【 Abstract 】 With the pure electric drive as the main strategy for the development of the new energy automobile industry and the transformation of the automobile industry, intelligent manufacturing has become a national strategy, and the correct assembly of high-voltage wiring harness is an important part of the vehicle assembly. Combining the general principle of cybernetics and the factors affecting the process control, by improving the discernibility of the information source and reducing the interference items during the information transmission, using the mature process control, the anti-misinstallation scheme in the synchronous design stage is studied. Based on the characteristics of human cognition, targeted measures are formulated in the cable assembly stage. Combined with the application of intelligence in error prevention, it is briefly introduced to reduce the chance of misassembly and improve the assembly efficiency. After the production line verification, the whole process error prevention specification and operational guidelines will be used as the standard for the development of new models.

01 Quotation

With the release of the relevant policies of the "Energy Conservation and New Energy Automobile Industry Development Plan", pure electric drive will become the main strategic orientation for the development of the new energy automobile industry and the transformation of the automobile industry. The correct assembly of the high voltage cable harness used to connect the power drive, controller and energy storage equipment is an important part of this.

Compared with the fixed arrangement of fuel vehicles, the arrangement of new energy vehicles is more flexible, different suppliers have their own specifications, a wide variety of connecting wiring harnesses, diverse arrangements, and different product specifications, which make the probability of high-voltage wiring harnesses connecting errors in the assembly process high, and bring great inconvenience to the subsequent vehicle debugging work. According to the feedback of debugging problems, wiring harness virtual connection and misconnection problems account for more than 70% of wiring harness problems, and high voltage wiring harness connection error prevention is an urgent problem to be solved.

Since the early 1950s, some principles of Wiener's Cybernetics have penetrated into all aspects of people's lives. Combined with some basic principles of cybernetics and the requirements of the process, the whole process of high-voltage wire harness connection error prevention from product design to production cable assembly has been studied, which can provide operational principles for on-site assembly and the design of new models.

02 Overview

The assembly of high-voltage wiring harnesses of new energy vehicles mainly includes the series and parallel connection of positive and negative wires between different boxes of the power battery, the connection between the power battery and the battery management system BMS and the multi-in-one controller, and the connection between the BMS and the multi-in-one controller and the drive motor. Wiring harness connection is mainly manual connection, generally connect one end of a group of wiring harness first, and then connect the other end, error occurs in the connection of the other end of the connector and terminal.

The ultimate purpose of high voltage wiring harness connection error prevention is to transmit the correct connection information to the assembler and ensure the accuracy of information transmission. The whole process of information transmission includes information source, transmission channel and information receiving. High voltage wiring harness connection information through standard design, multi-channel, multi-media transmission, operation process control, to achieve correct information transmission, and process control has a close relationship.

The error prevention requirements are mainly reflected in the rapid determination of the corresponding relationship between the harness end and the wiring port. Error prevention is to eliminate the uncertainty of the corresponding relationship between the wiring harness and the joint in the connection information transmission process, combined with the whole process of vehicle development, its common principles are as follows:

1) Exclusion: Eliminate the causes of errors and avoid errors from the source, mainly reflected in the structural error prevention design in the design stage.

2) Substitution: The use of more accurate operation methods to avoid the occurrence of errors, which is represented by the use of automated equipment instead of manual labor.

3) Simplification: Reduce the error rate through easier operation, manifested in modular design, simple unified design structure, making the operation simpler.

4) Exception check: in the case of an error, it can be detected in the next process.

03 Fault prevention status of high-voltage cable harness connections

At present, the high voltage wiring harness connection error prevention scheme mainly relies on appearance. The wiring harness used on commercial vehicles is mainly distinguished by the color on the appearance, the text description on the joints at both ends of the wiring harness, and the shape of the connector, which is used to prevent misinstallation.

The series-parallel wiring harness between the power battery is connected by terminal connection, and the wiring harness has part identification. The positive and negative poles are distinguished by the color of the heat shrink tube (red, positive, black and negative).

