comparison of packaging hydraulic and electric components in a hev power … evs24 international...

EVS24 International Battery, Hybrid and Fuel Cell Electric Vehicle Symposium 1

EVS24Stavanger, Norway, May 13-16, 2009

Comparison of packaging hydraulic and electriccomponents in a HEV power line

Panu Sainio1, Matti Heiska2, Teemu Lehmuspelto3, Jussi Suomela2

1 Helsinki University of Technology TKK, Department of Engineering Design and Production, Vehicle Engineering,PL 4300, 02015 TKK, Finland, [email protected]

2 Helsinki University of Technology TKK, Department of Automation and Systems Technology, Generic IntelligentMachines

3 Helsinki University of Technology TKK Department of Engineering Design and Production, Vehicle Engineering

Abstract

Scientific papers usually do not present ‘lessons learnt’ results, what comes to engineering aspects in

vehicle design. A lot of valuable information is collected during research and prototyping projects, but this

is not shared in public often enough. This paper is a general discussion about the engineering matters

related to the implementation of hybrid systems in mobile work machines. The target of this paper is to

underline the importance of paying attention of these matters already in very beginning of the research and

development.

The discussed aspects are related to the energy transmission, packaging of components, vehicle assembly

and service. The energy transmission section compares benefits and drawbacks of hydraulic and electric

transmission implementations. Packaging of components presents some issues to pay attention to when

accommodating components into vehicle. Service aspect highlights the benefits and drawbacks of different

solutions in maintenance operations.

The discussion is limited to explain only differences and analogies between hydraulic and electric

components. The cost factors can be estimated only by the reader, because they are very case sensitive. The

key factor is number of machines made in serial production. In case of passenger cars the cost structure is

very different compared to small series mobile work machines.

Keywords: hydraulic pipe, hydraulic tube, electric wire, electric cable, power cable, connector, assembly, service

1 IntroductionGeneral discussion and remarks about theengineering matters are often ignored in resultfocused scientific papers. Engineering aspectsmay be considered to be as well-known facts orthey are too general for scope of the papers.These general engineering remarks are valuablewhen new technologies are adapted to new

applications. It helps to get the commonacceptance for new technologies inside thecompany, among suppliers and developmentpartners, and most importantly within market andcustomers. Any kind of documented information isalso helpful for young engineers and engineeringcompanies, or engineers with different technicalbackgrounds to understand the benefits anddrawbacks of different technologies.

World Electric Vehicle Journal Vol. 3 - ISSN 2032-6653 - © 2009 AVERE

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This paper points out some findings made duringsome hybridization projects of heavy vehiclesand mobile work machines. These machines areusually dominated by hydraulics, whereas highpower electrical systems are relatively new. Forhybridization projects there is a demand in thefuture to understand constrains and advantages ofthese two different ways to move energy insidemobile work machines.

The items discussed here will be related to thepower transmission, packaging, assembly, andservice when using hydraulic or electric systems.In this paper there are only general remarks ofdifferences and analogies between hydraulic andelectric components. The cost factors cannot bediscussed here. They depend very much of thevolume of production. Readers can find out howmuch is too much by calculating the paybackperiod if all lifetime costs are considered.

Often engineers have strong opinions which ofthese two technologies are the best, based ontheir background on mechanical or electricalengineering. This paper tries to give an objectiveopinion of both of them. It is also important topoint out, that the best solution combines the bestcharacteristics of these technologies and supporteach other in their weaknesses.

2 Power transmission

2.1 GeneralToday diesel engine is the most common energysource in mobile working machines. What comesto power transmission from engine drive shaft tosystems, mechanical and hydraulic links areused. Electricity is a new option for powertransmission in hybrid vehicles and evenmandatory in fuel cell powered machines.

Mechanical power line is very common, but notvery simple or cost effective solution for powertransmission. With mechanical transmissionthere is often need for several different gearratios including some steps. Mechanical powertransmission is used in vehicle drive lines.However, in some cases, e.g. with bucketmovements in wheeled loader, the mechanicalpower transmission is even impossible toimplement in reasonable way.

