Consumer buying habits for automobiles are changing, driving the growth in the automotive electronics industry. Each year, automotive manufacturers are integrating more new and enhanced electronics into passenger vehicles. The current growth rate of body electronic systems is outpacing vehicle production by a factor of four to one.
Some of the current trends in new or enhanced features are directly related to incorporating increasingly complex electronics to improve brand reputation, competitive differentiation, and consumer comfort and safety. Hybrid-electric vehicles are trendy, as is connecting an iPod® to an in-dash entertainment system. Consumers now consider Bluetooth connectivity between handsets and integrated hands-free units a standard feature.
However, such features are merely the surface. Other highly engineered, complex features, which passengers may not be able to see or touch but effect their experience, are also increasingly incorporated. These include adaptive forward lighting, multi-axis adjustment seating, intelligent climate control systems, collision avoidance, and dynamic cruise control. And there is expectation of receiving a high-quality dashboard experiencebut implementation of these transcendental systems within the automotive framework comes at a price.
One challenge for automotive electronics designers is quickly introducing new electronic components for passenger comfort, safety, and enhancements. Engineers are required to shorten the overall design and qualification cycle and must increase functionality of existing systems without compromising ever tightening quality, reliability, and cost targets. To address these challenges, automotive designers look for more highly integrated solutions and to increase systems functional densities. Large scale integration in mixed-signal ICs is one attractive alternative.
Capture, compute, communicate
Nearly every embedded automotive system must perform three functions: capture, compute, and communicate. Capture refers to extracting information from the real world and translating it into the digital domain. This could be an analog voltage from a pressure sensor used in a tire pressure monitoring system or the rising edge of a waveform as seen from an I/O pin in a collision detection sensor, which would be connected to an airbag firing mechanism.
Compute refers to the ability to take digitized information and manipulate it in the context of the application. An example would be an airbag controller making a split-second determination not to deploy because it has detected a child in the seat.
Communicate refers to taking this result and distributing it to other systems that may require that information. For instance, a simple function would be energizing an indicator lamp. A more complex function would be using a network bus to send CO levels from an exhaust system to the engine management computer in order to increase oxygen in the fuel/air mixture. The degree to which the system can perform all three capture, compute, and communicate functions will ultimately determine the effectiveness of the solution.
New design challenges
Fuel tank sensing is an excellent example of the challenges being placed on automotive design engineers. Only a few years ago, a fuel level sensor was a relatively straight-forward design problemconsisting of a simple float mechanism with a sweeping brush contactor across a resistive surface. The result was an analog output proportional to the level of fuel remaining in the fuel tank.
Fuel tank implementation in today's vehicles occurs at the tail-end of a platform design, and frequently the design is required to take advantage of any remaining unused space. This can result in exotic tank geometries that have non-linear volume to displacement attributes which complicate the implementation of float systems.
Even more significant, the introduction of alternative fuels and fuel derivatives make the composition of the fuel in the tank of interest. For example, the ratio of petroleum and ethanol based fuels can have effects on engine dynamics such as ignition, timing, and emissions. Determining fuel composition and communicating that information to other electronic control units (ECUs) in the automobile is now considered an application requirement for next-generation fuel tank sensors. So what was once an elementary-level sensing design is now a complex analytical control challenge.
It is important to note, such feature-set expansion is occurring in nearly every system within the automobile. Windscreen de-fogging functions are being replaced with active dew-point controllers to prevent or eliminate the conditions necessary for condensation to ever form. Rain sensitive wiper systems integrate both the motor control and rain sensing functions in a unified system. Next-generation anti-pinch window and sunroof closures are another application that is representative of the integration now required in the microelectronics of these safety systems.