Powertrain Testing with Wheel Slip SimulationThe Total Powertrain Optimization ApplicationThe development goals are as follows:
- Assuring durability and wear-resistance of the gearbox and entire powertrain
- Reduction of the weight by optimizing the complete powertrain
- Optimization of driveability
- Development of electronic driving aids
- Optimization of control units
The following development tasks are carried out on the test bed:
- Fatigue limit test with realtime simulation methodology
- Testing of all (all-wheel) systems
- Investigation of torque build-up in the powertrain
- Function tests on gearbox
- Function tests on transfer boxes and clutches on vehicles with all-wheel drive
- Testing of configuration and durability through optimization of weight
The AVL solutionAVL can supply a unique – tested and patented - solution that offers realistic simulation of driver, vehicle, track, tires and road surface so that tests can be moved from road to the all-wheel drive/powertrain test rig.
Comparability of the test results is guaranteed – which makes the total optimization of the powertrain simply possible.
Five Reasons for Choosing AVL- 1. AVL is the only supplier that can realistically simulate the dynamic behavior of tires and road surface (wheel slip simulation). Fewer expensive and time-intensive tests on the road due to the shift from road to rig.
- 2. AVL enables you to implement holistic optimization of all the powertrain components with respect to configuration, weight, driveability and consumption using the wheel slip simulation function.
- 3. AVL optimizes driveability by realistic simulation of the complete vehicle on the road using deep modeling (vehicle, tires, track) and therefore guarantees better simulation quality.
- 4. The AVL solution allows you to test any (including all-wheel drive) system without requiring knowledge of the load distribution and the control mechanisms in the powertrain because the test bed automatically adjusts the load distribution as if on the road.
- 5. Uniform parametrization using the standardized tire model reduces parametrization costs in the development process.
Mechanical ComponentsThe mechanical design of the test bed has to be matched to the very specific requirements of a powertrain test bed which can vary considerably.
With all-wheel vehicles, for instance, the different wheelbase has to be taken into account. The challenge for the mechanics therefore is that the dynamometers have to be adjustable. The AVL solution allows simple axle and track adjustment by manual (or as an option automatic) shifting of the DynoWheel machines.
All the other modular mechanical standard components are specified to the requirements of powertrain testing and comprehensively tried and tested.
The special mechanical configuration of OptimaTest Powertrain test bed is modular and open for future extensions.
The flexible mechanical configuration of the AVL solution gives users a test bed with multi-configuration capability. The highly dynamic all-wheel powertrain test bed can easily be reconfigured for testing vehicles with front and rear-wheel drive. Different tests can therefore be carried out on the same test bed which makes for enormous cost savings.
The versatility of the test bed with its multi-configuration capability guarantees operators higher productivity, saving time and money.
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AVL Dynolution – AVL DynoWheelAn AVL OptimaTest Powertrain Test Bed has to be suitable for dynamic simulation of driver, vehicle, tires and track. That requires a dynamometer with a moment of mass inertia which approximates to that of the actual wheel on the vehicle.
The AVL DynoWheel dynamometer that AVL recommends for this test bed application has a very low mass inertia of 0.9 kgm² and therefore perfectly fits the bill.
Using DC machines in permanent excitation with this minimal moment of inertia makes it possible to realistically simulate the actual wheel inertia. The dynamic properties of the tire (e.g. tire-road contact) can then be added to these simulation models which can be used, for example, to develop electronic drive aids.
AVL developed a special converter with extra high control frequency to enable realistic simulation of the dynamic tire behavior. The converter also has a fast digital connection to the AVL KIWI higher-level control system.
It is the uniquely low mass inertia of the AVL DynoWheel that makes simulating tires, driver, vehicle and road possible.
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Online Simulation: AVL ISACThe hardware that is physically absent has to be replicated by simulation models in realtime for work on the test bed. Tires, vehicle, road and driver can be simulated with AVL ISAC's unique realtime models.
- Tires: the tire model describes the dynamic phenomena between the tires and the road. It takes into account the vehicle's transferable torque in response to different road surface conditions, e.g. vehicle on tarmac or ice.
- Vehicle: in addition to the dynamic properties, such as acceleration in the longitudinal and transversal directions and rotating motion of the vehicle around the vertical axis, quasi-steady-state vehicle resistances are also simulated, such as wind resistance.
