Customer Solutions

LabVIEW Real-Time Manages an Endurance Test Bench for Renault Engine Components

Author(s):

Marcel Auboiroux, MVI Technologies

Industry:

Automotive

Product:

Data Acquisition, LabVIEW, LabVIEW Real-Time, PXI/CompactPCI

The Challenge:

Creating a test bench for Renault engine components, taking irregular rotational speed into account.

The Solution:

Developing a test bench driven by a real-time board, data acquisition devices, and LabVIEW.

Testing Engine Components
The test bench division of MVI Technologies, a subsidiary of Technicatome, develops test benches for automobile manufacturers, and equipment manufacturers. We designed the test bench for engine components, known as ORMO (ORganes MOteurs), to test engine components, such as the timing belt, water pump, oil pump, or the camshaft. We selected an electronic generation of irregular rotational speed to overcome limitations imposed by thermal engines, including fuel, pollution, and difficulty of automation, and to meet performance requirements. To closely replicate the behavior of a thermal engine, the electric engine must act in an acyclic manner by varying its speed around an average speed.

Thanks to a real-time board, we embedded the control loop that is independent from the operating system.

Designing the Test Bench with NI Software and Hardware
The test bench consists of a mechanical bed mounted with the electric engine, the thermal engine undergoing the test, equipped with a simulated crankshaft, but with an actual camshaft and with the test components (belt, water pump, oil pump, etc.) housed in a thermal enclosure. Once we install the engine to be tested is installed, we replicate its life cycle until breakage of the timing belt.

The greatest challenge is to produce an irregular rotational speed with an electric engine. To achieve this, we measure the irregular rotational speed of the engine at a specific time. Based on this information, we send a piloting rule through a control loop. Each read and command cycle must complete within 20 ms. To eliminate the possibility of lockups and delays caused by Windows, we use a National Instruments PCI-7030 real-time data acquisition board running LabVIEW Real-Time. The PC controlling the test bench also contains a PCI-6602 counter board and a PCI-6025E multifunction data acquisition board.

The endurance test bench uses a counter input of the PCI-6602 board at 10 kHz to read an optical encoder. This reading provides the instant angular position of the engine crankshaft, from which we can derive the phase and amplitude of the irregular rotational speed.

We then use an RTSI bus to transfer the top dead-center information to the real-time board. The real-time board obtains the average speed and acyclic amplitude data needed to compute the instructions that will control parameters, including average speed, amplitude and phase, based on the required profile. Renault provides the required acyclic profile in easy-to-read Excel file format. By using a real-time board, the control loop can run onboard to perform independently from the operating system. This ensures that the tests conducted are deterministic – they occur precisely every 20 ms and will not be disturbed by any interference. It also results in greater control over the engine and security constraints. The multifunction board on the bench controls the security digital I/O of the engine and acquires the engine instructions from an analog input. Each endurance test can execute for several months, until one of the parts breaks. This provides longevity of data on this particular part.

To perform additional measurements, we can add an instrumentation bench as an option to the endurance test bench. Optical encoders provide data on average speed and irregular rotational speed for the camshaft. Using this data, it is possible to derive the amount of torque provided by the electric engine to the system through an analog input and other sensors that we can add as needed.

Reducing Development Time with LabVIEW
We have been using LabVIEW for six years, so the implementation of LabVIEW Real-Time has been effortless, because it follows the same logic. The real-time data acquisition board is perfectly suited to applications that require a control loop. Programming with LabVIEW has resulted in shorter development times, directly impacting our ability to offer final products at a more competitive price. In the future, we plan to supply Renault with ten test benches identical to this one.

For further information, please contact
M. Marcel Auboiroux
Phone:04 42 90 17 30
445, rue Ampère, L’Étoile
Z.I. Les Milles, BP 376
Aix-en-Provence CEDEX 13799 France
E-Mail: marcel.auboiroux@mvi-technologies.fr