Hydraulics, as a whole has several great benefitsand features what have made it to dominate as

transmission path for energy in mobile workmachines. The flexibility of hydraulics is muchbetter than in mechanical power transmission.Hydraulics can be used to change the gear ratiocontinuously with variable displacement pumpsand motors. It also has a great power density,which make it beneficial to use hydraulics innarrow places where high power is needed, likewith bucket.

Electricity is the most flexible way to deliverpower between systems. The drawback is the lackof components for heavy machinery. Electricmotors usually have lower torque but higher speedcompared to hydraulic motors. That is why moregear ratio is needed between electrical actuator andsystem if we compare it to hydraulics. In manycases, the electric motor with a gearbox is oftentoo big to place it near to the actuator. Thebeneficial use of electrics would need a totalreconstruction of the machine and new kind ofelectrical actuators.

2.2 Characteristics of hydraulic andelectrical transmission paths

The scope of this chapter is to compare hydraulicand electrical transmission paths. It is mainlyremarks for comparison of hydraulic hose andelectric cable. These remarks are somewhatapplication sensitive and can be utilized whenhaving discussion cost structure and engineeringprinciples of hybrid power lines in moving workmachines.

Hydraulic hose is a high tech product despite of its“round and black” type of appearance.Manufacturing, selecting and making the proper,cost effective assembly demands much more thanis visible to outside. The structure of hydraulichose is presented in Fig.1.

Figure 1: Structure of typical hydraulic hose is presentedin the picture. It is flexible rubber hose with differenttypes of reinforcements typically made from metals.Hydraulic tube or pipe is typically a firm metal tube

The demand for high quality manufacturing is thecase also with electric cables. Signal and control


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cables are somewhat different, but having anumber of wires and very complicatedconnectors they are worth of own review. Thestructure of shielded cable is presented in Fig.2.

Figure 2: Structure of typical electric cable for HEVuse [5]

Hose in Fig.1. and cable in Fig.2. has similarstructure, but for different reasons. The core ofthe cable and hose is for power transmission. Theouter metal layers have different purposes.However, the protection against mechanical wearand chemical stress are common characteristicsfor both.

In hydraulic hose the inner radius is dependent offlow. Typical inner diameter for 100 kW poweris 19-25 mm. Outer diameter of hose depends onthe pressure rating, because more reinforcementlayers and higher wall thickness is needed. Theouter diameter is 33-40 mm for 1” hoses withpressure ratings required in mobile workmachines.

Cable in Fig.2. can be used in same power classas the hydraulic hose mentioned earlier. The corein 35 mm² multithread cable has diameter of 10mm. The outer diameter depends on insulationrequirement. The metal shield depends on therequirement for electromagnetic compatibility. Inthis example the cable has outer diameter of 15mm and it is accepted in vehicle use.

The example above shows, that the need forspace is five times more with hydraulic hose thanwith cable. Actually this is much more, becausehydraulic hose is stiffer and the allowedminimum bending radius of hydraulic hose ismuch higher.

Hydraulic hoses and electric cables can bereplaced by hydraulic tubes and busbars, if thespace is more limited or if there is a need formore rigid assembly. Hydraulic tube has the

same requirements for inner radius than tubes. Theouter diameter can be few millimeters less. Tightercorners can be made with tubes, but you have toremember the effect on flow quality of hydraulicfluid and pressure. Too tight corners and increasednumber of connectors and fittings causes powerlosses. They can have significant effect on energyefficiency at high power.

Busbars are used in rigid electric systeminstallation. Basically they can be any size andshape. Usually the cross section is rectangular, notround like with cables. Tight corners are not aproblem in case of power losses. Disadvantage isthat shielding against EMC is difficult. Highfrequencies affect electrochemical actions onsurface of busbars, which creates a need for propercoating to avoid oxidation and poor contactsbetween busbars.

