Advanced Motorcycle Development – from engine, vehicle structure

Advanced Motorcycle Development –
from engine, vehicle structure and safety to
electronics and design
Cornel Stan
Introduction
The diversity of motorcycles from scooter, tourer, chopper and enduro to
supersport and racing leads to numerous particular solutions for engine, vehicle
structure and dynamics or safety concept. The motorcycle is a remarkable
argument for the development of technics and technologies. The technique
began with an ingenious two-wheeler, not far away from a bicycle, but even with
engine, as shown in Fig. 1. This first type in series production worldwide (1894)
is on the origin of the name of motorcycle (motorrad in german), patented in
1897 by Wolfmüller.
Fig. 1
First motorcycle in series production worldwide
On the other hand, the technology began as illustrated in Fig. 2, by the example
of the workshop of Wilhelm Maybach (1895).
Fig. 2
Wilhelm Maybach – the Co-Developer of the Ride-Bike with Petrol
Engine (1895)
During eleven decencies the requirements to a two-wheeler strongly changed
[1] – as mentioned in Fig. 3:
Fig. 3
Requirements to advanced motorcycles
The characteristics with crucial importance for every kind of motorcycle are the
weight-to-power ratio as well as the systems and measures for active and
passive safety.
The decrease of the weight-to-power ratio in all motorcycle type classes in the
last years, as illustrated in Fig. 4 demonstrates a strong technical development
[2].
Fig. 4
Time related development of the weight-to-power ratio of different
motorcycles types (BMW)
Much more impressive and important appears the decrease of mortal incidents
(Mrd. Km per year) as shown in Fig. 5 in base on statistical data for Germany.
Fig. 5
Mortal incidents in Germany per Mrd. km per year (BMW)
Furthermore, the spirit of the time recommends an appropriate motorcycle
comfort and design, but also modern infotainment functions.
During the previous four international motorcycle conferences since 2002
numerous specialists have shown development ways, concepts and results in
all these areas. This paper is conceived as an overview of some representative
examples, in order to underline the complexity as well as the most important
stations of the advanced motorcycle development.
Optimization concepts for motorcycle engines
The weight-to-power ratio is primarily determined by the engine. Low weight for
a power value, or vice versa, a high power-to-weight ratio begins from a high
power-to-swept volume ratio. There are three ways to improve this ratio:
•
Two stroke or four stroke is a problem with a multitude of well known
objective and subjective aspects, which will be not commented in this
paper.
•
High engine speed is a particular symbol of the motorcycle engines in
comparison with automobile engines – the reason is even the
obtainable power-to-swept volume ratio. However, high engine speed
provokes the increase of the mean piston velocity thus of the friction, an
effect which is partially attenuable when increasing the bore-to-stroke
ratio, but in the detriment of the combustion chamber design or of the
compression ratio.
•
The thermodynamic path consists on the increase of the effective
energy density we (bmep).
Following this path there is a ramification to a quantitative way when
increasing the mixture density ρM or to a qualitative way when
increasing the specific work wcycle of the thermodynamic cycle:
The mixture density can be increased by supercharging or turbocharging (for a
motorcycle engine the supercharging is more recommendable because of the
torque characteristics):
The specific work wcycle can be improved by a steeper pressure rice during
combustion which is obtainable by an intensified mixture turbulence provoked
by fuel direct injection and by controlled auto-ignition leading to a short
combustion duration. Obviously, the functions around combustion must achieve
the required effectiveness and have to be adapted to each other – from gas
wave tuning, valve timing, internal mixture formation and homogeneous charge
compression ignition up to exhaust gas recirculation, as illustrated in Fig. 6.
Fig. 6
Ways of function improvement of future internal combustion engines
(FTZ)
Both effectiveness and adaptation depend on the load/speed situation, requiring
– when possible – a function map with electric actuation of supercharger, valves
and direct injection, as shown in Fig. 7 [3].
