Series Hybrid Cycles

Definition

In a 'series hybrid cycle' (SH) or "electronic bicycle"

human power is converted into electric power using a 'pedaled generator'.

In "chainless" SH cycles chain, belt or

shaft drives are substituted by pedaled generators.

SH cycles can be bicycles, tricycles or quadracycles, or they can have

the form of boats or other kinds of machines.

How series hybrid cycles work

For maximum efficiency, during the ride, pedaling power is fed directly

into the electric motor, not into the battery. The battery however delivers

current while the pedaled generator accelerates from stand still to nominal

cadence. The motor of a SH cycle delivers about twice the torque of a

parallel hybrid cycle motor because the SH cycle has to start (on hills)

without the help of a chain or a shaft drive. With SH cycles every mode of

operation is possible between 0 and 100% pedaling effort.

History

The first publication known is from May 1975 and is by Augustus Kinzel (US

Patent 3'884'317). However since there are no power electronics Kinzel's

version of the electrically powered cycle had difficulties to start and

would only work at elevated speed of pedaling and rolling.

The first persons to understand that technology is mature enough for series

hybrid human powered vehicles were Bernie Macdonalds and Thomas Müller in

1994 and 1995. Macdonalds and Müller recognized that brushless electric

machines with modern, strong permanent magnets and power electronics allow

to actually build efficient series hybrid drives. The power electronics load

the generator and allow recuperation of kinetic energy by loading the motor

during braking of the vehicle.

The Electrilite by Macdonalds is not a cycle, but a lightweight commuter

sports vehicle with two seats. The concept dates from 1994 and 1995.

Thomas Müller designed a "Fahrrad mit elektromagnetischem Antrieb" in his

diploma thesis from winter 1994/95 as an industrial designer and actually

built a sporty mountain-bike like bicycle which was test-ridden already at

this time!

At Berne University of Applied Sciences Jürg Blatter and Andreas Fuchs built

a ridable bicycle with pedal generator to simplify a complex

electro-mechanical human-electric hybrid drive of an ultra-lightweight

mobile somewhat similar to Electrilite but with only one passenger seat,

built during winter 1995/96. The early work is documented in "Bicycling

Science" 3 by D.G. Wilson, third edition, or in the proceedings of the 1999

Velomobile Seminar on "Assisted Human Powered Vehicles". In 1998 the drive

with pedal generator was mounted onto a Leitra chassis where it continued to

work reliably for years.

In the 1999 Velomobile Seminar proceedings Harald Kutzke describes his

concept of the "active bicycle". Part of the concept is that an active

bicycle compensates the losses and the drag associated with the bicycle, but

not of the rider: Aim is to electronically approach the ideal bicycle

weighing nothing and having no drag at all. In Hannes Neuperts book "Das

Powerbike" Kutzke wrote about this topic under the title of the so called

"Electronic-Bike".

Since a pedaled generator can be built as lightweight as a chain drive it

has very low rotational inertia and therefore, upon start of pedaling, the

pedal starts much faster than on a bicycle with chain. Such acceleration is

too quick to be ergonomical. Therefore Andreas Fuchs worked on solutions to

this problem which is described e.g. in patent EP 1165188.

For Swissmove, Peter Lacher built power electronics which

allow to sufficiently brake the pedal of a two-wheeled working model so

that ergonomical starting behavior of a series hybrid bike

can be realized using a reasonably sized electric machine.

In 2008, Peter Lacher also implemented CAN Open for communication

with a well working motor controller. This step allowed to improve

the two-wheeler which now runs very well.

Until 2008 five series hybrid bikes, trikes and quadracycles with ever

improving components have been built.

According to experiences from test rides range per Watt-hour battery capacity is as good

as in traditional electric bicycles because human and electric drive

do not interfere by mechanical means.