- Track: in vehicle simulation tests it is compulsory to predefine the track topology. Input parameters for the simulation models of driver and vehicle are the demand values, e.g. road gradient, lateral incline, bend radius, maximum speed and desired speed. The Track and Drive Editor is used for the track description which saves time when creating the test run.
- Driver: just as in a real vehicle, the tasks of the driver simulation model are acceleration, braking, speed control and steering.
The development goals outlined above are easy to achieve with these unique simulation models because the AVL solution allows the following activities:
- Realistic tests on all-wheel drive systems
- Realistic simulation of drive-off characteristics
- Both requirements are met by the vehicle and tire simulation models.
- Realistic simulation of driving maneuvers
- Realistic simulation of driving maneuvers is guaranteed by the interaction of the driver, track and vehicle simulation models.
- Realistic simulation of the intrinsic vibrational behavior
- The mechanical structure and the right simulation makes it possible to imitate realistically the intrinsic vibrational behavior.
- Intelligent, vehicle-like load distribution between front and rear axles
Intelligent, vehicle-like load distribution between the front and rear axles is the result of the wheel slip simulation with four separate wheels and synchronized vehicle model.
Simulation of the highly dynamic phenomena of the tire/track contact requires a control system close to the converter. AVL KIWI allows the tire model to be integrated in the converter so that the control is handled from inside the converter at a sampling frequency of 4.6 kHz. In addition to the simulation / control of the four wheels in the converter, the higher level AVL ISAC / EMCON 404 feedback control system is responsible for the vehicle simulation.
The mechanics, dynamometer, simulation software and control system together constitute a unique simulation environment for the optimization of the complete powertrain.
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AutomationMeasurements have to be carried out quickly and very frequently in powertrain testing to be able to determine and assess fast gear shift processes, especially in automatic transmissions. More measuring points also have to be allowed for than on an engine test bed (for automatic transmissions, approx. 20-30 pressures). That requires sampling frequencies of at least 1 kHz. The special Automation for Powertrain Testing permits a sum sampling rate of at least 50 kHz and can easily meet the challenge.
The realtime recorder with up to 100 channels and a band width of 50,000 values/sec can record all the relevant quantities during a test run.
The data acquired in powertrain tests is evaluated based on integral criteria. For example, the classification plays an important role in assessing endurance (rev count classification or rainflow classification). These methods require incredible amounts of data which has to be sensibly reduced to essentials. AVL can supply a special tool for the job providing impressive methods for reducing and post-processing data.
The methods developed by AVL for gearshift evaluation are also based on a sensible data reduction method. Characteristic quantities are determined during gearshifts so that any changes in the gears can be detected early and optimized.
The enormous amount of data is acquired and evaluated sensibly with the development goal in mind.
Fast limit value monitoring with absolutely minimum response times is necessary to ensure the safety of the test bed and operator. That is taken care of by AVL's realtime operation system, ARTE. can track a current measurement quantity against a limit value.
Immediate response when limit values are exceeded.
Numerous interfaces, such as COM via VB Scripting, CAN, Profibus, FireWire, CDH allow customers' own software functions, a range of measuring instruments and the ECU/TCU to be integrated quickly and easily.
AVL supports customers' enthusiasm for experimentation as well as supplier independence.
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InstrumentationFor injection systems with vapor bubbles in the return line, AVL recommends the tried and much tested AVL 734 Double Fuel Balance and its conditioning system for powertrain test beds. The Balance offers exceptionally high accuracy (0.12% measurement accuracy). The special conditioning system is designed for fuel consumptions of up to 360 kg/hour and can condition the fuel from 0 to 60 deg. C to an accuracy of 0.5 deg. C. Stable temperatures are an absolute must for reproducible results.
Alternatively, AVL can also recommend the AVL Fuel Mass Flow Meter in conjunction with the AVL Temperature Control. The improved Mass Flow Meter is extremely reliable in test bed operations and easy to use with new mixture preparation systems such as direct injection systems in gasoline and diesel engines. Quick and easy to integrate in the test bed environment, it minimizes downtimes while the graphic user interface makes it highly user-friendly.
AVL can also quote for special oil and water conditioning units to customer specifications on request.
The engine instrumentation recommended by AVL for the powertrain test bed application means that the test bed can easily be extended to handle future changes.
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