Wires are just wires, you may think. How complicated could that possibly be?
Well, extremely complicated in fact, at least since our cars started morphing into computers on wheels. The 50s and 60s are long gone. Back then power steering, electric windows, and the occasional aircon were the height of luxury motoring. Nowadays the metal skin of a premium car hides a multitude of sensors, actuators, control units, high-performance computers, infotainment system etc., and more features and components are being added at breathtaking speed: Five years ago, vehicles had 25 per cent less circuits than today’s cars. Five years from now, that number will increase by another 30 per cent.
The wire harness is the spider’s web in the middle of it all, and it is indispensable to nearly all aspects of a modern vehicle. That is why designing the wire harness of a state-of-the-art car, bus or truck requires both a general understanding of car components like sensors, actuators, batteries, motors etc., as well as knowledge of the nuts and bolts of electrical systems design.
You need to know everything about wires and connectors, and you need to understand the vehicle as a whole to be able to design a wire harness, that is clever and cost-efficient, while being easy to assemble and service as well.
Welcome to the world of wire harness design, right now struggling with a nasty cross-pressure: How do we connect an ever-increasing number of components with less and less space at our disposal?
inContext is one of a handful of specialist companies focusing on wire harness design, and its 80+ developers are involved in a broad range of projects in the Swedish vehicle industry. Their expert skills in Complete Electrical Systems Design go into the development of new cars, buses and trucks that incorporate cutting edge technologies. For instance, inContext is working on a new electro powered bus, electrification of a plug-in hybrid truck, and providing wire harness design for the special requirements of military vehicles. Also, inContext contributes to future autonomous vehicle concepts with interconnect, electrification and software development.
The next generation harness
In short, the inContext people know what they are talking about, when you ask them what the next generation wire harness will look like: It will enable more powerful electrical systems to operate vehicles, as the latest electrical connectivity allows ever more signals from on-board sensors, other vehicles, road-based infrastructure and satellites to be streamed into a high-performance computer. That computer, in turn, will transmit signals through the wire harness to braking, steering and other control systems.
All this is gradually maturing into a technical infrastructure for electrification and autonomous driving – an exciting vision, indeed, but a vision not without challenges.
More stuff, less space
To begin with, as mentioned above, there is the cross-pressure issue: A growing number of sensors and other devices are being added to the vehicle, and thus needing more wires to integrate them into the car’s system. But at the same time vehicles want to become smaller, thinner and lighter. So, where to put the new wire spaghetti when you’ve got less space at your disposal? It’s hard to discard anything, as you still need all the traditional vehicle components for it to work properly.
Wire harness designers are competing fiercely with all the other teams in charge of developing a new vehicle. They all need their piece of the shrinking space to be allocated for their specific use, so everybody needs to compromise to make it work.
Modularity is one of the keywords in that specific dilemma, looking into the future of wire harness design. Designing with modularity in mind can help cope with the cramped space and rising amount of wires in a modern vehicle, particularly because many vehicles are produced in a number of different variants.
In theory, you could design a wire harness that could handle all the vehicle options and features on offer. But that would be too costly, it would add to the vehicle’s weight, and it would take up too much space. Instead you need to think LEGO. With a modular design you can expand the basic harness with sub-harnesses where needed.
That approach also facilitates assembling and servicing, especially in the heavy vehicle industry, where many inContex customers operate. When assembling a vehicle, instead of rolling out the complete wire harness and installing it at once, you can do it in sequence. This plug-and-play approach to assembling makes good sense, when a vehicle comes in many different variants, as is the case in the heavy vehicle industry. And what makes sense in assembling makes sense in maintenance as well. It is a lot easier to replace a wire harness designed in a modular fashion. You avoid having to replace the whole thing because of one cable breaking down.
Handling high voltage
Another significant challenge for wire harness design is electrification. The magnetic field created by high-voltage cables tends to disturb low-voltage systems, so when designing a harness you need to factor in this EMC noise (Electro Magnetic Compatibility). To protect the signals running in the low-voltage communication cables you have to be careful not to put them near to their high voltage siblings. And that is quite a challenge, especially with limited space at your disposal.
High voltage cables can pose a threat to humans as well. If a passenger riding an electric bus carries a pacemaker the EMC noise coming from the bus motor could interfere with it. That is yet another risk has to be addressed by wire harness designers in collaboration with component owners. And apart from EMC noise there is the sheer size of high voltage cables, not to mention their cost. For both reasons they need to be as short as possible.
Everybody is talking about self-driving vehicles. inContext is contributing to this megatrend, as well as to electrification, by designing reliable, cost-effective wire harnesses that are easy to assemble and service.
Moreover, next generation wire harnesses may enable extremely powerful electrical systems to operate vehicles without human intervention. For that we need more sensors, more bandwidth, bigger computers – and all this is leading to a re-engineering of automotive wire harnesses. The industry is thinking about architecture in new ways, for instance finding inspiration in high-security domains like aerospace. Think multi-layer redundancy, fault tolerance, advanced connectivity, and cyber security. Those are the requirements of the future, and you have to think really hard trying to meet these goals while keeping down weight, power consumption, and overall cost
New types of cables
One way of addressing these trends is rethinking the wires themselves. We are going towards using a larger variety of wires, compared to the regular wires used in a standard vehicle CAN system.
CAN is not enough to transfer the huge amounts of data in the system, and CAN cables need to be complemented by coax- and ethernet-type cables. However, many of them are not really adapted to the automotive industry, so manufacturers are working to develop new types of cables to meet the changing requirements in the industry.
The harness of the future
No doubt, wire harnesses are evolving rapidly, to meet the challenges posed by electrification and autonomous driving. But what are the long-term perspectives? Looking into the future, what will a state-of-the-art vehicle wire harness look like in 10 years?
According to the inContext experts, wire harness design will probably be totally different from now. Today we use wires because they are flexible and easy to route, but the future of wires may not even be wires. Most of the signals could be communicated via wireless, provided we find satisfactory solutions to all the cyber security issues that inevitably will follow.
Wireless technologies have a number of advantages, for instance when it comes to saving weight and avoiding EMC noise. However, power cables are difficult to replace entirely. To simplify that part we might begin using modular busbars going through the whole vehicle, functioning as the main power source for vehicle electronics.
No matter what, the use of wires will most likely go down, while vehicle complexity will continue to increase. When it comes to the brain and nervous system of a vehicle, a paradigm change is on its way – we are pushing the boundaries of wire harness design.