Simulation and Test

DEVELOPMENT Simulation and Test

of software development and application An enhancement for tools developed questions that are better answered is gaining importance. However, this does in-house that is particularly helpful in through offline simulation. The influence Simulation-based Development not eliminate the need for comprehensive motorsport is the use of a driving simula- of changed driving resistance on lap hardware development. and drive tor with a motion platform. Simulator times can be evaluated with greater accu- control systems help tap into all the specific hardware and software are not racy through offline simulations as the Process for Motorsport and potential offered by the overall system. regarded as core competencies and are variance of a human driver does not In the LMP1 racing car, new software therefore procured from a system supplier apply in this case. versions can also be developed and (VI-grade). However, the same vehicle In-house development of tools has sev- Series Production introduced between races. In contrast to model developed in-house and used in eral advantages. hardware development, this brings the remaining simulation tools is used as –– Models and evaluation software serve improvements to the vehicle without the vehicle model and integrated into the as an executable knowledge database involving major lead times. For road simulator environment. The use of the and communication platform for all vehicles, it is also already technically simulation models can therefore also be users, allowing for a lively exchange feasible to retrospectively load new soft- extended to the area of subjective evalua- between all the departments involved ware versions into the customer vehicle. tion by the driver. The driver is essen- as well as between motorsport and However, new functions can only be tially serving as an evaluation tool, series production developers. Custom- tested using model-based variant studies whereby subjective impressions are used ised integration into the processes due to the high number of vehicle, model in addition to objective key figures in ensures that they can be used effi- and software variants. order to evaluate handling. The vehicle ciently and with ease. model delivers reproducible, deterministic –– In-house development significantly behaviour in a safe but still sufficiently improves understanding of both tools SIMULATION AS AN EXCHANGE realistic environment. This permits rapid and vehicle handling. It provides the PLATFORM development and meaningful preliminary opportunity for quantitative evaluation One of the core competencies at synchronisation of connected functions and creation of objective and authori- during vehicle development is objective that are relevant for handling. A positive tative key figures. evaluation of vehicle dynamics. side effect of using the same vehicle –– Using methods, models and evaluation © Porsche Although commercial software packages model for this type of application is the programs jointly across projects and are available for this task, Porsche pre- increase in model quality across the mod- departments automatically creates the fers to use tools developed in-house for el’s entire application area. Evaluating lap need for close collaboration and com- simulation of vehicle dynamics and times on the driving simulator is particu- munication and therefore ensures a objectification of vehicle handling. All larly useful for issues relating to vehicle constant exchange of knowledge AUTHORS The Porsche development centre in Weissach (Germany) is home to models and programs developed stability limits. In contrast to offline sim- between the different areas in the both of the vehicle series production development as well as the in-house are provided centrally for mot- ulation, a human driver cannot tap into development centre. It also results in orsport and series production applica- the entire theoretical potential of a vehi- common metrics and a common lan- motor racing application and development departments. We can see tions. In areas where competition is less cle. Vehicle handling close to the individ- guage for describing driving physics. clear parallels when we look at the tasks and challenges involved in relevant, it makes more sense from a ual stability limit has a significant influ- In addition, tool extensions and strategic perspective to use commercially ence on the lap times a human driver can improvements will benefit all users, the development of road vehicles and racing cars. Both areas only available products. achieve. On the other hand, there are FIGURE 2. Dipl.-Ing. Kai Fritzsche is Consultant Performance LMP1 at have short development periods and limited resources available. Porsche in Weissach (Germany). These overlaps suggest there ought to be close collaboration in the areas of method and tool development.

2.0-l V4 turbo petrol engine

RETURNING TO THE TOP TIER FIGURE 1, has an electric motor at the Li-ion battery AT LE MANS Dipl.-Ing. (FH) Florian Strecker front , giving it a temporary all- is Special Consultant Driving wheel drive with an additional power of Dynamics, Calculation & System In addition to making a major commit- 300 kW. However, there are upper limits Dynamics at Porsche in Weissach ment to GT and road racing vehicles, on the amount of electric and fossil-fuel (Germany). Porsche Motorsport has been participat- energy released per lap. To ensure racing ing in the LeMans-Prototype-1 (LMP1) success, the focus is therefore on devel- class of the FIA WEC racing series with oping overall vehicle efficiency. the Porsche 919 Hybrid since 2014. The WEC includes nine races per year: eight VEHICLE DEVELOPMENT 2.0 6 h races and the . Exhaust energy recovery system The manufacturer vehicles in the LMP1 Systems are becoming increasingly com- Dr.-Ing. Malte Huneke category are hybrid vehicles for which plex both in road vehicles and racing is Head of Performance LMP1 at Electric machine at the front axle Porsche in Weissach (Germany). the regulations allow a great degree of cars. Due to the growing influence of soft- FIGURE 1 Technical details of Porsche technical freedom. The 919 Hybrid, ware on vehicles in both fields, the issue 919 Hybrid (© Porsche)

