Customer Solutions

Automating Functionality Tests on Car Doors at Saab Automobile

Author(s):

Göran Berntsson, Centaur AB

Industry:

Automotive

Product:

CAN, Data Acquisition, LabVIEW, PXI/CompactPCI, Signal Conditioning

The Challenge:

Creating an automated functionality test of car doors during development at Saab Automobile AB.

The Solution:

Developing a portable, rugged, LabVIEW-based system using an industrial computer with National Instruments I/O cards and signal conditioning.

We used 5B modules to achieve galvanic isolation and signal conditioning.

Increasing Demands Call for Advanced Equipment
Our company, Centaur Design AB, is a technological company specializing in the field of design and testing. Saab Automobile tests the wear of car components during development, and the company contracted Centaur Design AB to develop new automated testing equipment to meet increased demands. The system had to handle temperatures as low as -20 ºC and more than 90,000 cycles at each test period. When measuring the wear of components, the test had to stop if the component met certain conditions.

Simultaneous Test Functionality
The test mechanically opens and closes the doors, and also exercises the locks, rear mirrors, and side screens. Mechanical arms powered by air pressure, pull and push the door open and closed with a strap connected to the door handle. By implementing CAN communication with the car electronics, Saab can test the electrical and mechanical systems simultaneously to produce measurement data for evaluation. Test engineers and operators can supervise the operations over the Internet. Operators receive an e-mail generated from a list on the HMI, informing them of errors and tests completed.

Using Multifunction Capabilities of NI Software and Hardware
We chose a pneumatic solution for opening and closing the car doors because of the number of cycles and the low temperature the test requires. Using proportional pneumatic valves and a software regulator, we can fully control the speed and position of the test system. We achieved position feedback through linear potentiometers integrated with pneumatic cylinders, making the structure robust enough to withstand the testing conditions. We used force sensors to measure the closing force of the doors, and accelerometers to measure the deceleration.

We used three PCI-6071E multifunctional DAQ boards to read the analog input on 87 channels. For the analog output, we used a PCI-6704 16-bit data acquisition board for nine channels. By using 5B modules, we can achieve galvanic isolation and signal conditioning between the sensors and I/O cards. We perform CAN communications with a PCI-CAN card.
By implementing the CAN protocol for communicating with the door electronic control unit and simulating car commands, we can control the locks, rear mirrors, and glass movements.

By measuring the current demand with shunts, we can control the conditions of electric actuators. An alarm system makes it possible to halt the testing when it detects a preset level of part wear. When an alarm triggers, the system generates an e-mail to the operator.

Circular buffers save data at a higher rate than used for controlling the system. This lowers the demand for processing power. We used LabVIEW multitasking capabilities to control and synchronize the various parts of the test. We also implemented a number of asynchronized communication state machines. The modular design of this system makes it possible to test not only certain components, but also the whole system.

With a WebCam and Web pages, a test engineer or operator can inspect and verify the status of the test without visiting the test site. The system saves the results in Excel-compatible files.

Creating a Flexible Operator Interface
Because of the large number of parameters, we used the dialog tab control and pop-up windows. The first tab, called “Main & Door,” handles global settings for the entire test. Saab can test the doors using one of three methods we developed:

• In random order with no correlation between the different door movements
• In correlated mode, where the back doors must be closed when the front doors close
• In all doors mode, where all doors must be open at the same time
  
  

The “Latch & Locks,” “GlassRun,” and “Rearview Mirrors” user interface pages each handle the named components. “Internet” is the name of the final page, which the operator uses to input the e-mail addresses of the people that require notification.

Two pop-up windows handle parameters that change at lesser frequencies. The first, named “Open Door Actuator Panel,” handles details of the door movement. Parameters such as closing speed, energy, or retardation can control the door movement. The second pop-up window, “Open CAN Actuator Panel,” handles communication over the CAN network.

The operator can put the system in either manual or automatic mode. When the system operates in manual mode, the operator can shorten the operation of each part of the test. When operating in automatic mode, the test runs for a defined number of cycles.

Developing a Flexible Solution
LabVIEW provides a flexible solution that fulfills all the requirements of our test. Using LabVIEW, Saab can determine the source code and modify and expand the application. We used only standard parts, so we can easily build more equipment as testing demands increase. Prior to the automated test system, Saab Automotive was only counting the number of cycles until the door broke. With this new test system, Saab can use the measurement data as input in FEA analysis for new door designs, saving time and money in the design process. This also increases efficiency of testing because the system stops testing once it detects certain conditions.

More more information, contact:
Göran Berntsson
Centaur AB
Aröds Industriväg 54
SE-422 43 Hisings Backa
Sweden
Phone: +46 31 744 55 00
Fax: +46 31 744 55 90
E-Mail: goran.berntsson@centaur.se
Web: www.centaur.se