“My nontechnical friends are astonished at the amount of technology in a seemingly simple product,” says Kostal’s, Matthias Richwin, whose department makes full use of computer simulation in the development of Kostal’s technologies. “They are equally intrigued by the fact that behind every switch in their cars, there is a multidisciplinary team of engineers.”
Richwin’s friends are not unusual. There are drivers everywhere who turn on their headlights or windscreen wipers with no awareness of the development effort behind a switch. Yet from freezing winter to sweltering summer, on dull rainy days and in bright sunshine, switches are expected to function consistently for the lifetime of a car.
Considerations of style, safety, space-saving, and user convenience have been the drivers for 60 years of innovation at the Automotive Electrical Systems division of Kostal Group. Since the early days when the company placed indicator switches by the steering wheel and created integrated-function pushbuttons, it has registered a wide range of patents.
Core product areas include steering wheel column, centre console, and roof module systems, with customers including BMW, Daimler, Ford, and the Volkswagen Group. So, how did simulation became an intrinsic part of the design process at Kostal? Matthias Richwin again:
“We have some specialist tools, such as FEA software for mechanical design, but were increasingly in need of thermal simulation and anticipated a requirement for electromagnetic simulation, so I began to investigate the options.
"We selected Comsol Multiphysics because it had by far the best user interface and offered integration with the CAD, electrical design, and manufacturing applications we use. In 2009, we began using the software for the thermal simulation of roof modules.”
Simulation is now so embedded in new product development at Kostal that it is simply considered a common design task, but with particular relevance to three key areas of the Group’s activities: lighting, EV battery charging and touch-sensitive switching.
The lighting inside today’s cars is complex and highly integrated, and has moved far beyond the courtesy light that comes on when a door is opened. The roof module in a premium car is likely to house anti-theft and satellite navigation systems as well as extras such as ambient lighting.
“The industry has moved away from the classic bulb to LED displays,” says Mr Richwin. “Although LEDs are much more efficient because they require less power, 90 percent of the heat they dissipate goes into the printed circuit board (PCB) of the roof module.
"We tackle this particular challenge by using Comsol Multiphysics to predict thermal behaviour and optimise performance. Whereas we previously had to build and test, we can now easily predict performance and, for example, show a customer that a roof module will work at optimal brightness over the whole environmental range.”
One of the disadvantages of an electric car is the need to charge it regularly, and as charging typically takes from six to seven hours, forgetting to do it one day may mean being stuck without transport the next. The team at Kostal therefore expanded on the electric toothbrush concept, as Mr Richwin explains:
“The idea is to charge a car not by using a cable, but by moving it to a contactless charging system. As with a toothbrush and its covered charging base, there are no contacts. We worked on the basis that if a transformer is cut in two and the two halves are moved apart, it would still perform through inductive power transfer, albeit with less efficiency. Our task was to optimise the coil on each side so that the end product would be as effective as a cable-based system.
“We used Comsol Multiphysics for the electromagnetic simulation of different options such as a ground plate partnered with a coil on the underside of the car, and a mounting on the wall partnered with a coil placed behind the number plate. It simply would not have been possible to develop this type of product without simulation.”
Smartphone expectations
The third area in which simulation plays a key role at Kostal is all to do with the industry’s trend to move away from the use of mechanical switches, which are both complicated and vulnerable to fluid entry. At the same time, customers used to smartphones and tablets now expect similar touchpad-style sensors in a car.
The transfer of this technology into cars is, however, not straightforward. Interaction with a smartphone is strongly visual; the user must look at a screen. In a car, though, there must be nothing that distracts the driver’s attention, so user feedback has to be non-visual. In addition, the environment of a car is complex because its interior is densely packed with driver interface functions.
Extremes of temperature, moisture, and dust – depending upon location and climate - pose further demands on components. According to Mr Richwin, capacitive sensors present various challenges: “We have to consider the potential for many different sizes of fingers and thumb pads, and the presence of additional material, such as a glove or hand cream. Then we have to decide on the level of sensitivity: whether we want proximity, whereby a finger has not yet touched a surface but is within a few centimetres; actual touch; or a combination, in which the sensor first detects the approach of a finger and then registers the touch.”
The general aim is to make the sensor covering as thin as possible, which means that the team is looking for reliable and predictable performance from a plastic surface that is just one millimetre thick. Simulation is used to maximise sensitivity by optimising the dimensions of the sensor installed on the PCB.
Kostal is also developing new surface materials; for example, pre-manufactured plastic foil on which the conductive structure could be printed to allow more flexibility and increase reliability. Mr Richwin concludes:
“The use of Comsol Multiphysics enables us to check the feasibility of a technical concept very quickly, then optimise the quality, robustness, and cost of a product in development. We also save money by reducing the number of physical prototypes. However, it is in innovative areas such as inductive power transfer and capacitive sensor design that simulation becomes truly indispensable, because the alternatives are impossibly expensive or time-consuming.”
Jennifer Hand is a writer and regular contributor to Comsol News
This item is based on an original article that first appeared in the current edition of Comsol News