**5.4 Ultrasonic sensing system**

*Models and Technologies for Smart, Sustainable and Safe Transportation Systems*

range-radar (MRR), and long-range-radar (LRR) sensors or systems.

**Property Present in systems Comment**

• Adaptive Cruise Control • Lane Change Assistant

• Adaptive Cruise Control • ACC/Stop &Go

• ACC/Stop & Go +Foresight • Lane Change Assistant • Automatic Parking

Frequency: 24 GHz • Forward Collision Warning Forward looking, long

• Lane Keeping Assistant • Obstacle & Collision Warning • Rural Drive Assistance

• Pre-Crash Collision and Mitigation System

Mitigation System

• Obstacle and Collision Avoidance

Radar • Near field Collision Warning

Infrared Radar • Pre-Crash Collision and

*Summary table of the properties of a radar sensor in certain ADAS, source: Ref. [12].*

Long range, Pulse Doppler,

Active sensor,

Short range

Range

Range

Side looking, short

Active sensor,

Active sensor,

Long range, Pulse Doppler,

Short range, Active sensor,

Near InfraRed (NIR), Far Infra Red (FIR),

• Side Obstacle Detection Side looking, short range

*properties of a radar sensor in certain ADAS.*

Frequency: 76–77 GHz Range: 1 to 200 m Search Area: 12°

< 0.2 km/h

• ±

Speed measurement precision:

Angular Precision: < 0.3° Frequency: 24.125 Ghz Distance range: 10 m Velocity range: 60 m/s

Field of view: • ± 50 0Horizontal

0,5 m/s Accuracy: • ± 0,05 m • ± 0,5 m/s

Frequency: 24 GHz Frequency: 5.8 GHz

F = 76.5 GHz Resolution = 100 cm Bandwidth = 100–500 MHz Range = 7–150 m

Smallest object: Metal bar 10 mm dia (vertically placed at 1,5 m) Dimensions: 90 x 40 x 15 mm

Frequency: 24 GHz UWD (Ultra Wide Band) Resolution = 3 cm

Transmission Power = −41.3

Bandwidth = 5 GHz Range: 0.3–30 m

dBm/ MHz

is dedicated high-frequency (HF) technologies to realize the frequencies (24 GHz or 77 GHz) and the corresponding output power. **Table 2** presents *summary table of the* 

Multiple transmitters and receivers are generally are in-built to determine range, angle, and velocity of objects in their field of view. As various sensors are concerned, it consists of ultra-short-range- radar (USRR), short-range-radar (SRR), medium-

**224**

**Table 2.**

The primary philosophy of working with the ultrasonic technology is to transmit short bursts of sound waves that return back after hitting objects for which the measurement are to be taken in terms of time required to bounce back with speed of approximately 346 m/s which is the speed of the sound. For detection of short distance range obstacle, Ultrasonic sensors are increasing being used in the automobile industries which is generally characterized by with a sound pressure kHz and detection covering range of one to three meters supported by horizontal beam width of maximum100°and60°vertical. The ultrasonic and radar technology complements each other to determine the higher degree of accuracy,

Ultrasonic sensing is generally meant for short-distance applications at low speeds, such as park assist, self-parking, and blind-spot detection. For maximum coverage, an automotive ultrasonic system typically performs with multiple sensors placed in the wing mirror and front and rear bumpers. Ultrasonic sensing is a more cost-effective approach than cameras, which have poor close- distance detection. Though infrared sensing is cheaper than ultrasonic, it's less accurate and cannot function properly in direct sunlight. Objects closer to the transmitter generate a stronger echo than an object with more distantly located. In order to avoid false

### **Figure 10.**

*This ultrasonic system features a PGA450 analog front end (source: Author/PGA450-Q1 PDF).*


### **Table 3.**

*Summary table of the properties of an ultrasonic sensor in certain ADAS, source: https://www.embedded.com/ how-smart-sensors-enhance-adas-designs/*

positives, the system neglects all inputs that are less than that of the noise. The important parameters related to the specifications of ultrasonic sensor are the frequency, sensitivity, and directivity. The system is further characterized by the tunable transformer that is required to excite the transducer.

A tuning capacitor built into the system is concerned with matching the resonant frequency between the transducer and transformer. The speed of sound in air is affected by air temperature, humidity, and wind. If multiple sensors are applied, they must be placed in sufficient space so that the sensor signals do not interfere. **Figure 10** shows the features of ultrasonic system (**Table 3**).
