Developing a Validation System for Passenger Compartment ECU Software with LabVIEW Real-Time

Author(s):
Mo Sergio - Magneti Marelli

Industry:
Automotive

Products:
CAN, LabVIEW, PXI/CompactPCI, Serial,

The Challenge:
Developing an automatic real-time tool for the functional verification and validation of application software for complex automotive electronic control units (ECUs) used in passenger compartments to simulate the car environment.

The Solution:
Simulating a car compartment to acquire the body computer ECU responses and generate signals in real time using an 18-slot PXI Chaisis, a PXI-8176 real-time controller, data acquisition (DAQ) boards, LabVIEW Real-Time software, matrixes, load boxes, and signal conditioning boards.

To execute the functional testing of the body computer ECU, we must supply the unit’s inputs and outputs with a simulation of the signals and loads available during operation, under normal conditions, under stress, or with possible electric and electronic failure. While these signals and loads cannot be static, they must comply with a specific time-based sequence in relation to test requirements. At the same time, we must record all ECU outputs in analog mode to verify that the internal control software accurately executes the reactions generated by the environment where the ECU is located.

For years, we have been investing in the verification and validation of application software for our products to provide customers with increased quality and development times that meet current and future market requirements. We used LabVIEW Real-Time to develop a system with standard PXI instrumentation, reducing overall system costs by 25 percent and increasing test coverage without extending development time. This body computer ECU controls virtually all passenger compartment functions.

We developed the test machine in cooperation with GEAS, a National Instruments alliance member in Turin. We based our test machine on a TestMaster 2400A platform to achieve the required modularity, configurability, and reliability for the implementation of a complex test system.

The issues related to the development of the system include:

• Dynamic simulation of different types of loads and signals
• Management of multiple communication lines
• Multiple acquisition of analog signals from the ECU
• 2 ms fixed-cycle time
• Time-based logging of all events
• Free customization and generation of test sequences by the system user
  
  

The mentioned requirements resulted in a real-time, versatile, and modular system. We based this system on LabVIEW Real-Time architecture to achieve an accurate, reliable, fast solution.

Developing a PXI-Based Test Machine
We based our system on a PXI-1006 18-slot chassis, which incorporates the PXI-8176 real-time controller, the PXI-6071 multifunction DAQ board, PXI-6508 digital I/O module, PXI-8420 four-port RS interface module, and the PXI-8462 dual speed CAN interface module. Our PXI system also includes a signal matrix chassis, 30 A power matrix chassis, boards for 0-32.767 Ohm decade resistors, RS-232 K line converters, RS-232 A bus converters, I/O conditioning boards, TTL conditioning boards, relay boards, and 30 A load boxes with typical impedance values.

We met supply requirements using two supply units -- one for power to supply the ECU and one for service with the signal matrix.

For the electric and mechanical connection to the ECU, the system provides a connecting fixture with an additional measurement panel and status LED for the ECU outputs.

Using LabVIEW Real-Time to Deliver a Fast, Accurate, and Reliable Solution
The software consists of the real-time program, the real-time control manager, the pattern editor, and the data analyzer.

With these tools, we can manage any test sequence easily and efficiently. Using these tools, the users can generate a test sequence on a host PC, download it to the real-time controller, execute the sequencer, generate an event report, download the report to the host PC, and analyze the data to verify the test results.

The real-time program dynamically sets the signals and massages on the communication lines according to the test sequence. The program acquires the outputs and messages sent by the ECU, logging information on a time basis into the event report while maintaining a 2 ms fixed-cycle time. This system incorporates lean programming based on binary variables, management queues for the test sequences, and report generation using high-level VIs for management of DAQ boards, CAN, and serial messaging, as well as a coded and compressed format for the test sequence and the report. Finally, we use binary files to transfer data between the host PC and the real-time controller.

The real-time control manager is located at a higher level than the real-time program working as a filter between the machine and the user. The code streamlines communication through TCP-IP with the system controller to download the test sequence, start its execution, and acquire the report at the end of the sequence.

We can extrapolate the leis of tests and related functions from suitable databases to link the physical resources of the system to easily associated intuitive names. This offers a clear and intuitive view and edit of the events we must generate.

With the data analyzer, we can view the values acquired and generated during the test. In addition, all messages sent through the CAN, K line, and A bus lines are available. We can represent data in graphs or tables. This code integrates the data and measurements acquired with the information from the database.

We designed the program for an easy, time-based correlation of the different events and the calculation of the response time to the test-generated signals.

Through the performances and the configurability of this system, we can create test scenarios that, until recently, were not achievable in a short time with standard instrumentation. By synchronizing all system resources deterministically, we ensure the machine performs repeat tests and automatic generation of the relevant measurement reports. Now, designers can focus on the creation of more effective test scenarios other than nonregressive test techniques.

For more information, please contact:
Magneti Marelli Powertrain Systems
V.le Carlo Emanuele 118
Venaria Reale (TO) - Italy
Web: www.marelli.it

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