Andreas Fuchs

updated Dec 2015

THOUGHT

The series hybrid bike drive system as a plattform

If the components of a series hybrid drive system are linked with a bus system (such as e.g. energybus, or industrial ethernet, ...) the complete drive system is transparent to e.g. tools for monitoring and parameterisation. In the series hybrid drive system human pedal power is converted to electrical form, and in electrical form it is easier to measure and control. Previously only in mechanical form available parameters are measurable, and this without having to use complex and expensive sensors such as torque sensors or traditional power meters.

If there are gateways to the world of mobile communication and the internet, the vehicle becomes remotely transparent also to the user and/or the supplier and/or the entity that operates e.g. such vehicles as public or shared vehicles or the organisation that maintains the vehicle(s) and keeps them up and running.

Dataloggers, mobile devices like smartphones or direct or asynchronous cloud-connectivity allow to sample massive data. Once the data is available, methods of data analysis, also learing algorithms may be applied. Computing power and storage today is cheap so such may happen on bord of the vehicle or in a mobile device, or, since also the price for connectivity drops more and more, analyses may be done in the cloud.

The advantages are manifold:

- Theft may be better avoided thanks to tracking of the vehicle

- Energy supply may be remotely supervised to maximize disposability

- Maintenance may happen based on monitoring and predictions. Such data allows to maximize the life span of components and can help lower life cycle costs. E.g. the battery may be managed in ways as to maximize its useful life cycle

- The components of the drive system may be optimized based on such data

- System control and the ergonomics of this chainless pedalled vehicle, the series hybrid cycle, can be optimized

- Training and rehabilitation of the rider(s) can be monitored and optimized. The behaviour of the vehicle and especially of the pedal(s) can be tailored according to the specific needs or wishes of the user

- etc.

Andreas Fuchs, October 30, 2016

Articles

An article that was published later in Bike Europe Oct 2012:

Draft: Berne, May 29, 2012

Electronic Bicycles are free of Costs for (automated) mechanical Transmissions

Dr.phil.nat Andreas Fuchs, Berne, Switzerland

Electronic bicycles work like pedelecs or e-bikes, but human power is converted into electricity rather than being transmitted to the drive-wheel by a mechanical element such as a chain, a belt or a shaft. The unit that converts human power into electricity could be called pedal-generator. If the motor that drives the wheel is rotating, the current generated by the pedal-generator is going directly into the motor. If the vehicle is standing, the generator-current is fed into the battery and is hence stored.

A pedal-generator is an encapsulated module consisting of pedals, a single speed gear, a generator as well as power-electronics. The pedal-generator completely substitutes the set of components for drives of mechanical and electromechanical respectively pedelec or electric bicycles. So, in order to build an electronic bicycle, one only needs four modules: one pedal-generator, one drive-module such as for example a hubmotor, a storage element such as a battery, and a human machine interface HMI. These modules are connected by a wire-harness. Mechanical elements like bowden cables and chains are absent, except maybe for the brakes.

Electronic Bicycles have a software-defined Drive-System

Once human power is converted into electricity, it is much easier to handle than in its mechanical form. Torque and cadence and thus pedal power are measured by the power-electronics of the pedalgenerator. No additional sensors such as the pedal torque sensor like in electromechanical pedelecs are needed. Human power in electric form can be fed into any number of motors, or it can be stored in the battery, for example during fast descents the rider can continue to pedal.

In dependence of pedal-cadence and generator-current set-values for speed and torque of the drivemotor can be calculated. This is how the pedelec behavior comes into existence in the chainless drivesystem of an electronic bicycle. Usually, an electronic bicycle transmission is operated the way an automated CVT works (CVT: continuously variable transmission) – no changing of mechanical gears at all! The pedal-generator has a speed range from 0 km/h up to maximum speed, whatever that is. In comparison, mechanical gears have a lower and a higher speed limit of their range of operation. In electronic bicycles, the resistance against pedaling is defined by the power-electronics of the generator. In order to make pedaling interesting, a software defined feedback makes the “pedal-feel” dependant on what is happening at the drive-wheel. More resistance at the wheel can then be felt in the form of more resistance at the pedal.