Using busbars is common solution inside powerelectronic devices. This technique offers multiplebenefits for assembly and dissipations. In futureperhaps busbars might be used also betweencomponents and they could be fixed in vehicleframe. There can be seen new application withbusbars made of thin sheets with insulation (seeFig.3.). These might offer us cost benefits whatcomes to connecting, guidance and continuouscurrent-carrying capacity. [2]

Figure 3: The summarization of the advantages claimedfor modern insulated busbars compared to the classicalelectric cabling. [2]


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2.3 ConnectionsThere are much different type of connections forhydraulic hoses and tubes, as well as electriccables and busbars. We all who have beenstruggling with crimping, pressing or evensoldering connectors to cables have seen howdifficult it is. The very same or even worsesituation is with hydraulic hoses. There isdemand for special tooling and there arenumerous differences between fittings andsealings. Fig.4. is really only a glimpse from thatworld.

Figure 4: Fitting for hydraulic hoses

There is said a very rough estimation the third ofthe turnover of hydraulic systems industry wouldbe related to hoses, pipes, fitting, filtering andother that kind of stuff. This rule of thumbestimation could perhaps be used as a referencewhen comparing to the costs of cabling,connectors and fuses.

The simplest way with electric cabling is boltconnection. This can be made with differenttypes of cable lugs. Flexible busbar in Fig.3.allows making bolt connections by punchingdirectly through the laminates. Since there are nolugs to purchase, fewer parts are required andinstallation is simpler and faster. Compared tocables tools to make this kind of solutions aresimple enough for research, prototyping and evenin serial production. However, this kind of non-insulated connection can only be used inside ahousing or additional protection against contactand electric shock must be implemented. Fig.5.shows an example of safe and EMC shieldedcable connector for high voltage systems inHEV.Easy bolt connections are not possible inhydraulics. The closest to do that is probably abanjo bolt or flange mounting, but compared tobolt connection for busbars, they are much more

impractical. The benefit of connectors of hydraulictubes and hoses is that they don’t need extraprotection. Fittings for hydraulics are alwayssecured for rated pressure if installed properly.HEV.

Figure 5: Connector for high voltage system [5]

Both hydraulic hose and electric cable connectorshave larger diameter that the hose or cable itself.This means that there is need for large lead ins. Ofcourse this offers good possibility for properbushing for leads in but has to be considered forassembly. Especially when it comes tomanufactured wire harness there is goodpossibility to have demand large cross section inthe cable routing. For service a large connectorwith angle at the end of stiff hose is for sure achallenge.

3 Manufacturing and assembly

3.1 GeneralThe engineering task of packaging and assemblycomponents in the vehicle is a complex matter. Itincludes a lot of tacit knowledge insideorganization, and it is rarely documented. Oftenthis tacit knowledge is gathered by experience andco-operation with service people. The aspects inthis chapter are heat transfer and generalmanufacturing and assembly issues.

3.2 Packaging and heat transferExtensive heat production due to bad efficiencyand constant demand for cooling has always beenthe challenge in vehicles and mobile workmachines. With combustion engine and hydraulicsa certain level of temperature is wanted for properoperation. There are remarks to warm enginesbefore using full power. The viscosity of hydraulicfluid, which is highly dependent of fluidtemperature, has a great effect on system behavior.The hydraulic fluid has certain operationtemperature about 50-80 degrees of Celsius. Withelectric components typically all heat is unwantedand the overall accepted temperature level is


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lower. Usually it is under 65 °C in powerelectronic devices of today. These differentthermal levels have to be taken into accountwhile engineering packaging.

The hydraulic oil has very important function ofcooling besides energy transferring. The targettemperature for hydraulic oil is relatively cool inwork machine operated by combustion engine atoutdoors in summer. But when comparing thistemperature of demands rising from electronics,battery or capacitor, it is much more difficult. Inconventional mobile work machine the surfacetemperature of hydraulic pipes and tubes is not amajor worry. They also have significant role ofcooling down the hydraulic oil. Insulating themwill lead us to increscent cooling capacity tosome other location. For protecting singlecomponents insulating or routing hydraulic lineother way around are good solutions.