The two ends of the wire harness connected to the controller have special name marks, and the corresponding controller or electrical equipment on the connection position has the same name marks, and the relationship is one-to-one. 

The connection connector on the controller distinguishes different connection wiring harnesses by different shapes, and the same shape structure is matched by the concave and convex body inside. According to the above analysis, the existing error prevention program has partially reflected the exclusion principle, according to the field feedback, has played a certain error prevention effect, in the subsequent vehicle development process according to the error prevention principle further exploration and research.

04 Anti-misinstallation solution

Some cognitive characteristics of human beings, including memory, forgetting and learning, thinking and decision making, attention and constant vigilance, still play an important role in the assembly process, and tend to the characteristics of simple memory. Based on this feature, the following three error prevention principles of exclusion, simplification and exception checking are studied and analyzed.

4.1 Design Phase

As one of the standard design methods, universal and integrated design is widely used in the development of new products, and it has gained more and more attention in improving product reliability, simplifying assembly maintenance and support. In the initial stage of high-voltage wiring harness design of new models, establish standardized design principles, maintain a high degree of consistency, and choose the modular design of black box mode.

4.1.1 Specification design

The general design of the series model and the development according to the demand make the arrangement of the high voltage wiring harness regular, more regular, convenient recognition and memory.

1) Layout specification. The corresponding layout planning is carried out around the core components. Taking a certain model as an example, the wiring harness is uniformly arranged on the same side in combination with the layout diagram of the power battery, which reduces the routing of the wiring harness cable assembly and facilitates identification.

2) Plan the wiring harness end and controller interface. Unified naming is carried out according to the naming rules, and the wiring harness design specifications (examples) are shown in Table 1.

3) Plan wiring harness joints according to requirements. In the design of wiring harness, the design standard is unified, and the corresponding relationship between color and polarity and auxiliary machinery is established, so that different colors represent different polarity and auxiliary machinery systems. Before the harness development, plan the colors of different parts of the harness, such as positive and negative connection wires, U/V/W connection wires, etc. For example, the main sheath color of the wiring harness design, the color of the logo on the wiring harness, the color of the connector or terminal, and the corresponding color is established in the CATIA software, and finally reflected in the three-dimensional data.

Use differential (using different notches inside the connector) or different color connector schemes to achieve one-to-one correspondence through color or shape matching. For example, the round connector corresponds to the air conditioning compressor, the square connector corresponds to the battery cooling water pump, and the same external connector is provided with different bumps and gaps in its internal corresponding to different auxiliary machines.

4.1.2 Integrated design

The battery Pack matched by the existing model is a series parallel scheme of multiple power battery packs (Packs), and there are more wiring harnesses between packs and more error points. The new CTB scheme adopts a simplified design scheme, through the internal core module design, the copper bar is connected to the core module, by combining 3 or 4 packs into 1, the external connection point will also become 1/3 of the original.

In the case that one end of the wiring harness has been connected, if the position of the connecting port is not on, the distance between the wiring harness and the connecting port is long or short, it will cause the connection is not connected or the wiring harness is wrapped too much. The length of the wiring harness in the design of the wiring harness circuit can also be used as a fault prevention scheme.

4.2 Assembly Stage

When the design structure is determined, the error prevention of the assembly link is equally important. In the determination of the high-voltage wiring harness connection process, the 6 principles of man-machine material method are , among which the 5 items of equipment, raw materials, method, environment and measurement are relatively easy to determine. The high-voltage wiring harness connection requires deep manual participation, and it is difficult to use the alternative principle of the error prevention principle. The assemblers themselves are subject to personal cognition and skill proficiency, which is difficult to control. As we all know, on the one hand, memory helps humans quickly identify the objects they remember, recognize new things, adapt to new environments, etc., on the other hand, memory will erase some details, compress the memory content, and make it shape

It's an unconscious reaction. Cybernetics requires that neither too much nor too much information be delivered to the receiver of the message, leaving it vulnerable to interference. The interference of the assembler is mainly subjective interference, which is dominated by the consciousness of the assembler. The main task in the process of transmitting the correct information to the assembler is to remove the interference so that it receives the correct information.

