Smart harnesses enable protection functions such as short-circuit and overheating protection, as well as reporting capabilities. By integrating common functionalities, they can reduce the amount of wiring in vehicles and eliminate the need for modules like fuse boxes. Smart harnesses are used in military, construction, commercial, and public transportation vehicles. They are now beginning to be adopted in light internal combustion engine (ICE) vehicles and electric vehicles (EVs).
Improvements in harness performance are incremental rather than revolutionary. These advancements began with Controller Area Network (CAN), Local Interconnect Network (LIN), and FlexRay technologies. CAN and LIN reduce the amount of wiring required, simplifying harness design (Figure 1). However, they are relatively slow and unsuitable for safety-critical communications such as brake-by-wire systems.
Figure 1. Using a CAN bus significantly reduces harness complexity. (Image: NI)
FlexRay takes this development to the next level. It is approximately 10 times faster than CAN or LIN. Fewer wires can carry more data, reducing harness complexity, weight, and cost. The next step is incorporating smart distribution modules into harnesses to add intelligence.
Smart Distribution Modules
Smart Distribution Modules (SDMs) are commonly found in emerging smart harnesses. SDMs can include microcontroller units (MCUs) to provide adaptability, edge processing for sensor inputs, and communication capabilities. SDMs are being developed for low-voltage and high-voltage wiring as well as specific lighting functions.
One SDM implementation supports six channels, each capable of handling up to 13 A. It replaces switches, relays, actuators, fuses, and circuit breakers. SDMs offer enhanced features such as resettable and programmable electronic fuses. The system architecture includes a central bus for power transmission and a single communication line to each SDM (Figure 2).
In addition to electronic fuses, SDMs may include sensors to detect overcurrent, overvoltage, or overheating on all powered devices. Detection can be completed in less than one microsecond.
In some cases, communication can be sent via the power bus, further reducing wiring and harness weight. The basic system is designed to handle voltages from 5 to 60 Vdc. High-voltage adapter boards can be added to manage EV battery packs and drivetrain power. A fire prevention algorithm has been developed to analyze sensor data and identify potential fire hazards.
Retrofitting Lighting Harnesses
Specialized smart harnesses have been developed for adding or retrofitting LED lighting in vehicles. A key feature is the built-in microprocessor, which can automatically detect whether the existing system uses positive or negative switching and adjust the smart harness operation accordingly (Figure 3).
Figure 3. Smart harness for retrofitting vehicle lighting systems. (Image: Stedi)
Retrofitting kits also include HB3 and H4 adapters. The HB3 adapter supports auxiliary lighting installation without splicing or soldering into existing factory wiring. It is commonly used to replace halogen bulbs with LEDs. The H4 adapter connects to headlights.
The article is reproduced from the WeChat public account: qicheyanjiuyuanauto.