Connectivity standards for electric self-driving cars continue to evolve

Vehicle systems generate and consume large amounts of data, raising concerns about data integrity and security.

The growth of plug-in hybrid and electric vehicles, as well as the increasingly complex development of advanced driver assistance systems (ADAS) and autonomous driving systems, are changing industry standards for electrical and electronic connectors. Power transmission is only one aspect of connectivity, but as vehicle systems generate and consume large amounts of data, there are also concerns about data integrity and security, as well as the ever-present challenge of electromagnetic compatibility. In this rapidly changing scenario, what industry standards do designers need to keep in mind?

The automotive industry is constantly changing, and this has become especially prevalent during this decade. As technological change occurs in one area, the resulting evolution is that technology can spur change in several other areas.

Moving towards semi-autonomous or fully autonomous vehicles. Autonomous vehicles require a large number of sensors around their bodies to navigate safely. Modern vehicles already have a variety of ADAS features, such as adaptive cruise control, emergency braking, and blind spot detection. With these increasing features, the ability to integrate and interpret sensor data becomes possible, enabling basic autonomy. Sensors located around the vehicle need to be networked, and timely innovations in Single Pair Ethernet (SPE) protocols, such as multi-point 10Base-T1S and long-distance 10Base-T1L, make this possible.

Another important industry trend is electrification. The growing demand for electric vehicles (EVs) is driving a shift in the way automotive engineers develop. For example, the considerable weight of EV batteries and the increase in wiring around the vehicle require automotive engineers to consider a new approach to vehicle electrical/electronic (E/E) architecture to reduce weight, reduce costs, and simplify implementation. Most automakers have adopted a zone architecture, which greatly reduces the number of cables reaching specific locations. For example, the driver's door zone only requires power and network connectivity, and the zone controller manages communication with the door mirrors, blind spot sensors, locks, window motors, and turn indicators.

The basis of any electrical and electronic installation are the cables and connectors that connect electronic control units and computers to sensors, actuators and motors.

The automotive environment places demands on all required components. Devices, cables, and connectors are subject to extreme temperatures, humidity, and dust. Since each component is critical not only to the performance of the vehicle, but also to its safety, it is vital to maintain reliable and robust connections. Sensors that measure everything from cabin temperature to wheel traction effects need to be fit for purpose.

Environmental:

Whether inside or outside the vehicle, the environment is challenging for cabling and connectors, with extremes in every factor from temperature and humidity to vibration and shock. Oscillating motion can fatigue cables and associated connector joints, so special attention needs to be paid to connector placement, installation, and construction. For some applications, connectors may be frequently immersed in water, so sealing is critical.

application:

The application will determine the type of cabling and connectors specified, ranging from unshielded twisted pair data cables and coaxial antenna feeds to high current, high voltage power connectors used in electric vehicles. Exposure to environmental conditions should also be reviewed.

The mechanical strength and ruggedness of the connector is critical. Protection from environmental factors and application requirements will guide connector specifications, such as the use of locking rings or latches, ingress protection, quality of the connected cable, and bulkhead or in-line retention. Other mechanical considerations include insertion force and retention force.

The electrical parameters of the connector include voltage, current, EMI shielding and isolation voltage. Increasingly, hybrid connectors may contain small signal sensor outputs, high-speed data networks and regional 12V/24V power rails. E/E engineering teams must consider multiple factors when taking this approach.

Consideration should also be given to how the connector will be assembled. Can a standard off-the-shelf connector be used to meet the requirements, or will a custom part be required? Will it be installed during the production process on a wire loom? All of these factors will impact connection selection, labor, and material costs.

Some automotive applications, such as electric vehicle charging, require specific connectors. Engineering teams should check with the relevant automotive standards bodies to determine if a defined specification exists for a specific use case.

In addition to the evolution of the above factors, several standards organizations have published automotive connector specifications that can help designers select appropriate components.

IEC 62196: This standard applies to plugs and sockets for AC or DC conductive charging of electric vehicles. It has several parts, including -1, which specifies general connector requirements; -3, dimensions and interchangeability specifications for DC and AC connectors; and -3-1, thermal management effects and precautions for DC charging connectors. Parts of this standard are also consistent with the single-phase connectors of SAE J1772 and the three-phase connections of SAE J3068.

USCAR12-6: This standard provides specific and measurable design requirements that manufacturers must follow when designing automotive electrical connectors. The performance standards for related connections specified in USCAR2 must also be followed.

USCAR2: Compliance with USCAR2 is an essential component of any automotive connector. The specification provides manufacturers with a measurable performance standard that covers all types of coaxial cables from low voltage (defined as 0 to 20VDC) to RF applications. It does not include any connector carrying more than 20VDC, board-level connections, or eyelet terminals.

SAE J1742: This standard outlines the test methods and performance requirements for connectors used in high-voltage on-board electrical harnesses. It covers full development and production testing for vehicle systems with any current level from 20VDC to 600 VDC or any vehicle system carrying more than 80A, regardless of voltage. In mixed connector arrangements, for example, high-voltage batteries and data from battery management system sensors, other connections must comply with the SAE J2223-2 standard.

Major trends in the automotive industry, such as the move to 800VDC infrastructure, regional wiring architectures, and the removal of traditional 12V batteries, all have an impact on current electrical standards. Working with automakers and equipment suppliers, standards organizations ensure that connector standards keep pace with these advances.