The wiring harness is the combination of electrical cables, or assembly of wires, that connects all electrical and electronic (E/E) components in the automotive vehicle, like sensors, electronic control units, batteries, and actuators. The wiring harness handles the energy and information flow within the E/E system to fulfill primary car functions, such as steering and braking as well as secondary car functions, such as ventilation and infotainment.

Automobiles and other road vehicles such as trucks and buses are one of the most demanding applications for mechanical and electrical design. The electrical systems in these applications must operate properly over a wide range of environmental conditions, facing extreme temperature, humidity, sunlight, dirt, vibration, and more. The electrical system must also meet user expectations of reliability and mandatory safety-critical design practices. With the growing focus on autonomous driving, advanced driver assistance systems (ADAS), and infotainment platforms, a sophisticated electrical system that underlies the vehicle must be handled efficiently and should not generate any electrical hazards for the safety of the passengers and vehicle as well.

Automobiles contain many wires and cables which would stretch over several kilometers if fully extended. By binding them into a cable harness, they can be better secured against the adverse effects of vibrations, abrasions, and moisture. Constricting the wires into a non-flexing bundle optimizes usage of space while decreasing the risk of a short. Since the installer has only one harness to install (as opposed to multiple wires), installation time decreases, and the process can be easily standardized. Binding the wires into a flame-retardant sleeve also lowers the risk of electrical fires. Designing such a modern vehicular electrical system is a significant task in the automotive development process and this is done in wiring harnesses.

How is a wiring harness created?

The electronic contents inside an automobile are increasing day by day and posing newer challenges in terms of managing the wiring harnesses that connect them.

A wire harness is a specially designed system that keeps numerous wires or cables organized. It is a systematic and integrated arrangement of cables within an insulating material.

The purpose of the wiring assembly is to transmit a signal or electrical power. Cables are bound together with straps, cable ties, cable lacing, sleeves, electrical tape, conduit, or a combination thereof. 

Rather than manually routing and connecting individual strands, the wires are cut to length, bundled, and clamped to the terminal or connector housing to form a single piece.

The wiring harness is created in two stages. It is designed in a software tool first and then the 2D and 3D layout is shared with manufacturing plants to build the harness.

The specific process of vehicle wiring harness design involves the following steps:

  1. First, the electrical system engineer provides the functions of the entire electrical system, including the electrical load and related unique requirements. The state of the electrical equipment, the installation location, and the form of connection between the wiring harness and the electrical equipment are all key considerations
  2. From the electrical functions and requirements provided by the electrical system engineer, the complete vehicle electrical schematic is created by adding components required for a function and connecting them together. The functions which are commonly used across multiple vehicles in an architecture platform are stored together.
  3. After the schematic is defined, the wiring harness design is created. In one platform, the end customers can have a variety of requirements. It is very time-consuming and expensive if different designs are created for each end user’s requirements separately. So, the designer takes care of the multiple variants while designing the wiring harness.
  4. At the end, a 2D representation of all the wiring designs is created to show the way different wires are bundled and how the bundles are covered to secure the wires. End connectors are also shown in this 2D diagram.
  5. These designs can interact with 3D tools for the import and export of details. The wire lengths can be imported from the 3D tool and the end-to-end connection details are exported from the wiring harness tool to a 3D tool. The 3D tool uses these data to add passive components such as straps, cable ties, cable lacing, sleeves, electrical tape, and conduits in relevant locations and send them back to the wiring harness tool.

After the design is completed in software, the wire harness is manufactured in the manufacturing plant starting from the cutting area then the pre-assembly area, and finally in the assembly area.

SaberESD Flow | Synopsys

What are the challenges in creating a wiring harness?

The wire harness design process is time-consuming, difficult, and task-oriented. As the electronics content grows in automobiles, the design challenges and complexity of the wiring harness continue to expand. It also becomes indispensable to handle these challenges in the modern automotive industry. When it comes to globalized design using consolidated platforms for wire harness design, the three major challenges for creating a wiring harness are:

  • Data inconsistency and limited reuse
  • Lack of system integration
  • Problems and errors found late in physical prototypes

Successfully migrating to shared (or consolidated) platforms requires consistent data across the teams and locations. If each team is doing its own design on its own set of EDA and CAD tools, there is a high likelihood of “shared” data becoming inconsistent over time. Design reuse, one of the main reasons for globalization, is much harder when the designs do not match. In addition, the ripple effects of inconsistent data can delay time to market (TTM), and consistency issues found late in the project often require going back to earlier design stages to resolve them.