Fig. 7
Engine function modules able for a electric actuation
Following examples are representative in this sense:
The air pressure waves within the intake duct of a motorcycle engine, as shown
in Fig. 8. are strongly dependent on engine speed and partially on load,
achieving values which can considerably improve or disturb the cylinder filling
with air [3].
Fig. 8
Pressure waves within the intake duct of a motorcycle engine (FTZ)
The intake pipe length and the intake valve timing have to be adapted to this
behavior.
A variable length of the intake duct and moreover, their continuous adaptation
to the engine speed are practically not feasible for a motorcycle engine. It
remains the way of the variable valve movement. The possible parameters and
valve actuation solutions are shown in Fig. 9 [3].
Fig. 9
Variable valve movement – parameters and actuation (FTZ)
Surely, such actuation appears much more complex for a motorcycle engine
than for an automobile engine. However, a relative low electric support allows a
considerable variability of the valve movement, as illustrated in Fig. 10.
Fig. 10
Combined electrical/mechanical valve actuation with variable valve
lift and opening duration (Mahle)
A high efficiency of the combustion process for improving the specific cycle
work as well as the consumption and pollutant emission is obtainable when
controlling the formation of the fuel/air mixture also during the combustion
process – consequently by fuel direct injection.
The mixture formation within the intake duct – by an electronic carburetor
system, as shown in Fig. 11 or by injection, as shown in Fig. 12 has the benefit
of more space and time before scavenging and compression, as suggested by
Fig. 13.
Fig. 11 Electronic carburetor system (Dell’Orto) [4]
Fig. 12
PGM-DSFI-System: programmed duel sequential fuel injection
(Honda)
Fig. 13
Fuel injection – injection into intake duct / direct injection
On the other hand, the direct injection of fuel droplets at higher pressure into the
air within the combustion chamber provokes a noticeable mixture turbulence, as
basic condition for an efficient combustion. Furthermore, the combustion
process itself can be controlled by the shape of the injection flow, as
represented schematically in Fig. 14: within the combustion chamber take place
in this case 3 simultaneous
Fig. 14
Mixture formation and combustion – time and space related
sequencies (FTZ)
process sequencies – during the combustion of the first injection fuel quantity a
second fuel part is evaporated an distributed on air, whereas a third and last
part is just injected [3].
The complexity of such process is illustrated as example by the heat transfer
between different zones of the combustion chamber, as shown in Fig. 14. The
control of this process by means of the injected fuel droplets necessitates an
exact knowledge about the time and space related properties of fuel and of
mixture – such as liquid density, vapor saturation, local mixture concentration or
air/fuel ratio, as shown in Fig. 15 [3].
Fig. 15
Internal mixture formation and combustion (FTZ)
This knowledge implicates an efficient combination of three-dimensional
process simulation with experimental analysis. Figure 16 presents an example
of such combination, related to the fuel spray development during the injection
into a combustion chamber for different values of the air pressure within the
chamber.
Fig. 16
Spray images at different time-steps after start of injection (SOI) for
different values of the pressure in the chamber – comparison
experiment–simulation (FTZ)
The comparison of simulation and experiments allows the validation and
calibration of the simulation program, as base for the calculation of mixture
formation and combustion [5]. Figure 17 shows as example the threedimensional simulation of such process stages, determining the fuel droplet
diameter and the reactive flow temperature in every elementary cell of the
combustion chamber at every time step.
Fig. 17
Internal mixture formation and combustion – 3D simulation spray
droplet diameter and reactive flow temperature (FTZ)
Especially for motorcycle engines with a very large range of engine speed and
with frequent transient load conditions, the exact control of combustion offers a
remarkable potential for the improvement of engine performances.
Performance begins for a motorcycle engine with the torque characteristic and
maximum torque level. Could be benefic to adapt hybrid technologies from the
automotive sector? As shown in Fig. 18, the power addition from a piston
engine and from a coupled motor allows a torque increase – in the illustrated
case 30% - at low engine speed, as ideal condition for the acceleration of a
motorcycle [6].
Fig. 18 Advanced internal combustion engines: charged or electrified?
