In recent years the techni- cal inner life of our motor- cars has changed dramati- cally. Whereas formerly components such as carbu- rettor or ignition distribu- tor could still be recogni- zed if the engine bonnet was opened, nowadays electronic control units have taken command. But this would not be practica- ble any other way when we consider what we as purchasers and drivers of the cars expect in terms of functions and attributes. These include, for instance, low fuel consumption and the reduction of exhaust gas, but also systems which raise the active and passive driving safety such as air- bag, anti-lock braking system or vehicle dynamics control, to name only those which already rank among the standard systems today. Moreover, driver assistance systems and technical devices to increase comfort such as air conditioning, navigation systems or automatic seat adjustment play an impor- tant role. The prerequisite for the fact that such systems are marketable is a favourable proportion of many pro- perties such as weight, designed space, perfor- mance requirement, easy replaceability and (much more important in the auto- mobile branch, for ex- ample, than in aerospace) MechatronicCarLab 36 MechatronicCarLab Aerospace Technology for Road Vehicles The MechatronicCarLab as a driving simulator at the Hannover Fair 2002 A System Development Environment with Real and Virtual Mechatronic Vehicle Components Various engineering disciplines are involved in the development of mechatronic components: The know-how in the fields of mechanics, electronics and infor- mation technology is in demand when the most diverse functions become inte- grated into one product within a confined space. At the DLR in Oberpfaffen- hofen this technology already has a tradition - in the meantime automotive engineering has become an extensive area of application.
Transcript
In recent years the techni-cal inner life of our motor-cars has changed dramati-cally. Whereas formerlycomponents such as carbu-rettor or ignition distribu-tor could still be recogni-zed if the engine bonnetwas opened, nowadayselectronic control unitshave taken command. Butthis would not be practica-ble any other way when weconsider what we aspurchasers and drivers ofthe cars expect in terms offunctions and attributes.These include, for instance,low fuel consumption andthe reduction of exhaustgas, but also systems whichraise the active and passivedriving safety such as air-bag, anti-lock brakingsystem or vehicle dynamics
control, to name onlythose which already rankamong the standardsystems today. Moreover,driver assistance systemsand technical devices toincrease comfort such as airconditioning, navigationsystems or automatic seatadjustment play an impor-tant role.
The prerequisite for thefact that such systems aremarketable is a favourableproportion of many pro-perties such as weight,designed space, perfor-mance requirement, easyreplaceability and (muchmore important in the auto-mobile branch, for ex-ample, than in aerospace)
MechatronicCarLab
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Aerospace Technologyfor Road Vehicles
The MechatronicCarLab as a driving simulator at the HannoverFair 2002
A System Development Environment with Realand Virtual Mechatronic Vehicle Components
Various engineering disciplines are involved in the development of mechatroniccomponents: The know-how in the fields of mechanics, electronics and infor-mation technology is in demand when the most diverse functions become inte-grated into one product within a confined space. At the DLR in Oberpfaffen-hofen this technology already has a tradition - in the meantime automotiveengineering has become an extensive area of application.
Institute of Robotics and Mecha-tronics are simulations of the roll-over stability of trucks and buses.Elastic deformation of the vehicleframework, the exact characteristicsof the tyres, the reaction of the dri-ver, sloshing fluid in the tanker aswell as the interaction of vehicleand elastic roadway (e.g. whencrossing a bridge) are examples ofquestions for which simulationmodels and new simulationmethods are developed.
A project carried out jointly in1996 by BMW and the Institute ofRobotics and Mechatronics laid thefoundation stone for the virtualdrive train. When using the noveltechnology of the object-orientedmodelling with Modelica® simpleengine models and, if necessary,detailed gear models ranging frommanual transmission to six-gearautomatic transmission are simula-ted in combination with real elec-tronic control units, i.e. in real-time. The modelling of vehicledrive trains is presently promotedwithin the scope of the project„Test and Optimisation of VehicleElectronic Control Units withHardware-in-the-Loop Simula-tion“ which is supported by theBavarian State Ministry of Econo-mic Affairs, Transport and Techno-logy. This project is being dealt
running behaviour of railwayvehicles on tracks. The main focusof the work, which is also promo-ted by the Bavarian State Ministryof Economic Affairs, Transport andTechnology, is the simulation ofthe dynamics of road and railvehicles. In the course of time alaboratory infrastructure has thusdeveloped in Oberpfaffenhofenwhich is composed of real hard-ware and virtual components. Thevirtual components consist ofmathematical models. A mechatro-nic unit can thus be developed andanalysed taking into considerationthe interaction with the entirevehicle. For example, the not reallyexisting sub-systems of the vehicleare simulated in real-time andconnected with the real compo-nents via suitable interfaces (hard-ware-in-the-loop-simulation).
