New Ultrasonic Parking Sensor System in Automobiles
A highly accurate ultrasonic parking sensor system for use in air is described. The proposed system uses a method which combines both the time-of-flight (TOF) method and the phase-shift method. The proposed method can obtain larger range measurement and a
- PDF / 446,395 Bytes
- 7 Pages / 439.37 x 666.142 pts Page_size
- 81 Downloads / 183 Views
Abstract A highly accurate ultrasonic parking sensor system for use in air is described. The proposed system uses a method which combines both the time-offlight (TOF) method and the phase-shift method. The proposed method can obtain larger range measurement and also get higher accuracy compared with the TOF method. A single-chip microcomputer-based two-frequency continuous signal generator and phase detector was designed to record and compute the TOF, two phase shifts, and the resulting distance. In the test embodiment to confirm concept feasibility, three cost 40 2 kHz ultrasonic transducers allow flexibility on bumper for transmitting and receiving ultrasound. The ultrasound transducer on the middle of bumper is transmitting the ultrasound. Two ultrasound transducers on the left and right sides of bumper are receiving the ultrasound simultaneously for detecting multiple objects. Experiments were done in air using two-frequency continuous wave (TFcw) with the frequencies of 40 and 41 kHz. Distance resolution of 0.05 % of the wavelength corresponding to the frequency of 40 kHz was obtained. The range accuracy was found to be within 0.05 mm at a range of over 3,000 mm. The main advantages of this ultrasonic parking sensor system are high resolution for detecting multiple objects, low cost, narrow bandwidth requirements, and ease of implementation. Keywords Phase-shift method • Time-of-flight method • Ultrasonic parking sensor system
C.-F. Huang • C.-Y. Liu (*) Department of Computer Science and Information Engineering, Cheng Shiu University, Kaohsiung, Taiwan e-mail: [email protected] J. Juang and Y.-C. Huang (eds.), Intelligent Technologies and Engineering Systems, Lecture Notes in Electrical Engineering 234, DOI 10.1007/978-1-4614-6747-2_69, # Springer Science+Business Media New York 2013
593
594
C.-F. Huang and C.-Y. Liu
1 Introduction The techniques of distance measurement using ultrasonic in air include the time-of-flight technique [1], binary frequency shift keying (BFSK) [2], and a multifrequency AM-based ultrasonic system [3]. In the TOF method, the pulse propagates through the transmission medium and is reflected by a suitable reflector. The time taken for the pulse to propagate from transmitter to receiver is proportional to the reflector’s range. In this case, system errors are primarily due to amplitude degradation of the received signal. However, so the TOF method of range measurement is subject to high levels of errors (about 1 cm) when used in an air medium, thus limiting its applications. Thus, in most applications of range measurement in air using ultrasonic, a phase-shift analysis of single-frequency continuous-wave transmission is used to reduce error [4]. The ranging distance L can be determined by the phase shift of a single frequency if the maximum ranging distance does not exceed a full wavelength; otherwise a phase ambiguity will occur. Ultrasonic sensors are used as parking aids on many vehicles. Most ultrasonic parking sensors detect the objects by using the TOF method. Every ultra
Data Loading...
