Reinforcing its commitment to make quality, fuel-efficient, safe and technologically advanced vehicles, the Ford Motor Company has radically improved vehicle quality and is working hard to rank number one in quality performance. This turnaround strategy hinges on focused efforts throughout the Ford organization, including the FEAD group where LMS Test.Lab helps double the number of torsional and other vibroacoustic tests to ensure high quality standards on all the automaker’s US front-end accessory drive designs.
Ford Motor Company is on the move and ready to pass the competition. A recent study conducted by the market research and consulting firm RDA Group indicates that the quality of Ford’s domestic brands improved eight percent versus last year in terms of things-gone-wrong per 1,000 vehicles during the first three months of car ownership. This places the company in a statistical tie with the traditional quality leaders in the global automotive market.
“Our world-class quality is one of the most important aspects of our turnaround in North America, says Mark Fields, Ford’s Executive Vice President and President of the Americas. “This consistently strong quality improvement should offer today’s customer renewed confidence, setting the stage for important new products.”
Ford Drive One Campaign
As part of this campaign, Ford announced that every one of their new cars and trucks, including the 2008 Ford Focus, launched with improved quality versus its predecessor. The company’s Fusion, Taurus and Escape Hybrid models are all winners of the 2008 Consumers Digest Best Buy Awards. Additionally, Ford’s domestic brands pushed customer satisfaction up one point to 77 percent.
“Everyone from the top floor to the plant floor is working together to deliver the highest quality vehicles for our customers,” explains Bennie Fowler, Ford’s Group Vice President of Global Quality. “We are extremely proud to be among the industry’s quality leaders. But that’s not why we’re in the game. We want sole possession of first place, and we will keep working to earn it.”
Continuing to ratchet up quality performance while meeting tight launch schedules for its product portfolio is a huge challenge for a manufacturer of this size and complexity. Every phase of the quality process is a potential bottleneck, especially so-called “squeeze point” operations that handle work for the entire company. Ford managers are particularly concerned in keeping these critical quality process paths running at maximum efficiency.
Ford’s FEAD lab
One such key group in ensuring vehicle quality is the test lab in Allen Park, Michigan, just outside Detroit where they perform vibro-acoustic testing of front-end accessory drives (FEADs): the serpentine belt system with pulleys, tensioners and idlers for driving equipment such as the alternator, air-conditioning compressor, power steering, and water pump. FEAD Lab Coordinator Joe Skrobowski explains that quick-turnaround and accurate testing is vitally important to Ford’s vehicle quality and launch schedules because the lab works on FEADs for all Ford vehicle models developed in the US, plus some for Europe and Asia beyond the capabilities of labs in those regions. Tests are done throughout the development cycle: early bench testing of prototype drive systems, validation tests of FEADs on bare-bones “workhorse” vehicle prototypes, and pre-launch tests on production vehicles to resolve issues just before release to manufacturing.
Three types of tests are performed. Acoustic measurements record noise levels inside the passenger compartment. Structural vibration tests determine resonant frequencies and response functions for various components as well as the vibration levels of acceleration in g’s or m/s^2 present at each accessory for a range of frequencies during engine run-up. Torsional vibration tests use signals from encoders mounted on rotating components to measure oscillatory angular motions produced by engine firing pulses and torque variations that cause twisting in shaft sections and couplings throughout the FEAD at various idle and operating speeds.
“We devote considerable time and attention to torsional vibration, since this causes most of the noise associated with the FEAD: belt squeal, chirp and flutter along with idler bearing rattle and tensioner rattle,” says Skrobowski. “Such noise is unacceptable for passenger comfort and also indicates high levels of destructive vibration that can damage components such as bearings and shorten fatigue life.”
When such problems are found, the FEAD test team proposes changes to make the drive design robust against such vibrations: beefing up tensioners, adding decouplers, changing belt wrap, adding pulley flanges or modifying brackets to shift natural frequencies, for example. “Quick turnaround in getting results and recommendations back to designers is a must,” he notes.