Electronic Pedal

Since the power-electronics of the pedal-generator-module allow to operate the electric machine in the pedal-generator both as a generator or as a motor, many functions not possible with a mechanical pedal can be realized. Working models built in Berne by friends of mine and myself for example keep pedal speed constant through one single pedal revolution. There is no “dead-point” anymore. Effects like the one by elliptical chain wheels could be simulated. Pedaling backwards but driving forward is possible. The generator operated as a motor can help a weak leg over its “dead-point”, while at the same time the other “strong leg” is braked harder. So individual training of legs becomes a possibility.

History

Do you think this is science fiction? It is not! Since the 90ties, in Berne, Switzerland, people around Andreas Fuchs have built five working models that all ran. A significant contribution to the invention of the electronic bicycle was by Thomas Müller, a german student of industrial design, who actually built an electronic bicycle in the time period 1994-95. However, the power-electronics he used did not work as expected. It is the merit of the bernese researchers to have built the first electronic bicycle in 1996-97 with properly working power-electronics. In a time period that ended in 2005 most basic concepts and features of the chainless transmission, the pedal-generator, the series hybrid drive for electric bicycles or the electronic bicycle – however you want to call it – were studied. After 2005, Andreas Fuchs mainly concentrated on figuring out how pedal-generators and wheel-drive-modules for electronic bicycles with a good price-performance-ratio could be made. Now, the concepts have been developed so far that industrialization of the electronic bicycle could start.

Weight, Efficiency and Costs of Electronic Bicycles

For about the WEIGHT of a complete drive train of a mechanical bicycle including also a chain guard, that is between 4 and 5kg’s, it is possible to build a pedal-generator that can even brake an average standing human pedaler hard enough. Braking torque and thus weight can be reduced if the pedaler is sitting on the saddle. A pedal-generator for a tricycle and quadracycle can even be made more lightweight, since there the weight of the human can fully be supported by a seat.

In an electronic bicycle the drive-motor has to be able to push it up the hills without the help of a chain, belt or shaft drive. Fuchs recently finished a feasibility study for a strong geared hubmotor able to climb continuously 8 to 10 percent of slope without overheating, weighing less than 5 kg.

EFFICIENCY is the topic where the author encounters the biggest disbelief. One part of the story is, that many people overestimate the efficiency of mechanical bicycle drive trains. An other part of the story is, that combining two drives into a hybrid as is done in pedelecs always comes at a cost, also an energetically one. Therefore even so called “experts” believe that the efficiency of drives of electronic bicycles would be comparably too low. The author and colleagues believed this too, until they rode the first working model – then they started to rethink the whole concept and since then never stopped working on it!

In order to understand the issue of efficiency, let us consider the widespread bottom bracket motor. If pedelecs equipped with such a bottom bracket motor are operated more like a mechanical bicycle, that is if electric power is low compared to human power, efficiency is good. It is then close to the efficiency of a standard, non-electrified bicycle. However, if lots of electric power is transmitted by the mechanical drive train in addition to human power, overall efficiency drops. This is because electric power has to go through a very long transmission, from the battery through many elements before reaching the chain drive and finally the drive-wheel and the street.

In electronic bicycles, the situation regarding efficiency is like mirrored compared to bottom bracket motors. Under mainly electric power, efficiency is as good as can be in an electric moped or scooter. The transmission from battery to wheel is very short, chances for energetic losses are minimal. Under mainly human power, overall efficiency is lower because human power is converted from mechanical to electrical, is then fed into the intermediate electrical circuit that leads to the motor controller and motor. So a conclusion could be that electrical bicycles with bottom bracket motor are comparably better for touring since on tours, human power is dominant. One can always go on even with a fully discharged battery thanks to the mechanical transmission. An electronic bike with pedal-generator and hence chainless transmission however may be more suitable as an urban pedelec, to pull trailers, as a cargo ebike, as a fast pedelec and as a climber in hilly or alpine regions since in all these use-patterns acceleration is statistically very prominent compared to constant speed. According to the tests by extraenergy the ratio of electric to human power is in most pedelecs anyway between 1 and 2, and hence it makes a lot of sense to have maximum efficiency in the transmission for electric energy as is the case in electronic bicycles.