An alternative to the hybrid propulsion is the supercharging combined with
turbocharging. An example is presented on right side of Fig. 18: the
turbocharging leads to a double torque in comparison with the aspirated engine,
but not under 2500rpm, because of the enthalpy required at turbine input. The
combination with a screw type compressor leads to the increase of the
maximum torque up to 2,5 times in comparison with the aspirated mode.
Would be other alternative scenarios benefic for two-wheeler? The electric
propulsion with energy from battery or fuel cell is object of many scenarios at
the present.
Fig. 19 Fuel cell scooter (Honda)
Fig. 19 shows a fuel cell scooter with remarkably compact modules of the
propulsion system. With the necessary hydrogen infrastructure which could be
determined by the automotive industry, such solution appears as a rational
completation on the two wheeler sector, for pure transportation vehicles.
However, between rational and emotional there are sound, torque response,
vibration, exciting design.
Vehicle structure and aerodynamics
The motorcycle? What for an adaptable connecting element between two
dynamic systems – the Rider and the Road, both of them having particular
degrees of freedom in terms of time- and space-related movement.
Rider and motorcycle structure are at the present object of intensive analysis by
experiments and simulation. Some example are representative in this sense:
Fig. 20 Bike Rider – numerical simulation in typical driving position (BMW)
The numerical simulation of the bike rider in typical driving positions, as
illustrated in Fig. 20 [7], shows noticeable differences in comparison with a car
driver. Such analysis allows an appropriate development of the vehicle
structure. This development is a complex task between architecture, materials
damping modules and design in conditions of compact volume, low mass, high
mechanical resistance, damping of vibrations and shocks and stability on the
road. Fig. 21 shows as example such a complex structure, whereas Fig. 22
gives some details regarding the combination of materials [8].
Fig. 21
Vehicle structure (Ducati)
Fig. 22
Structure and materials (Ducati)
The air properties – pressure, velocity, temperature, humidity, turbulence zones
– around the system formed by rider and bike are of determining importance for
the driving stability. Fig. 23 shows calculated velocity vectors around a bike with
rider [9].
Fig. 23
Relative velocity vectors – calculated (BMW)
The simulation results are compared for validation and calibration with
experimental analysis, as illustrated in Fig. 24 [9].
Fig. 24
Experimental setup (BMW)
Of particular interest appears the air drag distribution along vehicle length and
height, as shown in Fig. 25.
Fig. 25
Drag distribution along vehicle length (BMW)
Last but not least, the air flow plays an important role for the cooling system of
the engine, as presented in the example in Fig. 26 [9].
Fig. 26
Flow field at radiator (BMW)
Finally a dangerous reaction of the rider in the case of an incident should be
attenuated by the vehicle structure and response. Such example is presented in
Fig. 27.
Fig. 27
Left: motorcycle jumps too short at an angle of 75 degrees
Right: Head-first impact with a rotation of 60 degrees leads to lateral
hyper flexion (BMW)
The vehicle adaptation requires the knowledge about the rider in three
dimensions: geometry, force, reaction. In this manner the kinetic and dynamic
properties of all rider members can be determinate in terms on way, work (as
way force) and power of decision (as work per reaction time). Fig. 28 shows the
geometrical model of a biker and data about posture, motion, typology and
comfort [7].
Fig. 28
Structure and model of the RAMSIS System (BMW)
The typology takes into account the following elements:
ƒ
ƒ
ƒ
ƒ
ƒ
Sex:
Body height:
Corpulence:
Proportion:
Hand model:
male/female
very short, short, medium, tall, very tall
slim waist, medium waist, large waist
short torso, medium torso, large torso
mitten-like, 5-finger-hand
ƒ
ƒ
ƒ
ƒ
Foot model:
Reference
Age group:
Nation:
ƒ
Child model:
Naked, Gino, DIN/SAE
year: 1984-2010
18-29, 30-49, 50-70 and 18-70
Germany, USA/Canada, Japan/Korea, South
America, France
9 month – 12 years
A posture prediction model enables the calculation of the most probable posture
in consideration of boundary conditions (restrictions). The calculations are
based on angle probability functions that are acquire in tests with several
subjects. Motorcycle posture model was deduced from car posture model (low
number of subjects does not allow creation of distribution functions). In order
that all motorcycle types can be handled with one posture model, functions of
probability are opened. The effect is: one joint got several angles of the same
probability.
