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Test Bench of the Future

Highly dynamic engine test bench system

The current development process of automobiles is shaped by the different demands of the legislator, the manufacturer and the customer. The main interest of the legislator lays hereby in lower exhaust gas emissions whereas the customer wants a car with a low fuel consumption.  In addition to demands getting ever harder to meet, the development times decrease more and more.
But decreasing development times ask for earlier tests of vehicle components especially of components of the power train. In the past therefore a new trend of developing philosophy was being followed by the car manufactures. This new trend is often revered to as: "From Road to Roller to Rig". Which means that test which were carried out on expensive test drives  with real vehicles on the road are shifted to a roller test-bench. But because a car is still needed (which is most likely not available in an early phase of development) these tests are shifted to an engine/transmission test-bench system (rig). On such an engine test-bench system a calibration of the engine's electrical control unit (ECU) can be carried out. This is normally done for stationary operation points only.
If one would like to perform a such a ECU calibration also for dynamic engine operations certain conditions have to be met. One is that engine test-bench system must have a highly dynamic operation range. Another being that a load which is normally applied to the engine during a test cycle has to be supplied as a control signal in real-time to the test-bench system. This means that it is necessary to set up a test-bench system together with a real-time computer.
Because of a cooperation of Chair of Electronic Measurement an Diagnostic Technology (MDT) with the IAV GmbH we are able to use such a highly dynamic test-bench system. This test-bench system (⇒ "Test Bench of the Future") went into service in May 2005.

The first focus being the acceleration of ECU calibration processes by automation and usage of Design of Experiment (DoE) methods. But because of the highly dynamic capabillities of the test bench system it is possible to investigate not only drive trains of classical car concepts but also alternative drive train concepts (e.g. hybrid electric vehicles).
In the future "Hardware-in-the-Loop"  (HiL) simulations will be used to pursue the following targets:

  1. Bring test drives from the road to the rig to improve the calibration of engine and transmission ECUs
  2. Investigation of integration and automisation DoE methods in the calibration process
  3. Investigations of different hybrid electric vehicle powertrain concepts and components (e.g. size of energy storage, electric motor, etc.) in respect to lower fuel consumption and lower exhaust gas emissions.


As developing environment for the simulation models Modelica®/Dymola® and MATLAB®/Simulink® in connection with the Software RT-LAB® of the company Opal-RT are beeing used.

Especially the mechanical components are modelled with Modelica®/Dymola®. This object oriented Simulation environment has become more and more popular in modelling mechanical components due to some advantages in respect to other signal-flow oriented modelling tools.

Setup of the "Test Bench of the Future"

For this project, a highly dynamic engine test bench system of is used:

Lupe

The combustion engine is directly coupled with the Dynamometer, which is controlled by a power converter (⇒ Drive). The test bench control system is responsible for the control of all parts of the test bench. Signals are exchanged between the Control System and the Drive (⇒ Dynamometer Control), as well as between the Dynamometer (⇒ speed and torque signals) and the engine (⇒  Pedal Value Source - PVS) via physical input/output cards (e.g. A/D and D/A cards). The whole communication and the data acquisition take place in real-time. Due to the direct coupling of the dynamometer and the combustion engine, the clutch and the transmission have to be modelled in addition to the remainder of the vehicle’s drive train (e.g. train resistance and so forth). For this purpose, a HiL Simulator is used consisting of standard PC hardware running the real-time operating system QNX®. The HiL Simulator and the Control System communicate via a high-speed Gigabit Ethernet connection (UDP/IP). This solution represents a costeffective alternative to a "Shared Memory" solution. However, in case of high latencies of the UPD/IP connection, the usage of shared memory is still a fallback option.RT-LAB provides a variety of scripting language interfaces, such as MATLAB® or Python®, for example. Data can be displayed either directly in a Simulink®-Scope or in a display created with LabVIEW®. One major advantage of the HiL-Simulator connected via network is also the possibility of remote control and remote access of measuring data (e.g. via (S)FTP).

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