Measurements show that in electronic bicycles energy spent from the battery per unit distance (Wh/km) is in the range found in electromechanical pedelecs and e-bikes. The reason is that user behavior influences the Wh/km of electromechancial drives very much in that chosen gear and chosen cadence and pedaling torque have a huge influence on energy use. In electronical bicycles the rider can choose from many different software defined riding programmes, but he or she cannot choose wrong gears and suboptimal cadences and pedaling torques because there are no mechanical gears at all.

A comparison of the COSTS per piece can easily be made, because a pedal-generator substitutes a complete mechanical bicycle drive train. The rest of the components, the battery, the motor and the HMI are quite similar both in electric and electronic bicycles. Of course the motor of the electronic bicycle needs to be stronger, but according to the Fuchs feasibility study the cost differential between a weak motor and a strong motor does not need to be big.

If a mechanical drive train is very low-cost, an electronic bike will cost more than an electromechancial pedelec or e-bike. However, if the mechanical drive train consists of high end components such as (automated) multi-speed internal hub gears or (automated) CVT’s, electronic bicycles become cheaper. The cost comparison is even more in favor of the electronic bicycle if maintenance costs are taken into account. Chains and toothed wheels wear out and have to be replaced up to several times throughout the life of an electric bicycle, whereas the encapsulated modules of an electronic bicycle can be made to work maintenance free for years.

However, the real big cost savings will come all along the value-chain of electric bicycles.Electromechanical hybrids like today’s pedelecs and e-bikes have two drives in parallel: the mechanical and the electrical drive. Designing two drives in parallel into a bicycle, and prototyping, purchasing, storing, assembling, maintaining and recycling those two drives is of course more expensive than doing the whole process using one integrated drive like in the electronic bicycle only, consisting of a mere four modules and a wire-harness.

The Future of Electronic Bicycles

The feasibility of the electronic bicycle is given, and the technology is available to actually industrialize it. Question is now merely: Who will be the first to market an electronic bicycle, and who will be the followers? The author assumes that there are quite some factors that will motivate companies to actually enter the field of electronic bicycles soon.

Fact is that industrial designers foresee hidden or eliminated mechanical transmissions in order to arrive at urban vehicles that are very ergonomical, that is, easy to operate, have highest reliability and minimal maintenance cost at the same time. Submissions into bicycle design competitions often have faired transmission elements, and quite many industrial designers were or are in correspondence with the author. Of course totally new designs are possible if there are no mechanical transmissions at all: It is easier to hide a wire-harness than it is to hide a chain or a belt!

Another factor is that it is cheaper to build electronic bicycles than some kinds of pedelecs. Electronic bicycles have by default the functionality that can be reached by combining bottom bracket motors and automated mechanical CVTs, but at much lower parts count, and hence lower cost. In addition to that, it is cheaper to define new functions in software rather than to build hardware to realize a function.

At the moment many new players enter the field of electric bicycles. Competition will intensify, and as a consequence some companies will try to find possibilities to leap forward, to bring new bicycle designs with nicely integrated drive-systems. For sure, the electronic bicycle is a way to do a giant step forward while keeping the costs confined.

Contributions to Conferences:

Blatter Jürg und Fuchs Andreas. Vollelektrischer Muskelkraft-Elektro-Hybridantriebsstrang. Reader for the workshop participants on March 13, 1998, at the University of Applied Sciences Berne, HTA Bern, named ISBE

Fuchs Andreas und Blatter Jürg. Zweck und Einsatzbereiche von kettenlosen Muskelkraft-Elektro-Hybridantrieben in schnellen Fahrrädern, Velomobilen und Ultraleichtmobilen. Konferenzband des Extra Energy Symposium, IFMA Köln, Sept./Okt. 1998 (german and english)

Blatter Jürg und Fuchs Andreas. Vollelektrische Muskelkrafttransmission für Ultraleichtmobile. Konferenzband des Extra Energy Symposium, IFMA Köln Sept./Okt. 1998 (german and english)

