Development of Customized Modular System of Automobile Harness

1 Introduction

With the development of society, car users have higher and higher requirements for car configuration, and custom-made cars will become the future development trend. However, customer customization will inevitably lead to the diversification of parts, and the Wiring Harness, as a separate individual part in the automobile, connects all the electric appliances in the automobile, and needs to meet different functional configurations. With the new four modernizations and the increasing configuration of electronic appliances, the complexity of wire harness is also increasing rapidly, showing the characteristics of "less base and more changes". If automotive wiring loom is designed according to the traditional mode, there will be many problems, such as long change period, heavy production pressure, and many kinds of inventory.

2 Harness Modular System Development

2.1 Principle of Modular System in Automotive Wiring Harness

The wiring harness is composed of different modules, and the wiring harness assembly is broken into wiring harness structures (modules) related to various functions, and each function is composed of a module. Harness can be divided into basic module, functional module and optional module according to requirements.

The concrete implementation of wiring harness modularization involves design splitting, pricing, testing, logistics pulling, final assembly, etc., which requires multiple systems.

At the stage of design and production, we, Kable-X, uses PowerB2O (Business-2-or-Ganization) system to split the wiring harness assembly into different modules, design each module separately, and constrain the modules with UC (UsingControl) constraints with relevant characteristics. Modular production is carried out according to different modules provided by the supplier's OEM. When the OEM's vehicle scheduling order is broadcast or the vehicle body goes online, the OEM will send the order information to the supplier through EDI (Electronic Data Interchange) system according to the configuration of the vehicle production order. After receiving the OEM's order configuration requirements, the supplier will configure and combine the different modules already produced, and finally form the harness assembly.

According to the lead time agreed by the supplier in advance, the Wire Harness shall be delivered after production, and each wire harness shall have a separate material box, and the corresponding label shall be printed. When the host machine receives the wire harness produced by the supplier, it scans the code and receives the goods, and finds the empty warehouse position according to certain strategic requirements, and informs the material personnel to place it. When the whole vehicle enters the final assembly, the wiring harness sequencing action is triggered, the wiring harness used by the vehicle is found according to the vehicle number, and the logistics personnel are informed to pick up the goods and send them to the sequencing area for sequencing.

When the whole vehicle goes offline, the settlement action will be triggered, and the usage of a single module will be generated according to the situation of the harness modules used by the whole vehicle, and the information in the settlement state will be released to the supplier platform, which will facilitate the supplier to issue and settle invoices. Finally, the supplier checks the settlement information on the platform to form the corresponding invoicing basis.

2.2 Modular Splitting Principle

The principle of module splitting is: firstly, make sure that the module covers all the configurations of the whole vehicle; Secondly, the modules are clearly divided according to configuration or function, and no loops or repeated loops can be missed; Finally, redundancy can be made when necessary to reduce the types of modules.

In the early stage of development, the modules must be clearly divided, and then each part should be divided into different modules. At present, according to the parts' functions, the vehicle electrical appliance modules are divided into two types: basic modules and functional modules.

The basic module, also known as the required module, is unique and has the highest priority. The parts in the basic module are the required configuration of all models, and these parts do not contain multiple configurations. At this time, the wiring harness drawing should have only one basic module, which is shared by all models.

The function module contains a variety of selectable modules. The modules are divided into transmission module (AMT/MT), CAN network module (high CAN/low CAN), ABS module (ABS/ESP), reversing image module, electric rearview mirror module, window breaker and other modules. These functional modules are divided into mandatory functional modules (such as transmission module and ABS module) and optional functional modules (such as reversing image module and electric rearview mirror module), among which the priority of mandatory functional modules is higher than that of optional functional modules. The required module means that one of the sub-configurations in the required module must be selected regardless of the vehicle configuration; Optional modules indicate whether these modules need to be selected by customers. If customers choose the configuration of optional modules, the sub-modules of functional modules need them; otherwise, they don't need them.

After dividing the modules, set the optional rules for the basic modules, required functional modules and optional functional modules in the system in advance. If the selected modules are repeated or omitted, the system will report an error, which is conducive to the back-check of the multi-module wiring harness and reduces the probability of module errors.

