Hardware-In-The-Loop: Assuring Performance & Quality By Combining The Real & The Virtual

Dealing with the complexities that multiple electronic control units present can be demanding. But it can also be automated, which makes a whole lot of sense for companies that want to catch the bugs before they arrive in customers' driveways.

The issue is both complex yet simple. The complexity is that which is occurring in vehicles as there are increased numbers of electronic control units (ECUs). They're being installed in prodigious numbers in high-end vehicles. The Mercedes S-Class has about 70. Yet according to Herbert Hanselmann, CEO, president and founder of dSpace (Paderborn, Germany; Novi, MI; www.dspaceinc.com), even the VW Golf has some 40 controllers. ECUs are being installed for reasons both regulatory (e.g., in order to handle the safety requirements) and competitive (e.g., additional distinctive functionality, be it in terms of active suspension control or the like or for some infotainment needs). And the simple thing is that as there has been—and continues to be—this proliferation of ECUs, vehicle manufacturers are finding that it is exceedingly difficult to deal with the problems that these processors can engender as they are expected to function flawlessly. The trouble is, just as it was discovered in the physical world that even if you have a series of parts within specified tolerances, the assembly of those parts can result in a product that is out of spec due to the stacking of the tolerances. But in this case, as the ECUs are added and integrated, some highly unexpected things can occur, which leaves the owners of the vehicles highly unhappy. There are some people who suggest, for example, that one of the reasons that the Mercedes E Class has been plagued by quality problems is directly ascribable to the fact that there are problems with the multitudinous ECUs.

Consider the opportunities for things to go wrong. There can be insufficient definitions. Late changes. Simple programming errors. (Apparently, about half of the programming errors are caused by late changes.)

So what's a vehicle manufacturer to do? One possible answer is found by the systems offered by Hanselmann's company. The systems that they have developed—both hardware and software—are meant to help engineers be assured that the ECU-based systems designed for deployment in vehicles do what's expected without failures or other unintended consequences.

While there is the possibility to perform simulations of systems, Hanselmann suggests that due to the vagaries that can occur between the virtual and the real, there will always be the need for physical prototype testing to be performed. And realize that this is coming from a man who has a doctorate for work he'd done in mathematics.

The trend that he says an increasing number of vehicle manufacturers are creating is called "hardware-in-the-loop" (HIL) testing. That is, it's one part simulation system and one part actual ECU. By creating a simulation of the vehicle software and then hooking up an actual controller, engineers are able to observe the performance of the ECU functionality under a variety of conditions, with the conditions being programmed into the system. The ECU can be exercised so as to see how it works (in one dSpace lab, for example, there was a setup with a display screen, steering wheel, and set of pedals; the technician could "drive" the vehicle on the screen and determine whether the stability control system was working as planned; there were racks for vehicle dynamics, engine, and transmission simulation, each networked with a high-speed optical link and signal bus to each other and to a central control unit). HIL can be done at component level, which is something that Tier One suppliers are doing, or complete vehicle systems. Hanselmann says, for example, that DaimlerChrysler deployed a full-vehicle simulation system during the development of the new A-Class.

Will the number of ECUs continue to grow? Hanselmann points out that some vehicle manufacturers that presently use numerous ECUs, like Audi, have said that they want to greatly reduce the number from double to single digits. After all, the ECU connections require plenty of connectors, which have long been Achilles heels of electrical and electronic architectures in cars. But this doesn't mean that there will be any less functionality and interactions occurring. The ability to know well ahead of product manufacture that turning on the windshield wipers won't affect the audio system which won't affect the seating system which won't affect the cruise control which won't affect the . . . well, you get it. HIL is certainly a useful tool for those who are looking to assure vehicle quality.