Fuchs Andreas. Chainless Electrical Human-Power Transmissions and their likely Applications. Proceedings of the 1999 Velomobile Seminar, Future Bike Switzerland, 1999

Luc Bergeron, Laurent Clement, Fuchs Andreas. Urban Quadracycle. Proceedings of the 1999 Velomobile Seminar, Future Bike Switzerland, 1999

Fuchs Andreas, und Blatter Jürg. Steuerung mit CAN-Bus für Hybridfahrzeuge oder Anlagen und Geräte mit dezentralen Steuerungsaufgaben. Automotive Day 2001, ACN-CH, HTA Biel, 14.11.2001

Blatter Jürg, and Fuchs Andreas W. The smallest series-hybrid vehicle in the world is a PowerNet compatible, fully electronical, chainless cycle! Published in: Graf, Alfons, The New Automotive 42V PowerNet Becomes Reality. Stepping into Mass Production. In coop. w. 24 co-authors, 2003, ISBN 3-8169-2170-1

Fuchs Andreas. Modular Propulsion System for Series Hybrid Electronic Cycles, Series Hybrid Scooters and many other kinds of small Vehicles. Proceedings of EVS 20, Long Beach, 2003

Fuchs Andreas. Series Hybrid Drive-System: Advantages for Velomobiles. Published in:

a) «Atelier 3: Vélomobiles ou l’extension du domaine du cycliste, 8ème Journée d’Etude de la FUBicy», Vendredi 21 Avril 2006, in Amiens, France

b) www.hupi.org, Mai 2008

Fuchs Andreas. Principles of Human-Electric Hybrid Drives for Human Powered Vehicles. Paper for the 6th European Seminar on Velomobile Design, Copenhagen, October 16-17, 2009

Andreas Fuchs, Digital Drive Systems - "The electronic pedal“ (Series Hybrid EB). LEV Components Special Exhibition, EUROBIKE, Friedrichshafen, August 27 – August 30, 2014

Andreas Fuchs, Das kettenlose Lastenrad: Zwischenbericht vom Weg von der Vision zur Realität. CarVe.2014, Cargo Bike Konferenz, Bern, 2.9.2014

Andreas Fuchs, Zahlreiche Anwendungen rufen nach industriealisierten, digitalen Fahrrad-Antrieben. E-Bike Festival, Kitzbüheler Alpen, E-Bike Fachkongress, 10.7.2015, Hotel Alpenhof, Kirchberg, Tirol

Editor of conference proceedings:

Fuchs Andreas and Theo Schmidt (Editors). Assisted Human Powered Vehicles. Proceedings of the 4th Velomobile Seminar, Interlaken, Futurebike CH, 1999

Articles in trade or specialty journals:

Fuchs Andreas and Blatter Jürg. Chain reaction. Bike Culture 15, Spring 1998

Fuchs Andreas und Blatter Jürg. Kettenreaktion. Bike Culture 15, Frühling 1998

Fuchs Andreas. Neuartige Transmission für wettergeschützte Elektrofahrräder. Info-Bit 2/98

Fuchs Andreas. Elektrische Fahrradtransmission an internationaler Fahrradmesse. Info-Bit 2/99

Fuchs Andreas. Are Electronic Bikes Truly Revolutionary? Bike Europe, Vol. 16, No. 10, October 2012

R&D Report:

Fuchs Andreas. E-Management-Integration – Serie Hybrid E-Fahrrad-Antrieb. Final report, Swiss Federal Agency of Energy, 2005

Master Thesis (FES cycling using a pedal generator, and very likely a tricycle, or quadricycle):

Fuchs Andreas. Application of Human Electric Series Hybrid Vehicles in Neuro-Rehabilitation. Master Thesis, Swiss Federal Institute of Technology, Zürich, 2008

In a book:

In Bicycling Science, Third Edition: Electrical transmission by Blatter and Fuchs described, p. 337 to 340

PEDAL-GENERATORS

Pedal-Generators have two main functions:

1. Allow intuitive interaction of human and machine. In that respect, a pedal-generator is a

human-machine-interface HMI. Using a pedal-generator allows training.