After the module is determined, the plastic parts, terminals, connectors, etc. on the wiring harness are divided, and each sub-part should have certain attributes. Especially for connectors shared by different modules, connectors are generally divided according to the number of holes, and the connectors are classified as modules with more holes. C Connector has four holes, one hole belongs to this module and the other three holes belong to another module, so this connector belongs to another module.

2.3 Harness Development Verification Strategy

The accuracy of the module after wiring harness is too large to be fully verified by physical objects, so the following strategies are generally adopted in each verification link.

1) Virtual verification: with the assistance of special design software, simulate and analyze the feasibility of matching each module.

Its advantages are short time and low cost. The disadvantage is that the unexpected situation in the actual production process of wire harness cannot be predicted.

2) System verification: select several harness assemblies such as high, medium and low, and confirm the feasibility of the harness module. The advantage is that it can simulate the verification of real vehicles, but the disadvantage is that only some vehicles can be verified, and all configured vehicles can't be verified. Considering the cost, cycle and other aspects, modular wiring harnesses are mostly verified by this method.

3) Real vehicle verification: verify the option strategy with the same system to ensure that all modules are covered by the harness assemblies of all test models. Has that advantage of ensure that vehicles with various configuration are verified and fully verified. Disadvantages are many vehicles, long verification period and high cost.

3 Advantages and Disadvantages of Modular Design of Wiring Harness

3.1 Limitations of Modular Design of Wiring Harness

The modular wiring harness mode saves a long list of workflows, greatly improves the response speed and reduces the inventory. However, "different wheelbase" models under the main model are not suitable for KSK mode, because the wiring harness modularization is suitable for circuits with different hole positions in the same connector, and two functions with different lengths are not suitable for being divided into the same sub-module.

3.2 Advantages of Modular Design of Wiring Harness

1) Reduce the Design Process and Workload of the Main Engine Factory Wiring Harness.

In the traditional wiring harness design mode, a new drawing corresponding to each vehicle configuration, if the basic wiring harness of a certain vehicle type is changed, all drawings need to be changed, and the workload is very heavy. If KSK modular design is adopted, it is only necessary to update the drawings of the wiring harness of the changed related modules.

2) KSK Mode Greatly Reduces the Warehousing Logistics Cost and Inventory Cost of OEM.

In the traditional wiring harness production mode, there will be a lot of stock for each wiring harness part number in the mainframe factory, while in KSK mode, there is basically zero stock for wiring harness parts in the mainframe factory, which greatly reduces the inventory cost. Moreover, the modular design is adopted, and each wire is tailor-made, which will not generate redundant branches and reduce the single-piece cost.

3) Shorten the Cycle.

Modular wiring harnesses are classified based on the function and layout of electrical appliances. Designers don't need to find out whether similar treatments have been done in previous models, but only need to confirm whether new functions appear. If new functions appear, the wiring harnesses with new functions will be designed first and then added to the list of functions, which greatly shortens the development cycle. In the traditional mode, it takes about 5 weeks to develop a wiring harness tooling, and the parts delivery needs to be ordered about two weeks in advance. In the KSK mode, the wiring harness development cycle tooling takes about 2 weeks, and the parts delivery needs to be submitted three days in advance.

4 Summary

The system development of KSK mode requires the OEM and the supplier to establish a complex information interaction system, and it also requires higher personnel in design, production, logistics and other aspects. However, the modular production of wire harness KSK can greatly shorten the development cycle and save costs.

With the increasing demand of consumers for vehicle configuration and personalization, KSK harness design is the initial embodiment of customer customization. Among the Chinese market brands, the harness of SAIC Datong Automobile Co., Ltd. has adopted modular development and production mode on the whole platform, Chery Automobile has also adopted modular production initially, and joint venture brands such as Audi and Volkswagen have adopted semi-modular production mode. China's self-owned brand cars are booming, and wiring harnesses have great potential in the direction of modular design. In the end, KSK's wiring harness production method will become the mainstream, and it will not be limited to the automotive field, but will continue to expand into different fields to achieve high-complexity production in mass production, so that everyone can experience customized products that fully meet their own needs.