When making hybridization of mobile workmachine, one has to remember the heat flowfrom hydraulic lines. The advantage of electricpower cables is that they are targeted not to risein temperature significantly due to current.

Hydraulic system also generates heat during idle.Even if the bucket is not moving but thecombustion engine is running and circulating theoil, there is heat generation from few up todozens of kilowatts. Fig.6. presents thisfundamental difference between hydraulic andelectric energy transfer paths. The hydraulicsystems start to heat up immediately after startdue to oil circulation, electric until whenworking. Electric cables as transfer paths do notproduce heat while idle and electric system as awhole has very low heat generation during idle.This might be used as an advantage whileengineering cooling system for hybrid workmachine. Especially for those components, whichare used seldom during the working cycle, theremight be possibilities to survive with limitedcooling capacity. Here we have to remember thatthere are major differences of working cycle ofdifferent working machines and their functions.Specifying and identification of the workingcycle of a certain working machine is one of thefirst steps in hybridization feasibility study.

For hydraulic fluid and cooling of it advantage isthat it can be piped to separate cooler. If there isexcessive heat production inside electric devices,typically a separate water cooling circuit is

needed. If in worst case, there is from some reasonexcessive heat production inside cabling, there isnot much to be done. Of course type and sizing ofthe cable as well as the mounting and the routingof the cables may offer some instruments tocontrol the temperature.

Figure 6: Example of an infrared picture taken from thehydraulic oil tank only 2 minutes after start up theloader. The pipes on the left side are for buckethydraulics and on the left marked with dashed line is a150 litres hydraulic tank.

It is also worth of mention, that development ofhigh power semiconductors is focused on moreheat sensitive components. The temperature ofpower electronic devices could be increased by 10-20 °C in the near future with silicon carbide basedsemiconductors.

3.3 Vehicle installationsFor costs, wear and ease of guidance in hydraulics,there are used pipes for longer distances, and hoseswith minimum length in locations, where isdemand to allow movements. Hydraulic hoses aresubjects of wear when mounted in movingcomponent by external abrasion and there is alsopossibility for internal erosion.

Hose routing is a challenge, as well it is a majormatter with electric cables. Replacement hosesmust be restrained, protected, or guided typicallyusing clamps to minimize excessive flexing andwhipping. Flat metal armor and wire springguards, or a special sheath made of abrasion,temperature, or chemical resistant material willhelp protect a hose. Electric cables have similarneeds but with major difference not havingtendency to whipping due to change of powerflow. Hydraulic hoses vibrate and change theirstiffness when power flow is varied.


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Also when determining correct hoses length,consideration must be given for length changesunder pressure (being as a rule of thumb about5%), machine vibration and motion, and hoseassembly routing. A special remark forhydraulics is that high and low pressure linesshould not be clamped together. In electric cablesthere are no change of the length and stiffness.However in electric cables one should considerwhen clamping together cables with differenttypes of signals and levels of power. Theengineering of wire harness in terms ofconduction of heat and EMC-matters can be achallenge.

Fig.7 presents situation of center pivot inarticulated frame steered wheel loader. There isneed to transfer energy by hydraulic hoses overthat joint and with very limited space. Thismakes hydraulic hoses to contact each other.Also there are hoses for high and low pressure,and for different circulation. This makes hoses tomove at each other due to pressure fluctuation.

Figure 7: Hydraulic hoses in wheel loader witharticulated steering (frame steering). This typicallychallenge both for assembly and external wear of thehoses.

Center pivot is a challenging point also forelectric cabling. But as learnt earlier, electriccables are more flexible and don’t need so muchspace. They do not change their stiffness as afunction of energy either. The electric cables arealso subject to external wear and we have toremark there is limited experience of them inconnection between moving parts. This mayforce us to protect soft cabling by canal or such.Presence of oil and other chemicals form an otherthreat to cabling. However the same situation iswith hoses.

