Bringing Life to an X5 Hybrid

10 H Y B R I D D R I V E 11R E A LT I M E S 1 / 2 0 1 0

By Prof. Dr. Dieter Nazareth,

Landshut University of Applied Sciences

ETAS tool chain supports development of new hybrid functions

Even before the recent auto industry downturn, automotive hybrid power was a much talked about topic. All automakers

and some of their suppliers are working on related concepts and components. To give his students real-life experience

in this subject matter, mechanical engineering professor Dr. Prexler came up with the idea to have his students develop

a roadworthy, hybrid-powered prototype vehicle in three semesters.

In a mere 18 months, a joint projectby the faculties of Mechanical Engi-neering, Electrical Engineering, andComputer Science at the LandshutUniversity of Applied Sciences hassucceeded in developing a driveableserial plug-in hybrid dubbed “MBLex-drive“.

Vehicle platformThe basic vehicle, a BMW X5 SUVprovided courtesy of BMW AG, hadits entire factory powertrain removed.Drive power is now supplied bytwo electric motors, one of which isintegrated in each of the two axles.As a result, the hybrid – as was theoriginal vehicle – is equipped withfour-wheel drive. The X5’s third rowof seats needed to make way for thelithium-ion batteries with their com-bined output of 400 volts. The bat-teries are charged by means of astandard, 230 V house current outlet(hence the term “plug-in hybrid“). Onthe X5 Hybrid, the braking energythat is typically lost with conventionalpropulsion is reclaimed by a processknown as recuperation, and then

stored in the batteries. In this way, thebatteries’ combined capacity yields arange of about 62 miles (100 km).

However, it is possible to significantlyincrease the vehicle’s range throughthe use of a range extender, that is, adiesel engine driving a generator thatin turn charges the batteries whiledriving. The diesel engine was takenfrom an emergency generator set,and operates in a stationary setup atthe optimum working point for fuelconsumption. This type of hybrid isknown as a serial hybrid. Its complex-ity, compared with a parallel hybridthat uses two different means of pro-pulsion, is distinctly lower.

Vehicle system architectureNot only the X5's powertrain wasmodified – the vehicle’s onboardelectrical system also needed to bechanged. In order to intervene withthe existing installation as little aspossible, a new hybrid bus, theHybrid CAN, was added to carry thenew hybrid functions. This new busis connected to the two inverters

Function development was handledwith the aid of the ASCET develop-ment tool. Aside from the actualdrive function, which translates thedriver’s intentions into control signalsfor the two inverters, a host of func-tions related to temperature, voltage,and short-circuit monitoring, wereimplemented. Also, the communica-tions of the missing transmission ECUneeded to be simulated, along with agateway function between the twoCAN buses.

As a definite benefit to the computerscience student, the large variety ofmodeling techniques provided byASCET enabled them to specify notonly continuous processes, such asthe drive function, but also state-based processes, as they occur in

voltage monitoring, at an adequatelevel. The quality assurance for themodels was the result of an offlinesimulation with an environmentmodel. The next step consisted oftransferring the function model tothe ES910 Prototyping and InterfaceModule with the aid of INTECRIO.Testing the module in the physicalvehicle was preceded by an additionalquality assurance step compared withresidual bus simulation.

TestingThe new drive system is currentlybeing tested both on a roller dynamo-meter and on the road. The testingobjective is to optimize vehicle res-ponsiveness by modifying a multitudeof parameter sets. The major issue inthis is the distribution of torque to

both of the vehicle’s axles, whileconsidering the energy present, thetemperature of all components, andthe speed of the vehicle. In addition,experiments with various acceleratorcharacteristics are conducted. Be-cause safety concerns precluded amodification of the conventionalbrake, the accelerator pedal is used toinitiate electric braking (recuperation).This is accomplished by dividing thepedal travel into separate functionalranges. Initial tests have shown that –given proper calibration – the drivergets used to the combined acceler-ator/brake pedal quite quickly.

At the time of this writing, testing isstill being handled directly by meansof the INTECRIO tool, with studentsof both computer science and me-

that supply AC voltage to the electricdrive motors.

Although the original engine man-agement ECU remains in the vehicle,it now reads only the acceleratorposition. To handle the new hybridfunctions, an ES910 Prototyping andInterface Module has been pressedinto service as the control unit. Atthe same time, it serves as the gate-way between the original powertrainCAN and its new hybrid counterpart.In addition, the ES910 handles thebus communications of the trans-mission ECU that was removed. Thiscompact module, which found aplace in the footwell on the passengerside, facilitates the real-time execu-tion of all relevant functions.

Function development with ASCETETAS development tools were usedfor the development of the newhybrid functions. The declared ob-jective was to develop a prototypefor collecting concrete experiencewithin the shortest possible timespan.

Monitoring the internal operating states with INTECRIO.

Components of a hybrid drive for four-wheel drive vehicles.

chanical engineering working sideby side. The next step is the develop-ment of an INCA user interface thatwill enable the mechanical engineer-ing students to calibrate the drivefunctions by themselves.

