Designing in-vehicle infotainment systems
Long gone are the days when the only form of in-vehicle entertainment for long journeys was a simple. Since those early days, in-vehicle entertainment has progressed through 8-track and compact cassettes to compact discs (CDs) and solid-state solutions. Some American cars were even equipped with record players – presumably for use only when stationary.
Modern in-vehicle infotainment (IVI) systems are now highly sophisticated systems that form the heart of modern vehicles, keeping drivers and passengers informed and entertained on the road.
In terms of ‘look and feel’, these systems can vary significantly from one automaker to the next and the IVI is a key part of the vehicle operation and branding. In the past, safety, economy and performance were key decision-making criteria for the car-buying public. These days, IVI is added to that list – often as the most important factor, especially with younger people – further highlighting the importance of IVI to automakers.
IVI architecture, applications and requirements
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Figure 1: Block diagram of a typical IVI system |
Generally speaking, IVI tends to be modular in architecture. This allows different functional elements to be placed around the vehicle, making good use of the limited available space. The modularity is also useful to automakers as they can configure different models within a range differently, while keeping the same fundamental core to the system. This allows higher-end vehicles to have a premium specification, while entry-level models receive a lesser configuration as standard. And consumers can often add features (at a cost) at the time of purchase.
Typical IVI systems will be centred around a processor system, to which all of the system elements link, either physically or wirelessly. The core HMI is usually a large touch screen, placed centrally in the dash within easy reach of the driver. In many vehicles, this is combined with physical switches and knobs although the trend is to reduce these elements in favour of an ‘all glass’ cockpit. The inclusion of voice control further reduces the need for a physical HMI.
Audio entertainment remains core to modern IVI systems but these days, alongside the traditional AM/FM receiver, many vehicles will include digital audio broadcasting (DAB) radio. While some vehicles still include CD players, these are becoming far less common as they’re replaced by solid-state music formats including .mp3 and streaming services.
While navigation was previously considered a luxury, it’s now available on most vehicles, either as standard or as an optional extra. As vehicles become more ‘connected’, navigation functionality can be enhanced, incorporating advanced mapping and traffic and weather data, which can be taken into consideration when choosing the optimum route for a journey.
In fact, communication is one of the key challenges for IVI system designers. With the number of vehicle-mounted modules to be connected, it’s quite common to require a number of interface standards including LIN and CAN. As cameras based upon image sensors are becoming more common, and increasing in frame rate and resolution, the rate and amount of data to be transferred to the central processor is increasing rapidly.
As a result, designers need to add interfaces like automotive Ethernet to cope with the data requirements. New Ethernet protocols that have been developed specifically for vehicles can manage the flow of data while prioritising safety-related messages (such as the detection of an object in the vehicle’s path).
However, it’s not just vehicle-mounted devices that need to be included in the IVI system. Smartphones are incredibly feature-rich and with applications like music streaming, navigation and hands-free messaging and more, they can become an integral part of the IVI. This is especially useful in entry-level vehicles where, if the automaker provides an interface for the smartphone (either Bluetooth or USB or both), then a low-cost, highly featured IVI system can be provided, based upon the smartphone.
Design challenges and solutions
The complexity and variety of modern IVI systems, unsurprisingly, result in numerous design challenges. As with all automotive design, reliability is crucial. While the failure of an IVI subsystem may not stop the vehicle in its tracks, it will almost certainly be inconvenient to the driver, especially if it relates to the navigation system.
Most components of the IVI system are located in or around the cabin. While they’re not subjected to the extreme shock and vibration experienced by under-the-hood devices, or those mounted on the chassis, vibration is an issue for every automotive design.
While cabin temperature might appear to be fairly benign, for components mounted in small spaces behind the dash with relatively little airflow, the ambient temperature can be high, especially on sunny days when solar gain via the windscreen pushes temperatures up significantly.
Given the small spaces available for electronic systems in vehicles, miniaturisation is a common requirement for IVI systems – either to fit a module in the smallest space possible, or to fit as much functionality as possible in the available space.
Electro-magnetic interference (EMI) is another common challenge in automotive applications, especially within IVI where electrical noise from switches and induction motors can interfere with radio reception as well as data connections. Even the smartphone, upon which the functionality of some IVI systems relies, can generate unwanted EMI that needs to be suppressed.
Although not solely a hardware challenge, the ergonomics and usability of IVI systems is particularly important in vehicles. The driver has to be able to operate all of the main functions while driving the vehicle safely, with their primary attention outside the cabin. Type and placement of switches and other elements of the HMI are crucial to making this a success and haptic features provide physical feedback to drivers. Increasingly, gesture-based HMIs are being implemented to avoid the need to select a particular menu option, or find a small switch / button.
The critical role of passive components and connectivity
While devices such as the displays and high-end semiconductors are obviously important to IVI systems, it would not be possible to complete a design without careful consideration of passive components and connectors.
One of the main roles of passive components such as inductors, common-mode chokes, ferrite beads and capacitors is to filter the EMI that’s inevitably present in automotive applications. IVI systems contain high impedance audio signals that must be reproduced faithfully – whether that’s music or the voice of the navigation system.
The use of wireless communication such as Bluetooth for connecting to mobile devices and on-board cellular for cloud connectivity as well WiFi for an on-board network further exacerbate the EMI challenge for designers.
In IVI systems, due to their modular nature, connectivity is a particularly important topic. There is a wide variety of signal types that have to be routed around the vehicle including audio signals from the central IVI unit to speakers, video signals from remote cameras, GPS antenna and a whole variety of control signals that will control everything from cabin lighting to adaptive suspension. Alongside these signals, power also passes through a range of connectors.
Connectors are some of the simplest components, yet their failure can cause the complete failure of the IVI system. Therefore, reliability is one of the primary considerations, ensuring that connectors will not degrade over time, even when subjected to the elevated temperatures and high levels of vibration found in typical automotive applications.
Summary
Some people are now describing modern vehicles as ‘computers on wheels’, reflecting the high level of computing power in most vehicles. The IVI system is at the heart of this and contains the broadest range of technologies of any on-board system, encompassing audio, video, displays, HMI, wireless communications and control systems, among others.
The need to reproduce high impedance analogue signals faithfully means that passive component performance is crucial in IVI systems. And the modular nature of a typical IVI system relies on high quality connectivity to meet the increasing expectations and demands of the modern automotive consumer.
Below we’ve highlighted our leading suppliers of components for designing in-vehicle infotainment systems.
If you require advice on selecting the right components for your design, our technical specialists are on hand to help.
