Connectivity Standards Evolve For Electric, Autonomous Cars
Vehicle systems produce and consume vast amounts of data, raising concerns around data integrity and security, and the ever-present challenge of electromagnetic compatibility. In this fast-changing scenario, which industry standards do designers need to keep in mind?
The growth of plug-in hybrid and electric vehicles and the ever-greater sophistication of advanced driver assistance systems (ADAS) and autonomous driving systems are changing the industry standards around electrical and electronic connectors. Power transfer is only one aspect of connectivity, but as vehicle systems produce and consume vast amounts of data, there are also concerns around data integrity and security and the ever-present challenge of electromagnetic compatibility. In this fast-changing scenario, which industry standards do designers need to keep in mind?
The automotive industry is experiencing a huge transformation
The automotive industry is constantly changing, and this has become especially prevalent this decade. As technological changes occur in one area, the eventual evolution is that technology can spur changes in several other areas.
Take the move toward semi or fully autonomous vehicles. A self-driving car requires a host of sensors around its body to navigate itself safely. Modern vehicles already have multiple ADAS features, such as adaptive cruise control, emergency braking, and blind-spot detection. As more of these features are available, the ability to consolidate and interpret sensor data becomes possible, leading to basic levels of autonomy. Sensors located around the vehicle require networking together, and the timely innovation of single-pair Ethernet (SPE) protocols, such as the multi-drop 10Base-T1S and long-reach 10Base-T1L, makes this possible.
Another significant industry trend has been electrification. The growing demand for electric vehicles (EVs) has driven a shift in how automotive engineers approach development. For example, the considerable weight of an EV’s batteries and the growth of cabling around the vehicle has required automotive engineers to consider a new vehicle electrical/electronic (E/E) architectural approach that saves weight, reduces cost, and simplifies implementation. Most automotive manufacturers have adopted a zonal architecture, significantly reducing the number of cables going to a specific location. For example, the driver’s door zone requires just power and a network connection, with a zonal controller managing communication with door mirrors, blind-spot sensors, locks, window motors, and turn indicators.
Fundamental to any electrical and electronic installation are the cables and connectors linking electronic control units and computers to the sensors, actuators, and motors.
Reliability of connection in the automotive domain
The automotive environment is demanding on all the required pieces. Equipment, cables, and connectors experience temperature, humidity, and dust extremes. As each piece is critical to not just the vehicle’s performance but also its safety, maintaining reliable and robust connections is paramount. Sensors measuring everything from the cabin temperature to wheel traction effectiveness need to be fit for purpose.
When selecting connectors for automotive applications, the engineering team should review multiple factors.
Environmental:
Whether inside or outside the vehicle, the environment is challenging for cabling and connectors, with extremes of every factor, from temperature and humidity to vibration and shock. Oscillatory movements can fatigue cables and associated connector joints, requiring careful attention to connector placement, mounting, and construction. For some applications, connectors may experience regular immersion in water, so sealing is crucial.
Application:
The application will dictate the type of cabling and connectors specified, ranging from unshielded, twisted pair data cables and coaxial antenna feds to high-current, high-voltage power connectors used in electric vehicles. Exposure to environmental conditions should also be reviewed.
Mechanical:
The connector’s mechanical strength and robustness are vital. Protection from environmental factors and application requirements will guide connector specifications, such as using a locking ring or catch, ingress protection, attached cable mass, and bulkhead or in-line fixing. Other mechanical considerations include insertion force and retention force.
Electrical:
A connector’s electrical parameters include voltage, current, EMI shielding, and isolation voltage. Increasingly, a hybrid connector may incorporate small signal sensor outputs, high-speed data networking, and a zonal 12V/24V supply rail. The E/E engineering team must consider multiple factors when taking this approach.
Assembly and production:
How the connector will be assembled should also be considered. Can the requirement be satisfied with a standard off-the-shelf connector, or is a custom part needed? Will it be fitted during wiring loom production? All these factors influence connection selection, labor, and material costs.
Regulations and standards:
Some automotive applications, such as EV charging, require a specific connector. The engineering team should check with the relevant automotive standards authorities to determine whether a defined specification exists for particular use cases.
Popular off-the-shelf connector formats have evolved and are available from various suppliers. Examples include the 2-pin to 32-pin rectangular low voltage (LV) connectors, used for everything from single-pair Ethernet to hybrid power and signal connectors to support zonal architectures.
Standards organizations involved in automotive
In addition to the evolution of the above factors, several standards organizations publish automotive connector specifications that can help designers select the appropriate component.
- Society of Automotive Engineers (SAE) is a global association of more than 128,000 engineers and related technical experts in the aerospace, automotive, and commercial vehicle industries. It has a formal, well-established standards development process covering every aspect of vehicle systems, materials, and methods.
The standards development process used by SAE.
- The United States Council for Automotive Research (USCAR) collaborates with member organizations and the SAE to define and publish automotive standards. Its EWCAP specifications, for example, stipulate formal performance testing methods for a range of electrical connections. In Europe, the LV214 standards are broadly in line with those of USCAR.
USCAR provides technical drawings of popular connector formats.
- The International Electrotechnical Commission (IEC) provides standards that cover every function of electrical and electronic equipment.
Automotive connector standards example
IEC 62196: This standard applies to plugs and sockets for the AC or DC conductive charging of electric vehicles. It has several parts, with -1 stipulating the general connector requirements; -3, the dimensions and interchangeability specifications for DC and AC connectors; and -3-1, the thermal management implications and considerations for DC charging connectors. Parts of this standard are also harmonized with SAE J1772 for single-phase connectors and SAE J3068 for three-phase connections.
USCAR12-6: This standard provides specific and measurable design requirements that manufacturers must follow when designing automotive electrical connectors. The performance criteria for the relevant connection, as specified by USCAR2, must also be followed.
USCAR2: Compliance with USCAR2 is a fundamental part of any automotive connector. The specification provides measurable performance criteria for manufacturers and covers every type, from low voltage, defined as 0 to 20 VDC, to coaxial for radio frequency applications. It does not cover any connector carrying over 20 VDC, board-level connectivity, or eyelet terminal posts.
SAE J1742: This standard outlines the test methods and performance requirements of connectors for high voltage on-board vehicle electrical wiring harnesses. Covering the complete development and production testing, it covers vehicle systems from 20 VDC to 600 VDC at any current level or any vehicle system carrying more than 80 A, regardless of the voltage. In a hybrid connector arrangement, for example, high voltage battery and data from battery management system sensors, the other connections must comply with the SAE J2223-2 standard.
Connector standards continue to evolve
Key automotive industry trends, such as the move to 800 VDC infrastructure, zonal wiring architectures, and removing the legacy 12 V battery, all have implications for current electrical standards. By working with vehicle manufacturers and equipment suppliers, the standards organizations ensure that connector standards are kept up to date with these advances.
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- Connectivity Standards Evolve For Electric, Autonomous Cars - August 6, 2024