Inconsistencies and design quality issues are usually found only when the designs from the globally dispersed teams are combined into a full electrical design. This merging point is late enough in the schedule to negatively affect TTM and consume valuable engineering resources. Furthermore, vehicle requirements may change over the course of the project due to emerging competition or new industry standards. Any updates to the platform require changes in all tools and databases, a semi-manual effort that is ripe for mistakes and omissions. Without some form of ongoing system integration, design changes in multiple teams increase the risk of inconsistent data, create multiple merge points, and exacerbate the challenge.

Even if the merge goes smoothly and no major inconsistencies are found, there is no guarantee that problems or errors will not be revealed when physical prototypes of the electrical system are built and tested. Fixing these issues delays TTM even further and consumes even more resources. The traditional flow performs limited analysis on the design and relies on lab testing for both verification and validation. One of the key arguments for use of better EDA tools is more thorough verification before the physical prototyping step, relying on the lab only for final system validation.

What are the benefits of creating a wiring harness using an EDA tool?

The process of creating a wiring harness using an EDA tool brings many advantages over the conventional way of creating a wiring harness. In addition to reducing the time to market, it brings better consistency of data, complex variant handling capability, reliability, comfort of use, effective monitoring, data integrity, and better design validation.

  1. Better Data Consistency. Tools and methods are created in such a way that they support platform-driven design generation to ensure data consistency and sufficient reuse throughout the flow to impact time to market. This can be achieved by top-down connected design flow and correct-by-construction integration.
  2. Data Integrity. All functions are built together and designed together to ensure there is no lack of integration leading to design quality problems. This can be achieved by one design database and option handling and a multi-user environment for concurrent design.
  3. Design Validation. Simulation can be integrated at all levels for sizing and robustness to ensure problems and errors can be found during the design stage itself by built-in simulators for advanced verification and automation for rapid setup and reuse.

Wiring Harness and Synopsys

Synopsys SaberES Designer offers a complete solution for electric system design and verification. This software provides a solution for wiring harness design challenges to ensure data consistency, data integrity, and design validation. This solution, also called as the top-down “connected” design flow, is built on a single design ESD database shared by all teams, ensuring consistency across all parallel projects.

It allows designers to choose content and parts from approved libraries and databases, ensuring correct-by-construction design while integrating the systems. The extensive capabilities for design generation, validation, and multi-domain verification lead to higher design quality and better electrical system robustness. The top-down generative flow improves the designer’s productivity, saving resources and reducing TTM. The single, unified database addresses the lack of system integration in the traditional flow. By using approved parts and maintaining consistency, the integration process is much smoother. There is no “big merge” step where numerous issues are uncovered.

The top-down flow also makes it much easier to share an architecture platform and to create concurrent variations for individual design projects. The shared database represents a “200% design” in which all possible options for the electrical system exist. As designers work on a new project, they use assembly filters to create a unique product. This makes it easy to choose among the available options to create modular and composite wiring harnesses. The filters are reused throughout the development process, including generating netlists for circuit simulation, exporting data to a 3D MCAD tool, and generating the manufacturing outputs.

The database and flow are shared by a diverse group of users. In addition to the roles managed by designers, other roles include the librarian who maintains the symbols and other information in the company library, the administrator who controls which users can access and change which data, and superusers who can make fundamental changes in the architecture platform. The design flow must be highly customizable, including adding additional types of libraries and controlling data access to follow company and project policies. Superusers have a lot of flexibility in tailoring the solution to fit the needs of the other users. SaberES Designer can handle such complexity seamlessly and is the preferred wiring harness design tool used by for several OEMs.

The common database means that all changes are available to all users immediately. There is no need for time-consuming manual import or export and no risk of data corruption by external interchange formats. Informational messages about changes are sent to the users, who assess the impact on their specific areas of the design. Users are alerted when design updates are required.

The only way to avoid unpleasant surprises when physical prototypes are built is through verification using circuit simulation. The goal is to “shift left” the design process by identifying any issues at the earliest possible project stage. For SaberES Designer, the simulator is a built-in solution so that users can readily try out options and variant combinations. This improves circuit robustness and quality, and it also enables “what-if” exploration of the design space. Simulation can analyze far more design permutations than building and testing multiple physical prototypes.

This allows the designers to right-size the electrical system and load-balance across the wiring harnesses and electrical components. The built-in simulator supports the following:

  • DC simulation
  • DC/voltage drop analysis
  • Connectivity checking
  • Fuse/wire sizing checks

The built-in simulator also supports transient simulations, variation and reliability analysis for robust design, and fault analysis to meet the requirements of the ISO 26262 functional safety standard.

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