By Brent Boecking

Imagine driving around an unfamiliar neighborhood at night, looking for a specific house buried deep in a residential subdivision. Maintaining control of the car is difficult enough without the added duty of looking for street signs covered by low-hanging trees or poorly lit house numbers. Now, imagine how much easier it would be if you had a navigation system that told you, in advance, where to turn and how far you were from your destination. Modern technologies, when applied to the appropriate problems, can have a significant impact on how well we can accomplish everyday tasks. In this article Brent discusses the impact of intelligent in-vehicle test systems on the problems test engineers encounter and compares the new technology to in-vehicle data loggers.

What is an in-vehicle test system?
In-vehicle testing is a common practice for several industries including automotive, aerospace, and military. Using in-vehicle testing, design engineers can determine how the vehicle reacts during normal and extreme use. Extreme use means that the vehicle is driven in conditions that tax its subsystems: extreme temperatures, humidity, salinity, and vibration. Automobile subsystems, including HVAC, suspension, brakes, body, and safety, endure extensive in-vehicle testing before design engineers can be sure they are ready for the mass market, as shown in Figure 1. Engineers examine and interpret completed test results so that adjustments may be made to the vehicle design before production. In-vehicle applications require the test system to be placed in the vehicle during use (see Figure 1), causing a special set of environmental considerations to apply. Even though the in-vehicle test system resides inside the vehicle, external conditions can and will affect the test system to varying degrees.

Data logger or decision maker?
The market offers test engineers many purpose-built, in-vehicle test systems, as well as a number of general-purpose test platforms, including PXI-based systems. However, the majority of in-vehicle test systems are not test systems at all, but data loggers with limited feedback capability. Being limited to non-existent feedback is acceptable assuming the data you collect during the test run permits you to make design decisions after the tests are completed. However, there is always a chance that the test results will be inconclusive, incomplete, or completely unexpected. The consequences of taking the wrong data can mean the difference between successful projects and consistently slipped deadlines. This is especially true when you consider that many in-vehicle tests are expensive to coordinate and take place over a day or up to a week at a time. Real-time processing and feedback are the keys to taking the right data the first time. These test system characteristics give the test engineer the ability to change test vectors while the test is being performed instead of days after the data has been collected.

For an in-vehicle brake noise test, real-time processing and feedback can pay big dividends. Brake noise is an industry-wide problem that costs OEMs millions of dollars every year. Warranty issues related to squeaking and squealing brakes are among the highest of any vehicle system. Furthermore, experts say a typical city traffic test of brake noise will absorb up to six weeks of critical prototype development time, require 300 to 500 man-hours of driver and engineering effort, and can cost up to $25,000. Determining failure conditions in real-time dramatically shortens test time, as the current test can be completed as soon as the failure occurs, and the next test can be started. Conversely, determining in real-time whether the test is inputting the expected stimulus permits the driver or the test engineer to change the test plan on-the-fly. In the brake test example, this is applicable when the test plan is not causing a failure. However, a failure may be required to determine the robustness of the design. Using a simple data logger, a day or more may be wasted before the information is processed and examined, possibly wasting test time. Using an intelligent in-vehicle test system, engineers could have changed the test plan much earlier in the process.

The PXI platform, based on PC architectures, utilizes the latest Intel Pentium processors, advanced graphics, deep memory, high-speed hard drives, and high-speed bus architectures, making it a prime choice as an in-vehicle test platform. Not only does the hardware facilitate real-time processing at speeds in excess of 2 GHz, minimizing the data footprint, but it also permits the test engineer to view the right data instead of raw data. Furthermore, the latest Windows-based test software, such as NI LabVIEW, permit the engineer to create rich graphics for real-time feedback in very little time. Using such a powerful platform, features such as voice recognition can be added without significantly taxing the test system.

In addition to the primary benefits of PXI as an in-vehicle platform, there are many secondary benefits because of its PC-based architecture. These benefits include high stream-to-disk rates, high memory capacities, connectivity to the latest high-performance modular instrumentation hardware, and connectivity to many PC-based peripheral items such as memory sticks and advanced high-speed networks.

Stretching PXI to other in-vehicle applications
The PXI platform expertly handles many traditional in-vehicle applications. In addition, it is taking hold of new applications such as rapid control prototyping, as auto companies try to shrink vehicle development times. Rapid control prototyping in the automotive industry is the process of deploying newly developed control code to a hardware target. The hardware target will be used in the vehicle to control a vehicle subsystem that can be as complex as adaptive cruise control or as simple as controlling the electric windows and locks in a car door. Rapid control prototyping lets control engineers test how their control algorithms will function in a real-world environment and quickly change them as necessary. Features that a rapid control prototyping target must have include modular hardware for changing algorithms and re-use, some level of ruggedness, and connectivity of open real-time software platforms.