Depending on concrete questionsand availability, real and virtualcomponents can be exchanged forone another. The virtual compo-nents are scaled according torequirements, i.e. they are con-sidered with exactly the level ofdetail and effort as is appropriate tothe type of problem.
For the simulation of multibodysystems the SIMPACK softwareprogramme was developed at theInstitute of Robotics and Mecha-tronics. This programme is nowmarketed and further developed bythe company INTEC GmbH. As aresult of interfaces to a variety ofCAE programmes, SIMPACK hasoutgrown pure multibody simula-tion. As a tool for the analysis anddesign of complex mechatronicsystems, it is also adopted by manyrenowned companies in the auto-mobile and railway industry bothhome and abroad. Among theinvestigations carried out at the
low costs. These requirementshave contributed towards the factthat today mechanical, electricaland electronic parts are combinedinto highly integrated mechatroniccomponents. In connection withinformation technology and soft-ware algorithms, to some extentthey possess a very high degree ofintelligence and autonomy. Thefusion of sensors, control andactuators into compact units fullycomplies with the trend of modula-risation in the vehicle industry. Asa result of the bloom of mechatro-nics in vehicles and its commercialimportance, this topic also plays animportant role in the Oberpfaffen-hofen Institute of Robotics andMechatronics. The expertise in thefield of integration of highly com-plex mechatronic systems wasacquired from the development ofcomponents for aerospace robotics.Today the institute with its many-sided main pillars has become amuch sought after partner in indus-try. The interest is not only cen-tred on the mechatronic compo-nents themselves, but also on themethods for their development aswell as the scientifically establishedmethods and tools for controlengineering.
Research and development are car-ried out within the scope of the„Bayerisches KompetenznetzwerkMechatronik“ (Bavarian Compe-tence Network of Mechatronics).In addition there is commissionedwork for the automobile industryand its suppliers. Vehicle systemdynamics, dynamics analysis andthe evaluation of vehicles have along tradition which began withthe analysis of maglev (magneticlevitation train) systems and the
37MechatronicCarLab
New Possibilities as a resultof object-oriented Modelling
Flexible Boundarybetween Reality
and Computer Worlds
Vehicle dynamics simulation with Modelica®/Dymola
Tanker simulation model with sloshingfluid
with by the Institute of Roboticsand Mechatronics together withBMW and Liebherr Aerospace.The results are incorporated in thecommercially marketed drive trainlibrary PowerTrain which is usedby several automotive manufactu-rers and suppliers.
Right from the start the Institutewas significantly involved in thedevelopment of the modelling lan-guage Modelica® (as an open stan-dard for the creation of multi-phy-sical models of complex systems).Besides the development of thisstandard, the availability of com-prehensive component libraries isof vital importance for the applica-tion of this technology. In this waybase libraries for control-engineering and electrical compo-nents, drive trains, mechanicalmulti-body systems and heat con-duction, as well as special librariesfor robots, flight and vehicle dyna-mics etc. were developed at theInstitute of Robotics and Mecha-tronics in cooperation with othermembers of the Modelica Asso-ciation.
The simulation of vehicle dyna-mics in the MechatronicCarLabcan be performed in real-time withthe aid of 3D-graphics, simulta-neously in multiple projections,from the perspective of the driveror any other view. One of manyapplications of the Mechatronic-
CarLab is there-fore that of adriving simula-tor. The drivercan be offeredvarious interfa-ces for opera-ting: A force-reflecting stee-ring wheel isavailable whichreceives the dri-ver’s request anddisplays steeringtorques to thedriver. The actu-ator for this is a compact electricalmotor unit with Harmonic-Drive-Gears. The difference to conven-tional servo drives is an outputshaft torque sensor which permitsa swift and precise torque control.The drive unit was developed onthe basis of the joint drive of theDLR lightweight robot and offersthe foundation for the latest spin-off of the Institute. The company
SENSODRIVE GmbH has madeit its business to make use of inno-vative torque-controlled drives inthe fields of industrial and servicerobotics, rehabilitation and trainingas well as in plant engineering andconstruction. A force-reflectingsteering wheel was also deliveredto the Braunschweig DLR Institu-te for Transportation Systems.With this steering wheel newassistance systems are analysed therein the driving simulator and drive-by-wire experimental vehiclewhich assist the driver also whensteering. Furthermore, in theMechatronicCarLab a high-perfor-mance joystick with force feedbackenables the analysis of novel con-trol concepts alternatively to theconventional steering wheel. Aforce-reflecting accelerator pedalcompletes the configuration.