This analysis allows an appropriate dimensioning of the operating elements of
the motorcycle. Fig. 29 shows an example.
Fig. 29
Concept dimensioning – handle location (BMW)
Active and passive safety
The rider protection measures follow three directions:
−
The active safety, which is concentrated especially on the brake system
(ABS, CBS). Fig. 30 shows the hydraulic circuit of an integral ABS for
motorcycle, with the main actuators and sensors
Fig. 30
Hydraulic circuit diagram of an integral ABS (Honda)
The intelligent braking system requires an appropriate material support
in form of the braking discs: light, with high resistance against
deformations, vibrations, high temperature, impurities or shocks. Fig. 31
illustrates an advance design of braking discs [10].
Fig. 31
−
Floating brake disc Ø320x4.5 for Ducati 996 (Ducati)
The passive safety, which is mainly polarized on the airbags
configuration. Fig. 32 shows such example
Fig. 32
−
Airbag prototype for a big scooter (Honda)
The preventative safety, which concerns rider training and simulator,
taking into account objects – pedestrians, obstacles, road signs, traffic
lights, road surface and marking – but also environmental factors – rain,
fog, snow, road conditions.
Electronics and informatics
Electronic structures are the support of the most functions of automobiles and in
the last time of motorcycles as well.
Propulsion, comfort applications and infotainment are supported on different
electronic structures – CAN FlexRay, CAN Most, CAN Lin – which must be
connected and adapted to each other.
Fig. 33 presents as example the configuration of an electronic system for the
torque control [11].
Fig. 33
Torque structure (BMW)
Similar electronic structures in automobiles and motorcycles allow the
development of inter-vehicle communication systems which have a remarkable
potential in respect to the driver protection. Fig. 34 illustrated such concept.
Fig. 34
Inter-vehicle communication system (Honda)
Conclusions
The motorcycle will never be a transportation vehicle with two wheels and
standard components, the motorcycle is a true symbol of diversity as well as of
harmony between high-tech and feeling. Motorcycle means no longer only
mechanical jewel – but a system of functions, from the combustion, vehicle
structure, safety and intelligent control up to the interaction with the surrounding
systems, in conditions of very restricted place, weight and electric energy.
From the workshop of Wilhelm Maybach as an excellent technician the
development of motorcycles moved to the laboratories of simulation specialists,
of experts in thermodynamics, materials, fluid mechanics, electronics and
infotainment, of physiology and psychology doctors.
The last word has the designer, but in different conditions as for automobiles –
there is not only car body, but a system of bike and biker with esthetic quality
and personality.
References
1
Stan, C.: The Motorcycle from the Research Perspective; Development
Trends of Motorcycles (Entwicklungstendenzen im Motorradbau);
ISBN3-8169-2272-4
2
Braunsperger, M.: Entwicklungstendenzen im Motorradbau aus Sicht
von BMW Motorrad, Internationale Konferenz, „Entwicklungstendenzen
im Motorradbau“, Zwickau, 2002
3
Stan, C.: Alternative Propulsion Systems for Automobiles (Alternative
Antriebe für Automobile), 2nd Edition, Springer Verlag Berlin
Heidelberg, ISBN 978-3-540-76372-1
4
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Cylinder Two Wheeler Applications; Development Trends of
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5
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Development Trends of Motorcycles (Entwicklungstendenzen im
Motorradbau); ISBN3-8169-2272-4
6
Stan, C.; Täubert, S.: Charging Strategies for a Compact GDI Engine,
9th International Conference on Engines and Vehicles –ICE 2009, SAE
Paper 2009-24-0075
7
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8
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9
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the
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Group;
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of
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10
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11
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