PXI is becoming an enabling platform in this arena because of its open, PC-based roots, coupled with a more robust form factor. PC software technologies such as LabVIEW Real-Time allow engineers to target PXI with complex control algorithms. Furthermore, PXI provides the automotive modular hardware that is needed to generate data for these applications. This includes automotive serial protocols such as CAN and LIN, as well as required measurement features including isolation, filtering, and high voltage ranges.

As an example of how PXI is used as a rapid control prototyping platform, several of the FutureTruck 2003 teams used PXI to control their hybrid-electric vehicles. FutureTruck is a unique four-year program in which 15 top North American university engineering schools compete to re-engineer an SUV to improve fuel economy while reducing emissions. The FutureTruck competition brings together government, industry, and academia to explore clean, fuel-efficient automotive technologies. For FutureTruck teams as well as automotive test engineers, the flexibility of PXI provides test engineers with a fast learning curve across multiple applications. These applications include traditional in-vehicle testing and rapid control prototyping, for which the user interface and form factor are identical.

Figure 1: Example of In-vehicle Testing and Rapid Control Prototyping.

PXI in-vehicle implementation
The first question when mounting PXI in the vehicle is usually, “Where do I mount the mouse, keyboard, and monitor?” The option of mounting all of the components separately exists, but this can be cumbersome and requires multiple mounting brackets. The advantage of this method is that the individual components are cost effective and the mounting hardware is reasonably priced. The second, and preferable method is to control the PXI embedded controller via Ethernet using a laptop. Laptops have a well-integrated monitor, keyboard, and mouse, and mounting brackets are easily found and inexpensive. There are two main methods used for controlling an embedded PXI controller via Ethernet: Windows Remote Desktop and embedded operating systems such as LabVIEW Real-Time. Technologies embedded into Microsoft Windows XP, such as Remote Desktop, allow the user to easily setup, view, and control the desktop of a remote computer. The embedded operating system choice decreases usability, compared to Remote Desktop. However, using an embedded operating system reduces the operating system burden on the embedded PXI controller. Both methods can take advantage of the laptop’s ability to perform as a terminal machine without requiring high-performance components, thus saving expense. The PXI chassis can be mounted in multiple areas around the car, most likely including the trunk or rear seat.

Figure 2: PXI Chassis Can Be Mounted in the Trunk Area of Vehicle.

Other feedback methods, though less often used, include using a PDA or a Windows CE interface as the feedback link between test engineer and the test system. Also, wireless networks, such as 804.11, are easily setup within most operating systems and permit ground crews to gather information while the test vehicle is moving around the proving grounds.

Few weaknesses with workarounds
The standard in-vehicle data logger is designed to meet all of the extreme environments that a test vehicle might encounter. However, that is not entirely the case with PXI. PXI is designed to be used as a broad test platform, so tradeoffs must be made when using it in-vehicle. These tradeoffs include lower operational temperature limits, lower operational vibration limits, and limited DC power options. Many of these limitations can be worked around without significant additional investment.

The number of PXI chassis with DC power options is on the rise. Companies such as National Instruments, Chroma, Pickering, and Dolch offer ruggedized, DC-powered PXI chassis. However, if the PXI chassis combination that your application requires does not have a DC power option, there are inverters available that have been tested to work with PXI chassis.

Today’s hard drives are getting faster and more robust, but the combination of extreme temperature and vibration from in-vehicle testing can cause intermittent or complete failure over time. However, a limited set of off-the-shelf controllers, such as the NI PXI-8145 RT, are completely solid-state and will survive the rigors of in-vehicle testing. Solid-state hard drives can serve as drop-in replacements for most PXI embedded hard drives. Flash drives, for instance, are offered in a variety of capacities, temperature ranges, vibration ranges, and access rates. The majority of these choices are well suited for in-vehicle testing.

Even if several of the above workarounds are employed for an extreme environment, the total PXI system cost remains low because it’s based on common off-the-shelf PC technologies. Purpose-built in-vehicle data loggers commonly suffer from relatively high prices due to proprietary hardware architectures, buses, and software architectures.

Shorten in-vehicle test time with PXI
Incorporating intelligent real-time feedback into in-vehicle testing saves money and shortens development time. The PXI test platform provides the necessary ruggedness to survive the in-vehicle environment, while providing the needed real-time processing and feedback. In addition to the typical in-vehicle applications, the flexibility of PXI is being stretched to other in-vehicle applications such as rapid control prototyping. As the automotive industry continues to evolve and is pushed to innovate, design times will continue to shorten. PC-based technologies, such as PXI, are providing the innovation and speed to address many of the automotive industry’s shrinking time-to-market needs.

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Brent Boecking is a National Instruments product marketing manager who sets strategic direction for NI data acquisition products. Current projects include management of E Series Multifunction data acquisition and analog output product lines. Before his involvement in marketing, he worked as an applications engineer and product support engineer for NI signal conditioning products. Brent holds a BS in mechanical engineering from Texas A&M University in College Station, TX.

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