Automotive Sensors Design

Automotive sensors are critical components in modern vehicles, providing essential data for various systems to ensure safety, efficiency, and performance. These sensors monitor and report on various parameters, such as pressure, position, and more, enabling advanced functionalities like adaptive cruise control, self-driving, and engine management. These sensors' product design and development are crucial to their effectiveness and reliability.

In this post, we will explore some mechanical design aspects when designing an automotive sensor, focusing on some considerations and processes involved in creating reliable and efficient sensors for automotive applications.

Examples of Automotive Sensors

Each type of sensor has a specific role in the vehicle's operation. For example, temperature sensors help manage engine cooling, while pressure sensors ensure proper tire inflation pressure.

Categorization: Automotive sensors can be categorized into several types based on their functionality:

Acoustic Sensors: Detect and analyze sound waves within the vehicle. For example, acoustic sensors can be used for noise, vibration, and harshness (NVH) analysis to improve cabin comfort by identifying and mitigating unwanted noises. They are also used in parking assistance systems to detect obstacles.
Temperature Sensors: Measure the temperature of various vehicle components.
Pressure Sensors: Monitor the pressure of fluids and gases within the vehicle.
Position Sensors: Detect the position of various parts, such as the throttle or camshaft.
Speed Sensors: Measure the rotational speed of wheels or the engine.
Oxygen Sensors: Monitor the oxygen levels in the exhaust gases to optimize fuel combustion.

Mechanical Design Considerations

Durability and Reliability:

Designing sensors that can withstand harsh automotive environments is crucial. These sensors must endure extreme temperatures, vibrations, moisture, and exposure to chemicals without compromising their performance.

Temperature Limits: Automotive sensors must operate reliably within a wide temperature range. For example, engine temperature sensors typically function from -40°C to +130°C, while exhaust gas temperature sensors can handle temperatures up to +1000°C. These limits are often guided by standards such as ISO 16750-4, which outlines environmental conditions and testing for electrical and electronic equipment in road vehicles.
Vibration Limits: Sensors must also withstand significant vibrations. According to ISO 16750-3, automotive sensors should be tested across a frequency range of 10 Hz to 2000 Hz with varying levels of acceleration. This ensures they can endure the vibrations experienced during vehicle operation and transport.
Moisture Limits: Moisture resistance is essential to prevent sensor failure due to water ingress. Automotive sensors are often tested to meet IP67 or IP69K standards, which ensure protection against dust and water immersion up to 1 meter for 30 minutes (IP67) and high-pressure, high-temperature water jets (IP69K).
Chemical Corrosion Limits: Sensors must resist corrosion from exposure to various chemicals, such as road salts and engine fluids. Standards like ISO 22858 provide guidelines for monitoring atmospheric corrosion using electrochemical measurements. These sensors are designed to withstand exposure to corrosive environments, ensuring long-term reliability.

By adhering to these standards and limits, automotive sensors can maintain their performance and reliability in the demanding conditions of automotive applications.

Material Selection:

When it comes to the selection of materials, automakers prefer certain types of materials according to the sensor’s functionality, loads, and location in the vehicle. The most commonly used materials include:

Metals: For structural components due to their strength and durability.
Plastics: For housings and connectors, offering lightweight and corrosion resistance.
Ceramics: For components that require high-temperature stability and electrical insulation.

Here's a table summarizing the mechanical properties of commonly used materials in each category:

Category	Material	Density (g/cm³)	Tensile Strength (MPa)	Young's Modulus (GPa)	Thermal Conductivity (W/m·K)	Operating Temperature (°C)
Metals	Aluminum Alloy	2.7	200-600	70-80	150-235	-40 to 150
	Stainless Steel	7.8	500-1000	190-210	15-25	-40 to 800
	Copper	8.9	210-250	110-130	390-400	-40 to 200
Plastics	Polypropylene (PP)	0.9	30-40	1.5-2.0	0.1-0.22	-20 to 120
	Polyamide (Nylon)	1.1-1.2	70-100	2.5-3.5	0.25-0.3	-40 to 120
	Polycarbonate (PC)	1.2	60-70	2.0-2.4	0.19-0.22	-40 to 135
Ceramics	Alumina (Al₂O₃)	3.9	300-600	300-400	20-30	-40 to 1600
	Zirconia (ZrO₂)	5.6	900-1200	200-220	2.5-3.0	-40 to 2400
	Silicon Carbide	3.2	400-600	410-450	120-200	-40 to 1600

These materials are selected based on their mechanical properties, which ensure the sensors can perform reliably under the demanding conditions of automotive applications.

