K.Anitha Journal of Engineering Research and Application www.ijera.com ISSN : 2248-9622 Vol. 8, Issue 11 (Part -I) ov 2018, pp 31-37 www.ijera.com DOI: 10.9790/9622-0811013137 31 | Page Discrete Extended Kalman Filter Based Ultrasonic Time-Of- Flight Estimation K.Anitha #1 M.Srinivasa Rao #2 1, 2 Associate Professor, Department of ECE, Prasad V Potluri Siddhartha Institute of Technology, Vijayawada, A.P, India Corresponding Author: K.Anitha ABSTRACT : In mobile robotics applications, the existence of noise measurement may impact on the performance degradation. The noise measurement of the sensor is produced due to several reasons, such as low specification, external signal disturbances and the complexity of the measured state. Therefore, it should be avoided to achieve the good control performance. One of the solution is by designing a signal filter. In this paper, a new digital signal-processing method for ultrasonic time-of-flight (TOF) estimation is presented. The method applies the discrete extended Kalman filter (DEKF) to the acquired ultrasonic signal in order to accurately estimate the shape factors of echo envelope as well as locate its onset. It is so possible to assure reduced bias and uncertainty also in critical TOF measurements, such as those involving low signal to noise ratio (SNR) as well as severe distortion of echo shape. A number of numerical tests are conducted on simulated signals with the aim of highlighting the good performance of the method when operating in critical conditions. Keywords— Ultrasonic Sensor, Mobile Robotics, Temperature Compensation, Discrete Extended Kalman Filter. -------------------------------------------------------------------------------------------------------------------------------------- Date Of Submission:02-11-2018 Date Of Acceptance:16-11-2018 --------------------------------------------------------------------------------------------------------------------------------------- I. INTRODUCTION Ultrasonic based measurements are extensively used both in research and production field, spanning in endless applications: environment sensing of autonomous mobile robots, high definition imaging of biomedical devices, precise location of micro-flaws in materials, accurate estimation of the level of flammable fluids or dangerous rivers, and so on [11]. The reason of this success mainly relies upon the opportunity offered by ultrasonic‟s of conceiving rather simple methods or building up relatively cheap meters, characterized by satisfactory accuracy, reduced measurement time, and, above all, high level of intrinsic safety. Ultrasonic sensors are generally used for non-contact presence and proximity measurements in all industrial areas. Ultrasonic measurements are based on determination of Time of Flight (TOF) [2] i.e. the time necessary for an ultrasonic wave to travel from the transmitter to the receiver through the target over which it is reflected back. The distance of the object from the transducer „D‟ is estimated from the product of one half of the time measured and the propagation velocity of the ultrasonic wave i.e. (1) T)/2 (C D   Where C is the propagating velocity of the ultrasonic burst and T is the round trip time of flight as shown in Fig.1 Accuracy of the measurement depends on the knowledge of c and the correct estimation of T. The sound velocity shows an almost linear dependence with temperature which can be easily compensated. Typical value of C at room temperature is 343.5 m/s ) 2 ( / 15 . 273 1 31 . 331 s m T C   Fig. 1 Illustration of Ultrasonic Ranging Time of flight can be determined by using Continuous wave technique and Pulse echo technique [3]. The Pulse echo method of ultrasonic sensing is popular because of its reliability and compactness. In pulse echo method there are many techniques for TOF estimation but the most common ones are threshold method and cross-correlation estimation [2]. Threshold method is simple and fast, where the detection occurs when the received signal exceeds the given threshold level. The problem here is that on the RESEARCH ARTICLE OPEN ACCESS