. assistance by 3.5 times the human power for mixed service for test bike 1

Power measurement – human power vs. electric assistance

� Approx. 500 W continous rated power as defined for this bike by design

Time response

0.00

800.00

200.00

400.00

600.00

200.00 410.00 250.00 300.00 350.00Time (seconds)

14 : 1X+ 14human power crankS-Pedelec Sparta

21 : 1X+ 21el. power motor

S-Pedelec Sparta

22 : 1X+ 22Speed km/h

S-Pedelec Sparta



Power Measurement - Conclusion

� A limitation of the ratio of the added auxiliary propulsion power dependent on the actual pedal power is necessary to provide a safe handling for starting, during cornering or for low speed cruising. This proved to be a safety issue found during test drives with manipulated control for the electric motor. Without a limitation dangerous driving situations may occur due to too hard unintentional acceleration or the impossibility for slow speed riding.

� For the investigated Speed EPACs where the motor control is kept in original condition a maximum assistance in auxiliary propulsion power by factor of approx. 3.5 is found

� In many driving conditions, especially riding at constant speed, this factor (electric power / human power) is identified by measurements within the range of 1 to 2.

� These factors (maximum of 4, typically at 2) result in good handling and driving experience.

� For speeds between 30 to 40 km/h (cruise speed) for the driver a power requirement of 100 …150 W results – meaning no exhaustion for the driver for longer periods.

� A limitation to a factor of 4 for the auxiliary power by electric assistance as scheduled in regulation (EU) No 3/2014 proved to be very reasonable .



Load Data

� Load histories applied to components are irregular in nature, whereas fatigue test data are usually obtained from constant amplitude loading.

� In order to use test data of irregular load histories for fatigue analysis, load cycles must be extracted.

� Best proven are counting techniques that take into account that for fatigue hysteresiseffects are essential and therefore cycles between the highest peak and lowest valley in the spectrum are combined.

� Most commonly used methods: range-mean-pair and rainflow counting

Front fork

Seat post

Pedalling force

Chain stay(stress)

Handlebar left

Handlebar right

Speed

Motor current

Distance


March 2015

Load spectrum pedalling forces measured distance of 17.7 km

10,0

100,0

1000,0

10000,0

1,E+00 1,E+01 1,E+02 1,E+03 1,E+04 1,E+05 1,E+06 1,E+07 1,E+08

Number of cycles [-]

Fo

rce

[N

]

Woehler k=6,2

Max. load 17.7 km

Load spectrum pedalling forces measured distance of 17.7 km extrapolatet to 1000 km

10,0

100,0

1000,0

10000,0

1,E+00 1,E+01 1,E+02 1,E+03 1,E+04 1,E+05 1,E+06 1,E+07 1,E+08

Number of cycles [-]

Forc

e [

N]

Woehler k=6,2

Max. load 17.7 km

Extrapolation 1000 km

Figure 13 / 15

Example Fatigue Analysis - Rainflow Counting – Extrapo lation by multiplying of events

Test load: 1000 N100 000 LC

Calculation of Damage ratio



Loads for dynamic (100 000 cycles) and static tests of safety relevant components

1) Changes compared to prEN 15194 printed in bold2) Values for standards EN 14766 resp. EN 14764 given

in square brackets

270 N

270 N

270 N

270 N

370 N

370 N 370 N

370 N270 N

270 N

270 N

270 N

370 N

370 N 370 N

370 N

±850 N



• Due to increased speeds the loads caused by road excitation (surface roughness, potholes, cobblestones) in service for Speed EPACs are higher than for EPACs(250 W - 25 km / h).

• Demands acc. to EN 14764 are insufficient , but test methods according to EN 14764, EN 14766, prEN 15194 or ISO 4210 with adopted loads are suitable.

• In normal driving conditions, loads are found only slightly higher than found for EPACs, but the "bandwidth" of loads is quite large influenced by the driver. Based on a sporty driving style of a driver of 95. percentile male the measurements lead to higher damage ratios most notably for front fork, handle bar and seat post.

• Since Speed EPACs are expected to a more frequent use (commuters) and longer driving distances, these should be taken into account for structural testing.

• For an intermixed route profile (mostly asphalt roads, partly cobblestones and rough or unpaved roads) the loads are below or comparable to that of mountain bicycles, so parts that are suitable for mountain bicycles according to Standard EN 14766 are sufficiently dimensioned for Speed EPACs.

Load Data - Conclusion

Documents

POWER MEASUREMENT AND ROAD LOAD DATA ACQUISITION FOR SPEED ... › sd › a › 1c9ee424-a2ae-4c05... · Power Measurement and Road Load Data Acquisition March 2015 Figure 2 / 15