Size and Weight:

Minimizing the size and weight of sensors is essential to reduce the overall vehicle weight and improve fuel efficiency. However, this must be balanced with the need to maintain sensor performance and durability.

Automotive Product Development Process (PDP)

Agile Iterative Design:

Incorporating the agile iterative design concept makes the design process more flexible and adaptive. This approach involves breaking down the design process into smaller, manageable iterations or sprints. Each iteration includes planning, designing, prototyping, testing, and reviewing. Feedback from each iteration is used to refine and improve the design continuously. This iterative process helps identify and address issues early, leading to a more robust and reliable sensor.

Concept Development >> Design and Engineering >> Prototyping and Testing >> Production Planning >> Manufacturing

Concept Development: This initial phase involves identifying market needs, generating ideas, and defining the product concept. It includes feasibility studies, market analysis, and initial design sketches. The primary focus should be on functionality, ensuring the sensor meets its intended purpose. If the sensor is exposed, industrial designers should also consider:
1. Functionality
2. Ergonomics
3. Aesthetic appeal
4. Marketability
Design and Engineering: In this stage, detailed design work is carried out using tools like CAD (Computer-Aided Design) software. Engineers focus on creating detailed 3D models, selecting materials, and ensuring the design meets all functional and regulatory requirements.
Prototyping and Testing: Prototypes are built and tested to validate the design. This phase includes rigorous testing for performance, durability, safety, and compliance with standards. Iterative testing and refinement are crucial to address any issues that arise.
Production Planning: This stage involves planning the manufacturing process, including tooling, production line setup, and supply chain logistics. It ensures that the product can be produced efficiently and at scale.
Manufacturing: The product is manufactured according to the planned processes. Quality control measures are implemented to ensure consistency and adherence to specifications.
Launch and Post-Launch: The product is launched into the market. Post-launch activities include monitoring product performance, gathering customer feedback, and making any necessary adjustments or improvements.

Integration with the Vehicle

Mounting and Installation:

Automotive electronics use common automotive-grade wires, sockets, and plugs. Depending on the type of communication needed, ready-made sockets from suppliers like Rosenberger can be used. A hermetically sealed connection should be considered to maintain the sensor's IP/NEMA rating. There are two options to consider:

A built-in plug/socket in the sensor’s enclosure.
A built-in wire with a plug/socket at the free end.

The installation location should be predefined, and sufficient testing should be performed on the sensor’s performance with the vehicle's vibration and harshness.

Automotive Sensors Connectors (Plugs and Sockets)

Below is a list of top connector vendors:

TE Connectivity
Yazaki
Aptiv (Delphi)
JAE
J.S.T
Sumitomo
Rosenberger
AVX
Amphenol
Molex
ACDelco

Automotive Cables

The following properties are important to know when selecting your cable:

Data transfer rate
Shielding material
Core material
Core type (fiber or solid)
Clock frequency
Insulation material
Impedance
Maximum diameter of the single wire
Nominal diameter of the conductor
Number of strands
Electrical resistance at 20 °C max. (ohm/km)
Temperature range
Capacity [max. pF/m]
Jacket material
Weight (kg/m)
Twisted pair or Multiconductor
Strand coating
Flammability
Cable Resistance RDC

Below is another list of top automotive cable suppliers:

BorgWarner, Inc.
Furukawa Electric Co. Ltd.
Lear Corporation
LEONI AG
Nexans Autoelectric GmbH
Motherson Group
Sumitomo Electric Industries, Ltd.
AmWINS Group Inc.
YAZAKI Corporation
YURA Corporation

Automotive Compliance

Compliance with industry standards and regulations is crucial for the success of automotive sensors. Adhering to directives such as the Electromagnetic Compatibility (EMC) Directive and the Low Voltage Directive (LVD) ensures that the sensors do not interfere with other electronic devices and provide a high level of safety for users. Meeting these standards not only guarantees the product's reliability and safety but also enhances its marketability by building trust with consumers and regulatory bodies. Additionally, obtaining relevant certifications like AEC-Q100, ISO/TS 16949, and ISO 26262 demonstrates a commitment to quality and safety, which can significantly influence the product's acceptance in the market. Compliance with organizational standards such as IATF 16949 and ISO 9001 further supports the manufacturing of safe and reliable products, ultimately determining the product's success and longevity in the competitive automotive industry.

Electromagnetic Compatibility (EMC) Directive: Ensures that the product does not affect nearby electronics by emitting electromagnetic waves. For example, old cell phones affect radios and TVs.

