Rolf Hettel

Extended Flexible Environment and Vehicle Simulation for an Automated Validation

In FISITA 2010 IPEK (Institute of Product Engineering) introduced the vehicle-in-the-loop platform based on its X-in-the-loop approach (F2010-C-177) (Albers and Duser, Implementation of a vehicle-in-the-loop development and validation platform, FISITA world automotive congress, Budapest, 2010). It offers a methodology for multi domain product development and validation as well focuses on its key hypothesis that validation is the main task in every step of product development process. An open hardware and software platform allows integration of different real components and simulation models as well as the usage of established tools and methods for measurement and validation. The platform is based on a common hardware-in-the-loop System using extended I/O-communication to the vehicle and the test bench. The application is done in C code and Matlab/Simulink so an easy exchange of modular simulation models and test cases is feasible. The architecture of model-, component- and test case implementation simplifies the scalability as well as the modularization. IPEK uses this platform amongst others for its improved fully automated validation environment which allows the optimization of operating time for determination of shifting quality on the chassis dynamometer. The task is to perform several hundred gearshifts under particular reproducible conditions automatically such as engine speed or even battery state of charge, which normally a real driver had to perform on a real test track. Compared to road tests on the rig it is possible to reach time benefits of over 80 % by using a special driver model for acceleration (using gas pedal), deceleration (using dynamometer) and gear shifting (using tip signal at steering wheel). Since the vehicle behaviour on the road is constrained to different environmental conditions it is necessary to reproduce these conditions on the test bench accurately. Different resistances affect the vehicles responses such as shifting strategy, acceleration characteristics or fuel consumption which results in altering test results. State of the art for simulating environmental conditions and vehicle characteristics on the chassis dynamometer is the Road-Load-Simulation (RLS) which uses measured vehicle coast downs to map the static resistances of a real car on a real track onto the test bench. These coast downs have to be redone every single time components of the car or the environment changes. In addition, changing resistances during test like air drag due to headwind and rolling drag due to tire temperature or abrasion can’t be simulated based on that static coast down. This paper shows an approach for simulating all kind of resistances that can appear and vary during the test such as air drag (wind), road gradient, road friction, curve resistance etc. in real-time. It can be used to drive test cases like the determination of characteristic shifting map in a more realistic way to perform better validated results. Central point is a configurable vehicle and environment model which has to be parameterized with data from the real car and track and then calculates the necessary dynamometer responses. Applied with a four roller dynamometer (two or even four driven axles) it offers the possibility to perform complex all-wheel manoeuvres e.g. such as μ-split or cornering with independent wheel behaviour and slip. Besides the advantages of this approach, an analysis of different influencing factors is shown in this paper.

Time efficient testing of hybrid electric vehicles using automated identificated physical model structures

Validation and optimization of technical systems are central activities in the product development process. One part of it is the calibration and validation on a level, which covers the whole vehicle. The aspect, that plays the most important role in both validation and optimization, is the driving condition. Especially in the case of hybrid vehicles, state variables like the state of charge (SOC) have great influence on the operating strategy and therefore on assessment criteria.The article’s objective is to present a procedure, which performs the conditioning and brings the planned maneuver into an order, which reduces the total needed conditioning duration. Thereby a lot of time can be saved, according to the type and amount of the possible maneuver and state values. In addition to optimizing the order of conventional maneuver, the procedure can be used to optimize the list of maneuver in a DOE-Plan. Thereby the maneuver of the individual criteria can be re-sorted as well as the designparametervariation. The IPEK-X-in-the-Loop framework (XiL) is the basis for the approach and will be used as a validation environment in an acoustic roller test bench with vehicle-in-the-loop technology.

Time-efficient method for test-based optimization of technical systems using physical models

Technical systems must be continuously improved so that they can remain competitive on the market. Also, the time-to-market is an important factor for the success of a product. To achieve this goal, new methods and processes are needed. Especially the testing and calibration are important phases in the development process.This paper introduces a method, which helps to reduce the time effort while increasing the quality of the calibration process. The basic idea is to use measured test data to parameterize a physical (or mostly physical) model structure to create adequate models for the optimization. The main advantage of the method is the reduction of test effort because the number of variations of the design parameter is one, or extremely decreased (depending on the system). Another advantage is that the uncertainty and the limit of the model can be quantified more accurately compared to common approaches based on non-physical model structures. These normally use artificial neuronal networks (ANN) or polynomial approaches for the test-based optimization.This contribution illustrates the method by using the example of the calibration process of a double clutch gearbox (DCT) regarding energy efficiency and drivability on a roller test bench. First step is the test planning and test execution. In this step the method calculates the optimal execution order of the measuring points. In this example 81% timesaving can be achieved compared to the equivalent on the test track. The second step is the automated generation of the simulation model. In this step the unknown parameters of the model structure are calculated. The contribution shows different approaches for the identification of non-linear systems. In the last step the model is used to perform the optimization of the design parameters.Copyright

Auswirkung der Validierungsumgebung und Manöverumsetzung auf Komfortbewertungen hybridspezifischer Triebstrangphänomene

Parallel zum wachsenden Marktanteil von Hybridfahrzeugen steigen die Kundenanforderungen hinsichtlich des Fahrkomforts. Eine Studie des ADAC hat ergeben, dass dieser Fahrkomfort mittlerweile markenubergreifend das drittwichtigste Kaufkriterium neben Qualitat und Zuverlassigkeit ist. Gleichermasen steigt die Komplexitat von Hybridtopologien durch das Wechselspiel zwischen den einzelnen Antriebsstrangkomponenten (Verbrennungsmotor, Kupplung, Elektromotor, Getriebe, …) mit dazugehorigen, softwarebasierten Betriebsstrategien.

Validation environment for function development and coverage of ADAS in the car development process

Advanced driver assistance systems in modern vehicles have achieved an important role with the result that more and more new cars will be equipped with such a system. In addition to the demand of more driving-comfort, the needs for safer vehicles [1] also increases and results in comprehensive and complex assistance systems, which enables almost autonomous driving. On the other hand the manufacturers have to save time and costs in development, which is for example possible by „from road to rig“ approaches [2]. In this way time consuming road tests will be either transferred to the reproducible test environment of test benches or are replaced by early componenttests in a virtual environment, which validates the desired system behavior. Before that background, this contribution shows approaches how advanced driver assistance systems (ADAS) in the entire vehicle can be tested on the test bench under reproducible, customer-oriented conditions, like traffic jam, by using suitable stimulators. The focus of the solutions is on roller test bench testing environments with minimal interference with the test vehicle. Based on this, the stimulation of ultrasonic-distance-sensors for parking assistance as „automotive ultrasonic target simulator“ will gain knowledge on the development process and demonstrates it then on the roller test bench. In order to keep the development of increasingly complex advanced driver assistance systems manageable, the so-designed validation environment provides the developer an approach to be able to test highly in car networked assistance systems quickly and under controlled as well as reproducible conditions.

An Operating System for the Optimization of Technical Systems Using the Example of Transmission Calibration

Technical systems must be continuously improved so that they can remain competitive in the market. The duration and the costs of the development process are important factors of success for a company. Therefore practical methods and processes have to be provided to create an efficient optimization process. Within this paper an operation system for a time efficient, test based optimization of technical systems will be presented. Therefore methods from simulations and tests are being combined. Based on the X-in-the-Loop approach (XiL) it is possible to examine the Unit under Test (UuT) on an overall vehicle level in interaction with the environment and the driver. This way, even complex interactions between the systems can be emulated concerning examination- and optimization- goals. This also allows validating and optimizing modern, strongly interconnected drive systems. Especially hybrid powertrains present major challenges to the test because the additional state variables like SOC as well as engine and operating temperatures have to be considered and adjusted if necessary. This operation system provides the methods to reduce the time of conventional test runs as well as methods for model based optimization. Conventional approaches use non-physical models like polynomial-approaches or artificial neural networks for the optimization. In contrast, the presented approach allows the use of models partly consisting of physical parts. Thereby, the model quality and the expenditure of time for testing can be reduced significantly. Even conventional test runs with various measuring points, like monitoring of shifting quality, can be shortened significantly by this operation system. In the example of the gear shifting evaluation of a dual clutch transmission the expenditure of time can be reduced by 80 %. Therefore, several measuring points are being defined throughout the different shifting modes (different accelerator pedal positions, rpms, gears, driving situations and driving maneuvers) and put into an ideal order. This means, the system calculates the order for a minimum time of conditioning between the measuring points (reaching the desired initial condition).