Based on the above analysis, the focus of error prevention in the assembly stage is considered from the perspective of the assembler. The simplest way is repeated transmission, and the correct information is repeatedly input to the assembler. Another principle is to use different media to deliver a unified message. Therefore, the assembly error prevention mainly transmits assembly information in multiple ways, refines and simplifies the assembly worker's memory content, and confirms the anti-error assembly requirements in the process.

4.2.1 Obtaining Accurate Information

Initial assembly training before new structures and new models are launched, so that assemblers can understand the basic principles of high-voltage wiring harness connection, and deepen the memory of assemblers through the input of basic knowledge and principles. The assembly information is transmitted to the assembler on a unified process platform through various media such as live shooting video, 3D simulation animation, text description of key details and pictures.

4.2.2 Reassemble unit assembly content

Based on the principle of simplification in the error-prevention scheme, the process development from optimizing the distribution of processes to adjusting the assembly sequence can simplify the memory content of the assemblers.

The assembly contents of different models at the same station are not completely consistent. Through dismantling and reassembling the assembly contents, a reasonable assembly process is formulated for different layout methods, such as adjusting the assembly station of the cooling system of a certain model. In the control stage of the assembly process, the assembly process is rationally allocated according to the skill level of the assemblers, so that the assembly information of a single assembler is in line with the skill level of the employees, and the memory items are relatively few, so as to avoid errors in the assembly of mixed lines. For example, the pump motor, the steering motor, the air conditioning compressor motor, etc., belong to different assemblers.

4.2.3 Process Error Prevention

Add confirmation in the assembly process and follow the principle of abnormal inspection, which is embodied in the self-check and mutual check in the assembly process. Before the final assembly of the fusing wire of the vehicle, the confirmation process of the key wiring harness connection should be added. The technician should confirm the specific inspection items before assembly. The on-site assembly personnel should use a marker different from the inspection mark to mark the designated position before assembling the fusing wire. If both the assembly process and the confirmation process have a 1% chance of error, the chance of both making an error decreases to 0.01%.

4.2.4 Alternative Error prevention

At present, there is no alternative solution for the assembly process of high-voltage wiring harness, but for the assembly process detection, visual recognition and other technologies can be used to improve the detection accuracy. Based on computer vision, machine vision technology extracts feature information from the collected images, processes and processes them, and then applies them in the actual detection, recognition and measurement environment, and is widely used in the automatic production of the assembly line. The color of the controller body is mostly black and single, and the wiring harness connected to it has the characteristics of stable position and bright color. The visual recognition system can be arranged in the frame around the assembly station to recognize the color of the terminal and the color of the connector, and timely feedback the assembly result.

4.3 Summary

For new energy models, the connection of high-voltage wiring harness is a complex and tedious assembly task, and the whole process is completed by manual work. The completion of the assembly task means the completion of the vehicle assembly work to a large extent, and the quality of the connection and the assembly efficiency are decisive for the assembly of new energy models.

By correcting the harness color, name identification, adapter shape, and other control procedures, including assembly on-site training and increasing self-inspection, the high voltage harness assembly problem records from July 2023 to March 2024 have been compiled, and the wrong connection has been avoided, and the harness connection time has been increased from 2JPH to 4JPH. More than double the efficiency.

05 Conclusion

Starting from the cybernetics point of view and the core content of the assembly process of the high-voltage wiring harness, this paper makes the basic planning requirements for the development process of the new model in order to simplify the assembly information and combine the mature error prevention schemes in the existing market. In the process scheme determination, the human factor is the most difficult to control among the six factors of man-machine material measurement. From the perspective of assemblers, this paper proposes some error-prevention schemes, such as improving the theoretical understanding of assemblers themselves, transmitting assembly information to assemblers in multiple ways, classifying and reorganizing processes, reducing the identification of items by assemblers themselves and process control, etc. Good results have been obtained in practical application. With the country's realization of intelligent manufacturing and technology, combined with visual recognition, assembly workers can be reminded in advance during the assembly process to further improve assembly accuracy and assembly efficiency.