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Digital Drive Systems -„The electronic pedal“
(Series Hybrid EB)
LEV Components Special Exhibition
EUROBIKE, Friedrichshafen, August 27 – August 30, 2014
Andreas Fuchs, PhD, MAS ETH MP, Berne, Switzerland
Basic Configuration of Digital Drives
Wheel
Battery
Pedal Generator =
Converter:
Human Power → Electricity
Pedal generator also:- Torque sensor
- Part of the HMI: „displays“ a „software-designed„ pedalling
feel
- Motor: e.g. helps weak legsover „dead-point“
Remarks
- Charging of battery only if motor is standing or if there ismore human power than momentaneous drive power- Strong electrical braking possible
Pedelec with Digital Drive (Design Harald Kutzke)
Pedal Generator
- no chain anymore!
What is a Digital Drive?
Integrated, mechanically extremely simple drive-system for human-electric hybrids
If an e-bike/pedelec has an electrical motor anyway, why not convert human power into electrical
power?
Series Hybrid Drive, SHEB (Jamerson)„The series hybrid e-bike is among the "5 very new
products" ".... that could have a significant
impact on the design and technology of futureElectric Bikes„
(Today‘s e-Bikes/Pedelecs: PHEB, Parallel Hybrid)
Harald Kutzke: electronical or active bicycle
Hannes Neupert: Digital Drive
No 1:1 replacementof chain or belt
Technical naming
Other names
Two mechatronical Modules only make a Digital Drive
Pedal
Generator
Hub Motor or drive-swing-arm
Shaft Rotating: Pedal Standing
(Gears) 1:1 or 1:x 1:1 or x:1
Electrical
Machine
Generator-Motor Motor-Generator
Power Electronics Multi-Quadrant Multi-Quadrant
Casing Standing Rotating:
Hub body with spoke flanges
(and a battery and a wire harness)
State of the Art Technologies (=> feasible!) :• Electrical machines and power electronics having a sufficiently wide dynamic range
• Embedded software & industrial communication (e.g. energybus)
• Control of the components and the digital drive system, being inspired from the fieldsof human-machine-interaction, e.g. gaming, rehabilitation robotics, …
• Connectivity straightforward since human power is in electrical form
Pedal Generator Module schematically
≈
= Electrical Energy
Exchange with
DC-circuit
(motor/battery)
Information Exchange
with drive system
(bus, e.g. energybus)
Generator Control
Power Electronics,
multiquadrant,
„Gears“
mechanical
up-gearingGenerator-
Motor
Pedal-
Generator
Module
Pedal
Digital Drive Feasibility given (Track Record A. Fuchs)
� Conceptual models and calculations /
simulations / requirements specifications
� Ergonomics and biomechanics – safety andpedalling-mechanism / feel ! – well studied
� Calculations to compare „with/without chain“:
energetical losses and motor temperature
� Testing driveable working models
� Benchmark-tests „with/without chain“ (Wh/km from the battery same order of magnitude)
� Pedal generator and hub motor designs
� Concepts for ICT-architecture, connectivity(for communicatione.g. energybus)
� Other uses, e.g. rehabilitation, evaluated
� Different publications, ip, talks, workshops
� Networking and discussions with quite somedesigners, experts and interested consumers…
Several working„working models“
built & tested
Digital Drive on a Trike (Working Model, 2005)
Working model with already quite nicely integratedcomponents
(TWO WHEELERS are also possible!)
Advantages for the Rider
� Very simple, fully automated
� No chain / better traction: no torque ripple
� Better, since no mech. Transmission
� No manual gears interfering with dynamicriding
� Better predictable since no manual gearsand unoptimal choice of gears
� Stronger braking, more recuperation
� Low (brake pads and tires)
� Higher since no mechanical constraints(software-defined product)
� Estimated to be lower at same degree ofautomation
Ease of Use
Safety
Cleanliness & Foldability
Dynamics
Range
Recuperation
Maintenance
Functionality
Cost
Advantages of an „Electronic Pedal“
� Infinite: 0 to ∞
� Short, automated process. Steady power flow, no interruptions by gear-changing
� Automated by default, at no add. cost
� No mechanical transmission elements„catching“ clothing
� Ease of useLoading of human in optimal ways
� Electronic control allows things like e.g.:- avoid „dead-point“ in pedal circle- simulate elliptical chainrings- electronically limiting the loading oflimbs and links e.g. during rehabilitation
� Measured by default
Gear Range
Starting
Automation
Safety
Ergonomics
Biomechanics
Pedal Power
Wise Foresight by Designers 1
Harald Kutzke, 90ties
Active Bicycle
Wise Foresight by Designers 2
www.thomasstuder.com, 2004
Moby, shopping/cargo Trike
Wise Foresight by Designers 3
Design: Bergeron et. al., 1999
Urban Quadracycle
Efficiency – Some Remarks
� Efficiency is not a series hybrid bike “killing –factor”
� Because “efficiency” is used as a thought-terminating cliché by some we nevertheless discuss efficiency
� Consumers and some in the bicycle industry seem to overestimate (e-)bicycle efficiency and to underestimate series hybrid bicycle efficiency
More important than „efficiency“ is:
� Whether or not a vehicle has practicalapplications and works under real conditions
� Cost, volume, weight: limited
� New options by the „electronic pedal“
Remarks
What finally counts…
Efficiency: Human, Transmission
� Human efficiency the higher the more steady
the load.