The DLR lightweight robot canbe brought into the Mechatronic-CarLab for virtual analyses of thepositioning and design of opera-
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Descriptive and TangibleDevelopment of
Drive-by-Wire andVehicle Dynamics Control
Systems by „Virtual Reality“
The mechatronic drive unit with torquesensor is suitable for generating torqueson the Steer-by-Wire steering wheel
Gear Simulation with Modelica®/Dymola
MechatronicCarLab with force-reflecting steering input devices(steering wheel, joystick) and force-reflecting accelerator pedal,real-time vehicle dynamics simulation and visualisation
ting elements (e.g. a gearshiftlever) in a vehicle. The handling ofthe operating element can be con-veyed to a test person by moun-ting the control element on the tipof the robot. The lightweightrobot, which is equipped withhigh-precision force- and torque-sensor technology, is controlled insuch a way that it reflects the elas-ticity, stiffness and degrees of free-
dom of the operating element.Besides the standard operating ele-ments of present-day cars, with
this universal force feedback deviceany novel (e.g. multifunctional)operating elements can be exami-ned flexibly with regard to ergo-nomics and manageability. TheMechatronicCarLab can also beoperated as a test bench formechatronic components or entiredrive-by-wire systems. At presentthe work is concentrated on thetorque control of the steeringwheel actuator and the testing of asuperordinate steer-by-wire con-trol which restores the disconnec-ted mechanical connection be-tween steering wheel and frontwheels by means of the mechatro-nic actuators. The control determi-nes the steering feeling and thedynamics of the steer-by-wiresteering system and was developedtogether with the company TRWFahrwerksysteme.
Another field of application forthe MechatronicCarLab is thevirtual testing of vehicle dynamicscontrol. With active additionalsteering or with steer-by-wire,for example, automatic steeringintervention for the stabilisationof the vehicle state can be carriedout. A distinct reduction of therisk of skidding or rollover canthus be achieved. The steeringbehaviour of the vehicle can alsobe completely redesigned bysoftware in this way without addi-tional constructive alterations tothe suspension being necessary ora compromise at the expense ofother vehicle dynamics criteriabeing called for.
With a high-performance hydrau-lic linear actuator test bench an-other mechatronic steer-by-wirecomponent can be brought fromthe model and simulation dimen-sion into reality: The steeringmotor which shifts the tie rods ofa vehicle and thus adjusts thesteering angle to the front wheels.The load forces come from thevehicle dynamics simulation andare imposed onto the steeringmotor with the aid of a hydraulicpiston. Either the hardware of acustomer or one's own mechatro-nic linear actuator with positio-ning and force sensors can beused as a steering motor. The lat-ter has its origins in the gripperfor the world-wide first spacerobot ROTEX and is based onthe patented DLR Planetary Rol-
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Force-reflecting joystick as an alternativeto steering wheel and pedals
Development of steer-by-wire algorithms and components on the steer-by-wire testbench
Lightweight robot as force-reflecting inter-face for virtual operating elements
The notion of drive-by-wire invehicles generally indicates thereplacement of mechanical (alsohydraulic) connections by electro-mechanical components, sensorsand control devices which onlycommunicate with each other viasignal transmission. Steer-by-wire and brake-by-wire are spe-cial terms for steering or brakingsystems respectively. The advan-tages lie in the considerably moreflexible design possibilities; inter-vention in vehicle dynamics forthe improvement of drivingsafety, for example, is in manycases only possible in this way.Drive-by-wire systems obviouslydemand high costs to safeguardagainst system failure, but in thelong run they will substitute theconventional mechanical connec-tions in vehicles.
Mechatronic ComponentDevelopment under
Realistic Conditions
ler Spindle Drive (PRSD). Due toits high power density and pro-grammable dynamics the mecha-tronic linear actuator still offersmultifaceted potential for use invehicles, for example for activesuspension. This can also betested with the MechatronicCar-Lab.
The development of new con-cepts is also supported by furthertests with the already mentionedhydraulic test bench, inter alia forthe identification of mechatroniclinear components. The aim ofthe experiments, for examplewith the PRSD and a semi-active,magneto-rheological damper, is inboth cases to get to know thecomponents over a wide opera-ting domain and to derive realisticsimulation models from the gaineddata. With this information con-clusions can in turn be drawn onthe effectiveness of new con-cepts. An important field of appli-cation is the road-friendly sus-pension design of trucks. So-calledsemi-active shock-absorbers canbe used, the damping of whichcan be adjusted continuously andvery quickly depending on thedriving conditions. In this waythe vertical vibrations can bereduced by up to 15 percentdepending on the road condi-tions. Since it is above all thesedynamic loads which damage theroadbed, such concepts can con-tribute towards limiting mainte-nance costs for the road networkin Germany and Europe despiteincreasing truck traffic.