Fig.8. shows the flexibility of electric cabling invehicle installations. It is a picture of electricvehicle prototype in very early phase of functionaltests. Compare them in your mind to hydraulichoses and tubes. There are differences of sizing,bending radius, heat generation and demand forsupport. A lot of extra work has been neglected indesigning the power transmission paths andinstallations, because of the freedom what comesto lay-out and cable routing. Although this is just acase from prototyping phase, the same freedomremains in production phase.

Figure 8: An example of packing two Siemens electricmotors during first bench testing. Remark there is powercables, cooling pipes and control cables. [3]

Typically in both of our main cases, electriccabling and hydraulic hoses and tubes areforgotten in press material or even during makingthe first engineering concepts. Cabling and hosesdo demand volume inside of the vehicle orworking machine. In Fig 9 and Fig. 10 there aretwo typical presentations. It is natural,understandable and acceptable the new systems arepresented to the audience only by pointing out themain components and their main relations.However the reader has to keep in mind whenmaking the estimation of the feasibility of the newsystems, that most of the component has to beconnected by several means. There is very oftenneed for at least two hoses and some signalcabling.


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In case of power electronic components cablingmight be more assembly and service friendly bygood reasons. When using shielded cables due toEMC-matters we achieve at the same time onlytwo connection for one component. Havingpower phases inside same cable and allsignal/controls in the other cable the assemblyeasies up and we ensure to have better EMCperformance.

Figure 9: Components of the hydraulic hybridHydrostatic Regenerative Braking System. This isvery common way to present component in marketingmaterial, without pipes and cables although they willbe a challenge during application engineering. [1]

Figure 10. Here is much more realistic exampleof marketing picture including some tubing andwiring. Remark even presentation of hydraulicfluid tank in somewhat reasonable size. [1]

3.4 Assembly workThe engineering items related to assembly andthe targeted service life of hydraulic hoses andtubes are worth of short discussion. There isdirect analogy from many of these items to

electric cabling. However, there are some itemsthat are not present with electric power cables.These can be considering as benefits to hybridelectric systems. In discussion they have to beoften underlined because in the mobile workmachine industry all these aspects related tohydraulics are accepted as a part of everydaybusiness and cost structure.

Hoses, couplings, assembly equipment, andcrimping tolerances vary from one manufacturer toanother, and sometimes they are not inter-changeable. The main worry is to remember thatthe thread, seal or flange end of a coupling must bematched properly to other component to achieve aleak proof connection and safe. This problematic issimilar to connectors in electronics. When makingpower cable connections with bolt-based jointsome of this is surmounted.

There is also more difficult to design rigidhydraulic lines in to different sub modules so, thatthey could be fitted together when installing themtogether. In this case, only option is to use a pieceof hose between those modules to connect thepower line together. This is much easier andaccurate with electric busbars and cableconnections. You could even imagine fixing a rigidelectric bus in vehicle frame, and having acounterpart in sub module to fit to that in toleranceof few millimeters.

When making the first assemble, and sometimesalso during service, there is need in hydraulics toflush the system to prevent impurities to remainthe system. In electric cable there is sometimesneed to measure leakage current but no need toflush the system.

3.5 Safety aspectsGenerally high voltage electric systems areconsidered to be more dangerous than hydraulics.For electric cables, if there comes a crack or a cutthere is a danger for short circuit. For this there arepossibilities to be prepared by proper fuses andcurrent leak detectors. It is also mandatory to havea protection against contact to avoid electricshocks.

With hydraulic hoses there is danger for highpressure fluid to be sprayed or fumed out of theleakage point. High pressure spray may be lethalor at least leads to permanent tissue damage. Fumeis dangerous for its risk of fire. Both of them makeenvironmental risk of having hydraulic fluid (even


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tens or hundreds of liters) around the workingsite. Typically for customer it is easy to ask andto be afraid of the danger of electric cable to becut. But at the same time the same customeraccepts and can live with the danger of hosefailures and some regular, external leaks ofhydraulic systems.