Workload overburdens past test systems
Unfortunately, the lab’s ability to perform tests and report results quickly for the growing number of new designs was severely challenged by the limited capabilities of its past test systems. One major drawback was that structural, vibration, torsional and acoustic tests had to be run on different systems. Tests were all run separately, which essentially tripled the number of set-ups. Also, data exchange was cumbersome due to incompatibilities, numerical results were difficult to interpret, and reports laborious to create because so many manual steps were required to combine data in the proper format. In performing full vehicle track tests, difficulties were compounded by the large size and complexity of the former systems, which took considerable time and effort shipping to remote test track sites and mounting in vehicles.
To overcome these difficulties, the FEAD lab implemented a LMS SCADAS 310 32-channel front end data acquisition system and the LMS Test.Lab testing and analysis software solution for their vibroacoustic work. Replacing all the former separate equipment, the LMS system is an integrated platform performing structural vibration, torsional and acoustic tests all in one unified system.
“Doing all our work on a single platform lets us exchange data easily and run multiple tests simultaneously to see correlations, interactions and couplings,” explains Skrobowski. “Also, the Windowsbased interface is faster to work with than the text-based command structure of the former system, and automation of routine tasks speeds set-up and reporting operations.”
He notes that the convenient mobility of the LMS system was a major reason why it was selected. The LMS SCADAS unitis compact in size and fully equipped for field use, so technicians can easily take it on a plane as carry-on baggage and readily set it up on the passenger’s seat in the test vehicle. Signal conditioning and microphone amplifiers are built into the system, so there are no external boxes to worry about mounting in the vehicle.
Instead, instrumentation and sensors plug directly into the LMS SCADAS, along with 10 VDC power from vehicle batteries.
Faster, more accurate torsional testing
“Performing torsional vibration testing with LMS Test.lab is a big improvement over the previous system, which needed a separate unit for converting the variable frequency pulse tacho into a digital rpm signal,” he says. “This method was noise-sensitive and had limited resolution on high rpms. So more time was required interpreting data and repeating inconclusive tests. Also, output plots were time-consuming to create because the data had to be manually combined manipulated.”
With the LMS system, a QTV (Quad Torsional Vibration) module built into the LMS SCADAS unit automatically analyzes encoder signals with digital signal conditioning and accurately converts them into precise, high-bandwidth angular rpm variations. The estimation and interpolation algorithms used in these calculations are far more accurate than those of conventional torsional vibration measuring systems. One breakthrough capability is that accuracy is completely independent of rpm and sample frequencies, even for tacho frequencies up to 50 kHz. “This greater accuracy means that required torsional data is gathered in a shorter time and tests are much more accurate,” Skrobowski says.
He points out that considerable time and effort is saved during pre-test activities. A workbench capability in LMS Test.Lab has straightforward prompts for each particular type of test telling technicians what sensors to use and what calibrations are required. Moreover, technicians can easily drag and drop configuration data from other projects by working in the hierarchal tree structures of files.
“Doing this from scratch wastes time and increases the chance of mistakes,” he explains. “The automated features of LMS Test.Lab eliminated these barriers and lets us focus on doing the job right the first time rather than finding and correcting needless errors.”
When tests are complete, automated report generation features in LMS Test.Lab enable FEAD lab technicians to quickly prepare thorough test reports. “Previously, we would hand over a stack of paper log sheets and numerical printouts showing what equipment was hooked up, how tests were run, and results for individual channels. This was laborious to compile and time-consuming for engineers to interpret. Now instead of taking hours or days, reports are prepared in minutes with LMS Test.Lab through the use of pre-defined templates for producing standardized test reports.
Object-linking and embedding built into the LMS software allow the lab to combine different data into plots comparing a prototype to a production system, for example. This provides good insight into system behavior, a thorough record of the test, and an excellent historical archive to utilize in future projects.” Plots are not conventional static graphs but rather interactive representations of live test data that engineers and technicians can scale, combine, move around and otherwise manipulate as needed for different displays or re-use later in their own reports and other documentation. Live data from the LMS test system is also readily formatted as input into Ford’s proprietary AP-FEAD analytical powertrain FEAD multibody dynamics system that design engineers use for simulation in early development of the systems.
“The bottom line is that the efficiency of the LMS system in performing torsionals and other vibro-acoustic tests enables our lab to reduce typical testing cycles by half, start to finish,” Skrobowski explains. “That kind of gain enables us to do more tests in less time and is absolutely necessary for us to handle greater workloads, and for
Ford to continue improving quality second to none.”