At the Institute of Robotics andMechatronics components forBrake-by-Wire systems are alsodeveloped. The already men-tioned Planetary Roller SpindleDrive (PRSD) with its low fric-tion and high efficiency over 80percent is predicted a great futurefor the application to Brake-by-Wire. The „classic“ Brake-by-Wire principle uses a motor-PRSD combination in order toactively compress the brakeshoes. Normal forces in the rangeof 30 kN are not unusual. Thecompany Narr in Kirchheim/Teck,a licensee, was the first tosuccessfully establish methodsfor manufacturing the PRSDwhich allow production in a largeseries. With the first prototype ofa brake for railway vehicles, builttogether with the company KnorrBremse, the PRSD with a lifespan of far more than one millionbrake cycles recently proved to befar superior compared with allother spindles.
Yet another approach for a highlyefficient mechatronic brake origi-nated in the DLR Institute ofRobotics and Mechatronics. Inthe meantime it is much discussedamong experts as a possible brake
concept for the future. Resear-chers have rediscovered the self-energising braking effect of awedge from the times when therewere still no virtual or mechatro-nic vehicles, but only coaches. Inthose days the coachman stuck awedge between the wheel andwheel house and the wedge tigh-tened itself. This very energy-efficient way of braking can alsobe applied to a modern brakeunit. Mechatronic concepts withforce sensors and swift controlavoid (in contrast to the coach) ajamming of the wedge and
blocking of the wheels. At thesame time the energy demandcompared with conventional bra-kes is reduced by up to 97 per-cent, for almost the entire powerrequired is taken from the kineticenergy of the vehicle. At the
40 MechatronicCarLab
eBrake® - the self-energising mechatronic brake with RoboDrive propulsion unit
Mechatronic Brake-by-Wire
The Planetary Roller Spindle Drive ascentre-piece of novel mechatronic brakesfor railway vehicles has an unrivalledhigh life cycle.
Mechatronic linear actuator on the basisof the Planetary Roller Spindle Drive
same time the best possible bra-king effect remains. The develop-ment of a mechatronic brake ofthis second type (eBrake®) is inthe meantime carried on by ano-ther spin-off of the Institute, theSeefeld company eStop. It canalready demonstrate the first pro-totypes and for the wedge positi-on control it has integrated boththe PRSD spindle and the new,extremely low-loss DLR robotjoint motor RoboDrive. Thisnew, intelligent, torque-control-led and highly integrated light-weight drive is particularly opti-mized towards applications whichdemand a perpetually reversingoperation with high dynamics andhigh torque, but low dead weightand low dissipation loss. Further-more, this motor offers a quasi-linear (low-ripple) torque beha-viour and is therefore also extre-mely well suited for applicationswhere a human operator sensesthe resulting uniform revolution.Thus at present, besides the firsttest models of the eStop brake,several steering wheel prototypesare also equipped with this motorconcept for steer-by-wire anddriving simulators.
The MechatronicCarLab of theInstitute of Robotics and Mecha-tronics comprises the experimen-tal infrastructure for testingmechatronic components forapplications in vehicles as well asa multitude of already developedcomponents themselves. It alsoincludes the total methods andtools for the development andanalysis of mechatronic systems.Working in the MechatronicCar-Lab, an inspiring building of vir-tual and real rooms, are „live“ col-leagues whose dedication, experi-ence and knowledge also belongto this laboratory. It is thereforealso the ideal for arousing andencouraging the scholars’ interestin technical questions. The roundtour of the laboratories which iscovered in this article will end inthe DLR_School_Lab in Ober-pfaffenhofen. Here, for example,pupils can test the behaviour ofself-built and self-programmedmobile mini robots. ASUROstands for „A Small and UniqueRobot from Oberpfaffenhofen“.The kit consisting of easilyobtainable components has al-
ready been assembled several timesby youngsters in theDLR_School_Lab and pro-grammed with free softwaretools. By means of integratedsensors, for example, ASUROcan follow a line or even spinlively pirouettes. If the robot isproperly programmed it avoidsobstacles autonomously or followsa preassigned track. Via infra-redeven its most diverse functionscan be commanded by a conven-tional TV remote control.Thanks to ASURO, many scho-lars have seen the light and in aplayful way realized just howinteresting mathematics and phy-sics can be. Hopefully thisenthusiasm over the knowledgegained will spur some of theyoung people on to come up withideas of their own for the vehiclesof the future or new paradigmsfor their development. First publication in the magazine „DLR-Nachrichten 106“,
December 2003, publisher: Deutsches Zentrum für Luft- und
Raumfahrt (German Aerospace Center).
Author:
Institute of Roboticsand Mechatronics,DLR Oberpfaffenhofen
Presentation of the „HERMES AWARD – HANNOVER MESSE International TechnologyPrize“ in April 2004 by Chancellor Gerhard Schröder to the company eStop for themechatronic wedge brake „eBrake“. This prize for outstanding scientific and technologi-cal developments was awarded for the first time this year and at 100.000 € is one ofthe world-wide highest endowed technology prizes.
