These trends are reshaping the application of ultrasonic sensors

Intelligent autonomous vehicles must be able to sense their surroundings in order to make timely decisions and ensure safe driving. For short-range applications such as parking and blind spot detection, ultrasonic technology is favored for its simplicity and robustness. Recently, ultrasound has opened up many new use cases with its versatility. This blog will briefly introduce the development of ultrasonic sensors, and combined with current and future applications, forecast the application field of ultrasonic sensors in the next few years.

Ultrasonic technology is often used to detect objects and find defects in solid materials, and its first patents date back to the 1930s. Ultrasound has always been used for detection applications, such as intruder alarm systems.

As vehicles were equipped with more electronics, automakers began to figure out how to fix the problems that caused damage while driving. An early solution was to install ultrasonic sensors into the bumper and combine them with a buzzer inside the car to alert the driver to potential hazards. A screen was later added to the buzzer to show the location of obstacles.

With the development of ultrasonic transducers, the performance has been improved, mainly by improving the signal-to-noise ratio (SNR) and increasing the detection distance. With improved performance, sensing technology can be used for more safety-critical automotive applications, such as detecting other vehicles in blind spots or detecting road conditions to adjust braking when the road surface is wet.

More recently, ultrasonic sensors have been deployed inside the cabin to detect passengers to trigger seat belt warnings and to ensure that airbags are deployed in response to anticipated regulations based on passenger size and weight. It can also be used to monitor driver alertness and detect breathing and heartbeat.

Given the complexity of modern dashboards, gesture controls are likely to become increasingly popular. In related applications, ultrasonic sensors track the movements of the driver's hands and use them as input signals to operate the vehicle in a manner similar to pressing a switch or turning a knob.

Ultrasonic sensor solutions from onsemi

Since 2007, On has been a market leader in providing dedicated ultrasonic sensor interfaces to major automotive Oems for parking assistance and autonomous driving. When combined with a piezoelectric ultrasonic transducer and some additional circuitry, On's NCV75215 ultrasonic sensor provides time-of-flight (ToF) -based distance measurement.

The advantage of this system is the ability to identify obstacles when parking or executing short distances at low speeds. When the circuit and transducer allow, this very sensitive device can detect standard 75 mm rods in the range of 0.25 to 4.5 meters.

For a comprehensive evaluation of the chip's performance in parking (or other similar) applications, designers can request the NCV75215R1GEVK Ultrasonic Parking Assist Kit from On. The evaluation kit is based on an advanced graphical user interface (GUI) that is simple to operate and enables full evaluation and detailed debugging of prototypes. The Evaluation Suite (EVK) has an EEPROM that holds important user data and configuration Settings. The chip supports full access, and key parameters such as receive (Rx) gain and transmit (Tx) current can be adjusted via the GUI.

Future trends and innovations

As ultrasonic technology advances and consumer expectations rise, especially in the automotive sector, innovative applications are emerging. Many expect the pace of change in this area to accelerate.

For example, in 4D sensing, microelectromechanical system (MEMS) microphones are placed side by side with ultrasonic sensors. MEMS microphones are able to pick up ultrasonic signals and detect other sounds, including the noise of an approaching vehicle. An important use case is the identification of emergency vehicle sirens, warning that appropriate action needs to be taken.

Challenges include the buildup of dust and moisture that can degrade the performance of ultrasonic sensors and front-facing cameras. Some recent innovations have incorporated piezoelectric devices into the sensor assembly, enabling the sensor to vibrate at high frequencies. This has been proven to remove raindrops, general dirt and ice buildup, ensuring the proper operation of safety-critical sensors.

Environmental concerns have prompted the industry to shift to electric propulsion, and understanding the charging status and health of traction batteries is critical. This is usually done with voltage and current measurements, but there are limitations to this approach. An ultrasonic transducer installed inside the battery can indicate the battery's state of charge (SoC) and health (SoH) with a high degree of accuracy.