The Low Voltage Directive (LVD): Ensures that electrical equipment within certain voltage limits provides a high level of protection for European citizens. The LVD covers health and safety risks on electrical equipment operating with an input or output voltage of between:

50 and 1000 V for alternating current
75 and 1500 V for direct current Link.

Relevant Certificates

Organizational Standards

AEC-Q100: Provides failure test qualifications for integrated circuits.
AEC-Q101: Provides failure test qualifications for discrete semiconductors.
AEC-Q200: Provides failure test qualifications for passive components.
AEC-Q103: Provides failure test qualifications for MEMS components.
ISO/TS 16949: Supports the manufacturing of safe and reliable products.
ISO/TS 25114: Intelligent transport systems — Probe data reporting management (PDRM).
ISO 26262: Road vehicles — Functional safety family (part 1 to 12).

IATF 16949: Automotive Quality Management Systems (for Manufacturers).
ISO 9001: Quality management systems — Requirements.
ISO 14001: Environmental management systems — Requirements with guidance for use.
ISO 45001: Occupational Health and Safety Management Systems.
TISAX: Automotive information security management standard.

Testing

Testing is critical in developing automotive sensors, ensuring they meet all necessary performance, safety, and reliability standards. Comprehensive testing helps identify potential issues early, reducing the risk of failures in real-world applications. By adhering to relevant standards, manufacturers can ensure their sensors are robust, reliable, and compliant with industry regulations, ultimately determining the product's success in the market.

Here's a table summarizing the testing values that could apply to most sensors, along with examples and relevant standards:

Category	Property	Example	Relevant Standard
Technical	Min. range	Minimum detectable pressure	ISO 26262
	Max. range	Maximum temperature measurement	ISO 16750-4
	Detection zone	Area covered by a proximity sensor	ISO 17387
	Safety level (ASIL)	Automotive Safety Integrity Level	ISO 26262
Dynamic	Sensitivity	Sensitivity of an accelerometer	SAE J211/1
	Frequency Response	Frequency range of a vibration sensor	ISO 5348
	Dynamic Range	Range of measurable speeds for a speed sensor	ISO 11452-2
	Phase Match	Phase accuracy in multi-sensor systems	ISO 6487
	Resonance Frequency	Resonance frequency of a pressure sensor	ISO 5348
	Temperature Response	Response time to temperature changes	ISO 16750-4
Electrical	Input Voltage	Voltage range for sensor operation	ISO 16750-2
	Current	Current consumption of the sensor	ISO 7637-2
	Electrical Noise	Noise level in sensor output	ISO 11452-2
	Output Impedance	Impedance of the sensor output	ISO 11452-2
	Bias output voltage	Nominal bias voltage	ISO 16750-2
	Grounding	Grounding requirements for sensor installation	ISO 11452-2
Environmental	Operating Temperature	Temperature range for sensor operation	ISO 16750-4
	Influence of Humidity	Sensor performance under high humidity	ISO 16750-4
	Storage Temperature	Temperature range for sensor storage	ISO 16750-4
	IP/NEMA Label	Ingress protection rating	IEC 60529
	Vibration Sensitivity	Sensitivity to mechanical vibrations	ISO 16750-3
	Magnetic Field Sensitivity	Sensitivity to magnetic fields	ISO 11452-8
Physical	Weight	Weight of the sensor	ISO 16750-4
	Case Material	Material used for sensor housing	ISO 16750-4
	Mounting	Mounting method and stability	ISO 16750-3
	Output Connector	Type of connector used for sensor output	ISO 15031-6
	Car connectivity	Compatibility with vehicle communication systems	ISO 14229
	Car communication	Communication protocols used by the sensor	ISO 14229

This table provides a comprehensive overview of the various testing parameters, examples, and relevant standards that ensure the reliability and performance of automotive sensors.

Future Trends

Advancements in Sensor Technology: The field of automotive sensors is rapidly evolving, with emerging trends and technologies enhancing their capabilities. One notable advancement is the integration of AI and machine learning for predictive maintenance, which allows sensors to anticipate and diagnose potential issues before they become critical. Additionally, developing more compact and energy-efficient sensors enables their use in a wider range of applications, contributing to overall vehicle efficiency.

Example—AutoHears: AutoHears is a cutting-edge example of future acoustic sensor technology. This innovative system allows vehicles to "hear" their surroundings, detecting, classifying, and localizing sounds such as sirens, horns, and even natural disasters like rockslides. AutoHears enhances safety by enabling vehicles to respond to auditory cues beyond traditional visual sensors' reach, making it particularly valuable for autonomous driving systems.

References

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