Measurement of road surfaces by reflection characteristics of airborne ultrasound

The automated driver as a new road user

“…Commercial ultrasonic sensors for automotive parking applications typically operate in the region of 40-60 kHz, and have a range of 30-450 cm (Nordevall, 2015). They provide distance measurements to objects at low speeds, which is beneficial for parking aids (Alonso et al, 2011), preventing car crashes (Alonso, Oria, Fernández, & Rodríguez, 2009), measuring characteristics of road surfaces (Hirata, Sun, Ueda, & Hachiyay, 2016), detecting moving obstacles (Ohya, Kosaka, & Kak, 1998), and detection of ice by friction analyses based on noise produced by tyre-road interaction (Gailius & Jacenas, 2007).…”

The evaluated signal-to-noise ratio for the alternate transmission of different chirp ultrasound to extend the measurable distance in the pulse-echo method

“…5,6) Pulse compression has been introduced to improve the SNR and distance resolution in the pulse-echo method [7][8][9][10][11][12] The transmitted signal is obtained by a frequency-sweep-modulated burst wave or pulse sequence coded by a pseudo-random number from the linear feedback shift register. [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] Then, the reflected signal and the reference signal are calculated by the cross-correlation function. The reference signal corresponds to each transmitted signal.…”

Ultrasonic position and velocity measurements for a moving object by the simultaneous transmission of preferred-pair M-sequences

“…Measurement using ultrasonic sensors has several advantages: low purchase cost, small size, and simple structure. In particular, ultrasonic measurement is expected to be applied in autonomous driving technology, together with millimeter-wave radar and camera images [1][2][3][4]. In this technology, the distance to the target and the velocity of the object are the most important information to be measured.…”

“…To improve the signal-to-noise ratio (SNR) of the received signal and the resolution of the TOF, pulse compression has been introduced to the pulse-echo method [4][5][6][7][8][9][10][11][12][13][14][15][16][17]. A long burst with a sharp autocorrelation property, which is modulated by a frequency sweep (FS) or coded by pseudo-random numbers or noise (PN), is typically transmitted in pulse compression.…”

“…The SNR improvement is determined by the bandwidth and the signal duration. In PN coding, a short pulse or its inverse pulse is assigned to each binary character [4,[10][11][12][13][14][15][16][17]. When the reference signal is composed of discrete binary characters, the compressed pulse corresponds to the accumulated short pulses.…”