2. Generate electricity

A pedal-generator can be combined with numerous applications using electrical energy. Batteries or

supercapacitors can store energy for later use.

Dependent on how much energy an application needs, the energetical contribution by pedaling a pedal-

generator can range inbetween significant and neglegible.

Significant energy contribution:

Propel light electric vehicles, e.g. series hybrid pedelecs

Feed systems of LED lighting

Recharge mobile devices like radios, phones, GPS

Propel winches e.g. on sailboats

Emergency power for yachts or other remote places (supercapacitors instead of batteries for reduced

ageing)

Training on stationary apparatus. No flywheel is required, therefore training apparatus with pedal-

generators are compact and easy to stow away. E.g. training on bord of passenger aircraft - pedal

generators could be flanged to the seats - may help prevent thrombosis

Some energy contribution:

In some vehicles, the electricity generated by pedal-generators can still be significant to operate

auxiliary devices like lights, e.g. in a vehicle like the Twike

Negligible energy contribution, but still relevant as a human machine interface:

Control, e.g. accelerate, propel or brake heavy vehicles, e.g. supertankers. The pedal-generator as an

HMI can "display" vehicle inertia to the operator

The electrical energy can be used to run motors, fans, lights, music equipment, to recharge batteries,

etc. Using inverters the energy could even be fed into the electrical grid.

Andreas Fuchs, 2020 May 12

SINGLE OR A MORE PEDAL-GENERATORS IN AN APPLICATION

There might be a single pedal-generator e.g. in a single seater vehicle, or more pedal-generators e.g. in one boat or in a bunch of pedal- generators set up for stationary training.

There are two cases:

a) The set value for cadence of a pedal-generator is calculated per pedal-generator individually (one inertia modeler per pedal-generator).

b) All pedal-generators share the same inertia modeler and then are hence synced in pedal speed.

PS. Please note: This information is not free to be used commercially since not free of IP rights

Andreas Fuchs, 2021 April 11

A Thought about Series Hybrid All-Wheel-Drive Mountain Bikes or Off-Road Vehicles

Especially for off-road vehicles, the implementation of traction control and anti-lock braking, electronic differentials etc. makes a lot of sense.

Since the surface of the ground encountered while riding such vehicles off-road varies widely, it makes sense to implement a wide spectrum of operational or driving modes. On one hand the ground may be very uneven, full of objects the wheels have to climb over, or, on the other end of the extremes, the ground may be very slushy and slippery.

The extremes of the spectrum of modes will be given by:

1. Direct coupling of pedal and traction wheel(s)

In order to ride on very uneven ground, to e.g. climb over roots and stones, a direct coupling of pedal and traction wheel(s) as if the vehicle had a mechanical transmission (chain, belt, shaft) makes sense.

2. Total mechanical decoupling of pedal and traction wheel(s), but recoupling by software, allowing to vary the degree of coupling digitally

Such a mode allows all necessary tricks like traction control to assure that the wheels driven by motors do at most slip minimally. Thanks to smart control of the pedal(s) of such an off-road vehicle, e.g. in the form of an AWD SH eMTB, the ergonomics of pushing the pedal(s) are still very good and the haptic impression is very bicycle-like and nice.

Andreas Fuchs, Belp, 2025 March 22

Links

Basic thoughts about the hybridisation of human and electric motor:

http://liggecykelforeningen.dk/designseminar/parallelhybriddrive

The electronic cycle:

www.futurebike.ch/images/1_wsj_shorter_1.pdf

Research about series hybrid tricycles (8 Mbyte report for download):

www.bfe.admin.ch/dokumentation/energieforschung/index.html?lang=fr&project=45975

http://www.bfe.admin.ch/php/modules/enet/streamfile.php?file=000000009153.pdf&name=000000250117.pdf

Also downloadable pdf’s under this link:

http://www.hupi.org/HPeJ/0015/0015.html

Presentations: