Within the next ten years, electric vehicles are expected to account for 90 percent of the market, including full-electric vehicles and various versions of hybrid vehicles. Many new test benches for e-mobility and batteries are being built. So what are the key points we need to understand for this new type of bench? How can we find our way around this new world of tests for electric or hybrid vehicles?
The list of challenges is long. First, and most importantly, are battery tests. Today’s lithium ion batteries provide an energy density 20 to 30 times inferior to gasoline, and to achieve cost parity with a petrol-driven vehicles, we have to cut their costs four-fold. This cannot be done overnight, but the calibration of the BMS (Battery Management System) must be optimized immediately, which requires precise means of optimization on the test bench. For battery test benches, a highly automated and staff-saving process is required. It must be able to react and supervise all the test benches in real time. File formats must be identical, irrespective of their source. In some centers, each device has a different file format, which affects the center’s productivity. In addition, safety is a prime concern with batteries. Great attention must be paid to extreme conditions, in which the internal chemistry in the battery can go out of control. Severe battery tests are necessary, including fire tests, overvoltage tests, crash tests or tests in which the battery goes completely discharged. While the battery is the most sensitive element to be tested, testing electric motors also presents technological issues. Upcoming motors can reach up to 25,000 rpm. In some phases, the temperature suddenly rises, to the detriment of the motor’s longevity. In this case too, the optimization of the global Energy Management System (EMS) will allow critical cases to be managed, increasing the life span of the e-motor.
FEV summarizes the keys to e-mobility test center and system development by highlighting three points: the automated management and global supervision of the processes and the test benches, using the FEVFLEX™ and MORPHEE® software suites. The standardisation of test bench solutions, or Test Cell Products. And, the calibration of the controllers and the optimization of energy management, which demands the extended use of simulation. This vision is the result of more than ten years of experience, with two test centers in Munich and Saint Quentinen-Yvelines (France), equipped with 22 test benches to test batteries, and numerous e-motor and e-axle cells.
Fully automated process
A fully automated process is a key factor in any modern test center, but it is particularly important in battery test centers. This is done through software, such as FEVFLEX™ and MORPHEE®. FEVFLEX™ is a modular software suite dedicated to manage and monitor the entire test field. All the information sent to FEVFLEX™ is produced by MORPHEE®, FEV’s automation system. The electric revolution is only just starting. Batteries, electric motors and general vehicle architectures are set to evolve even further. In this respect, FEVFLEX™ and MORPHEE®’s upgradeability and applicability makes it a complete must. These open tools can be easily configured by the user, at no additional development cost. MORPHEE can be connected to all types of devices using the same programming interface. It produces and synchronises result files in an identical format, irrespective of the equipment used.
Test cell products: standard solutions
2019 will be a very special year for FEV Software and Testing Solutions , with the launch of the test cell products and standard test bench solutions. Over the years, many benches have been built, both on FEV’s own sites and on customer sites in Europe, Asia and America, ranging from complete engineering projects, to simple automation. FEV has built on this experience to develop standard test bench solutions, or test cell products, that use FEV’s products and products from approved suppliers. Thanks to this standardization, FEV can control costs and propose shorter deployment cycles. This offer covers all the necessary dimensions of the field of electric vehicles, and the safety-related aspects in particular.
FEV proposes battery test benches covering every test case: cell benches with up to 24 cells per climate-controlled chamber, module benches with up to six modules and integrated pack benches, either in walk-in chambers, or in king-sized climate-controlled chambers.
FEV also proposes standard e-motor test benches that can be used to characterise electric motors. The key aspect of this type of test bench is its ability to test at very high speeds and in a highly-dynamic process where vibrations are taken into consideration. FEV produces state-of-the-art e-motor test benches, including dynamometers. It offers e-motor test bench solutions enabling rotational speeds of 25,000. The MORPHEE® solution used to control the bench replaces the bench controller, offering very easy connectivity with the calculators. The e-powertrain is optimized by taking several use cases (motorways, urban environments or rural areas) and several factors (voltage and current signals, frequency versus angular position and speed, transient torque management etc.) into consideration. In this case, FEV’s OSIRIS® Powermeter serves to analyse the efficiency of the e-powertrain system by measuring the power before and after the inverter and before and after the e-motor.
FEV offers unique solutions facilitating not only the optimization, but also the validation of the complete driveline. Durability tests simulating mechanical cycles (vibrations, reducer, differential) and thermal shocks (cooling, rotor thermal management) must also be conducted. In this configuration, a good solution is to test not only the e-motor, but also the complete drive chain. On the so-called e-axle test bench it is possible to test the entire system in the downstream steps of the development process and involves using both MORPHEE® and OSIRIS®, as well as FEV dynamometers and conditioning units for fluid cooling – the so-called eCoolCon™.
Energy Management System optimization
The final key factor of success of an e-mobility test center is its capacity to optimize the calibration of the various calculators and the EMS (Energy Management System) of the drivetrain. This was already one of FEV’s strengths in the field of conventional engines, and it is still the case with electric or hybrid motors. FEV has achieved this by developing tools with two characteristic features: a very high level of performance and complete compatibility with one another. In the initial development phases, xMOD™, a virtual experimentation and co-simulation platform, creates a system that was complex to develop by co-simulating the different models that describe it: the electric motor, battery, driver, complete vehicle, etc. Consequently, virtual experiments can be made on the same platform in order to prevalidate the control laws. In the following step, the bench controlled by MORPHEE® – in this case the battery and BMS bench or the e-powertrain bench – is used to integrate the previously validated models by replacing the battery or e-motor model by the physical part, and by keeping all the other parts to produce the most accurate representation possible of the drivetrain in its environment. Since xMOD™ and MORPHEE® share the same DNA, the interfaces, tests and models all follow the same process, from the beginning to the end, in what FEV calls the Collaborative Framework. It should also be noted, that the exceptional simulation performances of these tools, which are 10 to 40 times faster than any other solution on the market, enable highly complex models to run on the test bench in real time.
Part two of three of the series “Turnkey Vehicle Development From a Single Source”.You find the first part of the series here.
Within the last decade, FEV has become an engineering service provider capable of covering the entire service spectrum of vehicle development. Three articles take a closer look at vehicle modules, body shell, interior/exterior, light and sight and chassis modules. Vehicle properties, such as NVH, driving dynamics, passive and active safety, and fatigue strength are considered. Virtual and real-life testing are the development tools here. The activities are accompanied by various control tasks such as benchmarking with subsequent target setting, test and prototype planning, weight management and homologation.
FEV assumes responsibility for the complete scope of turnkey vehicle development, as well as for the development of individual modules and for the selective design and calculation scope of individual components. The fact that the development competence for powertrain, transmission and vehicle comes from a single source makes FEV an ideal development partner – also for electrified vehicles. FEV offers particular expertise in the conversion of conventionally powered vehicles into electric vehicles. The ideal results here can be achieved only through the closely integrated and parallel development of powertrain and vehicle. Some turnkey vehicle development tasks will be introduced in the following:
Light an sight
In automotive development, the field of “light and sight” assumes a central role at the interface of design, comfort and safety. Thanks to its years of experience, FEV offers its customers comprehensive support, with advance development projects, right through to series management. Its particular specialization is in the calculation, design and production-friendly construction of headlights, taillights, and side and interior lights. Be it laser light developments for headlights or transparent OLEDs for taillight applications, FEV is a leader in setting new standards. The company has a broad range of expertise and skills in the field of micro-optical components, such as MLA technology and REALEYES 3D technology. With the bionic approach of micro-lens array technology (MLA; Figure 1) for the first time enabling the implementation of LED projectors with completely new properties: the compact size of an LED projector with sharp projection images on arbitrary geometries with the smallest possible angle of incidence.
>> FEV IS A LEADER IN SETTING NEW STANDARDS
By using REALEYES 3D technology, it is possible to display 3D graphics and logos “in front” of a screen, without 3D glasses or further tools being necessary. This highly innovative technology is currently being further developed for the automotive sector and offers great potential in terms of driver information and safety, among other things.
Test and validation
Vehicle development is shaped by strict customer and market requirements. In addition to innovation, safety, and economic efficiency, reliability is an important prerequisite that has a direct impact on the follow-up costs. Country-specific legislation lays out the basic requirements of a complete vehicle. These are defined as the basis for each development project and thereby define the development process. An important step here is the validation that proves these requirements have been met.
The term validation covers the topics fatigue strength, function, and performance. For this, FEV has comprehensive test options, as well as extensive knowledge of the necessary target parameters. The fatigue strength of the powertrain, chassis components and cellular vehicle structure is validated during the endurance test drive. In a validation test program for the planned range of applications of a vehicle, the accumulated routes are divided proportionally into various sections of the journey, representing urban traffic, highway journeys and driving on country roads, and include roads with poor surfaces and mountain roads. Hot and cold climate testing is also included. Each section poses a different challenge for the powertrain and the overall vehicle.
>> GLOBALLY ACTIVE VEHICLE MANUFACTURERS HAVE TO MEET VARIOUS REQUIREMENTS AROUND THE WORLD
However, these test scenarios do not yet take into account the special features of ADAS/AD vehicles. New scenarios are defined that test the control units on various levels to develop a suitable test program for these vehicles. These new scenarios depend more on the surroundings of the planned route, such as traffic lights, road markings, and other road users, than the route itself. The influence of these surrounding elements and their monitoring must be examined systematically with regard to the performance of the control units. It is important to take into account that a significant amount of these elements is subject to change over time and depending on location. With the FEV Advanced Road Rating System (ARRS), the tests for ADAS/AD vehicles are based on objective assessment criteria to enable a comparison of the various test routes. The focus of the ARRS approach is on objective and efficient robustness tests for ADAS/AD systems in the real world. This enables FEV to develop test methods for the validation of future technologies, such as ADAS/AD systems, systematically and efficiently.
Noise Vibration Harshness – NVH
Inner vehicle noise and vibrations are experienced firsthand by the end customer and therefore represent an important, often subconscious decision-making criterion for the purchase of a vehicle. On the one hand, they should be perceived as pleasant, but on the other hand, depending on the vehicle class, they should also express the dynamics and match the brand. The ambient noise of the vehicle is subject to legal provisions. On the one hand, pass-by noise is limited to reduce the strain on other road users and residents, and on the other, warning sounds are required of potentially very quiet electric cars for pedestrian protection (Figure 2). Acoustics and vibrations have to be taken into account consistently, across the complete vehicle development process, to achieve these NVH objectives. This begins with a decisive definition of the target values at the overall vehicle level. These are then used to derive target values for individual components, such as the engine, transmission, bodywork, and engine mounts, based on experiences with the predecessor vehicle, competitive comparisons, and the systematic assessment of noise transfer paths.
In the early phase of the development process, simulations support the design of the full concept and the detailed layout of acoustically relevant components. This includes, for example, the multibody simulation of the powertrain and the finite elements simulation of the bodywork. With the hardware’s increasing degree of maturity, the achievement of acoustic objectives will be checked with the execution of measurements and subjective assessments in the later course of the project. applicable, necessary optimizations are reported to those responsible for the part (see Figures 3 and 4).
This established process is facing new challenges due to the current trends in the automotive industry, such as electrification and autonomous driving.Click here to read the third part of the series.