The wiring harness for vehicle power and signal distribution has become a major chokepoint for automotive makers, as the number and complexity of onboard electronics systems proliferates. Siemens is a major player on the design and engineering front and has just beefed up its capabilities by acquiring COMSA Computer und Software, a Munich-based developer of software for the electrical systems design and wire harness engineering.
Increasingly sophisticated infotainment systems, EVs (Electronic Vehicles) and autonomous driving systems are the three main factors expanding the size of vehicle wiring harnesses to the extent that they are now easily the third largest component of vehicles after the engine and chassis, both by weight and cost. Comsa’s LDorado suite will now add design and analytics capabilities to harness engineering products from Siemens PLM Software.
In a typical large family car, the harness weights at least 50Kg, and is proving ever harder to accommodate alongside all the non-electrical components in the engine and around the dashboard because there is a limit to how small the wires and sub-assemblies can be shrunk. This has put the onus on effective harness design to minimize the number of components and wires needed, as well as to lay out the circuits as efficiently as possible. But this process itself has become a major source of cost in vehicle design and assembly, accounting for around half the manual labor associated with manufacture.
The advent of safety systems and telemetry for monitoring driving behavior, as well as the sensors and actuators needed for self-driving, are meanwhile increasing complexity considerably. Hybrid and EVs raise the bar further by having high-voltage transmission from the battery to the propulsion motor, requiring greater shielding, especially as at the same time there is rapid growth in the amount of signaling and data transmission inside vehicles. Optimization of shielding itself is still evolving and a point of competition between providers of the major harness and electrical infrastructure providers, many of the largest of which hail from Japan, notably Yazaki, Sumitomo Electric, Furukawa, and Fujikura.
These companies are all investing in automation to simplify harness design while ensuring flexibility so that late changes can be incorporated to accommodate advances for example in autonomous systems. Siemens said the acquisition was motivated by disruption occurring in the harness industry caused in particular by the trend towards autonomous driving and EVs.
Siemens believes this is driving a revolution under the bonnet in electrical and electronic infrastructure design that is overdue as it has been lagging other aspects of automotive manufacture where much greater levels of automation have been achieved. As a result, harness design and installation has accounted for an ever-growing proportion of overall costs and threatens to impede progress on both the EV and autonomous driving fronts.
Comsa’s LDorado range encompass computer aided design (CAD) packages for laying out wire harness drawings and circuit designs in a hierarchical fashion, with a main focus being to automate layout as far as possible and avoid ever having to re-enter design features that have already been input. In the past the harness design involved separate creation of many different diagrams that are nearly identical but with small variations, which can now be handled via parameters of a single sheet. Amendments can be incorporated and activated at any stage of the design process without either having to go back to the start or imposing fudges that make subsequent maintenance and updates more complex and costlier.
The firm admits more advances are still needed but can now point to its acquisition by Siemens as evidence that it has made substantial progress automating some time-consuming aspects of harness design with changes easier to implement. It can also argue that CAD tools for automotive harness design are best designed from the ground up rather than being adapted from software that evolved in the IT industry.
It remains to be seen though how much progress such tools will make in addressing the still rather dysfunctional state of automotive harness design.