Automotive Testing Expo extends from squeaks to radar
The collocated Automotive and Engine Testing Expos in October featured fascinating technology such as micro-finished crankshafts and systems that applied antiwear coatings to cylinders. Great products, but not closely related to test.
In contrast, both Yokogawa and Newton’s 4th were displaying power measuring instruments, and Yokogawa also was showing the company’s line of ScopeCorders. Keysight Technologies featured the IntegraVision power analyzers.
Newton’s 4th will soon be introducing a new machine. Like the present model, it can lock onto a signal within half a cycle—apparently something that not all analyzers can do. Readings will be inaccurate if the source continues changing speed, and the instrument never completely locks to it. Noisy PWM signals can be hard to measure for this reason.
To avoid aliasing, some power analyzers filter the input. Great, but that destroys high-frequency content, which is a problem with fast switching PWM signals. ZES Zimmer, a German power analyzer manufacturer, runs two parallel acquisition systems, one filtered and the other not. If the outputs are similar, no aliasing has occurred. Otherwise, it has.
Similarly, the Data Physics 900 Series Dynamic Signal Analyzers with SignalCalc 900 Series software allow you to simultaneously measure data from the same channel at different sample rates and frequency resolutions.
Signal.X has developed software for big structured data sets: data of the same kind that can have simple tests applied such as to remove outliers. Also, the software helps develop metrics that allow you to filter the data to create a new data set having only relevant elements. What’s new is the way companies are using these data sets.
Today, people are preparing presentations as only an example of what can be done. Ideally, they want to share the large data sets among other researchers who can establish their own metrics and extract other details from the sets. It’s not just a bandwidth and storage problem, but also one of having the flexibility to access the data in many ways not necessarily originally intended when it was acquired.
The latest thing from Dewetron is an iPad-like user interface built into a Dewetron display. You can stretch/shrink waveforms to suit and save test setups so the results are reproducible. Hi Techniques emphasized rugged small DAQ systems specifically developed for automotive/aero applications such as strapping one of the waterproof systems to a jet ski for testing.
Spectral Dynamics was sharing its stand with Maryland Sound International-Direct Field Acoustic Test, a company that specializes in high-power acoustic test. For satellites, the complex sound developed during blastoff can excite more resonant modes than get exercised by conventional vibration test. As a result, they use stacks of amplifiers and speakers to develop a 1-MW sound field and measure the mechanical responses.
Astro-Med has changed its name to Astro-Nova. Just a rebranding: The company has not been bought but is dropping the medical reference. Nearby, Wineman Technology was displaying some of its custom test systems.
Rohde & Schwarz has developed a radar target simulator instrument. When all cars are autonomous, each one will need radar to sense what is happening around it, especially since there can be several simultaneous targets that each returns a slightly different signal.
The instrument receives the outgoing pulse from the radar, down-converts it, and adds copies with separate delays and losses to create a compound IF signal representing possible target situations. The combined signal is up-converted and returned to the radar antenna.
R&S is consulting customers to determine how best to evolve the instrument. Generating lists of standard scenarios is one direction the project may go—similar to some wireless standards.
HBM delivered a technical presentation about “eDrive” data acquisition and power analysis. By synchronously acquiring the input voltage and current, the frequency inverter output I and V, and the motor speed and torque, you have the raw data that you can analyze as required. And, all the events are correctly time-correlated.
A Newton’s 4th presentation stressed the difficulty of accurately measuring dynamic power. Factors include the necessity to use a discrete Fourier transform, not the FFT, because the DFT output includes the phase difference between V and I signals that are meant to be contributing power. And, you need a robust calibration procedure to ensure a flat frequency response across the entire analysis bandwidth.
In addition to electrical testing, physical things require environmental testing of all sorts—temperature, shake and bake, squeak and rattle, humidity, and so on. As might be expected at an automotive testing show, many companies that provide environmental test capabilities were there. A talk by a Volvo car engineer about squeak and rattle testing included a matrix showing the likely interaction when dissimilar materials were in contact.
And, on the shaker side, Vibration Research has developed a so-called instant degrees of freedom (iDOF) process for fast fixture mapping. So, before you dial up your latest custom-Kurtosis test, you can quickly run the iDOF process to determine the effects being added by the fixture that are not coming from your DUT.
Finally, with the continued emphasis on simulation, which is extensively used by all car companies, you might wonder if test expos have become totally passé. Can’t you just find somebody with a Cray installation, run some programs overnight, and build the prototypes the next morning? Why do companies still engage in extensive testing?
An editorial in the show issue of Automotive Testing Technology International by industry veteran Gene Lukianov summed up the situation. He said, “Mathematical analysis and simulations, while extremely powerful, are inherently limited by the assumptions made and the capability of the analysis to deliver narrowly focused results that need to be interpreted. Simulations don’t tell you what you did not ask: testing does.”