Where are ultrasonic sensors used? – Part 1
Ultrasonic sensors have been used in passenger vehicles for many years in applications like ultrasonic park assist, which help vehicles detect objects at low speeds when parking. However, kick-to-open liftgates and intrusion detection alarms are two other emerging applications for ultrasonic sensors; see Figure 1. In this post, I will explain why – and how – all three applications use ultrasonic sensors.
Ultrasonic park assist
Ultrasonic park assist is also known as a parking assist system, parking guidance system and reverse park assist. These systems vary from simply detecting an object’s presence and alerting the driver with a noise to autonomously parking the car with little to no driver interaction. Typically, these systems have between four and 16 sensors placed strategically around the car to provide the desired detection coverage, as shown in Figure 2.
Engineers designing these types of applications should seek out integrated circuits (ICs) driving an ultrasonic transducer (transmitter) while receiving, conditioning and processing the ultrasonic echo that determines the distance of an object from the vehicle. For example, the PGA460-Q1 can reliably detect an International Organization for Standardization (ISO) pole (polyvinyl chloride [PVC] pipe used in ultrasonic park assist as a performance standard) up to 5m away. The device has also passed stringent electrostatic discharge (ESD) and bulk-current injection (BCI) testing – common tests performed during ultrasonic park assist system developments.
Ultrasonic park assist cost pressures will continue to increase over the next several years as original equipment manufacturers (OEMs) face the need to add more ultrasonic sensors per vehicle. The PGA460-Q1 supports a competitive cost structure for high-volume Tier-1 suppliers.
Common requirements in ultrasonic park assist modules include:
- Object detection from 30cm to 5m.
- Time command interface (TCI) or Local Interconnect Network (LIN) communication from the module to a local electronic control unit (star configuration) or directly to the body control module (BCM) (bus configuration).
In order to meet the needs of autonomous vehicles, short- and long-distance object-detection standards will become more stringent. Beginning around 2025, ultrasonic modules will have to detect objects from 10cm to 7m away. Improvements in analog front end (AFE) sensitivity and drive methods by semiconductor suppliers will be crucial in meeting these distance requirements.
TCI and LIN are the two most common communication interfaces in ultrasonic park assist systems today. However, as vehicles advance in their advanced driver-assistance system (ADAS) vision-processing abilities, expect the use of higher-speed protocols like Peripheral Sensor Interface (PSI) 5, Distributed Systems Interface (DSI) 3 or Controller Area Network (CAN) to communicate larger amounts of ultrasonic echo data.
A kick-to-open liftgate is also known as a smart trunk opener. This feature enables vehicle owners to place their foot under the back bumper in a kicking motion to open the trunk of the vehicle without using their hands, as shown in Figure 3…