Advanced drive functionsFive students are currently developingadvanced drive functions based onthe current basic functions. This effortnot only includes comfort functions,such as cruise control or stopping ona hill. The development work alsoaddresses safety functions, such as

traction control for the electric drivesystem. These functions, too, arespecified in ASCET. The goal isto develop individual encapsulatedAUTOSAR software components. Asis the case with the entire X5 HybridProject, the main objective is to famil-iarize the students with modern de-velopment methods through the useof a contemporary training approach.The vehicle is slated for use as a de-velopment and training platform alsoin the coming semesters. The atten-dant topical spectrum will cover therange from quadruple-motor propul-

sion to high-voltage fuses, to batterymanagement and display and oper-ating concepts.

The bottom lineWith the X5 Hybrid Project, theLandshut University of Applied Sci-ences has demonstrated that it ispossible to build post-productionhybrid vehicles without having torelinquish the familiar comfort of aconventional vehicle. The develop-ment of the new hybrid functionsrelied heavily on ETAS tools and prod-ucts like ASCET, INTECRIO, ES910,and INCA, deployed in accordancewith the classic V-Model. Their con-certed interaction facilitated functionspecification and quality assuranceas well as in-vehicle execution withthe aid of rapid prototyping. All ofthe above enabled the computerscience students to bring life to thevehicle prepped by their mechanicalengineering counterparts in a rela-tively short time.

For more information on this project,please go to www.ex-drive.de

12 H Y B R I D D R I V E

THE CHALLENGETo develop a driveable, serial plug-in hybrid on the BMW X5 platform.

THE SOLUTIONAn ES910 Prototyping and Interface Module served as the ECU for the new hybrid functions. It permits the real-time execution of all relevant functions. Function development made use of the ASCET development tool, while the function model was transferred to the ES910 Prototyping and Interface Module with the aid of the INTECRIO prototyping environment. The user interface of the INCA calibration tool facilitated the calibration of driving functions.

THE BENEF ITThe development of the new hybrid functions relied heavily on ETAS tools and products like ASCET, INTECRIO, ES910, and INCA. Their concerted interaction facilitated function specification and quality assurance as well as in-vehicle execution with the aid of rapid prototyping. The project introduced provided realistic training approaches with contemporary development practices.

It took a mere 18 months to develop a driveable, serial plug-in hybrid named „MBL ex-drive“.

13FA S T E C U A C C E S S

High-Speed Calibration Tests Fast ECU access at the test bed – A solution by ETAS and D2T

The project BA6.2 in Munich is in full swing! Already fully operational, BMW’s brand new test center achieves unmatched

levels of performance with its 61 test beds. BMW called on partners who can deliver solutions for the future, capable

of calibrating ECUs and transient engine phenomena on a test bed. D2T delivered the test bed automation system, and

ETAS supplied the applications for the ECUs. Together, they proposed a solution offering quick access to the ECU, based

on standard market technologies.

D2T is well versed in test bed appli-cations. With its 30 engine test bedsand Euro 5 chassis dynamometers, thecompany already delivers turnkey cali-bration services for Europe’s leadingautomakers. It has developed theunique MORPHEE 2 system for testbed automation, the integration ofECU calibration functions, and theexecution of real-time models on testbeds. D2T always opts for the most openand dynamic standards on the market.MORPHEE 2 was the first automationsystem on the market based onWindows technology. The same sys-tem uses a market-standard real-timeRTX kernel and evolves in step withthe developments in PC (multi-core,etc.) and Windows technology. Italso uses an ultra-fast (10 kHz) Ether-CAT communications bus, which iscurrently considered to represent

the future communications standardfor test beds.

MORPHEE 2 is well suited to calibra-tion tests and, when used in combi-nation with the ETAS tools, it repre-sents a powerful solution that is alsowell adapted to transient calibrations.But just what is transient calibration?Today, calibration is conducted be-tween stabilized engine points, whiletransient calibration is a continuousprocess. The aim is to reduce thelength of tests by optimizing theengine on the bed and to limit thevolume of subsequent costly phasesconducted on chassis dynamometersand on the vehicle. The completeswitch from a calibration using stabi-lized points to transient calibrationrequires new methods and tools to bedeveloped – a long process that willlast several years. But the solutions

developed by D2T and ETAS at BMW’sBA6.2 test center for the fast ECUaccess are important milestones inthis process. Figure 1 shows theprocess as it exists today.

Currently, both dynamometer andtest bed equipment are controlledby the automation system, which, inreturn, receives the measurementstaken by this same equipment (gasanalysis cabinet, combustion analysissystem, etc.). Automation systemslike MORPHEE 2 work in real time,which means that the informationthey manage always takes priorityover other information in the PC.MORPHEE 2’s real-time kernel cancurrently operate at frequencies ofup to 10 kHz.

Measurement and calibration tools(MC tool), such as INCA by ETAS,

By Régis de Bonnaventure, D2T