AVL developed a GPS simulator that simulates a certain GPS position to the on-board navigation system. This GPS simulation can be fed into the original navigation system without having to make any adjustments. 2 9 F O C U S Photos: AVL The optimization of complex passenger-car powertrains on the road is gradually reaching its limits. There are several reasons for this: the number of powertrain elements (hybrid, torque-vectoring systems, etc.) is increasing steadily. The individual elements are also becoming smarter and smarter and are closely interlinked. Each component, the transmission for example, has its own control unit and operates by interacting with other systems within the vehicle. In the case of intelligent vehicles or powertrains, respectively, we correspondlingly have extensive information on the driving environment like the vehicle position, the terrain or the road conditions ahead, the traffic situation and, sometime soon even information supplied by other vehicles. To develop an optimum operating strategy for the driveline that is based on all the incoming data, the perfect development environment is the modern powertrain testbed in combination with a high degree of simulation. According to Hans-Peter Dohmen, Global Business Segment Manager Driveline, simulation is becoming increasingly important even in durability testing, which is the powertrain testbed’s classic application area: “OEMs generally have testing processes and procedures that have evolved over decades, defining exactly how durability tests for transmissions have to be conducted. Such tests, which are performed with a prototype on a defined proving ground, frequently take several months to reach the number of kilometers required.” The solution approach that AVL developed for an OEM several years ago to substantially reduce the time needed for such tests is the ‘intelligent durability test’ on the testbed. “In tests like these, the transmission is tested on a testbed with electric motors – in other words, without an internal combustion engine – and the route, the vehicle and the driver’s behavior are simulated. This helped us to cut the testing duration – initially three to four months – down to three to four weeks. On top of that, fewer prototypes are required, which led to very substantial savings for the OEM, which now has several of these testbeds in operation,” Hans-Peter Dohmen tells us. FROM REPLICATION TO SIMULATION While it used to be sufficient for many powertrain tests to accurately reproduce a previously measured road profile on the testbed, the onboard smart systems today have brought on a surge of new challenges. “As soon as you have on-board systems that are smart and timevariant, you need to switch your testing from replication to real-time simulation. If, for example, a torque vectoring system control unit decides that there has to be a shift of torque, the control process has to be realistically possible on the testbed too. We meet this requirement > by creating a model with which we calculate the force that each of the tires is able to transfer to the road surface, depending on the vertical force and the friction coefficient, and exactly this torque is applied by the dynamometer If the powertrain provides more torque than than the simulated tire can transfer, the dynamometer is accelerated at a high rate like a spinning wheel that has lost traction. Without requiring complicated control or simulation processes, this allows us to represent the behavior of a powertrain if there is wheel spin, and we can give the smart subsystems the freedom to react exactly as they would in a real vehicle on the road,” the expert explaines. REAL-LIFE TESTING WITH SIMULATION A key criteria for realistic testing on the powertrain testbed is that the required simulation models are quickly and easily fed into the test system. “This is where the real-lifetesting integration platform AVL InMotion, powered by CarMaker, serves us well. What it can do, for example, is to allow an integrated data generator to create a sufficiently accurate simulation model based
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