Temperature range of the hoses is a matter ofchoice with remark that hydraulic hoses musttolerate both the external ambient and internalfluid temperatures. Fluid compatibility has to beconsidered. Many hoses are not compatible withall of the common fluids that include petroleum-based, phosphate esters, water-based anddiesters. Here we have only limited analogy toelectric cables.

Standards and references for combustion andelectric vehicles are today under intensivedevelopment. Inside traditional electricalindustry there has been variety of norm, guidelines and standards to be followed. Often there isassumption of being stationary assembly or incase of moving vehicle low voltage (like forkliftswith 72 volts etc).

Electrical safety and even in some cases securityhas to integrated in to the life span of the vehicleor working machine. [6] This means we have toconsider safety as an item covering engineering,testing, and assembly maintenance and evenrecycling phases of the product.

4 Service and repairThe service costs are often calculated carefully incase of mobile work machines. They are handledas investments and factor of production.However, if and when there becomes demand forrepair, the effective process for trouble shootingis needed.

In operations model, where work machine isowned the same owner as manufacture (case ofgroup of companies or affiliated company etc.)and it is leased including service, the service costbecome more and more important. Practicallywhen there is clause of operational availability ofallowed down time, the role of trouble shootingmay becomes very valuable. Via this kind ofitems the higher price of hybrid systems maybecome feasible as part of total cost structure.The saving of the energy is only a one part.Especially this is valuable if the tendency ofleasing work machine even based on actual

performance becomes more common.

Service can be done either by beforehand plannedmodel or because of failure remarked. Oftenactions do to failure are referred also by term ofrepair. In future however, there can be predicteddemand for service when really needed, so servicein demand. There is assumption of having usageprofile and operating conditions predictable, ifservice interval is based on working hours. Forexample in hydraulics there is a good possibility toindicate service for filtering via pressure differenceover the filter, which indicates fulfillment of thefilter.

For the hoses there is only a visual inspection. Thatmay be difficult because hoses are clustered andthey are inside the machine. Of course leakage isan effective marker itself, that there is a problemsomewhere. However, it can be difficult see inwhat component the leakage actually is. Oil underthe machine can be detected at least on hard soil,but finding the exact section may be difficult. It isalso possible, that leakage is present only at hightemp and full power.

In case of electric cabling there should bepossibilities to measure cable sections separately,and define in which section or location theproblem is. Also self diagnostics could beexploited and taken into account already duringengineering phase of the system [4].

What comes to assembly and service demands foreasy connection and possibility to open and re-connect it to the hydraulics can fulfil them mostly.However when removing electric cable there is nofluid running to floor and into the machine as wellas there is no major danger for impurities enteringto the system. This is clear bonus for electriccables. Especially this is important for mobilework machines, because many service tasks aredone where the machine happens to be at the timeof breakdown.

One difference claimed between cables and hosesis case of great damages inside of the system. It issometimes believed in case of hydraulic pump,motor or other metallic component major damagethat the machine will never be the same again.There is obvious need to flush the system to getmetal particles away. But before noticing thedamage or excessive wear the particles may easilyspread to the whole system. And after the repairsand flushing, despite of several levels of filtering,


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there can be some parts of metal left in thesystem. In case of cables the damage is typicallyisolated to certain components by the assumptionthe over voltage protection is done properly.

Manufacturing spare parts for the vehicles oftomorrow is one item should be considered now.In case of hydraulic hoses and electric cablesthere is need for supply and availability ofselected connectors. This should not be aproblem, if standards are followed. Especiallywith cables done with bolt joints and lead-ins thisshould not be a problem. For hydraulics theremay be differences of threads and sizing betweencontinents and market areas what may causedifficulties to customers later on.