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similar steps are followed as during the A key issue as part of the race prepara- series production process between the tion is the development of the boost strat- 3 projectors, 120 Hz WUXGA, races, but within a shorter period of time. egy. It defines the permitted amount of 215° field of view, In the case of functional software electrical energy and the power level for screen height: 2.4 m, radius: 4 m updates, the steps are as follows: the boost in each sector of the track. Cockpit of Porsche 919 Hybrid, ECUs as HiL, –– Analyse the previous race as well as However, the entire amount of energy digital audio and intercom the upcoming race from the previous that can be released for each lap is lim- season to identify potential for ited; in Mexico it was limited to 3.92 MJ. improvement for the next race. The additional power of 300 kW could –– Develop potential for improvement therefore be applied for a duration of identified in the simulation. To that 13.07 s per lap. With a lap time of roughly end, the control system software is 1:26 minutes, this corresponds to 15.2 linked to various simulation environ- percent of the lap. It is always the goal of ments as software-in-the-loop. On the strategic energy distribution to minimise one hand, recorded track data can be the lap time. However, since the powerful

FIGURE 2 Central simulation environment as project platform (© Porsche) loaded into the software to analyse temporary all-wheel drive also influences Motion platform: 1 operator workstation, direct changes to the previous version handling, the influence on driving - VI-grade DiM 4 engineer workstations, (Driver in Motion) same working process as based on track data. On the other dynamics must also be considered. - 9 degrees of freedom on the race track hand, the software can be linked to The development of the boost strategy the dynamic simulation model to eval- for a new track begins with the optimisa- FIGURE 4 Profile of the Porsche LMP1 Team driving simulator with 3 projectors, cockpit, motion platform uate variants in the closed control loop tion of the energy distribution using the and (© Porsche) based on individual manoeuvres or vehicle model. The necessary prerequi- lap time simulations. sites for these lap time evaluations on 01:40 –– Test the newly developed software ver- the track typically involve high-quality sion on various levels. New functions measurement data that can be used to Lap times from 6 h of Mexico Collective Test, sorted in ascending order, are always tested on the hardware-in- derive the vehicle trajectory. 2 vehicles per manufacturer 01:38 the-loop test bench. This ensures that As an alternative, a driving line can be the functionality is also provided on recorded with a factory driver on the the target hardware in the compiled driving simulator, FIGURE 4, due to the state. In addition, innovations are highly precise track models. This driving 01:36 tested on the driving simulator as part line is then used as a basis for the first of the race preparations. This ensures simulations to prepare for the race and that the desired influences on handling therefore also to optimise the boost strat- 01:34 are working correctly in the closed con- egy. A first iteration variant of the boost trol loop. As a side effect, the test on strategy is available as the result of the the driving simulator in a realistic envi- optimisation. It is then used as a starting 01:32

ronment also checks the functional point for another session in the driving Lap time [mm:ss] robustness. The driving simulator also simulator. The goal of the session is to makes it possible to develop the appli- fine-tune the boost strategy in terms of 01:30 cation of the software based on the vehicle balance and driving quality. This Competitor 1 data gathered and subjective driver is done on the basis of a subjective eval- Competitor 2 evaluation in rapid iteration steps. uation by one or more factory drivers in 01:28 Porsche Updates, which to a large extent are the simulator. Furthermore, variants are FIGURE 3 Steps during the software development process between races (© Porsche) directly linked to the hardware, will developed that, for example, include a

continue to be released on drive test strategy for the start of the race or differ- 01:26 benches as well as during test drives on ent strategies to provide assistance with 0510 15 20 25 30 the test track where necessary a passing manoeuvre. As the original Total number of laps driven per vehicle –– In-house models and evaluation tools criteria and key figures that make it variant is used as a basis for comparison, FIGURE 5 Lap times from the 6 h of Mexico 2016 Collective Test (© Porsche) make it possible to work in a very quick, possible to compare measurement and all variants generated on the driving BOOST STRATEGY ON THE flexible and efficient way and to quickly simulation. simulator are evaluated once more dur- DRIVING SIMULATOR adapt to new requirements, different ing an offline simulation. At the end of vehicle concepts and new systems. The 2016 season race in Mexico is a con- the process, relative lap time differences tions, the interaction between tyres and the lap times from the flying laps by the WHEN ONE RACE ENDS, Generally speaking, simulation permits a crete example of the process and the inte- compared to the original variant without asphalt or the response to traffic condi- three LMP1 manufacturers in the first ANOTHER BEGINS high level of test coverage and thorough gration of the development tools as part of any driver influence are available. tions. Although the driving simulator is session of the 6 h of Mexico race (collec- screening of new system approaches The preparation for each LMP1 race can the race preparations. The WEC was held The result of this race preparation pro- not typically used as a driver training tive test) in ascending order. prior to setting up actual prototypes. be seen as an individual development in Mexico for the first time in 2016, which cess is a high-quality base strategy. The tool, it has a positive side effect on new The results show that, thanks to the The key factors for good integration process. Hardware changes between races meant that none of the competitors had time available during free practice can tracks in particular as the drivers are procedure described above, the lap times into development activities include a are only possible to a limited extent, but it any experience on the race track. This be used effectively to fine-tune the familiar with the track layout and have by the Porsche vehicle were already more sensible choice of model complexity and is possible to develop and introduce new made the importance of the simulation remaining unknown variables. This may already driven the vehicle virtually on consistent and faster during the first free an established catalogue of objective test software functions, FIGURE 3. This is why tools more evident than in other races. include the response to weather condi- the new track. The FIGURE 5 illustrates practice than those of the competitors.

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