Chained E-Bike: Good „load levelling device“
Series Hybrid: Best „load levelling device“
(least mechanical constraints, by defaultautomated)
� Kutzke, Fuchs, Couque, etc. noted this fact
� Savaresi et al showed effect of „load levelling“
in recent scientific work
http://www.datei.de/public/extraenergy/2014-
EnergyBus/savaresi_china-cycle_2014.pdf
� Battery to wheel: highest efficiency
� Human / Pedal to DC-intermediate circuit / battery: efficiency ok
� „Weighted efficiency“ comparably good
(weighting-factor = assist ratio)
Human
SHEB Transmission
Power-Flow Diagrams, BB Motor and SHEB
Human
Battery
Wheel
Bottom
Bracket
Battery
Human
Wheel
DC-Circuit/
Battery
Bottom
Bracket Motor
Digital Drive
(SHEB)
Chain,
belt, shaft
Pedal
Generator
Efficiency Comparison (schematically)
1:1Electric / Human Power
4:1Electric / Human Power
„Bicycle Mode“ „Moped Mode“Typical Range of Op. of e-Bikes/Pedelecs
„W
eig
hte
dE
ffic
ien
cy“
100%
50%
Bottom Bracket Motor
Digi Drive SHEB
(If gears, they would be included in Eff_genor Eff_mot)
Energy Budget
� When starting to pedal, human in optimal load point within a short time only (no time lost by changing gears) ⇒ „Produces“ energy efficiently very soon after starting
� Battery between human and wheel allowsto store any excess (kinetic) energy atwheel or at pedal:- “Energy banking”: If (traction power < pedal power)- Recuperation, no mechanical freewheelbetween wheel and traction motor/battery- Hard electrical braking due to strong wheel-driving motor(s) –the battery is the limit!
Dynamics
Energy storage
Published Benchmark
Speed (km/h) versus Range (km):
Figure 12 („Abb 12“) from: Fuchs Andreas. E-Management-Integration – Serie Hybrid E-Fahrrad-Antrieb. Final report, OFEN/ BFE, 2005
(Downloadable: See link in the appendix)
Legend:
Green circle: E-Bikes,
extraenergy test
2001/02, no pedalling
Red rectangle: Same
E-Bikes, with pedalling
Blue diamonds: SH working model, no
pedalling
Yellow triangles: SH working model,
pedalling
FAQ‘s
� Pedal generator and wire harnessreplace chain / belt / shaft, and internalhub gears or gears with derailleur
� Weight pedal generator ≈ Weight of chaindrive including gears, bowden cables, chain protection, etc.
� Prevents the pedal from having too littleresistance torque e.g. when starting topedal (advantage of the chain: transmitstorque very efficiently at 0 rpm)
� Allows the design of the pedalling-feel so that pedalling is „natural“
⇒ „Pedallingfeel-Design“ via Software
Weight
Control
Mechanical Complexity File Complexity_2a.xls
Andreas Fuchs PhD
Less Parts and simpler Processes File CostDiff_V2c.xls
Andreas Fuchs PhD
Cost Comparison
� You may use your own costs and use thetable on transparency 22 to calculate thedifference in cost between„electromechanical“ and „digital“ bikes
� Digital Bikes have less parts
� Assembly is simpler because there is oneintegrated drive only rather than a mechanical drive AND an electrical drive
� If the reference are automated e-bicycles:Digital Bike less costly
� If the production of the Digital Bike drivesystem is optimized: Digital Bike less costly, even when comparing tonon-automated e-bicycles
Remark
Author‘s preliminaryConclusion
Bicycle Industry: Development of Drives
19th century 20th century 21th century
Me
ch
an
ica
lC
om
ple
xit
y
Internal
gears Internal gears
with >3 gears
Automation
of gears
Modern electric drives in e-bikes
Lithium batteries
Electric
Bicycles
Electronic BicycleSHEB
Digital Bike
MechanicalBicycle
Electro-mechanical
Bicycle, PHEB
Andreas Fuchs, PhD, 2014
Derailleurs
New
Dimensions!�Functionality
versus
Simplicity�Performance
versus Cost
Now 3 Classes of Human Powered Vehicles
The mechanical
bicycle
The electromechanicalbicycle, today‘s
„eBikes / Pedelecs“
The electr(on)ical or
„digital“ bicycle
A classic: simple and
beautiful. Excellent,
remaining excellent !
Booming. Complexproduction since
„hybrid“: two
technologies in parallel
Mechanically simple, integrated, highly
functionally since
programmable
Key competence:
Mechanics
Key competences:Mechanics & electrical
engineering & sensor
technology
Key competences:Mechatronics &
power electronics
& software
Now coming!
Summary
� Is coming now(technically and economically feasible)
� Mechanically simplest „bicycle“ drive� Best (ICT) architecture to be „connected“� Highly dynamical adaptation to riding conditions:
load levelling for the rider, uninterrupted tractionforce at the wheel since no „disturbing“ bicyclegears
� Nicest vehicle designs possible
� Easy to operate� Minimal maintenance� Minimal cost (basis: automated e-bikes/pedelecs)� Urban e-bikes/pedelecs (commuting, shopping)� Public bikes
� Fitness bikes� Where chains are a hindrance: Folders, specialty
bicycles like velomobiles� Good climbers or pulling machines: Trailers,
Cargo Bikes� Solar-pedal boats etc.
Digital Drive
User friendlyness
Cost
Ideal applications
Links & References
Fuchs Andreas. Are Electronic Bikes TrulyRevolutionary? Bike Europe, Oct 2012
http://issuu.com/mark77a/docs/bike_europe_october__12__compressed_
http://www.bfe.admin.ch/php/modules/enet/streamfile.php?file=000000009153.pdf&name=000000250117.pdf
Designs by Harald Kutzke, p. 128/129, in:
Neupert, Das Powerbike, 1997
Overview
Benchmark chain / chainless, „Abb. 12“ in:
Early Designs