5 ConclusionsItems discussed here may be not the first pointsin presentation material of novel hybrid powerline solutions for mobile work machines.However, these aspects and observations mightbe useful when new technology enters toproduction phase or even before that whenhaving challenge of price setting, reliabilityestimation, payback time calculation to achievecustomer acceptance. Saving energy is oneobvious driving force in development of hybridsystem, but it has to be noticed that also there hasto be payback time, reliability and good coststructure before any system can enter toproduction and markets.

Electric power lines can bring more flexibilityand cost saving in manufacturing andmaintenance of mobile work machines. It is clearthat it is the most reasonable way to transferpower between systems. However, hydraulicsystems and components are still present inmobile work machines because of the very greatpower density of hydraulics.

When combining the best sides of electrics andhydraulics, it makes sense to conclude to serieshybrid construction in mobile work machines.The energy system with gen-set and electricalenergy buffers with sophisticated control systemimprove fuel efficiency. Electrical power linesmakes and serial hybrid structure can give usmore freedom in engineering. Electric drivenactuators benefits of hydraulic gear ratio, and canbe used close to the actuator.

AcknowledgmentsOur gratitude is to all those of our friends,colleagues, partners and customers who have beenexplained details, discussed solutions and havebeen giving their constructive criticism aboutengineering items we have phased during severalprojects in the wide field of work machinery.This paper is part of an ongoing project HYBLABfunded by the Multidisciplinary Institute ofDigitalization and Energy (MIDE) of HelsinkiUniversity of Technology TKK.

References[1] www.bosch.com, referred 2.4.2009

[2] www.erico.com, referred 10.4.2009

[3] Jussi Suomela, Panu Sainio, Peter Jakubik,Antti Leivo, Markku Degerholm, TeemuLehmuspelto, Control system developmentfor an 8-wheel off-road HEV by using V-cycle, Poster at EVS-22, October 23-28,Yokohama, Japan 2006

[4] Matti Juhala, Panu Sainio, Antti Leivo,Development environment for heavy vehiclehybrid systems, 8th International Workshopon Research and Education in Mechatronics2007, June 2007, Tallinn, Estonia

[5] Yazaki, www.yazaki-na.com, referred14.4.2009

[6] Jacobs, U., Rau, M., Anforderungen anHybridsysteme in Bezug auf Funktionale undElektrische Sicherheit aus normativer Sicht(Requirements to hybrid systems with regardto functional and electrical safety in view ofstandards) TÜV SÜD Automotive GmbH,VDI Berichte Nr. 2000, 2007 509-526


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AuthorsPanu Sainio, Lic.Tech. ChiefEngineer, Department of MachineDesign and Production, researchgroup for Vehicle Engineering,[email protected] has been working asLaboratory Manager and later asChief Engineer since 1998participating a number of nationaland international projects ofvehicle engineering and testing.His research interests are tyre-roadinteraction, non-visual informationfor driver’s and heavy hybridvehicles.

Matti Heiska received his M.Sc.degree in Vehicle Engineering fromHelsinki University of Technology(TKK), Finland, in [email protected] 2002-2008 he worked inPatria Land & Armament as a R&DEngineer. Since 2008 he has beenworking as a Research Scientist inDepartment of Automation andSystems Technology in TKK. Hismain research interests are in thefield of vehicle control systems andhybrid electric vehicle technologies

Teemu Lehmuspelto, M.Sc.Research Scientist, Department ofMachine Design and Production,research group for VehicleEngineering [email protected] has been working as a R&DEngineer 2001-2008 in PatriaVehicles Oy and as a ResearchScientist since 2008 in HelsinkiUniversity of Technology. Hismain research interests are vehiclecontrol technologies and hybridelectric vehicle technologies.

Jussi Suomela is senior researchscientist and project manager inDepartment of Automation andSystems Technology in HelsinkiUniversity of Technology TKKsince 1992. His main research areasare hybrid electric vehicles and fieldand service robotics. He received hisdoctoral degree from TKK in [email protected]


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